CDN35thSS

I've got a 02 SS 6 speed with a loud hum under load at 45 - 65 mph. I've had 2 different shops completely rebuilt it with GM parts and it still hums...a little differently after each rebuild. They measured gear contact area, etc etc and can't eliminate it. Driveshaft is in balance. I have access to a 14,000 mile rear end from another 02 SS but it's an auto with 323 gears and mine is a 6 sp with 373's.

What will the driveability and performance be like with the different axle ratios if I simply swap them ? Any other suggestions. It sounds like a Boeing 747... I can hear it with the top down!!

I plan on keeping the car...it's only got 50k on it now...

Thanks, guys

LLLosingit

iTrader: (4)

You'll want to keep the same ratio, Besides the speedometer being wrong the ratio drop will be noticeable when letting out the clutch and general driving. There are online calculators that will tell you the difference in speed versus rpm between the two ratios.

FirstYrLS1Z

iTrader: (4)

3.73s' to 3.23s' will result in a 13% loss in torque to the pavement. Clutch engagement in 1st gear will be more sensitive but you might like not having to shift out of 1st so soon.
BUT more important is channel compatibility. A rear end for ABS only is 3 channel, a rear end for ABS and TC is 4 channel. Not directly interchangeable. You can convert a 3 channel to 4 channel by swapping axles and backing plates. A 4 channel can be converted to 3 channel by adding the reluctor ring to the carrier and drilling the housing for the sensor, this conversion is EXTREMELY difficult.

CDN35thSS

Thanks. This is great info. Both cars have ASR, so that would mean I wouldn't have the traction control issue you describe, right ?

It's really a cruising car... driven from Canada to Florida..just a fun car that I'll never race.. so won't be a performance issue. One calculator i used said I'd be at 67 mph @1428 rpm with the original gearing and the swap would make it 71mph at 1162 rpm.

And I was wrong. I've got 3.42 now (not 3.73 as I said in my original post) so I'd be going from that to 3.23.

Sounds like it would be pretty driveable for what I do, don't you think ?.

FirstYrLS1Z

iTrader: (4)

Right, no ASR issues.
3.42s' to 3.23s' will result in a 6% loss of torque.
You'll be idling down the interstate with a frequent down to 5th/4th for passing. you'll probably use 5th for the interstates as 1100/1200 is too low as you'll be 'lugging' the engine fighting the wind resistance at 70mph.
Very driveable but more wear on the clutch which you'll get used to.

CDN35thSS

Great input. Sounds like not an issue for my specific situation. It will be changed over in the next month before I head to FL and I'll come back here with driving impressions once it is swapped. These cars have such a wide torque band... Which should also help.

FirstYrLS1Z

iTrader: (4)

I wouldn't expect better mpg as rpm would be too low for efficiency.
My situation is just the opposite, A4 with 4.56s'. And I travel from Ohio to Florida with them.