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Both rear wheels extremely hot after towing in tough conditions with 2500?


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I'm hoping to get feedback from others that are towing a lot of weight on steep grades, how hot is too hot for my rear diff/wheels? Here's the problem I'm having with my current setup. 

 

Vehicle: 2004 Yukon XL 2500 SLT with 8.1L  (weight/axle info here)

Trailer: 34' Rockwood 2901SS (dry weight around 5600)

Equalizer weight distribution hitch rated at 1200lbs. 

Fresh differential fluid about 2000 miles ago (Mobil 1 Synthetic Gear Lube LS 75W-90)

 

CAT Scale Weights when loaded (this was with kids/gas/dog and all gear). 

Steer Weight: 3440 lb 
Drive Weight: 5240 lb  
Trailer Weight: 5920 lb 
Gross Weight: 14600 lb 

Ambient temperatures have been between 85-100 degrees (very hot this summer).

 

The past few trips we have taken all require that I drive up 6-7% grades here in Colorado (Ike gauntlet) among other passes, then down the same grades. I'm typically towing for 3-4 hours and almost all of it is going up or going down. I know this type of towing is much much harder than the flat land towing, but I still don't think my wheels should be as hot as they are. I'm always using lots of gas going up and stressing the engine/tranny......or I'm going down the other side of a mountain and using the transmission 95% of the time to keep us around 50-60mph using gears....again very hard on the drive system. 

 

After towing, my front wheels are hot but I can usually hold my hand on them without yanking it away. To me they seem "normal" for the conditions I'm driving in. The rear wheels however are a different story, If I put my fingers on the wheel near the hub, I typically have to pull my fingers off after 1-2 seconds due to the heat....it would definitely burn your skin. Further out on the rim toward the tires seems to be less hot...but still very hot.  

 

Initially I thought it could be due to the brakes dragging, but I have never smelled any bad brake/brakes too hot smell. The vehicle doesn't smell hot at all when walking around it....if you didn't touch the wheels you'd probably think everything was functioning normally. 

 

My concern is that I'm going to probably ruin bearings/rotors/axle seals if it continues to run this hot. Wondering what others have for wheel temps when hauling their max GCWR under very stressful situations (not flat land towing). Also, given that I've probably driven 600 to 1000 miles with this sort of heat....have I already done some damage? 

 

Any help is appreciated. 

 

 

 

 

Edited by jlrosine
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How many miles on the Yukon?

Original rear axle bearings?

Bearings could be bad.

Bad bearings generate heat.

Are you sure the brakes aren't dragging.

:)

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16 minutes ago, diyer2 said:

How many miles on the Yukon?

Original rear axle bearings?

Bearings could be bad.

Bad bearings generate heat.

Are you sure the brakes aren't dragging.

:)

148K miles

I replaced a rear axle seal about 3000 miles ago due to a leak (inner/larger seal). I noticed it had a Timken bearing which I'm guessing is not stock, it looked like it was in great condition/no marks/no heat marks on race etc. 

 

The brakes were replaced on all 4 wheels around the same time the axle seal was replaced.

New AC Delco Brakes/Rotors and fluid flush was done. 

New Caliper bolts were installed on rear wheels to replace the dreaded torx head caliper bolts. 

Brake/Caliper slide area where the pads are installed was clean/free of rust, new slides installed and fresh grease on everything. 

I didn't notice either of the pistons being stuck, but they could be sticking/not releasing. 

Parking brakes were are NOT tight at all...in fact the parking brake doesn't work currently because I adjusted them in too far....so they don't touch when the wheel spins nor do they touch when the brake is applied :). 

 

 

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Do you have an IR thermometer?  It can give you a good temp number to see where you are at.  Then maybe contact a place like Etrailers  and see if they have any idea since they deal with trailers on a large scale.

 

Sounds like you have it all under control with the preventative maintenance you have done and are running a synthetic gear oil.

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5 minutes ago, Black02Silverado said:

Do you have an IR thermometer?  It can give you a good temp number to see where you are at.  Then maybe contact a place like Etrailers  and see if they have any idea since they deal with trailers on a large scale.

 

Sounds like you have it all under control with the preventative maintenance you have done and are running a synthetic gear oil.

Hmm that's a good idea. I'll go buy a thermometer if I can find the IR type locally. I should also probably go drive the car unloaded/loaded for comparisons on heat. 

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7 minutes ago, O_J_Simpson said:

Ok, I will be Captain Obvious and ask if you expected the tires to be cool after towing a trailer in 85-100F heat?

I have E rated tires, and I'm running just about 60psi rather than 80psi. The tires are surprisingly not super hot, but probably warmer than they should be given the wheel temperatures. 

 

It's like that Seinfeld episode when they made fun of the hot coffee lawsuit thing. I expect them to be hot...but "not that hot". 

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I purchased an IR thermometer at autozone, it appears the rear rotors have more heat than the front which seems to be a problem to me. Here's how I tested. 

 

I jacked up the rear end of the car and tested the following. 

- Spun the wheels to see if there was any drag....it really didn't feel like much drag at all, even after pressing the pedal down/releasing the pedal. It seems to release properly. 

- Took off the brakes/calipers/rotors, cleaned everything again, cleaned slides then re-greased everything. 

- Tested the caliper pistons outside of the rotor...watched as each piston clamped then released when the brake was released, it looked like both sides had good release on the pistons. 

- I used a dremel to slightly file the brake pad shoes where they make contact with the caliper bracket, they weren't gliding as freely as I wanted them to, now they seem to glide easily. 

- Put everything back together, torqued everything down. 

 

Test drive (not towing):

I went down the interstate for about 25 minutes, then turned around and came back for 25 minutes at about 75 mph. I then shot the rotors and got the following temps. 

- Both front rotors were around 100- 110F after the drive. 

- Both rear rotors ranged from 135-145F depending on where I took the measurement from on the rotors. 

- Rear diff/pumpkin was around 110F. 

 

It seems to me that the rear brakes should probably be the same or less temperature as the front....correct? I know it's rear wheel drive, but I can't imagine the hubs/driveline in the rear make the rotors heat up that much higher than the front. The test drive is pretty flat too, and I didn't really apply the brakes much other than when I absolutely had to. 

 

The only thing I can think of is that I replaced the rear caliper slide bolts with newer bolts...maybe the newer bolts don't slide as well, or are manufactured just slightly larger than the original/oem? 

 

Thoughts? 

 

 

 

Edited by jlrosine
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If you find out why this is please tell me. I have a 2500hd silverado and after pulling my trailer my rear hubs get hot as well. It to the point i can smell the diff fluid burning. Ive replaced the axle shaft flange gaskets and the seals for the hubs. Same as you i have no break drag and the diff is full of fluid. 

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Several youtube videos online where people have tested rotor temps using infrared cameras etc.  They have easily hit 60 or 70C (140 to 158f) and more just revving the engine and allowing the rotor to freewheel turn without the brakes even applied. Any brake application causes the temp to escalate into the 150C plus range within seconds. The large mass of rotor on a PU truck takes a long while to dissipate it will carry the heat for a long time. Not sure how scientific this is but would the front wheels may be getting more airflow just due to the fact that the front wheels rotated in and out of the airstream when driving and steering therefore keeping them a few degrees cooler than the rear?  

 Since you have the new thermometer lets test the axle tube/differential/rotor/wheel and tire temps. Can you get a spreadsheet filled out with all the data so the forum members can examine it?  This is going to be awesome.       

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2 hours ago, Ashton yellets said:

If you find out why this is please tell me. I have a 2500hd silverado and after pulling my trailer my rear hubs get hot as well. It to the point i can smell the diff fluid burning. Ive replaced the axle shaft flange gaskets and the seals for the hubs. Same as you i have no break drag and the diff is full of fluid. 

Sounds familiar I had a 97 that had a bad differential that got hot enough to smell the fluid. It was also making noise (bad center chunk bearings) I believe I was told that anything over 230f indicates problem with a differential if you are doing heavy towing. I saw those little IR thermometers on sale the other day for like 12 bones I bought one several years back and it is handy.

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I had same priblem when I had a 2004 1500 ( you should have bigger diff than 1500) I towed 12 hrs straight lots of steep grades  7000lb car trailer diff got very hot and I burned out pinion bearing  twice solution was large capacity diff cover   Added 50% more fluid temps went down dramatically. I added same cover on my 2010    1500 for towing. And now my 2017 with bigger diff I will check temps if meeded will do dsme 

 

not a chrome cover sheet metal cover 

but an alum finned cover true large capacity  with dipstik 

Mag Hytec is brand I use

Edited by CDNSS
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