Tow/Haul -02 7.3 PSD -- Should I use overdrive

[rcoker6493]

I have been told by several that when hauling heavy loads 12-15K that I should run the 4R100 out of overdrive in third gear.. I know that when I 'am hauling it does not always kick down easy when running in stock or especially when running the TS-Chip in 50 / 75 over stock.. Any body out there towing with a 7.3 that can give some advise on whether the over dirve should be OFF or not? I run the mountains all the time hauling horses and if running means over riding over drive while hauling then so be it. I just want to make sure that I 'am doing the right thing nd do not want to do anything to damage the truck unnecessarily.

[blk99]

I NEVER tow in O/D unless I am on the flats doing 70-75mph! I dont know about you but I have 3.73 gears and I cant be in OD on hills cause my temps sky rocket(at least 1200-1250) and the "Coal Really Roles"! But when I pull it out of OD the temps usually drop to 800-900. Anyway I will not hurt the truck to run it with a load out of OD. The only I time I found that being out of OD hurt is when I tried to speed(75+) up a hill with 16,000# and I was pushing the motors redline and it over heated but other than that time it has NEVER had a problem.
sorry for the long post.
~Jim

[lilredpowerstroke]

It all depends on weather or not the tranny is hunting or not. Since you have a chip Im gonna assume you have gauges in your truck. I live in Florida so the biggest hill I have to pull on is an overpass but if you watch your gauges and drive according to them then you should be safe.

[colo86GN]

Originally Posted by blk99

I NEVER tow in O/D unless I am on the flats doing 70-75mph! I dont know about you but I have 3.73 gears and I cant be in OD on hills cause my temps sky rocket(at least 1200-1250) and the "Coal Really Roles"! But when I pull it out of OD the temps usually drop to 800-900. Anyway I will not hurt the truck to run it with a load out of OD. The only I time I found that being out of OD hurt is when I tried to speed(75+) up a hill with 16,000# and I was pushing the motors redline and it over heated but other than that time it has NEVER had a problem.
sorry for the long post.
~Jim

I have the sam eissue and pull over mountains all the time. If i leave mine in overdrive and try to ease into it my EGT temps start rising and it doesn't go anywhere to fast. I always kick mine out of overdrive, my EGT's drop to a lower, safer temp, and it seems like it is easier on the truck to make it up the hills. Basically, the same as the post above says. I don't see anything wrong with putting it in 3rd gear, especially when the truck temps are reading better.

[jfines@cox.net]

I agree with all of the above. I am having my trans rebuilt right now. And I have been able to watch all the parts as they come out. The O/D looked good, you could actually still read the print on the clutches. But I had burned out the 2nd and 3rd clutches, which at 126,00o on the clock, I think that's good.

Well any way, the discussion came up about towing in O/D he said that it's not a good idea if your tranny keeps hunting for the right gear. Being that my rig with the 5th wheel is about 22,000 pounds, the hunting is often.

Of course I am getting all the upgrades for the trans, and he said I can tow in over drive with what I am getting. BUT, he also said that if you do, always downshift (turn off O/D) before you start to go down the other side.

So, I still think I am going to do it the old way. Since there is no reason to go 75MPH with the 5er in the hills, down shifting wont be a problem.

Also, I have the late E4OD, which I told was made in 98. Which from everything that I have seen at his shop, it is almost like the 4R100. And my rear axel is 4.10, that helps.

[jmcclellan]

I am pretty new to this diesel thing but I notice the same that everyone has mentioned above. But with a load of 15k there is no way I would tow in overdrive. If you do really keep an eye on the egt's they skyrocket until you feed that engine more air.

[rcoker6493]

Appreciate the feedback... Just curious about the trans temp running out of O/D.. Those of you pulling in the hills. What do you get for trans temps when pulling heavy weight out of O/D?

[jfines@cox.net]

Well actually, towing in O/D can raise you temps. Basically, what I have experianced, when the trans starts to search for gears, like shifting between drive and O/D, that creates heat. Plus, O/D isn't made for that type of stress unless you have had it rebuilt.

As for temps, with the stock trans,in good health, I would see about 200-210 going up hill.
A good piece of insurance, is to get a larger trans cooler.
Also, when I tow in the mountains, I take over and shift for the truck to prevent it from searching. Most of my uphill is done in second.

Also, with sifting down, your exhaust temps stay lower, i know it sounds funny, but it's true.

Plus, my 5th wheel weighs in at about 14,000 lbs.

[blk99]

On a hot day(90-100deg.) my trans temps are 200-210 on most days the temps average 165-185. That is with a small aux. trans cooler that has a fan but the fan is never used unless in town. Those temps are usually while climbing with a 16,000# sail on behind(5er)!