Achievement Get: 6.5 Diesel

[IBM]

Greetings fellow grease monkeys and gear heads!

I have been a big fan of diesels since I first started working on tractor/trailers with my dad back in 2008. After years of owning/driving only gas trucks/cars, I finally decided to get a diesel of my own. I looked high and low at all the options, and the one I settled for based on my criteria was the 6.5L GM. Even though it has known issues with the fuel injection system, and some more concerning flaws with the crankshaft and the engine block, it is still one of the most efficient and significant diesels of its time, and still a prominent example of superior fuel efficiency in diesels today! I love its simplistic design, it's ease of maintenance, abundance of parts, and of course... the distinctive sound! I could identify this engine solely on its sound no doubt. To me, it sounds sloppy, sluggish, clacky and broken in... sounds like a mechanical dream!

I purchased my 1995 GMC Suburban back in July of this year, and I had to do some work on it before I was satisfied. The man I bought it off of pointed out to me that he took a 1500 Suburban body and put it on a 2500 chassis back in 99 after the old chassis was damaged in an accident. With that upgrade came a 4L80E transmission and the upgraded suspension of course. Supposedly the 6.5 was already in the 1500. But the man did a great job. Everything was professionally done, and I am super satisfied with my first diesel truck purchase. So far, I've only had to replace the lift pump, install the Leroy Diesel WTS FP relay, and replace brake lines (I will never do this alone again). The truck has been pretty reliable aside from the FP randomly dying without warning and leaving me stranded. Chalk it up to the age I reckon.

It now has 267k miles on the engine, it was partially rebuilt at 239k (rings, seals, bearings, etc). I am really hoping to get the most mileage out of this engine and wondering if it is possible to squeeze 500k+ out of it. I don't do any towing or heavy hauling, it is a daily for me. Most I do is haul brush and trash, and furniture now and then. It is my new baby since my 2nd Gen RAM has rusted into oblivion.

Thanks for having me onboard! I hope to learn as much as I can about this engine to make it last. So far it has been worth the trouble, because it has definitely exceeded my expectations on fuel mileage, not to mention the OBS Suburbans are beasts! Nothing quite like a good old fashioned American Land Barge.


-IBM

 

[snarl95]

Welcome.

 

[btfarm]

Welcome to The Truck Stop!

 

[MrMarty51]

Welcome to the forum IBM. You are in the right place for any info You may need to keep Your Suburban on the road.
Stalling issue ?
Has the PMD been moved from the IP to behind the front bumper with an extension harness ? Do You pack along a spare PMD ?

 

[Will L.]

Welcome.
Plenty to learn here. Go through the library stickes. That time will pay for itself.
Exceeding 500,000 is unlikely -depending how your rebuild went and maintenance - you might get close.

 

[IBM]

Welcome to the forum IBM. You are in the right place for any info You may need to keep Your Suburban on the road.
Stalling issue ?
Has the PMD been moved from the IP to behind the front bumper with an extension harness ? Do You pack along a spare PMD ?

HI there! No stalling. PMD already relocated and the FSD heat-sync has been installed. The only engine related problem wasn't really engine related at all, it was just the lift pump! It appears that the DS4 had been replaced at some point prior to me buying the truck. Lucky me!

 

[Jaryd]

Welcome to the forum.

Always always always add some type of lubricity to the fuel when you fill up. The fuel nowadays don’t have much lubrication in it for these IPs to last like they used to. People prefer different lubes but I use TCW-3 2 stroke oil at 1 oz per gallon. Most say they go 1/2 oz per gallon but I double that and sometimes more.

 

[IBM]

Welcome to the forum.

Always always always add some type of lubricity to the fuel when you fill up. The fuel nowadays don’t have much lubrication in it for these IPs to last like they used to. People prefer different lubes but I use TCW-3 2 stroke oil at 1 oz per gallon. Most say they go 1/2 oz per gallon but I double that and sometimes more.

That I didn't know! I will get some at AutoZone and keep it with me. Like I said, I want this truck to last. So anything you can suggest really helps me bomb-proof this old truck. My next project is to remove the vacuum pump and install a manual waste gate on the turbo.

 

[JayTheCPA]

Get an external gauge for coolant temp. The OE dash gauge is more like an indicator rather than actual measurement.

For squeezing more economy out of the rig without sacrificing dependability, synthetic lubes for less parasitic loss and a tune for better torque converter lock-up. The tuner population is very small, so don't wait too long.

 

[Stoney]

Welcome to TTS... Nice rig!

 

[IBM]

Get an external gauge for coolant temp. The OE dash gauge is more like an indicator rather than actual measurement.

For squeezing more economy out of the rig without sacrificing dependability, synthetic lubes for less parasitic loss and a tune for better torque converter lock-up. The tuner population is very small, so don't wait too long.

Definitely will do! Also would you agree that the OE thermostat temperature is too high? If I remember correctly, I believe the OEM thermostat is 190-195F?? What would you recommend? I was thinking 180F.

 

[JayTheCPA]

If there is *no* towing in the plans, consider using 190*F. Can safely state that running up and down 81, 76, and 95 with either all seats loaded or stuffed to the gills did nothing to the temperature gauge.


But if we are looking at towing, that is a *completely* different beast. If you happen to load the Burb with a sizeable trailer and head over to Roanoke, expect some slow slogs up the grades as the OE cooling stack will not keep-up no matter what the thermostat's set temperature. Point is, lower thermostat temperatures will only buy time until needing to get off the throttle.

For a better cooling stack setup, take a look at AK's electro-viscous setup.

There are two issues with a completely OE setup when pulling hard: TCC unlock and shift tables. The OE programming unlocks the TCC *way* too much. A slipping TCC generates even more heat while trying to shed heat from pulling hard up a grade. Another factor with the OE tuning is that it allows RPMs to drop too low before commanding a downshift; this slows down the amount of coolant passing through the radiator. Add the two together and it is a heat building mess. Mitigation for the shifting issue is to manually drop a gear.

And for coming down the grade with a load on the ball, this is another OE mess. When the computer senses a push, it unlocks the TCC, so you get zero engine resistance and have to burn the brakes. This also does little for cooling as now the motor drops RPMs and reduces the coolant flow going through the radiator. It is also arguably not helpful for cooling the transmission as now the fluid is hot from the climb up grade coupled with an unlocked TCC.

Given the experience with semi's, consider ditching the 4L80E and drop in a NV4500 as this will solve a bunch of weak links.

 

[smokymtn65]

If your sticking with factory turbo, and vac system works leave it. You do not gain much on the power end, and will drop fuel mileage 1 - 2 points. If you manually raise boost you will need a boost fooler or tune, because as soon as it get past about where factory lets it go it will set a code and de-fuel, go in limp mode till you key it off and back on.

 

[MrMarty51]

Yup, I tried a manual turbo master waste gate controller that I had made. It worked real good, I had it set to not boost over 12 PSI but it would still set the SE LAMP to glowing until I would clear the codes.
It also did drop the fuel mileage a mile or two to the gallon. On My budget, that means a lot when it is 150 miles to get to anyplace.
I installed a new vacuum pump and WG control solenoid and been mighty happy with how it now performs.
I do carry along a new WG solenoid and a boost pressure sensor in case one of those fails while I am on the road. I also carry along the home made turbo controller in case the waste gate system should be more serious than the boost sensor or the WG solenoid.

 

[JayTheCPA]

FWIW, the ATT had no effect on fuel economy in the Burb.

If anything, I saw the ATT as a win for the motor as it developed the same amount of power at 12 - 13 psi as the Holsets reportedly do at 20+

Ditching the wastegate was another win for the ATT as this allowed removal of the vacuum pump with an end result of increasing durability (ie: lowering complexity and removing two failure prone items). And before anybody goes down the 'lag road', meh, whatever, go buy something with a puny turbo if the goal is to have no lag So far, the only negative I have seen for the ATT is that it seems to start losing its punch at altitude (ie: 6K'+).


About 500 miles before I installed the ATT, the vacuum pump died and rather than replace the pump, I pulled the vacuum wastegate and installed a manual. Did not notice any change in fuel economy or effect on the butt dyno. No dash lights either.


The changes which finally pushed fuel economy up were 3.42 gears and the NV4500.

 

[MrMarty51]

I’m liking the ATT that I got from War Wagon.
I dont notice that thing called lag, might be different if I was hauling a load or dragging a trailer.
I still have the vacuum pump and solenoid attached.I did’nt want to see the SE lamp illuminating so I left those on.
I’m never pulling with this truck now that the son got his new Dodge diesel, so why not go taller gearing ? I feel with some 3:xx gearing the fuel mileage would increase.

 

[JayTheCPA]

If the truck has 4.XX gearing, can see where lag is not noticeable with the ATT.

I did get some with the 3.37s / 4L80E and could feel the power difference when the turbo hit its sweet spot. Not a big deal though.

With 3.42s and the NV4500, I could easily eliminate lag by keeping RPM's in the turbo's sweet spot. Could spin the rear tires from a launch on dry pavement if I wanted to as well.

 

[MrMarty51]

If the truck has 4.XX gearing, can see where lag is not noticeable with the ATT.

I did get some with the 3.37s / 4L80E and could feel the power difference when the turbo hit its sweet spot. Not a big deal though.

With 3.42s and the NV4500, I could easily eliminate lag by keeping RPM's in the turbo's sweet spot. Could spin the rear tires from a launch on dry pavement if I wanted to as well.

Back in the day, 59 Chevy, 3 speed manual on the floor and 2:90 gears and a 409 four barrel.
It warnt real fast off the line but would beat a lot of other cars in about a 1/4 mile run.
While the was shifting gears that old 59 would still be winding up. Shift out of first just about the end of the run.

 

[JayTheCPA]

I did get some with the 3.37s...

Correction, 3.73s (not 3.37s).