Will 3.70's fit?
10-15-2009, 11:10 PM
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Will 3.70's fit?
I've searched around and am still not quite sure if I can figure it out. I have the RPO codes GH3 for the 2.77 gears and G80 for the positraction. I have the 9 bolt borg warner and wanted to upgrade to 3.70 gears. I'm not really sure what the 2 or 3 series means. If I got the 3.70 would they be a direct fit? http://www.summitracing.org/parts/MGR-GM9-370/ Also is this brand any good? I would be taking it my transmission shop to get installed. If it wouldn't fit, what would I need to do to be able to upgrade my gear ratio? Thanks.
10-15-2009, 11:16 PM
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Car: 87 GTA
Engine: L98
Transmission: 700R4
Axle/Gears: Dana M78 3.27 posi
Re: Will 3.70's fit?
You'd need a 3-series carrier, to fit the 3.70 gears. IIRC, the 2 series was only good up to the 3.08.
10-15-2009, 11:44 PM
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Car: 87 IROC L98
Engine: 588 Alcohol BBC
Transmission: Powerglide
Axle/Gears: Ford 9"/31 spline spool/4.86
Re: Will 3.70's fit?
The carrier is what holds the ring gear. Typically called a posi if it's a limited slip.
Changing gears requires a complete rebuild since you also need to pull the pinion gear and with the pinion depth controlled by shims under the inner pinion bearing, it's not something that the typical person can do properly.
To upgrade to a better gear ratio, you need to remove the ring gear and carrier and remove the pinion gear. To remove the carrier, the axles need to be pulled. To install a deeper gear, you'll need to track down a 3 series carrier. Unless you can find a donor 9 bolt diff with 3.27 or 3.45 gears, your best bet will be to get a posi from Australia. The 9 bolt was only available in third gens for a few years so there's very little available in the aftermarket except for a few gear sets and bearing kits. If you do find a used posi, it will probably be worn out.
Although it's a slight step backwards, it may be easier and cheaper to just install a 10 bolt under the car with a better posi than what was offered in the 9 bolt.
Changing gears requires a complete rebuild since you also need to pull the pinion gear and with the pinion depth controlled by shims under the inner pinion bearing, it's not something that the typical person can do properly.
To upgrade to a better gear ratio, you need to remove the ring gear and carrier and remove the pinion gear. To remove the carrier, the axles need to be pulled. To install a deeper gear, you'll need to track down a 3 series carrier. Unless you can find a donor 9 bolt diff with 3.27 or 3.45 gears, your best bet will be to get a posi from Australia. The 9 bolt was only available in third gens for a few years so there's very little available in the aftermarket except for a few gear sets and bearing kits. If you do find a used posi, it will probably be worn out.
Although it's a slight step backwards, it may be easier and cheaper to just install a 10 bolt under the car with a better posi than what was offered in the 9 bolt.
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