Transmissions and Drivetrain Need help with your trans? Problems with your axle?

gear upgrade recommendation!

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Old 08-12-2017, 04:24 PM
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Car: 1991 Pontiac Trans Am GTA
Engine: V8 305
Transmission: Automatic Transmission
gear upgrade recommendation!

I'm thinking about upgrading my stock 2:73's in my 91 GTA, any suggestions what to upgrade too? Recommended vendors? Links?

Car is pretty much stock.
Old 08-12-2017, 08:51 PM
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Re: gear upgrade recommendation!

Are you going to upgrade the differential too?

Quick Performance has some good kits to do the whole thing. They sell the Yukon Dura Grip with Motive gears and the USA Standard installation kit. These are all pretty high quality parts and you can't beat their prices.

The 3.42 gear is pretty popular.

Your '91 should have the 7.6 rear end with 28 spline axles. http://www.quickperformance.com/GM-7...t_p_20409.html

Last edited by big gear head; 08-12-2017 at 08:54 PM.
Old 08-12-2017, 08:51 PM
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Car: One owner '88 IROC 50k
Engine: L98 with bolt ons.
Transmission: T56
Axle/Gears: 3:42 again
Re: gear upgrade recommendation!

With a 700R4 3:42 is probably the best overall choice (assuming you have a TPI motor) with 3:73's it's spinning a bit fast to be in peak torque at hwy speeds... I tries both with my L98 and was happiest with the 3:42's
Old 08-12-2017, 10:44 PM
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Re: gear upgrade recommendation!

If you like the gas mileage and the low rpm's on the highway of the 2.73's, go to a 2,400 - 2,500 rpm stall torque converter. You will get a lot more off the line without losing the advantages of the 2.73's. If you want to add a posi., that would be fine.
Old 08-13-2017, 02:54 PM
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Car: 1991 Pontiac Trans Am GTA
Engine: V8 305
Transmission: Automatic Transmission
Re: gear upgrade recommendation!

thanks guys.. gas mileage is not the main concern.. i just hate the car gearing down on every hill lol.
Old 08-13-2017, 08:38 PM
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Car: 86 Imponte Ruiner 450GT, 91 Formula
Engine: 350 Vortec, FIRST TPI, 325 RWHP
Transmission: 700R4 3000 stall.
Axle/Gears: 9 Bolt Torsen 3.70
Re: gear upgrade recommendation!

I went to 3000 stall converter and 3.70 and I enjoy it quite a bit.

GD
Old 08-13-2017, 09:01 PM
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Car: 1991 base firebird
Engine: tbi 305
Transmission: 700r4
Re: gear upgrade recommendation!

i tried to go to 355s on mine. the shop took it apart and then realized that 355s wont fit in the stock housing. he put it all back together then called me and said I needed to buy a new carrier. I would have too if it hadn't taken him 2 weeks to get to that point. I was tired of not having the car. he originally said 2 days
Old 08-13-2017, 09:13 PM
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Re: gear upgrade recommendation!

The housing wasn't the problem. You just needed a 3 series differential.
Old 08-14-2017, 11:44 PM
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Car: 1991 base firebird
Engine: tbi 305
Transmission: 700r4
Re: gear upgrade recommendation!

a 3 series? I'm sure I will still upgrade the gears just not sure to what or when now.
Old 09-17-2017, 08:51 PM
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Car: 90 RS
Engine: 5.0 TBI
Transmission: Slushbox
Axle/Gears: 3.23
Re: gear upgrade recommendation!

2600-3000 converter
3.42 - 3.73 gears
Nice combination
Old 09-17-2017, 09:38 PM
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Car: 1984 LG4 Camaro
Engine: 350 Roller Motor
Transmission: Level 10 700R4
Axle/Gears: Strange 12 bolt 3.42
Re: gear upgrade recommendation!

3.42 is a great gear choice - many have moved to 3.73 and later realized that it is overgeared for the stock TPI power band and kills top speed.
Old 09-18-2017, 08:23 AM
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Car: 89 Firebird
Engine: 355 TBI
Transmission: 700R4
Axle/Gears: 10 Bolt.Posi-3.73s
Re: gear upgrade recommendation!

I went 3.73s, an S10 torque converter, corvette servo and shift kit to go along with it. Feels like a different car. 3.42s would be a better choice though I do agree.
Old 09-18-2017, 09:05 AM
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Car: '86 Bird, 96 ImpalaSS, 98 C1500XCab
Engine: LG4, LT1, L31
Transmission: 700R4, 4L60E, 4L60E
Axle/Gears: 3.73 Tors, 4.88 spool, 3.73 Eaton
Re: gear upgrade recommendation!

For a daily driver, I'd want 3.42's.
For the car in my sig, 3.73's are perfect; it's an occasional driver, sometimes 200+ mile trips, and a bracket race / test'n'tune toy. 3.73's don't really hurt the mileage much. I can still squeeze 26 mpg out of it .....if I try

With a more radical motor setup for primarily strip use, 4.10's would be logical.




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