in my 99 SS...

My rear end has some issues with whining currently and my tranny shop has it torn apart currently. While they're there i figure i'm going with 4.11's, but they(tranny shop owner and employees) want me to go bigger than this, they say 4.56 or 5.13's! Anyone go with these? I'm pretty sure i dont want to go bigger but i want some feedback.

The whining we believe is a pinion bearing?... the noise is a whine that is speed related(increases in intensity with speed). The noise also increases in intensity if there's torque on the system from the motor. This whine is so loud that it gave me a headache driving it for about 15 miles. Yes the fluid level is good, some does appear to be leaking out of the front seal however. no, the noise is not the brakes or the tires (had it running on the hoist, it's in the rear end). let me know your thoughts

 

To set the right gear size you need to list tire size, tire type (radial vs bias ply), ideal trap speed, and engine rpm. Generally the idea is to set yourself up to go out the back door at peak rpm in the 1:1 gear with 1-2mph breathing room to compensate for the difference in trap vs actual mph. That's assuming that you want all you can get out of the current setup, and don't care so much about street rpm etc.

 

With the two OD gears in the M6, highway use shouldn't be a huge issue. But it would be a very unusual 4th gen that needed more than 4.11's. Cars using those very short gears are usually using big (diameter) race tires and have a high rpm band.

As stated in the above post, if you are looking to maximize 1/4m. times, you need to consider the factors listed to get the right ratio. It's better to go a little "long" (lower ratio) than short - you want to avoid hitting the rev limiter or having to shift into 5th if runnning the /14m.

Gear whine has a number of causes. The whole thing needs to be gone through with a very critical eye towards the setup - especailly the gear pattern.

Rich

 

i think i'm going to go with the gm motive 4.10s... i know the owner of this shop so i trust them completely. They really know their stuff, just not sure they know their modern F-body ratios.

 

Okkkkkk... they took the rear end apart, everything seems to be ok. they kept looking and found frozen U joints so they replaced them. Put the rear back together and driveshaft back in, and the whine is STILL THERE. tranny shop says it could be the output shaft bearing in the trans. but they're not sure. SOOO... I can't find the whine in my drivetrain. Any ideas?

 

It is the gear pattern not being setup correctly in the vast majority of cases, that causes the gear whine. What brand of gear are you using?