I never took grade 12 mechanics (only 11) so I never got into driveline knowledge. Also, there are no stickies on rear-ends.

I have a 1991 Z28 with the stock 3.08 rear limited slip. I should also mention I have a stock T-5 tranny.

I assume since I counted 10 bolts around the rear cover that it is what people call a 10 bolt? And from what I have read in posts so far a 10 bolt is weaker than a 9 bolt? If I did not care about fuel economy and wanted some better throttle response I could up the ratio of the 3.08 rear? obviously I'd get a shop to do this but what am I looking at for price (time/parts)? Also I am a street driver, not a drag racer, so would something in the 3.50 range be best or get closer to 4.00? Finally, what do I also need to make the speedo stay accurate? new speedo drive gear or software flash?

Thanks.

 

I'm not sure why people do gears for street cars. Only reason I see for gears is racing. More gear will make it power better, but traction is usually a problem to begin with and more gear doesn't help that situation. If you want though, either 3.73 or 4.11/4.10 gears are the most common and useable. I'm not 100%, but program or flash should fix the speedo. I'd expect $500-$600 for a shop to do the gears.

 

4.10/4.11 is pushing it for a street car with the tiny 26" tall tires. I wouldn't recommend anything deeper than 3.73 unless you change the rear tires to 28" tall.

 

This is going to require a little more than just gears. The 3.08 gear uses a 2 series differential. The 3.23, 3.42, 3.73, 4.10... gears use a 3 series differential. The difference in these is the location of the ring gear flange. To go with any of these other gears you need a 3 series differential too, which will add about $450 to the price. I recommend the Eaton, which will be a very good upgrade for this rear end anyway. I'd recommend the 3.42 myself, but the 3.73 is very popular too. The 3.42 won't hurt your fuel mileage as much.

 

You could also buy a thick 3.23 or bigger gear that will fit the 2 series carrier. I think they are a little harder to find but I think summit or Jegs has them.

 

I keep forgetting that they make the thick gears for the 7.5 2 series. They don't make thick gears for the 2 series in other rear ends.

 

I like to drive my car the same way that you do, daily driven on the street, i have 3.42"s in my car and i like them alot i wouldnt really go up to 3.73 unless my car saw alot of strip time, which it doesnt. Its probably cheaper also to find a rear end at the JY with 3.42"s in it, or in the case of a 9 bolt 3.45"s just for the sole fact that it would probably run you a big bill in the shop to switch over everything.

 

its not that expensive to have it done. or to do it yourself. basically you need a differential rebuild kit, which comes with seals, and bearings, then you need axle bearings, and of course the gears. if youve got the tools and are mechanically inclined you can do it yourself. id say 3.73's are as high as you wanna go, youll see once you put them in that itll really wake up your cars take off speed.

 

i have a stock rear end not really sure what it is but i know that it has 2.73 gears in it which is stock can anyone help me and tell me which other gears i can put in my car without changing the carrier thanks

 

Does the same hold true for the 9 bolt? I know the 2.77 are 2 series and the 3.27 is 3 series.......but what about the 9 bolt 3.08? 2 or 3 series, and where can I find "factual" information, not someones "guess"?

 

I can't find any information on the 9 bolt 3.08 gears.

 

9 bolt ratios available from 9bolt.com

http://www.9bolt.com/gearsets.html

2.77 - The only 2 series gear set.
2.92
3.08
3.23
3.27
3.45
3.70
3.90
4.11

Ratios available in production third gens

2.77
3.27
3.45

Ratios once available from GM

3.70

 

I just purchased a 9 bolt disc rear w/ PBR brakes and 11.75 rotors(for $100 bucks!). It came out of a 89 Formula 350,and the RPO sticker indicated a 3.27 gear ratio.... but I believe it was a replacement unit.....nonetheless, I pulled the rear cover to inspect and the ring gear is stamped indicating 3.08 gears....I was shocked to say the least. But back to my original question, can I upgrade this to 3.27 /3.45/3.70 (would this be considered a 3 series carrier?????) Thanks for your help.

 

If the car is on jack stands under the diff can you disconnect the rear sway bars? Would it shift on me in that position and negate me being able to re-bolt it on?

 

Vincode8, never trust the numbers stamped on the gear. Always count the teeth. Check yours again and see if it isn't a 2.77 or 3.27. I have never seen a 3.08 in one of these rear ends, but that doesn't mean that there aren't any. Looking at the list that Stephen posted it would seem that you would have to have a 2.77, 3.27 or 3.45 if this is an original factory installed gear.

 

If your going to spend any amount of money, you could always put a ford 9" in it. Have 2 center sections, one for driving and one for fun! We build custom 9" rears and would love to do one for a 3rd gen Camaro. Just have to figure something out for the torque link.