I have a '94 LSD rear end on my '97 CTD 3500. I towed 16,500 lbs 5er for a couple of hundred miles and my rear end was so hot I couldn't keep my hand on it. Without the towing, it was hot , but I could still keep my hand on it.

Before all this I had the rear end cleaned and synthetic Amsoil put in with a friction additive..done at dealer.

One of my ABS sensors on top of rear end also went out and I had it replaced....Need help :-[

 

I to have a 97' 3500, I have installed a MAG-HTEC cover and run AMSOIL. My rear end temp empty runs around 140. And pulling it goes up to 160. It's kind of hard to say how hot your is without a guage. Do you happen to have cooking thermometer? You could run it around and get it hot, then remove your fill plug and put in the thermometer? Or, anyone you know have a inferred heat gun? Also, I have the limitied slip differental also, with the amsoil you don't realy need the friction modifyer. Good luck.

 

Talked to a dealer service manager. He said "don't worry" they run hot especially when they tow heavy. As long as I don't hear any noise and no leaks I should be OK....just moniter it...

 

[quote author=JImbo1 link=board=16;threadid=19723;start=0#msg185714 date=1063769476]
Talked to a dealer service manager. He said "don't worry" they run hot especially when they tow heavy. As long as I don't hear any noise and no leaks I should be OK....just moniter it...
[/quote]

I would make it a point not to go back to that dealer. By the time you hear a noise, it is too late. He also gets to sell parts when your rotating assembly falls out on the pavement smoking.

It is hard to tell temperature by your hand or touch. 100 or 120 degrees may seem hot to your hand but is perfectly fine for a rear end. Get some type of thermometer or even an infrared pyrometer to take the temperature with when it is hot. That will tell you the real truth. 120, 140, maybe 160 may be fine but anything higher than that, you may want to consider a different oil and adding the MagHytech cover like I did.

 

Until you measure the temp accurately and know how hot it is, I'm with the dealer - monitor it. What else could you do? Swap in another one? Possibly fix something that isn't broke? I am assuming its properly filled with lube too.

Better yet, as said above, get one of those little infrared thermometers, they are wonderful little gizmo's. I use mine all the time. Never had it under the truck after a heavy tow though.

I don't normally take rear end temps, nor do I know what "normal" temp readings should be. I would expect it to get HOT towing heavy loads though.

 

Go to www.mscdirect.com and look up part order number UK65155616. It is an infrared pyrometer that reads up to 600 degrees and is on sale for $74.99.

 

Opened this thread expecting to see J.Lo. ???

 

J.lo that's a good one!

I really don't think anything under 190-200 is too high. Granted, the lower the better, but even 180 or 190 is not to hot, especially while towing. A good rule of thumb for "normal towing temps" is about 100 degrees higher than the outside temps.

I ran a temp gauge in my 98 GMC 1/2 ton 10 bolt semi floater rear end. Running mobil one diff fluid, pulling a 6000 lb 5th wheel with 1000 lb pin weight, I would get temps of 170 to 180. I never had a problem with that rear end and fluid always looked good during change out. That was alot of weight (plus all the other camping gear) on just two bearings, and that was a 3.42 rear end (not the best for towing).

I agree watch it, if you can check the temps and compare with towing and not towing. Post your temps here. You could have an oil analysis done on the diff fluid as well. Good luck, Kevin

 

On my 96 the rear end temp runs 180. Now that is empty, but when I hook up to our fiver, 15K lbs, if I run 65 mph it will stay there on level ground. I have had it up to 195 in the mountians, but slow down and it comes down. The five speed is a different story. I've had that thing on 225. I try to stay around 180, but tow heavy and hard and up it goes. I also have the cover on the rear end and fast coolers but that is still what I get. I would like to run cooler but the only way I've found to do that is not move. That just won't work.

Oh yeah, Amsoil front to back.

..Preston..

 

turbo thom, before I read your post I was determined I had to buy the Magn-? cover for $295.

You say you have the cover and still have the problem of a hot diff.

I'm wondering how many degrees I would be lowering the temp pulling my 16.5 K lbs of 5er.

 

Well, It looks like I have to go for the Mag-Htec diff. cover.
Did some research and they look like the best out there. One of the owners said it lowers the temp by 40-50 degrees.

It makes sense..The cover holds twice the oil as stock. The thick alluminum also keeps the temp down. It's what I need.

Thanks for all the info. You guys again are a great help.

 

It really dosen't add twice the oil just a little more. Bout like 2 pints. But I like the dip stick and temp sender hole. As heavy as I tow I'm replacing the 75W-90 with 140W. At the price of the 140w I hope is comes down . That's a lot of money for lube.

..Preston..

 

I just don't understand what all the hubub is about the rear getting hot. They all do when working. After running on the freeway how long can you hold your hand on a radiator hose? No, not very long, same for the rear. Now if the axle housing at the rear brake assy is real hot that could be a problem, but the diff will always be too hot to hold your hand on after running.

 

Thanks for info "haulin in Dixie".

I should check the brake assembly to see if that gets hot.

Now I really don't know if I should buy that Mag-Htech diff. cover.

 

What I was referring to is that he axle bearing (hub bearings) are located in the area of the brake assy. If it is getting very hot the bearings are suspect. The more quantity of lube available the better, as in the larger cover. Water boils at 212 degrees, anything up near 200 is too hot to touch. If you could hold your hand on the pot that is cooking pasta, than I guess you could hold your hand on a 190 degree rear axle that is pulling a load. Hope that explains what I meant better. I think the thread is misjudging how hot is hot to the touch.