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

What rear gear ratio do I have?

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Old Mar 10, 2001 | 03:37 PM
  #1  
JDMZ28's Avatar
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From: Michigan
Car: 2KGTP
Engine: supercharged 3800 L67
Transmission: 4T65E
Axle/Gears: 2.93
What rear gear ratio do I have?

I have an 87' T/A 305 TPI auto. I think it has a 2.73 rear, did they come any smaller than that for this year? The reason I ask is because I put the numbers in CARTEST and it seems my rear end is smaller than that.

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1986 CAMARO Z28 ->
151,000 original miles, 43,000 on 89' vette 350 block, Holley 650 DP, Weiand intake, 1.6 rockers, 1 5/8" headers, no cat, 2 1/2" Flowmaster catback, Mallory coil, March pulleys, T5 with 3.35 1st gear and 0 miles, 90% Centerforce clutch, 3.73 posi, Eibach 1" drop springs, Spohn LCA's, Spohn adjustable panhard rod, Subframe connectors, polyurethane swaybar bushings/endlinks, 2 12" Sound Streams, 2 Infinity 6X9's, 2 Pioneer 6X9's, 800 watt Lanzar Vibe amp. ET 13.22@ 106.4MPH 3300lbs less driver and speakers Next mods-> B&M shifter, Extreme Energy 268 cam, Holley street dom intake.

1987 TRANS AM ->
73,000 miles, 305TPI, auto, all stock.
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Old Mar 10, 2001 | 04:09 PM
  #2  
GMTech's Avatar
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From: Vereinigten Staaten
Car: Take
Engine: Your
Transmission: Pick
Nope, 2.73 is the worst you could get. In '87, all that was offered was:

10-bolt:
2.73
3.08
3.23
3.42

9-bolt:
2.77
3.27
3.45

If its the original rearend, your option codes will tell you if you look them up.

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'87 Trans Am
S/D TPI retrofit including functional PassKey,
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Whatever chip I feel like burning,
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Old Mar 10, 2001 | 05:27 PM
  #3  
AlkyIROC's Avatar
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From: 51°N 114°W, 3500'
Car: 87 IROC L98
Engine: 588 Alcohol BBC
Transmission: Powerglide
Axle/Gears: Ford 9"/31 spline spool/4.86
1987 305 TPI cars with an automatic came with 2.73 gears but also had an option for 3.23 gears. (G92)

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87 IROC-Z Pro ET Bracket Race Car
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Altitude corrected rear wheel HP based on power to weight ratio: 476.5
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Old Mar 10, 2001 | 06:31 PM
  #4  
GMTech's Avatar
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Joined: Jul 1999
Posts: 2,767
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From: Vereinigten Staaten
Car: Take
Engine: Your
Transmission: Pick
Thanks, I didn't know what gears came w/ auto and which ones w/ manual.

------------------
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
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