Differential gets very hot when towing, should I be concerned?

[jimmyess333]

After towing a trailer for several hours at 70mph I did a hand touch check on the rear diff and it was VERY hot. It this normal or something to be concerned about?
Is there something I can do to keep the diff cool?
The trailer's total weight was under 1,000 lbs and I have a 7-1/2 rear.

 

[bcost882]

you can get a finned extra capacity cover, i don't know if they make it for the 7.5 but if you go with a 8.8 with a finned extra cover it will keep it cooler. Do you tow alot with it?

 

[jimmyess333]

Thanks, I will look for that cover.
I don't tow often but when I do it's usually for a long distance on the highway.
If I kill this rear I guess I'll have to go with a bigger one.

 

[schmoo]

synthetic gear lube may help.

 

[bcost882]

yea i heard synthetic lube can help, but if it dies go for an 8.8in

 

[jimmyess333]

just a thought...

Does anyone know of a small electric pump that will pump thick oil?
It doesnt have to be high volume or high pressure.
I thought about putting hose fittings at the top and bottom of the diff cover then hooking up a small oil cooler and a small pump to use when towing.
Maybe I can use a cooler similar to the ones they used on the power steering line on the old cars with the police package.

 

[bcost882]

first time i've heard of it

 

[-Nathan-]

A tube running from the bottom of your diff sounds like a BAD idea to me, what if it gets snagged, or comes off and you lose all your diff oil? I would just have a high capacity diff cover made; the extra fluid should help you. And like someone said, synthetic might be a good idea.

 

[4x4junkie]

I don't think it's uncommon for temps to go as high as 180°, maybe even 200° on a diff. You won't be able to hold your hand on that for more than a split-second or two. I suspect everything's fine, but a check of the oil's condition will quickly reveal whether you have a problem in there or not.

 

[Sasquatch_Ryda]

Yes, towing is going to build up heat in the differential. It doesn't sound like anything to be worried about at all.

 

[jimmyess333]

Thanks for all the input.
I was thinking about a fitting at the bottom of the cover(facing back) not at the bottom of the housing(facing down) so I don't think a snag should be a problem especially since I don't offroad.
I may be just overthinking a problem that isn't there as some of you have implied.
The cover was too hot to touch which I never experienced before(but I never touched a truck diff after towing before either).
The finned extra capacity cover is probably the best route but the fabricator in me wants to try the oil cooler anyway.
I originally wanted to put just a fitting at the bottom of the diff cover then run the return through a Y fitting to hose fittings near each end of the axle tubes to ensure complete circulation and possibly cool the bearings too. But the idea of driling 2 small holes in the axle tubes brings concerns of compromising the strength of the housing.
Plus, if I keep all the mods on the diff cover and don't like it then it's easy to throw out the cover and just replace it.
On one of my old street rods I ran a transmission temp guage in which the sensor installs inline with one of the cooling lines.
Maybe one of those could be installed in the bottom of the diff cover too to monitor temps all the time.

 

[BRUTUS_T_HOG]

there is nothing to worry about. i have trucks come into the shop all the time that were JUST driving unloaded and the diff is hot. its just normal friction..

check the condition of the fluid and if it looks anything other than green/goldish then change it.

 

[jimmyess333]

there is nothing to worry about. i have trucks come into the shop all the time that were JUST driving unloaded and the diff is hot. its just normal friction..

check the condition of the fluid and if it looks anything other than green/goldish then change it.

That's good to know.
I guess I just never knew that the diff was supposed to get hot.
In that case I'll just leave it alone and if it burns up I'll think about what to do to keep the next one cool.

 

[UrbanRedneckKid]

....Anybody every look at the rear of a circle track car...? A car the always turns left with a lot of centrifugal force. How do you think they keep the center section of the diff lubed...? Electric Oil Pump!

Although the OP's question is nothing to worry about, the oil pump/ cooler idea would "work" but is unnecessary.

 

[Captain Ledd]

Behold, a fancy 7.5" diff cover. Roughly 1/2 a quart over stock.

http://www.yourcovers.com/diffcover_9593.php

The also have a powder-coated black and polished version.

I've also heard switching to not only a full synthetic, but a wide range fluid (like 85W/140) or something to that effect. I don't recall the actual numbers. Supposedly it acts better at the higher temperatures.

Your diff temperature will increase exponentially while towing a load and when encountering increased resistance. When the fluid get's hot is when it breaks down, compounding the potential damage to your differential (much higher strain combined with fluid that has it's effectiveness decreased)

Now after all this doom and gloom, I've neglected my 7.5" to a degree I'm not exactly proud of.

When I "inherited it, it had 160,000 on it, it had never been changed. It now has 200,000 on it, I still haven't bothered to change the fluid. I'm kind of curious of just how long it will go now. I've towed cars, loads in excess of 4/5,000 lbs, every thing you shouldn't do and only lately has it been acting suspiciously.

Put high end fluid in it and you'll likely be fine. If it does break, put an 8.8" in it.