Loaded the 6.5 for the first long trip !

[M123KT-450]

I hitched the old 6.5 up to the car trailer 2000LBs then dropped 3 ATV's on its back a put 1 unit in the bed and 2 units on the trailer for the ride up to the atv park and for the ride back i put all 33 units on the trailer. . .So it was loaded decent prolly 4K or less with atv's n trailer. . .

I put the trans in 3rd gear reved the old 6.5 up to 3,000RPM and set the cruise as directed by the local shops and i do have to say they were right truck didn't hurt for power and it ran perfectly smooth and happy at 3000rpm under a load.

i'm just not sure it'll handle that with 9-12K hitched to the rear but it did it with 4k. . .

Mikey

 

[ak diesel driver]

I'd get a tranny guage withou the TC locked temps can build pretty fast.

 

[M123KT-450]

It dose have a HD cooler up by the radiator but yes i do have a few more trans cooling things in mind before i make another ATV trip on mem-day weekend. i just wanted to do a test run and the truck seems to have held the strain rather well i thought the 6.5 would gotten hot reving 3K but it really didn't only ran about 5-7*F hotter then its normal 185*F so it was around 190-195 water temp running 3k RPM towing 4K LBs. . .100miles each way. . .

next trip tho is 150 miles each way so thats an extra 100 miles round trip and the air temps will be another 30 degrees or so warmer towing the same 4K-LBs, So i will be doing some more add on cooling mods for the trans.

Plans:
Fluid n filter change for sure.
Adding some lucas for sure.
Trans pan cooler if budget allows.

I was thinking of going a synthetic fluid but with 130K on the trans i might just leave it dino Lubed not sure yet. . .

Mikey

 

[btfarm]

I'd get a tranny guage withou the TC locked temps can build pretty fast.

That's important!:iagree:

 

[M123KT-450]

Oh yes for sure. . .
I been kicking around the idea of getting a pillar mounted gauge holding device and having a Trans temp and oil temp gauges. . .

Mikey

 

[Joey D]

I hitched the old 6.5 up to the car trailer 2000LBs then dropped 3 ATV's on its back a put 1 unit in the bed and 2 units on the trailer for the ride up to the atv park and for the ride back i put all 33 units on the trailer. . .So it was loaded decent prolly 4K or less with atv's n trailer. . .

I put the trans in 3rd gear reved the old 6.5 up to 3,000RPM and set the cruise as directed by the local shops and i do have to say they were right truck didn't hurt for power and it ran perfectly smooth and happy at 3000rpm under a load.

i'm just not sure it'll handle that with 9-12K hitched to the rear but it did it with 4k. . .

Mikey

Why not use 4th?

 

[M123KT-450]

I was told NOT TO USE 4th gear for towing anything over 1200-1500LBs . . .
So being i was towing 4,000LBs i used drive as instructed by the GM dealers service department and My local Trans shop guy. . .

the trans shop guy stated my cooler was not big enough to handle that much heat build up and to use drive only.

I am working on getting a bigger trans cooler adding the trans pan cooler and synthetic fluid as instructed to do.

Mike

 

[Joey D]

I was told NOT TO USE 4th gear for towing anything over 1200-1500LBs . . .
So being i was towing 4,000LBs i used drive as instructed by the GM dealers service department and My local Trans shop guy. . .

the trans shop guy stated my cooler was not big enough to handle that much heat build up and to use drive only.

I am working on getting a bigger trans cooler adding the trans pan cooler and synthetic fluid as instructed to do.

Mike

If your truck has the 4l80, which it should as GM used only the 4l80 behind the 6.5's, your following poor info. The trans will build more than normal temps if you don't lock the converter up and that happens in 4th. The only reason to drop to 3rd is if the trans is hunting between gears as the constant shifting back and forth is not good at all.
3000 rpm can't be good for milage, how did it do on the trip?

 

[M123KT-450]

Running 3,000Rpm in third gear towing 4,000LBs truck did rather well the few times i put it in 4th gear the truck dogged out didn't seem to have much power so i shifted it back into 3rd n let Rev truck didn't lose but 3-5mph in the hills it ran about 10*F hotter then if it wasn't towing anything oil pressure stayed right at 62psi so really the truck did just fine in third gear.
Milage wise it ran 275miles on 3/4 of a tank so not really all that bad.
It normally runs 16-18mpg towing in 3rd n 21-23mpg running empty in 4th.
day to day running around truck stays in the 19-21mpg average over the full tank.

My transmission Guy Dose not recommend towing in 4th gear until i do some of the following cooling system upgrades.

1. HD trans cooler. i am to swap my 11x6x2 cooler for the 13x7-3/4x2 cooler.
2. Get the Cooling Transmission pan.
3. Upgrade to synthetic AFT and high end filter.

He is the one who suggested the lower gearing as it would make the truck run free, he then went on to explain that by running free he ment make the truck easier for the transmission and engine to move. he then in turn said this will now make any power adders more effective as less power will going to the operation the truck leave more power in surplus for carrying extra load or simply moving empty truck quicker.

So i figured with my tire sizes being 7.50-16D 32.2" Biasply traction tires for winter and my summer tires are going to be either 235/85R16E 32.2" or 265/75R16E 32" Radial traction tires,So i had already planned on going down to 4.56 gears. . .
Considering the power loss when i tried 4th gear as i had the 7.50-16's on it the gear change is for sure going to happen. . .

He was rather pleased he said with them 3 transmission upgrades and the gear change the transmission should Tow a rather heavy load in 4th gear no problem just drop into third gear for the hills but other wise it should be just fine. . .

he also did not recommend using Cruise control while towing as it dosen't always down shift for the hills it just opens up the throttle and the transmission takes the hit. . .if using cruise then down shift for it as the computer dosen't know the hill is there or coming up you as the driver do.

Mike

 

[JiFaire]

Mikey, you gotta stop listening to guys that don't understand these trucks. Your truck will pull 4K easy in OD if it's locked up... the advice the trans guy is giving you would be accurate if you had a 4l60e or a THM400, but the 4L80e won't build that much heat if the TCC stays locked up.

As for running at high RPMs, that's bad info, too... whoever told you that is thinking that you have a gas engine, not a diesel. These things build max torque around 1800-2200 rpm, and that's where they will pull the best. 4000 lbs won't even make your truck sweat, if you have a 3" downpipe, 4" exhaust, and good airflow in.

Not trying to be a pain in the ass, but seriously, those of us who HAVE these trucks and pull heavy with them have a lot more experience and knowledge than most mechanics out there... the 6.5 is NOT comparable with what they know about 'other' diesel or gas engines.

You do what you gotta do man, but... it's painful to watch.

 

[M123KT-450]

Nobody around here was forth coming with info when i first asked about towing in 3rd or towing in 4th gears. . .
So i asked the trans guy now he didn't ask weather it was a 700R4, 200R4, 4L60E or 4L80E. . .

all i really said was i have a 1995 GMC K-2500 sierra i am going to be towing about 4k-LBs around 100 miles one way what gear do i use ? the reply was "what cooler do you have ?" me: "I don't know" Trans guy: "go measure it. . .If its the 11x6x2 run 3rd gear if its the 13x7-3/4x2 run 4th"

The phone call progressed into me needing the 13x7-3/4 cooler the cooling pan and synthetic fluid n quality filter.
................................................................................................................
Now i found when i tried to run 4th gear on my own as i didn't like reving a diesel up to 3,000Rpm as that the RPM i run my Gas engined trucks at. . .eveen tho have been told i can run them 3100-3300rpm steady just fine loaded. . .I refuse to run them harder then 3,000Rpm. . .well anywho back on track. . .

The truck kept Dogging out i would hit a hill in 4th gear truck would be almost to the floor and still hasn't down shifted and has lost 10-12mph. now this was only a 4K load at best. . . i want to tow 12K loads i don't see it happening. . .
so after the second hill on my way out of town i dropped it into 3rd gear and let it Rev.

Tho my uncle even made the comment if its got 4.10 gears thats more then enought gear for a diesel it might even be a bit too much gear, As for the 235/85R16's and 7.50-16s both have been a Heavy Duty 3/4Ton GM tire sizes for decades you shouldn't need more gear. . .

Now here is the thing i don't just tow 4k on ATV trips this truck has had 9K n 12k loads hitched to its rear a few times it really really dose not like do it, Once i tried towing a loaded gravity box for the farmer up the road it just plain refused to move it tho Running in 4LO crawling along at Blazing 25mph it did move it to where it needed to go. . .

I think this truck should be able to tow as much as 12,000LB's respectibly Not Lugg out towing 4,000LB's. . .

Mike

 

[M123KT-450]

Mikey, you gotta stop listening to guys that don't understand these trucks. Your truck will pull 4K easy in OD if it's locked up... the advice the trans guy is giving you would be accurate if you had a 4l60e or a THM400, but the 4L80e won't build that much heat if the TCC stays locked up.

As for running at high RPMs, that's bad info, too... whoever told you that is thinking that you have a gas engine, not a diesel. These things build max torque around 1800-2200 rpm, and that's where they will pull the best. 4000 lbs won't even make your truck sweat, if you have a 3" downpipe, 4" exhaust, and good airflow in.

Not trying to be a pain in the ass, but seriously, those of us who HAVE these trucks and pull heavy with them have a lot more experience and knowledge than most mechanics out there... the 6.5 is NOT comparable with what they know about 'other' diesel or gas engines.

You do what you gotta do man, but... it's painful to watch.

you keep saying that. . .LOL but i am the 1 operating the throttle and in 4th gear this Rig that "shouldn't feel" a 4k load behind it REALLY dose.

Gear road speed throttle:
i can feel it 70mph 4th gear no load 1/3 throttle. 4th gear 65mph 4k load 3/4 throttle, 3rd gear 65mph 4k load 1/2 throttle.

Drive train:
6.5-T 4L80E 4.10 gears 7.50-16 tires.

Mikey

The Load:

 

[M123KT-450]

You seem 110% sure it's geared just fine. . . So if that is true then the only thing to blame is the engine itself, It is the problem then. So which is it lack of gear ? or lack of engine power ?

Now if the of this engines power really is on the bottom end then why did it seem to pull better when it was Reved up ?
I am NOT doubting your specs am sure it dose make all of its torque from 1800rpm-2200rpm, i am just wondering why this motor felt like it had all kinds of power from 2700rpm-3300rpm ? which is a good 500-800rpm beyond its peak torque curve ?

From what i gather your telling me this truck tow its best at about 2000Rpm correct ? so why dose it seem to tow better at about 3000Rpm ? is there some thing wrong with my engine that it has to rev to tow ?

I am just trying to understand whats going on here its got me all confused really HELP !


Mike

 

[buddy]

Do you have access to a scanner to verify your tach is correct. Mine is 450RPM high when it reads 3000RPM. Also your speedo is probably off with the tall wheels. Those dont look stock and the tires are probably taller. have you tried tailing someone and find out how accurate it is at 65mph? I put on 30.5" tires and when my speedo says 65 Im actually going 70.

The reason my tach is off is that the alternator was replaced by a mechanic with a gasser pulley on it, when PO had truck. The pulley is smaller, thus spins faster and that runs your tach.

 

[M123KT-450]

Speedo was checked via GPS and was right on !

Then I had a certified dealer also test it and it was also found to be right on and no correction needed.

I have no idea as to how the tach is but for how the truck performs all my power is from 2500rpm to 3500rpm where it shifts. Truck is rather doggy below 2400rpm.

Now using the speed to rpm calculator for the size tires n gears every thing matched up.

So the vin and repo codes are right on it dose have 4.10 gears third gear at 65mph is just a touch under 3000rpm.

70mph in 4th gear is 2400rpm.

Ill I'm on my phone now but I do have a sticker in my door jamb clearly stating not to pull a trailer in overdrive.

Mike

 

[Ed HD]

If you're interested, I have an autometer phantom Transmission temp gauge and a pod that fits a 1998 chevy truck/ SUV for sure, not sure what year the interior changed. PM me if interested.

 

[M123KT-450]

These are photos i attempted to get of my door jamb sticker. . .it says
" transmission OD mode should NOT be used when towing a trailer, Carrying a heavy load, On steep hills or off road "

Then it directs you to the owners manual.
The manual then states big bright yellow sticker:
" If the carried load should exceed 1,200LB's OD mode should NOT be used "
" If the towed load exceeds 1,500LB's OD mode should NOT be used "

Then it goes into a bunch of examples of how and when to shift from OD to DD for both the auto trans and manual trans.

Mikey

 

[JiFaire]

Dunno where that sticker came from, but mine doesn't have one, I have 3.73 gears, and pull more weight.

Wasn't always that way, though... is your truck still stock?

What I'm asking:

- have you changed out your exhaust? (Especially the downpipe, which is a real mess on the 94 and 95 years, and the crossover, whcih in 94 and 95 was double-wall and frequently collapsed)

- have you removed the snorkle from your airbox?

- do you have a boost gauge, so you can watch your boost?

- have you chipped it yet?

Seriously, Mikey, I wondered how much of a mistake I had made when I got mine... I hooked on that 5th wheel and things were OK, slow but OK. Then I got to my first hill.

AARRGGHH. The truck slowed down, I shifted down, the EGTs came up, the temp gauge came up, I pushed harder, the boost started ... to drop?? Then it started to defuel, I shifted to 2nd, turned off the air conditioning, opened the windows, and got over that first hill at 25 mph. I got passed going uphill by a Lada.

- Over time, I discovered that if I pulled with my TCC unlocked, I overheated.
- I found that shifting down before a hill helped, because if I could keep the rpm over 2200 in 3rd, it would pull better.
- I discovered that I was better off letting it drop to 45 mph in 3rd and letting it pull rather than trying to force things to 50 mph.

It was an awful vacation. When I got home, I started doing the mods that guys like Turbine Doc and Bill Heath recommended.

- I fixed my exhaust (I couldn't BELIEVE how messed-up it was... like, how did anything get through there?
-I fixed my air intake, pulled out the snorkle from the fender. I was amazed that MY engine was expected to run when it was pulling air through THAT little hole...
- I put in a TurboMaster and my boost problems disappeared - you know, where your boost craps out just when you seem to need it most? That never happened again.
- I did the TCC lock mod so I could decide when to leave the trans locked up, to let the engine really pull going uphill and help with engine braking going downhill.
- I got Bill Heath to put in a new chip and set my timing. THAT was the biggie. Heath chips rock!

When I pulled my trailer out of Ellensburg, WA up the biggest hill I had tackled yet (8 miles, 7.5* grade), I passed people going uphill... I never dropped below 55 mph, the truck ran cool, my EGTs were lower, and best of all, the fuel penalty for all this extra power and torque was... my pulling mileage increased from 11 to 13 mpg. And I was pulling faster.

That right there is the no-shit story, Mikey. You can change your gearing, run at super-high revs, pull in third, put in a deep tranny pan, use synthetics, all that stuff. And you can get advice from any of the mechanics and trans guys you want to... but I got the same advice and they were all wrong. Every friggin one of them.

The 6.5Turbodiesel is NOT the same as a gasser. Or a Duramax. Or a cummins. Or a Powerstroke. Matter of fact, expecting it to act like any of those will give you all kinds of issues. Some days, I think I know more about this engine than any of the mechanics at the GM dealers within 300 miles of me, and really, there are tons f guys on this site who know more than I do.

Like I said, my friend, it's painful to watch. Because we've all been there, and hoped to help others NOT learn the hard lessons we learned. But you have at it.

We certainly did.

 

[M123KT-450]

Im more Confussed then anything. . .2 dozen people say tow in 3rd 2 dozen more say tow in 4th. . .Some say use both gears depending load size and road conditions. . .Bla bla bla. . .

I dont have a clue what been done to my truck if anything other then it had alot nice Dress up look pretty items on it. . .

I was figuring the typical Pickup diesel seem to make all the pulling power in the 1500-2500Rpm range. . .

I thought you said the 6.5's ran the 1800-2200Rpm range or so i thought ?

MY truck seems to be making all of its power in the 2500-3500Rpm range. . .2400rpm and below it a real Dog empty loaded it don't matter it won't get up and go till it reving. . .

So could there be some things done to this unit to make it strong on the top end and Rather slow on the lower end ?

i am starting to think it might have some sort of Torque converter lock up Mod as you said it will only lock in 4th gear right ?

But when i made the long run in third gear it did Lock up the TC. . .

I can also say the truck ALOT more pulling power in 3rd gear then in 4th gear.
i 4th gear i was on the throttle all the time to keep a steady speed on the hills i would have it mashed to the floor and it wouldn't shift down unless i manual down shifted it.

I can only tell what it dose, Can't say why it dose what it dose. . .I was hopping you guys could help me with it. . .



Mike

 

[JiFaire]

It'll lock in third or fourth, but if you have to push on it below a certain RPM (can't remember what it is0 it will unlock. THEN your trans will generate big heat.

If you can keep it locked (which is why we do the TCC lock mod) then it will pull hard in third or fourth, but yeah, you're better off locked in third than unlocked in fourth.

You just have to watch it and learn wher ethe lock points are and where you can develop big torque.

I didn't say you should (or could) pull big hills in fourth. I can't. The trick is shifting down before you need to so the tranny doesn't 'hunt' for gearing, and to keep it from unlocking.

But on the level? Pull in fourth, 2200 rpm, locked.