just wondering what i should do about gears i know that i want 3.73 but not sure what to get and where to get them. i know that i need an installation kit to but which one? and how can u tell if u have an open end or posi rear end? its a 10 bot i do know this and i think there is a tag that says something bout special fluid to use and someone told me i need gm's rear end fluid for posi if i have that tag i cant read what it says though for sure..so if i order gears i need to tell them i ihave a 3 series rear end right? at 70 mph in drive (700r4) i am at 3200 rpm so what gear do i have? someone told me 3.08 or 3.23 so let me know thanks!

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1988 firebird ws6 formula350tpi msd 6al box blaster 3 coil accel 8.8 race wires hooker shorty headers hooker cat back system pro shift light a pillar gauge pod and water temp and air/fuel ratio gauges autometer oil pressure gauge b&m mega console shifter, march underdrive pullies, tpis airfoil cvr high torque starter (love it)
best 1/4 mile run of 14.44@ 96.53
this run is before the new exhaust system

 

You need to find out exactly what gears you have before ordering. If you have 2.73s or 3.08s, you have a "2" series carrier. If you have higher than 3.08, then you have a "3" series carrier, and need to order accordingly.

As for the posi, the misconception is that if you spin one wheel, and the other spins the other way, its open. Thats simply not true. This is characteristic of ALL differentials. That is the point of having a differential. To tell if its a posi or not, is the amount of resistance. If it spins freely, then its either open, or a posi with worn out clutches. If there is considerable resistance, then its a posi. You could also do a burn out and see how many "patches" you leave. I used to leave one long one with my "peg-leg" but now I leave two short ones with my posi. Its great.

------------------
If you live in Southeastern US, check us out!
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'87 Trans Am
S/D TPI retrofit including functional PassKey,
22# injectors,
Whatever chip I feel like burning,
JET AFPR, Ported Plenum,
TB Coolant Bypass, Custom Cold Air,
SSM SFC, KYB Shocks, Boxed LCAs, Wonder Bar,
8mm Accel wires,
Flowmaster Exhaust,
16" GTA rims,
Corvette Servo,
-->14.97 @ 94.9 MPH<--

'97 Bonneville SSE

 

ok thanks for the info so how do i find out what gears my car came with? i know turning the tire and counting how manytimes the drive shaf goes around but are there any other ways? thanks

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1988 firebird ws6 formula350tpi msd 6al box blaster 3 coil accel 8.8 race wires hooker shorty headers hooker cat back system pro shift light a pillar gauge pod and water temp and air/fuel ratio gauges autometer oil pressure gauge b&m mega console shifter, march underdrive pullies, tpis airfoil cvr high torque starter (love it)
best 1/4 mile run of 14.44@ 96.53
this run is before the new exhaust system

 

"All" differentials? Only those with spider gears. Those with a PowerTrax, for instance, would not have the other wheel turn the opposite direction. The point of the differential is to allow the wheels to turn at different speeds, not necessarily in different directions.

All 3rd gen factory rears would do what Tech says, though.

The best way to determine the ratio you have now is to pull the cover and count the teeth on each gear (or find the numbers stamped on the gears).

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82 Berlinetta, orig V-6 car, now w/86 LG4/TH700R. 2.93 limited slip. Cat-back from '91 GTA, Accel HEI SuperCoil. AMSOIL syn lubes bumper-to-bumper. Daily driver, work-in-progress (LG4 w/LB9 block, ZZ3 cam and intake, WP 305 heads ported & polished, Hooker headers & y-pipe, 3" Catco cat).
57 Bel Air, my 1st car. 0.030 over 396, Weiand Action+, Edelbrock 1901 Q-Jet, Jacobs Omnipack, 1-3/4" headers, TH400 w/TCI Sat Night Special conv & Trans-Scat shift kit, 3.08 10-bolt w/Powertrax, AMSOIL syn lubes bumper-to-bumper. Best 15.1 @ 5800' Bandimere. Daily driver while Camaro was being put together.

[This message has been edited by five7kid (edited February 25, 2001).]

 

An 88 Formula 350 will have either a 9-bolt 2.77 posi rear end, or a 9-bolt 3.27 posi rear end. If you have the 3.27 posi, you can get 3.45 gears, or 3.70 gears. You must get 9-bolt specific gears.

If you have the 2.77 rear end, you're out of luck, nobody makes the right gears to change this rear end. You'd be better off swapping to a 90+ 10-bolt rear end, or finding a 9-bolt with a 3.27 or higher rear end.

To see which you have, look at your RPO sticker in your center console. Write down all the codes that start with "G" and post them here. Or, tell us what your RPMs are at when you're cruising the freeway.

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West Coast GM Shootout 2001!
1991 Camaro Z28
5.7L 5-Speed (originally 305)
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Southern California
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well when i got the car i was under it changing the exhasut adn in like yellow chalk there was and '84 on the rear end. i counted teh bolts and there are 10. so i think some one must have put a 10 bolt in there sometime or another where do i find the rpo codes at? oh and at 70mph in drive not od i am at 3200 rpm adn i have a 700r4 thanks

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1988 firebird ws6 formula350tpi msd 6al box blaster 3 coil accel 8.8 race wires hooker shorty headers hooker cat back system pro shift light a pillar gauge pod and water temp and air/fuel ratio gauges autometer oil pressure gauge b&m mega console shifter, march underdrive pullies, tpis airfoil cvr high torque starter (love it)
best 1/4 mile run of 14.44@ 96.53
this run is before the new exhaust system

 

A 10-bolt at 3200 RPMs at 70 MPH would be 3.23 gears, assuming your speedometer is correct.

 

should i switch to a 3.73 gear?

 

Aren't there RPO codes to tell what rear gears you have?

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1986 Firebird, LG4 305, bored .040 over, Crane cam, Edelbrock headers, Hooker Aerochamber muffler, loud and fast.

"Gimme fuel, gimme fire, gimme that which I desire!" - Metallica, "Fuel"

 

yes there are codes but where are they at in the car? also if the previous owner put a different rearend in it as i think he did then they wouldnt help i think it has a 84 rear end in it so i need to figure out what gears it came with i think it must have 3.23 in it atleast that is what i am being told. thanks for all the info guys would a vin number help or not?

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1988 firebird ws6 formula350tpi msd 6al box blaster 3 coil accel 8.8 race wires hooker shorty headers hooker cat back system pro shift light a pillar gauge pod and water temp and air/fuel ratio gauges autometer oil pressure gauge b&m mega console shifter, march underdrive pullies, tpis airfoil cvr high torque starter (love it)
best 1/4 mile run of 14.44@ 96.53
this run is before the new exhaust system

 

I forgot about the Powertrax. And of course, it is so the wheels can turn at different speeds through a turn thanks to the spider gears, its just that the wheels turning in opposite directions is a by product of the driveshaft not being able to turn. Thanks for the clarification.



------------------
If you live in Southeastern US, check us out!
South East Thirdgen


ASE Master Tech + L1
Savannah, GA

'87 Trans Am
S/D TPI retrofit including functional PassKey,
22# injectors,
Whatever chip I feel like burning,
JET AFPR, Ported Plenum,
TB Coolant Bypass, Custom Cold Air,
SSM SFC, KYB Shocks, Boxed LCAs, Wonder Bar,
8mm Accel wires,
Flowmaster Exhaust,
16" GTA rims,
Corvette Servo,
-->14.97 @ 94.9 MPH<--

'97 Bonneville SSE