on my 99 silverado i swapped the g80 and 3.42s for some 3.73s and an eaton. i got everything in and it measured .010 on the backlash. when i take of in forward or reverse everything sound perfect. even at 30 to 45mph everything sounds perfect. when i start to slow down every once in awhile i hear a loud whirring noise. i only hear it when i slow down and it is every third or fourth time. anyone have any ideas?

 

You can try to tighten the backlash up some. I have been seeing some OE set up rears as tight as .006"!!! Decel whine can be caused by too much backlash or not enough pinion preload. So, check your pinion preload first. Depending on how long you have run it, look for about 15-20 in/lbs rotational torque to turn the yoke. It should have been 20-25 for new bearings, 10-15 for used bearings. If they are used bearings go for the 15, if they were new bearings go for the 20.

 

tighten yer backlash asap. dont break in those gears that loose..004 to.007 would be ideal.I built rears for the local dealer for years.Also check your pattern on the coast side. Good luck.

 

How did you go about setting up your pinion depth?

 

Did you use the same pinion shim as what came out of the 3.42?Did you use a new crush sleave?Did you get it to crush? .006 is ideal,they want these newer ones on the tight side.

Side note,how any here have seen mostly .035 pinion shim come out of these?

 

Your right oin the newer gears. The older ones with the diferent cut used to be good at about .010". The new ones can be set as tight as .005 or so safely, I personally wouldnt set them up tighter than that because you start to limit the amount of lube inbetween the gears.

 

Yep and refering to your last sentence,very important if you tow.

 

i installed new bearings on the pinion but accidently set it for the old ones. i tightened it and now they dont make any noise at all. i put 20 miles on it because it didnt make any loud noises at first. would 20 miles do any damage if it was just a little loose.