What rear end gear?

**daveb91** · 04-14-2007, 11:44 AM

What rear end gear do I have? I dont have a sticker that shows my codes so I cant tell that way. All I can say is I have a 4l60e and when I am at OD my tach is sitting at about 16-1700 RPMs any sugestion based on that?

Thanks.

edit I ment for the title to be What rear end gear LOL fat fingers.

**2001NBMZ28** · 04-14-2007, 12:10 PM

Stock was either 2.73 or 3.23. Go to www.f-body.org/gears/ and plug in both and calculate. Can't tell you by the RPM you posted without knowing the MPH.

**daveb91** · 04-14-2007, 01:09 PM

60 mph sorry forgot that

**daveb91** · 04-14-2007, 01:13 PM

Guess I dont get that calc. 60mph 4l60e in the OD gear is about 1650 RPM.

**2001NBMZ28** · 04-14-2007, 01:43 PM

Calculator assumes stock tire size (unless you change it) and speedo is correct.

2.73 @ 60MPH = 1500 RPM
3.23 @ 61MPH = 1800 RPM

Not always true, but steel drive shaft came with 2.73, alumimum with 3.23. You can also have the dealer run your VIN and get a list of the original RPO codes.

**daveb91** · 04-14-2007, 02:54 PM

so it looks like 3.23s considering it was higher than 1500 but not quite 2000 on my tach. And yes stock tire size. Thanks and also thanks for the vin info help I asked this once and was told it couldnt be used for that. I guess wrong info. Thanks again.

**2001NBMZ28** · 04-14-2007, 03:04 PM

I use that calculator when I reprogram my car from 2.73 to 3.42 for my gear swap and it's right on....and dealer can even cut you a key from the VIN.

**0rion** · 04-16-2007, 12:39 AM

you don't have the RPO codes on the drivers side door?

**daveb91** · 04-18-2007, 03:40 PM

Originally Posted by 0rion

you don't have the RPO codes on the drivers side door?

No.

**SteveC** · 04-22-2007, 06:55 PM

Here is a very easy way to tell.

Look at your driveshaft, is it rusted? If it is you have a steel unit, which was used on 2.73 ratio rearends. If there is no rust, it is aluminum, which was used on 3.23 ratio rearends.

SteveC

**purplebat66** · 04-27-2007, 04:34 PM

i thought all 98 and newwer f bodies came with the aluminum driveshaft

**2001NBMZ28** · 04-27-2007, 04:41 PM

My 2.73 car didn't. Some got them replaced w/alum if they had DS issues under warranty though.

**SteveC** · 04-27-2007, 05:45 PM

Originally Posted by 2001NBMZ28

My 2.73 car didn't. Some got them replaced w/alum if they had DS issues under warranty though.

Actually you have the situations reversed. The DS issues (not really an issue), was with the aluminum units, as they rotated and heated up, after driving when the vehicle was shut down, the aluminum DS would make a "cracking, or "tinking sound, so the dealer under warrenty would replace it with a steel unit which does not make this noise at all.

It turned out that the complaintents were getting a heavier sub standard unit in replacement for the lighter weight, better balanced aluminum unit.

JMHO

SteveC

**2001NBMZ28** · 04-27-2007, 06:05 PM

Thought the DS problem was a balance issue with the steel at high RPMs, not a "cracking" noise after the car was turned off? If I paid for the performance A4 axle option and the dealer wanted to put in a steel DS I'd be upset.