I have heard different answers to towing in OD. I have been told as long as the tranny can handle the load and terrain, without shifting constantly, OD is ok. Others have said noway. Last weekend I was traveling a down hill grade for over 20 miles. I put in OD and maintained 65mph. Tranny temps under 200F, eng temp 190F, EGT 800F. Everything going smooth. After approx. 18 miles down hill, the tranny either downshifted or tranny unlocked. RPM went up. Truck started slowing quickly. I down shifted, eccelerated, and had no power. Speed continued to slow to 25mph. I pulled over to check tranny fluid level. Level good and no burn smell. I proceeded on my way and everything was and still is working normal again. Did the tranny downshift or unlock? Others expirence towing in OD with all gauges monitoring in normal limits?

One of my best friends has been a tranny mechanic (trannies is all he does) for 25 years and he says never to pull in O.D. no matter what the load or transmission. I trust him so I don't.

I can't go over 55mph in Drive. I have to pull in OD or I would get a ticket for impeeding trafic on a interstate. Why would GM make a truck this way if you can't pull in OD? Been pulling 8,000# for two years and have not ever had a second of problems, Torque converter always locks and unlocks at the same place every time.

Just keep an eye on tranny temps, that's the killer about O.D.

I pull in OD must of the time, but I hardly ever have a laod over 3,000 lbs. The only time I don't pull in OD is if the trans keeps shifting out of OD then back to OD, normally on a road thats really got a lot of hills then I'll shift it out of OD. I've always been told that if your trans keeps down shifting alot it's better to just shift it into 3rd and leave it untill you get to level ground then you can shift it back to OD.

If the T/H button is on, what is the problem with hauling in OD? I have been hauling almost everyday for the last 50,000 miles with no problems. I would think they designed the T/H for that reason?

Pulling in OD is ok, IMO. Just watch your RPM's and temps. I believe lugging is what kills them. I have also found that when pulling a really heavy trailer on a hill or incline (10,000# or more) if I drop it in 3rd my EGT's and temps go down, then, as the terrain permits..I go back to overdrive.


Bottom line, watch your RPM's so the engine isnt lugging and the tranny isnt"hunting" which builds up heat and you'll be ok pulling in OD.

BTW, I got 236,000 miles out of my first tranny. Just maintain it.......

IIRC as long as your engine rpm is over 2500, its ok to tow in od. That makes sure that the tranny fluid pump has enough speed to pump efficiently

PS, I have towed in OD with no problems for years


If the T/H button is on, what is the problem with hauling in OD? I have been hauling almost everyday for the last 50,000 miles with no problems. I would think they designed the T/H for that reason?

HDINNC~ Aint no Tow/Haul button on a 6.5


Tim

[QUOTE=Cowracer]IIRC as long as your engine rpm is over 2500, its ok to tow in od. That makes sure that the tranny fluid pump has enough speed to pump efficiently

PS, I have towed in OD with no problems for years




HDINNC~ Aint no Tow/Haul button on a 6.5


OoOOPPPPSSSSSSS!! Sorry about that!

Unless you're towing MEGA weight, the tranny is going to stay cooler in OD than in Drive.

SnowDrift

Just because you are in OD does not mean TCC is locked. If TCC will not stay locked , you might as well downshift to 3rd and most likly TCC will lock up. Runs much cooler.

I always downshift before PCM commands a downshift, I also unload engine/drivetrain
before I down shift ( like a manual shift ) same on upshift...
I also run with the TCC locked via the " temp Resister " fooler...

I tow in OD always no problem even towing up to 18K, my tranny builder when I had HD clutches put in it said 4L80 one of the best trans out there, & you will never have problems as long as you keep up with filter & fluid changes, I also added extra 25K rated cooler, trans gage & deep 3 extra qt pan.