Gears!

[V8 Killer]

in a '91 automatic Firebird V6 Firebird. What would be the best gear ratio. I believe I have 3.23's stock. What would be a good upgrade? 3.42's or 3.73's? Also, can someone provide me with all the part numbers I need for this such as the pinion/gears etc I really dont know much about whats involved in a gear swap. APX how much would they cost to install? Any problems going to arise with them? Blown rear ends or anything? How much would they lower the top speed of the car if I went with 3.73's? Is a limited slip required or not?

Sorry for the ton of questions, thanks to whoever answers them and helps me out!

[img]graemlins/bowdown.gif[/img]

[North Cali Autocrosser]

You should have 3.08s with the auto, I've got 3.73s in mine and it gave it some pep but not night and day difference. You lose a little on your highway mileage and top end, obviously. If you went with 3.42s you probably won't notice anything. I use Richmond gears, got them from Summit along with the install kit. Just remember that when you remove the ring gear from the carrier that the bolts have left hand threads not right. You won't need a LSD to do the swap but I highly recommend it because you will love it! Traction is great, you can do a real burnout and if you like road racing or canyon roads accelerating out of a turn is fantastic because you won't be spinning that inside tire. Hope this helps.

[V8 Killer]

Yeah so I've decided with 3.73's. I need the ones for a 10 bolt rear right? How badly will these gears degrade my fuel economy? How long is the break in period? What weight gear lube is good to use? Synthetic or non synthetic or any additives required?

[North Cali Autocrosser]

Break in was like twenty minutes of driving at 50mph I think then I took it a little easy for a couple hundred miles. And yes, 7.625in 10 bolt rear with 3 series carrier. I don't remember the oil weight 75-90 I think, I used RedLine Oil with the limited slip additive. If your just doing a gear change you don't need any real special oil. The Summit part is RMG-4900461

[3.4 slow to go]

are yo sure it's a 3 series carrier? not that it makes any difference detween the 2/3 series iirc.

[V8 Killer]

How many quarts of gear lube are needed? Should I pick up a new differential cover gasket also?

How much would the installation charge run for a set of gears and an LSD?

[ January 25, 2006, 03:58 PM: Message edited by: V8 Killer ]

[V8 Killer]

Oh by the way, How can I get the speedo adjusted??

[North Cali Autocrosser]

I think it's a little over two quarts of oil. If you buy an install kit it will come with a gasket and chances are you will need it. I don't know how much someone would charge to put it in I did mine on my own. Speedo can be adjusted by buying a new gear that can be accessed by removing the speed sensor and just slide the gear off, you'll still be off by about two mph at 55 but it's as close as you can get without tearing apart the trans. You can get them from tranny shops or the dealer and it's the biggest gear in the group, I think it's the white one but don't quote me on that.