I was wondering if anyone could give me some useful information as to finding out what size gears I have in my rear end. I've heard that to switch to lower gears, the carrier must match whichever gear you go with. I'm looking for a little more zip out of the hole, and I'm just not gettin it with the rear end I have. I can't even break the tires loose. Is there a tag on the rear end which tells me what gears I'm running? (10 bolt gm on 85 T/A, stock)

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Put it in third gear(D)and drive to exactly 75mph,look at the rpms,mine was 2730 rpm which =2:73 rear,3230rpm=3:23,etc,another board member told me this trick,it really works:0

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Drive it like you stole it

 

If your not breakin the tire loose , it's definately a 2.73

 

The code should be stamped into the front side of the axle tube near the center. I don't remember if it is on the driver or pass. side. Then look up the code online or in a service manual.

 

Mark the driveshaft and both rear tires. Now as you turn the rear tires at exactly the same speed, count the turns of the driveshaft, down to the 1/4 turn. When you get the tires back to the starting point you are done. If you had lets say, @2&3/4 turns, you have 2.73's. If it was just short of 3&1/2 turns you have 3.42's, etc.

 

here is an awsome site that came up somewhere: http://www.f-body.org/gears/

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• 89 Formula 305 WS6
  SFC's, LCA's, Air Foil
  Spohn Panhard Bar
  Flowmaster Cat Back, Tranny Cooler
  A/F Ratio Meter (not a mod but it sure spurs interest)
  Trans Temp Gauge
  Most "Free" Mods
  3:73, Zexel Torsion Posi
• 90 Eagle Talon 2.0
  (Winter Beater)
  Mods? Um, no

 

70 not 75

 

I'll try that this morning. I looked for the code on the axle housing, but the number didn't match any in my service manual. Is there anywhere on the web I can go and put in the code I have and it will tell me?

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1985 Trans Am
transplanted 350 4blt from 83 'burban, stock
freshly rebuilt 700r4
tweaked Quadrajet on Performer intake

 

What axle code did you find? Perhaps we can check our resources for you.

My donor car had no tread left on the right/rear tire. I could easily break loose with the 3.08's in the car when I made the swap, and wasn't much harder with the 2.73's when I put that rear in for awhile. Even now, with the 2.93 posi, I can break 'em loose. Are you sure you have a gear problem? I'm talking about a mile above sea level!

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82 Berlinetta, orig V-6 car, now w/86 LG4/TH700R4. 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/'87 LB9 block, ZZ3 cam and intake, World 305 heads, Hooker headers & y-pipe, 3" Catco cat & 3" cat-back).
57 Bel Air, my 1st car. 0.030 over 396, 9.7 CR forged TRWs, Weiand Action+, Edelbrock 1901 Q-Jet, GK 270 cam, Magnum rockers, Jacobs Omnipack, 1-3/4" Hedders & 3" Warlock header mufflers, TH400 w/TCI Sat Night Special conv & Trans-Scat shift kit, LT MegaShifter, 3.08 8.2" 10-bolt w/Powertrax, AMSOIL syn lubes bumper-to-bumper. Best 15.1/95.5 @ 5800' Bandimere.

 

Okay, as far as I can tell, the code is an alpha numeric 3 digit code, right? The only such creature on mine is 9KR (with a C0781 after that). Other than that, I can find only the pumpkin case casting number of 22522676MN. It is a 10 bolt and not 9 bolt differential cover. I'm about ready to just be happy with what I've got!! (not!)

 

If the car is up where you can read the code, it takes @ two minutes tops to do what I said and you will know for sure what you have.

 

Hmmm....might that axle code really be 8KR? If so, it decodes out to be a 3.08 open rear.
I've got the codes for 82-89 on the tech page here-> http://www.hioutput.com/tech/ratio.html and other goodies here-> http://www.hioutput.com/tech.html ...check'em out....

Pete

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Pete's Place
HiOutput Tech Page
83 SC
originally a V6...now
210+k mile LG4/5-speed
14.935@94.14

 

It is completely possible that it is an 8kr instead of a 9....my neck was rather strained looking....it's on the passenger side axle tube, if I was looking in the right spot. I'm going to mark the driveshaft and the tires and do a check like was suggested tomorrow. I'll see if that is close to the 3.08 that the code may be. That would make it easier to upgrade to a 3:52 gear without having to change carriers. I'll cross my fingers and post tomorrow night. Thanks for the web tech pages....they are bookmarked!!

 

3.08 is still a 2 series carrier. stock type 3.42's won't fit(they are 3 series) However, you can get aftermarket gears in what every series you need. Such as 3.42 2 series gears.


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350 with stealth intake, holley carb, 470 lift cam. 700r4 with .5 boost valve, vette servo, tci lock-up kit, B&M megashifter. Richmond 3.73 gears, powertrax locker, timkin bearings, synthetic lube. Custom 3 inch single into 2 2.5 pipes. 1 1/2 drop springs, 1 5/16 solid front sway bar, 1 inch rear bar, custom subframe connectors, custom LCA relocation brackets. Kobel ground FX, current red metallic paint. Lots of other stuff...
82camaro