05 Tahoe Z71 Tranny/ Differential Grind

[mmichaca]

Hey guys, new to the forum and not really sure if this has been discussed before, sorry if it has. I have an 05 z71 with about 118K miles, recently a sudden howl or grinding noise has started. it sounds like it could be coming from the tranny or rear differential. It will only make a grinding noise in first gear, fourth gear, and reverse (faintly), it rarely does it if at all in 2nd and 3rd. It also only happens when I actually accelerate, idling is fine, cruising down the road (without pressing on gas pedal) is fine. When I get in and crank the car up everything works fine as its supposed to, no check engine light. When i put it in reverse, it is quiet until i press on the gas, at that point the same grinding noise begins, then when i put the car in drive, the grinding noise continues (once the gas pedal is pressed) until the car shifts into 2nd gear. At that point everything is fine and normal, no noise, no difference in feel or smell, until it gets to about 4th gear, then a smaller grinding noise then before begins. I am not too familiar with trannies or diffs but the fact that it was only in 1st and 4th led me to believe it was the transmission. Well I just spoke with Chevy Service Center, they said my rear end needs to be overhauled. My question is, does this make sense to anyone that has a bit more understanding of how these things work? I dont know much about them but I would think if it were the diff, i would hear some kind of grinding in all of the other gears as well, not just two. Any help or advice would be greatly appreciated guys!! Thanks

 

[MO Viet Vet]

I would drop the pan on the trans and inspect for metal. I would also remove the rear diff cover and inspect for metal. If has been long enough then is time for new fluid and filter in trans and new fluid in the rear diff. Make sure you use the correct fluid in each. Locker in the rear? Use some brake clean and spray off the rear gears good and let dry. Then drive again and see where the noise is and if changed. You can do the trans of rear diff first and then road test and see if can pin point the problem source.