Towing Question

[Scott Hammer TOXIC]

Ok, so I read the posts about Trep's Tranny and it starts me to thinkin' (this is normally very dangerous), why is it taboo to tow in OD? From what I understand, all OD does is keep the tranny out of 4th gear and shorten the electronic "shift points" so that you get more torque. If I'm on a long flat stretch of road I kick in the OD. I don't see the need to run in 3rd and burn up all that extra fuel. Now, hills and in-town or stop and go, would be different. I do have 3.73's and a t-cooler.



TOXIC

 

[Dave Muniz]

It is my understanding that when the trans is hunting for the right gear is when the heat builds up. Heat is the killer of the trans. If your cruising on the highway I don't see any reason not to turn OD on. If it's around town I would keep it off.



I have also heard (don't know how true it is) that GM transmissions bypass the trans cooler when OD is engaged. It's only pumping trans fluid through the cooler in 1, 2 and 3. Alot of GM transmissons have been killed towing in OD.



damuniz

 

[Texas Transplant]

I'm the same, as far as curious. 'Generally', I understand OD to be a lower (number) gear, so that you are turning less RPM's once up to speed.



On the tranny cooler - if your tranny lines already run to the radiator, are we talking about replacing that? Or are we just talking about vechicles where there is no external cooling at all?



Tex

 

[Bill McElroy]

GM Owner's manuals will always tell you to tow in "3rd",..NOT in OD....just an FYI....besides Tox,..you've got a 929 with a 225 on it and an SUV to pull it with...trying to save "fuel" while towing would be the same as you taking a "Beano" before you hit Taco Bell....it's pointless!!! LOL!!

 

[Staci Matheis]

With my two Jeeps: 300,000+ miles without transmission problems, towing in overdrive, no transmission cooler. (Plus many more miles with other vehicles pulling, towing and lugging other stuff around.)



It's not the towing in overdrive that hurts; it's when your transmission starts that hunting between gears.



I never tow using cruise control. And, when going up inclines, I will slowly back out of the gas just enough to keep the tranny from shifting. It takes some practice to be able to do smoothly and to not slow down so much that you hinder traffic. It's not something I would suggest everyone do..... But it has always worked fine for me!



me!

 

[Scott Wildwood]

I own an RV and spend quite a bit of time on RV boards. Here's a snip from one of the mechanics.





Two advantages for towing without overdrive:

1) Your transmission's oil pump is connected to the input shaft. The faster your engine and the input shaft turn, the more oil it's pumping through the cooler.

2) There's less torque on the input end of the transmission. Torque = HP x 5252 / rpm. If you're running steady at a steady hp, and increase the rpm, the torque drops...thus less strain on the input end of your transmission.



So...if you can run in overdrive with the torque converted remaining in the lock-up and not shifting out of lock-up nor down into 3rd frequently, OK. If it doesn't stay in OD lock-up, you're generating excess heat that will shorten your transmission life

 

[TOMMY RICH]

Tox.....my experience is it won't hurt a thing especially if you have a tranny cooler(like me) and don't try to force it in another gear. I usually run mine in drive only on two lane roads that are 55 or has hills. If I'm runnin' on flat road...I run mine in OD. 109,000 miles and no problems yet but, I do take mine in every year for transmission service too. But then again Tox....mine don't weigh near what your rig does either...

TEE

 

[Scott Hammer TOXIC]

Thanks guys....Veeeery Funny Mac, but you are right, I do have a hard time passing a gas station. You know it's bad when all of you directions use Gas Stations as reference points!!



And as for the BEANO analogy.......



TOXIC

 

[Texas Transplant]

Had the tranny serviced on my Mountaineer (big V8) this past fall. Did a minor repair, flushed, cleaned and adjusted.



When I tow, it's using OD. However, even with the amount of hills that we have here in the Carolinas, the tranny very seldom shifts. Only once in awhile. That engine/drivetrain does a very good job of keep a very steady pace on the road. In addition, I never 'stress' it when accelerating. It's a good steady acceleration to speed, where the RPM's stay in a comfortable range.



From the comments here, I think that I'm in good shape. However, I'll certainly pay closer attention to the shifting and take another look to see if the tranny is cooled through the raditor or not.



Thanks once again for the insightful discussion.



Tex

 

[TOMMY RICH]

I don't buy it...and I'll tell ya' why. Inside the driver's door on my 94 Silverado there is a label that states,"Do not use OD when pulling a trailer or going up or down steep grades". Now the owner's manual contradicts that by saying,"If it's not over 3000 lbs. and the tranny ain't searchin' thens it's O.K........go figure. If my boat weighed close to that...I might reconsider but,I'd say it would depend on whether or not I'm pullin' glass or tin and how heavy it was.

TEE

 

[Steve Rizza]

I think last time this topic came up it got pretty hateful.You would think somebody insulted somebodys wife.

 

[Bruce Freeman]

OK The Amazing Bruce will now offer his opinion. The searching between gears or lock up mode is what hurts the most..When in lock up mode the converter does not slip..During the 1-2-3 there is some converter slip to increase torque..this is why the MPG rateings are always higher on Standard trans cars and trucks compared to automatics..The proper way for a trans cooler install is from the trans to the rad to the cooler then back to the trans. So in closeing, when going up steep grades (steep depends on your tow vehicle combo) turn off the OD same goes for towns and such where you feel it jumping back and forth..Again these are just the opinions of a Redneck who happens to make a living fixing stuff...

BF

P.S You don't have to be towing to hurt your trans....

 

[Bob G.]

Bruce,



I never thought that I would say it, but I totally agree with ya!



Bob G.

 

[TOMMY RICH]

Amen Bruce...sometimes it depends on vehicle,age,set-up,tranny and various other things that fall into play also. Just use a little common sense when towing and you should be fine.

TEE

 

[Bruce Freeman]

Well Gee guys that makes me all warm and fuzzy inside...LOL

it's that or the Jack..

BF

 

[Charlie Nethaway]

ok I guess im in for it. I have a 95 yukon w/ 170,000 and I always drive in OD have never serviced the trans. and tow a TV-18 and a 2000lb trailer and carry about 700lbs inside(i try to unload when I tow the boat.

well now im realy worried I need to find out just what I should have done and who I can trust to do it.

I never drive in 3rd cause I think about the motor rather the trans. oh well guess i should take it in.

It does have a tow package with the extra cooling coil.



oh and you guys are funny like little brothers.

 

[TOMMY RICH]

That's right....we are one tough and tight little family here. We might beg to differ sometimes...but, hey..that's what makes it interesting and definitely fun.

TEE