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Old 03-19-2003, 08:23 AM
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Default how warm should the rear differential get?

i just noticed a new noise yesterday. it is not a really a grinding (bearing) noise, sounds more like the rumbling that the tires make, but it is not the tires. it is coming from the back somewhere. i thought that maybe it was in the diff so i felt it and it felt really warm. never really felt it before so not sure if that is normal or not. anyone shed some light on this? there is nothing leaking from it, but i guess i can break it open and check it.

thanks all
shawn
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Old 03-19-2003, 08:33 AM
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Default Re: how warm should the rear differential get?

The diff can get really hot. NASCAR racers have oil coolers and driveshaft-driven pumps. And gear oil is good into the 250* range.

On the highway in warm weather it can get well past the point where you could hold your hand on it.

The rumbling is more likely to be an axel bearing. Differential bearings are darn reliable.
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Old 03-19-2003, 09:54 AM
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Default Re: how warm should the rear differential get?

i agree probably axle bearing. want it to run a little cooler after ya fix it run synthetic lube in it. easier on the bearing too.
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Old 03-19-2003, 10:31 AM
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Default Re: how warm should the rear differential get?

any way to tell which side is bad? i know that ideally i should do both anyway. but don't really have the time for that right now.

thanks all
shawn
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Old 03-19-2003, 10:58 AM
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Default Re: how warm should the rear differential get?

Pull the tire off each side. Grab the axle flange and move it up and down or front to back. If you have any
movement, Say more than a few thousanths, The bearing may be bad. The most telling way though is to
grab the axle flange and turn it by hand and feel for roughness, There should`nt be any. It should roll nice
and smooth.
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Old 03-20-2003, 07:32 AM
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Default Re: how warm should the rear differential get?

You can also lift the wheels off the ground, put the transmission in top gear and let the engine idle. Then put a stethoscope or a hardwood dowel or a screwdriver against the hub, right behind the backing plate. Put your thumb on the end of whatever stick you use, and your ear against the back of your thumb. The stick will transmit the noise right to your ear.
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Old 03-20-2003, 08:09 AM
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Default Re: how warm should the rear differential get?

thanks all, i will check it out tonight.

shawn
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Old 03-20-2003, 10:21 AM
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Default Re: how warm should the rear differential get?

JUST TO CLARIFY:

You should put the knuckle of your thumb aginst the bone right behind your ear - not into the ear canal. That bone works fine at transmitting sounds into the inner ear, and it's a lot sturdier than the outer ear. If something slips and hits something that's moving, you don't want your thumb, or anything else, to get jammed into your ear.
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