great white
Well-Known Member
Disclaimer; Most (or all) of this will be nothing new to the "old dogs" on the board, but a newb or two might find a couple "nuggets" here that may help them along.
But not in "as delivered" form and certainly not after it has some age on it. If you think yours is “pretty new”, you better think again. The newest 6.5 (as delivered from GM) is now 10 years old…..
Having just finished towing an 8000+lb travel trailer from West coast to East coast as far as you can go either way without getting wet, allow me to share a few observations, recommendations and techniques.
You can use some or all of these things, but to get to where I ended up (and the “performance level”) you should seriously consider all of it. I will break it down into “need” and “want” which is pretty self explanatory. You can make your own decisions on that if you wish.
A word of warning, this is going to be an expensive list.
I’m not pulling any punches either. I would NEVER tow with one of these old rigs ever again without ALL of these improvements.
You may decide to just buy a newer Duramax, Powerstroke or Cummins after reading all this. Any of these vehicle options will give you a better, more capable rig right from the start. But if you like the old GMT400 chassis and want to spend way more on it that you probably should, read on.
The Truck:
As GM delivered it, it’s not a towing machine. It was made to deliver MPG and then GM “pumped up” the original design to try and compete with the offerings coming out from Dodge and Ford. They cut corners, tacked stuff on with what gives the appearance of very little R&D and the electronics are a half step measure towards full electronic control. None of this is a winning recipe for power or longevity. You can agree with that or not, your choice.
It needs some help if you intend to tow heavy or far. It can get by in stock form if it’s still healthy, but throw in anything other than a “Sunday drive” and it’s going to struggle. These trucks are also no longer “spring chickens”, so yours is probably pretty tired if you haven’t already entered the “rebuild/replace” cycle.
So, in MY order of importance (yours may differ), the list….
Engine-
Class ; depends
This is going to be a bitter pill to swallow, very expensive and not a popular reccomendation but replace it if there is any doubt to its condition.
Don’t go any less than a New 6500 Optimizer or a P400. Anything less is just a waste of time and money.
Don’t rebuild one, don’t buy a rebuilt one, they’re both a waste of time and money.
Assuming you can find a good block, it’s on borrowed time and will crack, leak or just plain old give out on you. Get some new iron, don’t waste your time on a design that was flawed and overstressed from the get go. You get a redesigned block and heads, fresh pistons and rings, as just an all around better lump.
Expect to spend at least around 7,000. Like I said, a bitter pill but you’ll have a solid base to build on that will handle the load for the next 300,000 kms without cracking mains, splitting heads or shattering crankshafts. It also wil put a complete end to any leaks you’re pulling your hair out chasing down.
You may get away with a military “take out” surplus unit (it should also be a GEP unit), but you’re taking your chances there. Many have reported good experiences so far. But it’s very much “Buyer Beware”….
I’ve been sitting by the side of the highway with a holed piston, an 8000 lb trailer, the family in the vehicle and semi’s whipping by. You absolutely NEED a solid base if you plan to trust your family’s well being to the vehicle, the Optimizer or P400 is it. GM’s original iron (or a “Chinese” block and heads) is not.
Injectors
Class: Need
These are a CRITICALitem. A bad set will kill your pistons in very short order. Even a brand new optimizer or P400 longblock.
If your injectors have any more than 100,000 miles on them with a basic daily driver, replace them. Don’t go for rebuilts, just order up some new BOSCH ones from a reputable dealer. I used Heath, but any reputable dealer will do as long as they’re NEW BOSCH units.
I originally ordered a NOS set from eBay. While they were good in just daily driving, once I started hammering on them with serious towing they deteriorated rapidly.
If you’ve got considerable towing miles on your injectors, chop about 20-30,000 off that 100,000 interval.
That’s not my recommendation; I got it from "someone" very knowledgeable about the whole issue.
Injectors are the silent killer for a 6.5……don’t cheap out, replace them often. Expect to spend around 600 bucks.
The Turbo
Class; Need
A healthy GM8 gets it done. At least, it did on mine. But it needs to be healthy. A previous model GMX is probably fine also, as long as it’s in solid shape. An “A Team Turbo” (Mitsubishi unit) may work better, but I believe it is an optional upgrade and it can wait until your healthy stock GMx is no longer “healthy”.
Expect around 7-800 bucks for an ATT or a bit more for a replacement GMx.
Guages
Class: Need
EGT’s - You absolutely MUST have an EGT guage (also called pyrometer). Brand doesn’t matter, but it must be good quality.
Boost - A boost guage is essential only if you add a turbo master. You need it to adjust the spring for maximum boost. Too much and you can be popping head gaskets, too little and you get black smoke and high EGT’s.
Expect to spend anywhere from a couple hunny to 500.
Class ; Want
Fuel pressure- for the lift pump. Loose the lift pump and bad things can start happening to power and the life of your injection pump.
Transmission temperature – you can get by without one, but you should have one. Heat kills transmissions.
Axle temp – good for seeing your temps, but the 14 bolt corporate GM unit is one strong diff. The G80 RPO code “gov lock” is a different story…
Transfer case temp- Good if you have a 4x4 and tow. GM transfer cases tend to run hot in normal driving, towing is worse. Change the oil regularly.
PMD
Class: Need
Don’t we all love this little piece of Kit! (sarcasm)
If you’ve ever experienced a failing PMD, you know what I’m talking about.
If you don’t know how old it is, get a spare. Get one now! Have it on a heat sink and ready to go.
If it is failing, get a new one on an extender and get it completely out of the engine bay. 3 things kill electronics; heat, vibration and voltage spikes. These buggers run hot, get it somewhere where it can shed that heat quickly. That means a good supply of moving, cool air.
Not trying to sound like a Heath diesel commercial, but his prices are highly competitive on these and he offers a 7 year warranty….hard to beat that anywhere…..
Expect to spend anywhere from 500-1000 smackers a pop for new.
Lift Pump
Class: need
How old is it? Don’t know? Better at least have a spare in the glove box. Bad things will happen if it goes out towing. Best case is reduced power and added strain on the Injection pump. Worst case scenario, it could cost you an injection pump…
Fuel filter
Class; need
Just keep up with regular maintenance.
Turbo Master
Class; depends.
Keeps the boost on while towing which keeps the fuel rate up. GM designed the stock program to pull back boost whenever it can to save MPG. Great on a truck built for MPG, bad for one that is towing. When the boost comes back, so does the fuel, then the power follows right behind that and then that big 9x8 foot 8000 lb sail behind you pulls the speed down. Now you have to “get it into it” to speed up and then the PCM pulls everything back again, and you have to get into it, and…..well, you get the idea. But you can get it done with the stock vacuum wastegate system. It’s just not as good at it unless you have the program “altered”.
You can cobble something up with threaded rod and some nuts for around 10 bucks or you can buy a readymade unit from Heath for around 120 bucks.
Your choice, I went with the Heath unit and have absolutely no regrets. Money well spent.
Note: If you go with a Heath PCM (discussed later) you should buy a turbo master. In my experience, it doesn’t play well with the stock vacuum system as it is programmed for the particular operation of a turbo master unit.
Exhaust
Class; need.
Get yourself a minimum mandrel bent turbo back 3 inch system and a 2.5” crossover pipe. The most popular these days are a 3” downpipe (largest that physically fits) and then a 4 inch back from that. Same price usually, so go for the 4 inch system. Mine is the 2.5” warpspeed crossover and a 4” turbo back Diamond eye with a stainless muffler.
Radiator
Class; Need
Your rad must be sound and clean. Inside and out. If you don’t know how old it is, pull it out and send it to a rad shop for testing and cleaning. They will clean the core inside and out. It will assure you get all the cooling it is capable of. The 6.5 produces a lot of heat due to it’s IDI design. You need a solid rad to support it.
Clean out the oil coolers and AC evap core while you’re got it apart. Get a “rad comb” and straighten what fins you can to help ease restrictions in front of the rad also.
Water Pump
Class; Need
Have a 98+ model year water pump in there. If it is and you don’t know how old it is, better think about replacing it. These pumps go forever and then fail all at once. they are good one day and are pouring coolant out the weep hole the next.
This is another key link in keeping that hard working IDI cool.
While you’re at it, replace the hoses also. Popped hose on an interstate/highway can really ruin your day. In the big picture, hoses are cheap, so are belts. Both are really maintenance items anyways.
Fan and Clutch
Class; need
You want a 9 blade steel fan and a solid working clutch as a minimum.
I’m running the stock 98 clutch and 9 blade steel fan and it gets the job done just fine. But it's all heathy and in good shape. years and wear may dictate you need to change the cltuch out.
Many have switched up to a Duramax fan and a SD clutch. Your choice, but it must be in top shape no matter what you choose.
Thermostats
Class; Need
Get a good set (or a single if you truck is not dual stats) of AC Delco 195 units. If you have no idea if they’re older than a year or two, replace ‘em. They’re cheap to buy and are really another maintenance item.
You can go with 180 units if you prefer, but I have had excellent cooling performance with a new set of 190 AC Delcos and I won’t have to deal with poor mileage unloaded or heater performance issues in winter. Your choice….
PCM
Class: I’m going to say need, but it could be want
If you’re going to tow, in hills or flats, I can’t recommend a modified program enough. I’ve run both a stock PCM, my own tuned PCM (not optimized for towing though) and a Heath PCm in hilly and windy conditions. To be blunt, the stock can get it done, but flat out sucks when compared to the Heath PCM. That’s for flat and uphill towing though. There’s no comparison between the stocker and the Heath PCM in the downhill portions.
If you tow in hills, you need a Heath PCM with his hill assist feature. I’ll say it again since it’s soooo good; If you tow in hills, you NEED a heath PCM with hill assist feature.
Engine and transmission Mounts
Class; need
If your mounts are deteriorated, replace ‘em. Trans mount is most subject to deterioration due to the heat and oil spatter it usually lives in.
‘Nuff said.
Fluidampr
Class; want
Seriously, if you put in a new optimizer, it’s going to come with a new stock damper. But the difference in “smoothness” and longevity between the stock damper and the fluidampr needs to be experienced to be understood. Plus, you don’t have to worry about the rubber coming apart and shattering your new crank. Call it 400 dollars of insurance for your 7000 dollar long block…..
Water Injection
Class; want
Look very closely at the words I chose; WATER injection, not Water METH injection. Water ONLY for a 6.5....
To tell the truth, with all the improvements listed above, my new optimizer 6500 almost doesn’t seem to care if the water is one or off, egt’s are pretty close to the same. It does seem to help keeping the coolant temps down.
It goes without saying the rest of the truck must be sound. IE: front end suspension and steering components, proper towing gear (Weight distribution hitch, etc), transmission, axles, bearings, electronics, etc.
You must also keep up with the maintenance items such as engine oil, trans oil, gear lube, etc….
With this combination, I towed from Ellensburg WA to Gander Newfoundland and finished with a truck showing 420,000+ km’s on the clock. Prior to that, I used the thrashed 599 block to tow it (almost to Ellensburg. It pulled equally well with everything you see below the optimizer recommendatioin, until it stove in a piston from just plain old age.
That’s 6471 kms or 3806 miles in one shot. 6983 kms (4107 miles) from start to finish.
It conquered 4th of july pass, vantage highway, lookout pass, the hills around Butte, the horrible hills heat and winds of Wyoming, the oppressive heat and humidly (34+ degrees before the humidex) of the plains, fast interstate running in the east, the Appalachians, high winds and hills it in the Maritimes and climbing and twisting through beautiful scenic Newfoundland. Once the PMD issues were sorted, it pulled our 8000+lb travel trailer with relative ease and power. Even before the PMD problems were sorted, it pulled the combo with confidence. Passing vehicles at and above the speed limit was not only possible, it was a fact. It could easily haul the combo up to 80+mph (scary on trailer tires!), even though I ran around 60-65 mph almost everywhere.
That brings us to the last (and maybe most important) category:
Driving
Class; need
This is a pretty gray area and almost an art more than a science. You just have to get out there and build up some experience.
My general recommendation for a 6.5 is this; Watch the EGT’s, watch the Coolant temps and what the fuel gauge. The speedometer is basically to keep you from getting tickets. If you’re moving slower than traffic or the speed limit, so be it. They may be pissed off moving slow behind you, but they’ll be even more pissed off if you break it and block the road. Not to mention, your wallet will be getting really light after blowing the engine…
Keep the coolant below 210, let off throttle and slow down if you have to. That goes for hills or flats. If you’re built it right though, it shouldn’t be much of an issue anyways. Spike 215 if you must, but only for shot intervals then slow down and cool it off.
Preferably, keep the EGT’s below 1000, don’t sustain much more than 1050. Spike 1100 if you have to, but get it out of there ASAP. Exceed 1100 at your own peril. Most hills I would set 980 on the EGT gauge and climb the hill at that EGT, maybe spiking up to 1050 if needed. This would get me 55 mph on 4th of July pass and 45-50 on Lookout Pass. Flat running I could almost ignore the EGT’s and watch the speedo, coolant and fuel.
Downshift to third before you speed gets up on the down hills. Again, the Heath program let me descend most hills without down shifting and no ( or minimal) brake applications. It’s just that good…
These are my recommendations for a solid, reliable travel trailer pulling GMT 400 6.5 Turbo diesel.
Your mileage may vary…
So you want to tow heavy and long with a 6.5?
I’m living proof that a 6.5 can take whatever North America can dish out while towing and towing heavy. From high and long mountain passes in the west, to rolling hills and oppressive heat in the foothills, to oppressive heat and high speed running in flatlands, to twisting roads in the Appalachian mountains, to high winds in the East. It can handle it all.
But not in "as delivered" form and certainly not after it has some age on it. If you think yours is “pretty new”, you better think again. The newest 6.5 (as delivered from GM) is now 10 years old…..
Having just finished towing an 8000+lb travel trailer from West coast to East coast as far as you can go either way without getting wet, allow me to share a few observations, recommendations and techniques.
You can use some or all of these things, but to get to where I ended up (and the “performance level”) you should seriously consider all of it. I will break it down into “need” and “want” which is pretty self explanatory. You can make your own decisions on that if you wish.
A word of warning, this is going to be an expensive list.
I’m not pulling any punches either. I would NEVER tow with one of these old rigs ever again without ALL of these improvements.
You may decide to just buy a newer Duramax, Powerstroke or Cummins after reading all this. Any of these vehicle options will give you a better, more capable rig right from the start. But if you like the old GMT400 chassis and want to spend way more on it that you probably should, read on.
The Truck:
As GM delivered it, it’s not a towing machine. It was made to deliver MPG and then GM “pumped up” the original design to try and compete with the offerings coming out from Dodge and Ford. They cut corners, tacked stuff on with what gives the appearance of very little R&D and the electronics are a half step measure towards full electronic control. None of this is a winning recipe for power or longevity. You can agree with that or not, your choice.
It needs some help if you intend to tow heavy or far. It can get by in stock form if it’s still healthy, but throw in anything other than a “Sunday drive” and it’s going to struggle. These trucks are also no longer “spring chickens”, so yours is probably pretty tired if you haven’t already entered the “rebuild/replace” cycle.
So, in MY order of importance (yours may differ), the list….
Engine-
Class ; depends
This is going to be a bitter pill to swallow, very expensive and not a popular reccomendation but replace it if there is any doubt to its condition.
Don’t go any less than a New 6500 Optimizer or a P400. Anything less is just a waste of time and money.
Don’t rebuild one, don’t buy a rebuilt one, they’re both a waste of time and money.
Assuming you can find a good block, it’s on borrowed time and will crack, leak or just plain old give out on you. Get some new iron, don’t waste your time on a design that was flawed and overstressed from the get go. You get a redesigned block and heads, fresh pistons and rings, as just an all around better lump.
Expect to spend at least around 7,000. Like I said, a bitter pill but you’ll have a solid base to build on that will handle the load for the next 300,000 kms without cracking mains, splitting heads or shattering crankshafts. It also wil put a complete end to any leaks you’re pulling your hair out chasing down.
You may get away with a military “take out” surplus unit (it should also be a GEP unit), but you’re taking your chances there. Many have reported good experiences so far. But it’s very much “Buyer Beware”….
I’ve been sitting by the side of the highway with a holed piston, an 8000 lb trailer, the family in the vehicle and semi’s whipping by. You absolutely NEED a solid base if you plan to trust your family’s well being to the vehicle, the Optimizer or P400 is it. GM’s original iron (or a “Chinese” block and heads) is not.
Injectors
Class: Need
These are a CRITICALitem. A bad set will kill your pistons in very short order. Even a brand new optimizer or P400 longblock.
If your injectors have any more than 100,000 miles on them with a basic daily driver, replace them. Don’t go for rebuilts, just order up some new BOSCH ones from a reputable dealer. I used Heath, but any reputable dealer will do as long as they’re NEW BOSCH units.
I originally ordered a NOS set from eBay. While they were good in just daily driving, once I started hammering on them with serious towing they deteriorated rapidly.
If you’ve got considerable towing miles on your injectors, chop about 20-30,000 off that 100,000 interval.
That’s not my recommendation; I got it from "someone" very knowledgeable about the whole issue.
Injectors are the silent killer for a 6.5……don’t cheap out, replace them often. Expect to spend around 600 bucks.
The Turbo
Class; Need
A healthy GM8 gets it done. At least, it did on mine. But it needs to be healthy. A previous model GMX is probably fine also, as long as it’s in solid shape. An “A Team Turbo” (Mitsubishi unit) may work better, but I believe it is an optional upgrade and it can wait until your healthy stock GMx is no longer “healthy”.
Expect around 7-800 bucks for an ATT or a bit more for a replacement GMx.
Guages
Class: Need
EGT’s - You absolutely MUST have an EGT guage (also called pyrometer). Brand doesn’t matter, but it must be good quality.
Boost - A boost guage is essential only if you add a turbo master. You need it to adjust the spring for maximum boost. Too much and you can be popping head gaskets, too little and you get black smoke and high EGT’s.
Expect to spend anywhere from a couple hunny to 500.
Class ; Want
Fuel pressure- for the lift pump. Loose the lift pump and bad things can start happening to power and the life of your injection pump.
Transmission temperature – you can get by without one, but you should have one. Heat kills transmissions.
Axle temp – good for seeing your temps, but the 14 bolt corporate GM unit is one strong diff. The G80 RPO code “gov lock” is a different story…
Transfer case temp- Good if you have a 4x4 and tow. GM transfer cases tend to run hot in normal driving, towing is worse. Change the oil regularly.
PMD
Class: Need
Don’t we all love this little piece of Kit! (sarcasm)
If you’ve ever experienced a failing PMD, you know what I’m talking about.
If you don’t know how old it is, get a spare. Get one now! Have it on a heat sink and ready to go.
If it is failing, get a new one on an extender and get it completely out of the engine bay. 3 things kill electronics; heat, vibration and voltage spikes. These buggers run hot, get it somewhere where it can shed that heat quickly. That means a good supply of moving, cool air.
Not trying to sound like a Heath diesel commercial, but his prices are highly competitive on these and he offers a 7 year warranty….hard to beat that anywhere…..
Expect to spend anywhere from 500-1000 smackers a pop for new.
Lift Pump
Class: need
How old is it? Don’t know? Better at least have a spare in the glove box. Bad things will happen if it goes out towing. Best case is reduced power and added strain on the Injection pump. Worst case scenario, it could cost you an injection pump…
Fuel filter
Class; need
Just keep up with regular maintenance.
Turbo Master
Class; depends.
Keeps the boost on while towing which keeps the fuel rate up. GM designed the stock program to pull back boost whenever it can to save MPG. Great on a truck built for MPG, bad for one that is towing. When the boost comes back, so does the fuel, then the power follows right behind that and then that big 9x8 foot 8000 lb sail behind you pulls the speed down. Now you have to “get it into it” to speed up and then the PCM pulls everything back again, and you have to get into it, and…..well, you get the idea. But you can get it done with the stock vacuum wastegate system. It’s just not as good at it unless you have the program “altered”.
You can cobble something up with threaded rod and some nuts for around 10 bucks or you can buy a readymade unit from Heath for around 120 bucks.
Your choice, I went with the Heath unit and have absolutely no regrets. Money well spent.
Note: If you go with a Heath PCM (discussed later) you should buy a turbo master. In my experience, it doesn’t play well with the stock vacuum system as it is programmed for the particular operation of a turbo master unit.
Exhaust
Class; need.
Get yourself a minimum mandrel bent turbo back 3 inch system and a 2.5” crossover pipe. The most popular these days are a 3” downpipe (largest that physically fits) and then a 4 inch back from that. Same price usually, so go for the 4 inch system. Mine is the 2.5” warpspeed crossover and a 4” turbo back Diamond eye with a stainless muffler.
Radiator
Class; Need
Your rad must be sound and clean. Inside and out. If you don’t know how old it is, pull it out and send it to a rad shop for testing and cleaning. They will clean the core inside and out. It will assure you get all the cooling it is capable of. The 6.5 produces a lot of heat due to it’s IDI design. You need a solid rad to support it.
Clean out the oil coolers and AC evap core while you’re got it apart. Get a “rad comb” and straighten what fins you can to help ease restrictions in front of the rad also.
Water Pump
Class; Need
Have a 98+ model year water pump in there. If it is and you don’t know how old it is, better think about replacing it. These pumps go forever and then fail all at once. they are good one day and are pouring coolant out the weep hole the next.
This is another key link in keeping that hard working IDI cool.
While you’re at it, replace the hoses also. Popped hose on an interstate/highway can really ruin your day. In the big picture, hoses are cheap, so are belts. Both are really maintenance items anyways.
Fan and Clutch
Class; need
You want a 9 blade steel fan and a solid working clutch as a minimum.
I’m running the stock 98 clutch and 9 blade steel fan and it gets the job done just fine. But it's all heathy and in good shape. years and wear may dictate you need to change the cltuch out.
Many have switched up to a Duramax fan and a SD clutch. Your choice, but it must be in top shape no matter what you choose.
Thermostats
Class; Need
Get a good set (or a single if you truck is not dual stats) of AC Delco 195 units. If you have no idea if they’re older than a year or two, replace ‘em. They’re cheap to buy and are really another maintenance item.
You can go with 180 units if you prefer, but I have had excellent cooling performance with a new set of 190 AC Delcos and I won’t have to deal with poor mileage unloaded or heater performance issues in winter. Your choice….
PCM
Class: I’m going to say need, but it could be want
If you’re going to tow, in hills or flats, I can’t recommend a modified program enough. I’ve run both a stock PCM, my own tuned PCM (not optimized for towing though) and a Heath PCm in hilly and windy conditions. To be blunt, the stock can get it done, but flat out sucks when compared to the Heath PCM. That’s for flat and uphill towing though. There’s no comparison between the stocker and the Heath PCM in the downhill portions.
If you tow in hills, you need a Heath PCM with his hill assist feature. I’ll say it again since it’s soooo good; If you tow in hills, you NEED a heath PCM with hill assist feature.
Engine and transmission Mounts
Class; need
If your mounts are deteriorated, replace ‘em. Trans mount is most subject to deterioration due to the heat and oil spatter it usually lives in.
‘Nuff said.
Fluidampr
Class; want
Seriously, if you put in a new optimizer, it’s going to come with a new stock damper. But the difference in “smoothness” and longevity between the stock damper and the fluidampr needs to be experienced to be understood. Plus, you don’t have to worry about the rubber coming apart and shattering your new crank. Call it 400 dollars of insurance for your 7000 dollar long block…..
Water Injection
Class; want
Look very closely at the words I chose; WATER injection, not Water METH injection. Water ONLY for a 6.5....
To tell the truth, with all the improvements listed above, my new optimizer 6500 almost doesn’t seem to care if the water is one or off, egt’s are pretty close to the same. It does seem to help keeping the coolant temps down.
It goes without saying the rest of the truck must be sound. IE: front end suspension and steering components, proper towing gear (Weight distribution hitch, etc), transmission, axles, bearings, electronics, etc.
You must also keep up with the maintenance items such as engine oil, trans oil, gear lube, etc….
With this combination, I towed from Ellensburg WA to Gander Newfoundland and finished with a truck showing 420,000+ km’s on the clock. Prior to that, I used the thrashed 599 block to tow it (almost to Ellensburg. It pulled equally well with everything you see below the optimizer recommendatioin, until it stove in a piston from just plain old age.
That’s 6471 kms or 3806 miles in one shot. 6983 kms (4107 miles) from start to finish.
It conquered 4th of july pass, vantage highway, lookout pass, the hills around Butte, the horrible hills heat and winds of Wyoming, the oppressive heat and humidly (34+ degrees before the humidex) of the plains, fast interstate running in the east, the Appalachians, high winds and hills it in the Maritimes and climbing and twisting through beautiful scenic Newfoundland. Once the PMD issues were sorted, it pulled our 8000+lb travel trailer with relative ease and power. Even before the PMD problems were sorted, it pulled the combo with confidence. Passing vehicles at and above the speed limit was not only possible, it was a fact. It could easily haul the combo up to 80+mph (scary on trailer tires!), even though I ran around 60-65 mph almost everywhere.
That brings us to the last (and maybe most important) category:
Driving
Class; need
This is a pretty gray area and almost an art more than a science. You just have to get out there and build up some experience.
My general recommendation for a 6.5 is this; Watch the EGT’s, watch the Coolant temps and what the fuel gauge. The speedometer is basically to keep you from getting tickets. If you’re moving slower than traffic or the speed limit, so be it. They may be pissed off moving slow behind you, but they’ll be even more pissed off if you break it and block the road. Not to mention, your wallet will be getting really light after blowing the engine…
Keep the coolant below 210, let off throttle and slow down if you have to. That goes for hills or flats. If you’re built it right though, it shouldn’t be much of an issue anyways. Spike 215 if you must, but only for shot intervals then slow down and cool it off.
Preferably, keep the EGT’s below 1000, don’t sustain much more than 1050. Spike 1100 if you have to, but get it out of there ASAP. Exceed 1100 at your own peril. Most hills I would set 980 on the EGT gauge and climb the hill at that EGT, maybe spiking up to 1050 if needed. This would get me 55 mph on 4th of July pass and 45-50 on Lookout Pass. Flat running I could almost ignore the EGT’s and watch the speedo, coolant and fuel.
Downshift to third before you speed gets up on the down hills. Again, the Heath program let me descend most hills without down shifting and no ( or minimal) brake applications. It’s just that good…
These are my recommendations for a solid, reliable travel trailer pulling GMT 400 6.5 Turbo diesel.
Your mileage may vary…
