[A.W.Dille]

I am in the process of working over an 85 Grand Prix and was wondering if there was a code stamped into the axle tube that might indicate what gear ratio was possibly in the car. If so where would I find a breakdown of what codes for what gearing. The reason I'm trying to find this out is due to going to a 400 and 700R4 trans and even though going to be street driven only I'm going to put an 068 or equivalent cam in the engine when I start putting it together. Thanks in advance.

[Fullhouse]

If you are going to just cruise and never get on it that 7.5 will last a long time. That rear won't hold up for long if you intnd on driving her hard. I've got an 87 le with a 455 / 200r4 in it and ended up putting a 8.5 342 in. Just on problem remains. TRACTION

[monzaz]

Traction is always the problem on the street. You can only expect so much tration because of that . Be realistic on your goals or you will be spending money carelessly in trying the impossible. That is why little car with turbo and blowers that kick in at higher rpms will kick you butt on the street. they rev more and pull longer through each rpm range. Your 454 is all low end grunt. Take them to the track and you will almost win everytime.

7.5 rear on the street.

If you intend to be mostly street bound, the 7.5 should have no troubles with it as long as you have a good installation of parts. If you expect a older 20+ year rear to keep up with a newer built engine and trans YOU EXPECTING a miracle. The rearend needs some money spent too. new bearings and a well set-up ring and pinion and a after amrket posi to .005 .008 backlash to handle performance driving. I have had 7.5 into the elevens with NO problems so do not under estimate that rear because of the size. Yes there are limits ...Tire shake burn outs are BAD for any rear diff and will destroy a set of gear quickly. Do your work on a smoother surface and remember all aspects of your suspension will help traction shocks springs control arm bushing etc. There is more to all this then slapping some parts in a car and going...if you really want to get it to the ground. Take care and good luck on your cars. Jim

[455_regal]

crawl under the car, passenger axle tube, front side facing the motor, youll see a bunch of lettes-numbers, you can goto autozone.com and look up the codes.

http://www.autozone.com/servlet/UiBr...3d8011b260.jsp

Click on Fig 16 below for all the codes.

http://www.autozone.com/servlet/UiBr...3d8011b6f5.jsp