IRS Diff. HOT after pininon seal install

[///m3]

While doing a differential cooler install, and also replacing a leaking pinion seal, the diff. seems to be getting too hot. I took it out for a 5 minute shake down drive and the diff. was too hot to touch when I got back. There wasn't any crazy launches or high speed runs, just normal every day driving. I replaced the old fluid with RoyalPurple 75W140

Anyone have any idea what could cause it?

 

[Charles236]

If the differential is getting hotter than it was before the pinion seal was replaced, the most likely cause is overtightening of the pinion nut. This will increase the preload on the pinion bearings, generating more heat than is normally the case. Best way to check preload is with the wheels off, brake calipers completely released (removed from the disc is even better), then turn the pinion flange by hand. If it turns with a small amount of resistance (if you try to spin it, it turns easy but stops as soon as you release it), it is probably ok. A small amount is normal with properly preloaded bearings. If you have to get a good grip and really turn it hard to get it to move, then it is too tight. Because of the use of a crush sleeve to maintain tension on the pinion bearings and flange nut, you shouldn't loosen it if it is too tight, the correct fix is to pull the pinion flange, seal, oil slinger and front bearing and replace the crush sleeve.

 

[///m3]

If the differential is getting hotter than it was before the pinion seal was replaced, the most likely cause is overtightening of the pinion nut. This will increase the preload on the pinion bearings, generating more heat than is normally the case. Best way to check preload is with the wheels off, brake calipers completely released (removed from the disc is even better), then turn the pinion flange by hand. If it turns with a small amount of resistance (if you try to spin it, it turns easy but stops as soon as you release it), it is probably ok. A small amount is normal with properly preloaded bearings. If you have to get a good grip and really turn it hard to get it to move, then it is too tight. Because of the use of a crush sleeve to maintain tension on the pinion bearings and flange nut, you shouldn't loosen it if it is too tight, the correct fix is to pull the pinion flange, seal, oil slinger and front bearing and replace the crush sleeve.

I was kind of leaning towards that, since I didn't have a torque watch to measure the resistance before I started. The differential was out of the car when I installed the new pinion seal. While I was tightening the pinion nut, I stopped about 10 times and checked the play in the bearings with my hand on the pinion flange. I stopped tightening as soon as I got all of the axial play out of the flange. I thought it was fairly easy to turn, but I didn't check it once I re-installed the half shafts.

Do you know if I can replace the crush sleeve with the differential still in the car? Is there a torque value that I should install it too?

 

[SlowSVT]

I think these diff's get how even when everything is working in properly.

 

[postban]

...snip...

Do you know if I can replace the crush sleeve with the differential still in the car? Is there a torque value that I should install it too?

20 in/lbs force required to rotate an axle out at the lugs. No torque spec for pinion nut except that. Tighten till then.

 

[///m3]

20 in/lbs force required to rotate an axle out at the lugs. No torque spec for pinion nut except that. Tighten till then.

Thanks Postban. Is this is with the driveshaft disconnected or just the transmission in neutral?

I appreciate the help from everyone. The write up I did for the diff. cooler is another thread under the mustangsally50 screen name. She's the beautiful woman I did it for.

 

[///m3]

I finally installed a temperature gauge. It appears that the diff. gets up to about 180 degrees while cruising at 70mph at 60 degrees ambient. It's a little hotter than I would like it to be, but it may be within the noise. I don't know what it was like before the seal replacement.

Any thoughts?

 

[Charles236]

When I installed 4.10s in my truck, I checked the temperature with a non contact thermometer after 3 miles (200* if I remember correctly) and regularly afterwards whenever I parked the truck. As the gears wore in, the temps dropped a good bit. After about 1,000 miles, I quit checking temps, but temps were stable by then, at 160* to 165*after 10 or 12 miles. This was with 75w140 synthetic lube, and running at speeds of 55 to 60 mph. So, I think your temps are probably not excessive, considering the speed, and ambient temp. In any case, you are not reaching a temp at which synthetic gear oil would lose it's ability to lubricate your differential properly.

 

[///m3]

Well, the good news is that the differential oil cooler works...and it works well. It drops the temp from 210 degrees down to 150 degress.

The bad news...it's hitting 210 degrees while highway driving at 75mph at 70 degrees ambient. That seems a little too hot, but I have no idea how hot it was getting before I changed the pinion seal. I might be blowing this whole thing out of proportion.