I have my yukon geared 4.88 rear third and it has been good for about a thousand miles. it was used with about 10k on it, it was rebuilt by a gear shop with all new bearings and re-setup. i run mobil1 synthetic in it, and it has just recently started to whine, but not like i have ever heard, it only does it under slight throttle, like barely pushing the gas, i have not heard it under load or under coast. but it has began to get more noticeable lately, even so passengers ask what it is... this would be the rear end right? not the fuel pump or something else? it changes frequency as speed changes... should i drain the diff fluid or am i going to have to take it back to the shop? they are a reputable shop here. they assured me that i did not have to follow any break in as they were already broken in properly before.

anyone??? i am not wanting to pull the third...

 

I'd expect you've already inspected the drums to make sure they don't have any diff grease coating them.

Other than that, why not take it back to the shop and see if they can diagnose the problem. Sounds like its probably the gears...

 

i'm gonna guess chipped ring teeth.
but for your sake i hope that's not it. good luck.

 

greeat.... im really hoping its not chipped...

 

My 4.56 Yukon's do it. It could be a dying pinion bearing but I doubt it. My guess is the gears themselves.

I've exploded my stock front end R&P as well as my re-geared rear Yukon's. The ring gear bolts backed out. It may be a good time to pull the third but I'd definetly take it to the installer first.

 

That happened to my friend's older Jeep Wrangler, blasted a bolt straight out of the rear diff cover

 

ok, stopped by the shop and talked with the guy, he is a taco owner so knows toyotas. he said that the noise is characteristic of a gearset worn in a little wrong and then reset better, but not exactly the same. his suggestions were changing the diff fluid and adding a gear oil stabilizer. he said most of the time they cant be heard due to tire noise, but my a/t's are pretty quite. as long as there wont be any damage, im ok, it doesnt bother me and cant be heard with a/c or radio on.... so we'll see if it gets worse or not..