Installed 3.73..... Now I Have Gear Whine....

GMC_BOI · December 12, 2009

A buddy installed some 3.73's in my 05' 2WD 5.3 Sierra truck with the G80, and now I have fairly loud gear whine.

The loud whining occurs when I press the gas. When I release the gas pedal, the whining stops. It only whines under accelleration.

He used Kendall 80W-90 Limited Slip gear oil to fill it up. It is non-synthetic... Could this be the problem?? I have read that I needed 75W-90 oil WITHOUT any additives... Should I use synthetic instead?

Also, could I have a backlash problem?

One last thing.......... Also, my ABS light, Traction Control Light, and "Service Brakes" indicator message are showing. Everything is totally fine until after about 30 seconds of driving, then the messages all appear. Justin from Blackbear mentioned to me a few days ago, that my ABS lights would come on after a 3.73 swap, and I would need to get my PCM flashed to the 3.73. Will doing this solve my problems?

Please chime in guys. I hate this annoying Whining sound!

Thanks so much..........

pm26 · December 12, 2009

This is not the gear oil problem. It is gear backlash adjustment problem. The gears are shimmed incorrectly. I had this same issue on a new 1995 Nissan Pickup. The whine would come in only under load and disappear while coasting, all in 45-55 MPH range. The differential was replaced under warranty, and the new one started whining too, but only under coasting condition. Go figure. It looks like they could not get their gear adjustments right.

Using heavy 80W140 viscosity rear end lube help to quiet the whine somewhat, but this is thick oil and you do not want to use it in colder climates, especially in the winter.

wayland1985 · December 12, 2009

I'm sure it's an alignment issue as well. Installing gears is no small project. Has your buddy replace gears before???

I'm usually not afraid to undertake my own automotive projects, but I don't think I'll ever attempt installing gears, just due to the amount of work required to shim everything up nicely.

Matt_ · December 12, 2009

Were the gears used or new? Used gears will tend to make this noise because it's near impossible to get the mesh exactly the same as the previous install.

If the gears are new, then its either the pinion depth and/or backlash isn't shimmed correctly. Backlash can be checked by taking the diff cover off if your buddy has the right tools. I would do that before driving very far... once those gears wear/mesh, it won't matter how they're adjusted they'll always whine at that point.

ken1mod · December 12, 2009

I had exactly the same problem with a buddy of mine. Setting gears is a black art. I took mine to dealer and they fixed it by setting up gears correctly.

nbuscemi · December 12, 2009

Setting up the pinion preload is probably the hardest part, plus you need a press and a strain gauge. If you keep driving on improperly set-up rear end will ruin your new gear set. Even if you put your old gear set back in, you;ll still need a new crush sleave for proper preload. I'd heave it checked out ASAP!

-Nick-

GMC_BOI · December 12, 2009

The gear and pinion were used. He used my factory shims I think. I also know that he did everything by hand. He did not use any special gauge to check backlash or anything. Since he did everything by hand, Im thinking that the gears are not shimmed correctly or the back lash is off.

I will take the truck to a repair shop and see what they say. I hope they dont rape me....

Also, what about those warning lights??? Do you think its because of the computer needing to be flashed again for the new gears?

compulynx · December 12, 2009

I used to setup rear ends (differentials). Unless you are up on mesh patterns and proper backlash and preloading, leave it to a pro. You will cost yourself less in the long run.

If you really want to learn, go buy a rear end at the junkyard, and start reading. It is not rocket science, but requires a good understanding of what moving one setting will do to the other.

Tooth contact pattern is the real buggar to master. One hint I will give you is to use some flat black paint (light dusting) to see your contact pattern.

Start your reading here. Very good along with charts on patterns:

Differential Repair

I can also tell you that YOUR factory shims will NOT be right for that R & P setup. Each one has to be set up individually, especially if you are changing ratios.

C

Silverado4x4 · December 12, 2009

As everyone said there right to the gears not being set up right and yes you need to get your computer setup for the 3.73 gears.

dlewis1111 · December 12, 2009

A buddy installed some 3.73's in my 05' 2WD 5.3 Sierra truck with the G80, and now I have fairly loud gear whine.

The loud whining occurs when I press the gas. When I release the gas pedal, the whining stops. It only whines under accelleration.

He used Kendall 80W-90 Limited Slip gear oil to fill it up. It is non-synthetic... Could this be the problem?? I have read that I needed 75W-90 oil WITHOUT any additives... Should I use synthetic instead?

Also, could I have a backlash problem?

One last thing.......... Also, my ABS light, Traction Control Light, and "Service Brakes" indicator message are showing. Everything is totally fine until after about 30 seconds of driving, then the messages all appear. Justin from Blackbear mentioned to me a few days ago, that my ABS lights would come on after a 3.73 swap, and I would need to get my PCM flashed to the 3.73. Will doing this solve my problems?

Please chime in guys. I hate this annoying Whining sound!

Thanks so much..........

Its the backlash on the gear set that is not properly set. Your buddy owes you a refund on the beer that you paid him.

Not sure if these trucks use an ABS sensor for the rear as part of the gear set. Some do and if yours does, did you install the replacement set designed for this? I am certain that Justin is correct too.

Zembonez · December 12, 2009

The gear and pinion were used. He used my factory shims I think. I also know that he did everything by hand. He did not use any special gauge to check backlash or anything. Since he did everything by hand, Im thinking that the gears are not shimmed correctly or the back lash is off.

I will take the truck to a repair shop and see what they say. I hope they dont rape me....

Also, what about those warning lights??? Do you think its because of the computer needing to be flashed again for the new gears?

You can't reuse shims and just install the gears. The rear end has to be set up properly for the gear set to match the housing properly. This is what is causing you r noise issue. Gear whine means the teeth are not meshing properly and will end up wearing out the gearset if left like that.

kbswear · December 14, 2009

Gears are a pain and require special tools to set them up right. My hardest gear install was of course my first one. I did mine and my buddies mustangs. I'm not sure if its different for our trucks but on mustangs 95% of the time you can re-use the shims, you just have to make sure you put them back in on the same sides they came out of. Pinion depth is a stickler. The crush sleeve can be a pain. The first gears i did i got the pattern right but did not set the pinion gear correctly. My problem was that i didnt crush the crush sleeve properly and the gears howled something awful. I went back with and zapped it with my impact wrench and then set it by feel. Grab the DS and tug back and forth (like from the rear of truck to the front of truck). If you have play than most likely it is your pinion gear. Let us know what you did. Good Luck.