Must be a direct bolt in please. Any more details appreciated.

 

Did you want to buy new or used?

Used will be hard to come by -- people that have one usually won't get rid of it unless it's broken.

New, you're looking at about two grand. Moser, Strange, and DTS all make bolt-in models, although I've heard the Moser requires some fabricating.

Be prepared to decide what gear ratio you want, whether you want posi, locker, or spool, and whether you need 3- or 4-channel ABS.

Also, put some thought into a Dana 60 instead (Strange and DTS have bolt-in F-body setups). It's a couple hundred dollars cheaper and significantly stronger, but it weighs about 25 pounds more.

 

The Dana would be O.K. too. Geez I might take a 9". I know I want something with 3.73's or close. Is the Dana a spool? I need something that is street friendly as I rarely go to the track but dont want to do this again.

 

You can get whatever diff style you want in any of them -- open diff, limited slip (aka posi), locker, or spool. I think an Eaton posi would be a good choice for you.

A 9" is more expensive than any of the other options, and stronger than a 12-bolt, but not as strong as a Dana 60.

Rear end strength correlates very closely with the size of the ring gear -- the bigger it is, the stronger it is. Your 10-bolt has a 7.625" ring gear. Old G-bodies had a 10-bolt with an 8.5" ring gear. Most Mustangs have an 8.8" ring gear. The 12-bolt has an 8.875" ring gear. A 9" has, surprise, a 9" ring gear. Finally, a Dana 60 has a 9.75" ring gear.

What gear ratio do you have now? In drag racing, there is a rule of thumb you can go by. It's generally considered a bad idea to get into overdrive (that's 4th in an A4 and 5th in an M6). That means that you want to be just below redline in 3rd/4th respectively as you go through the traps. So you figure out what MPH you think your car will run, and then choose the gear ratio that puts you closest to redline without going over. A 3.73:1 gear ratio, for instance, will have you hitting 6000rpm at about 123mph. If you think you'll go faster than that, you'll want to go with 3.42 gears, which are good to about 134. 4.10's will top out at 112.

If you don't care about ideal conditions on the strip, you can ignore all of that. Your gas mileage and cruising RPM will also be affected. If you're getting 25mpg with 3.23's right now, 3.73's will take you down to about 20mpg.

 

I'm leaning towards the S60 now and found a local dealer in Atlanta (moving there this week from Vegas) that has a better price than TByrne and can get my driveshaft hooked up for cheap. Thanks for the info.