SS #670 Modifications:

I ordered my SS with the Auburn differential SLP upfit option. In retrospect, this was a poor choice given the way I drive the car; the Auburn is better suited to drag than road racing. Even performing maintenance every 7K miles, mine lasted less than 50K miles and then started behaving like an open differential (except with more interesting noises, especially when cold).

Although I could have probably exchanged my worn out Auburn for less than $100 under their differential replacement exchange program (D-REX) I had already decided to go with a gear based limited slip made by Tractech (now owned by Eaton) or Torsen. Tractech had stopped producing their original Truetrac F-Body application and were at least six months away from releasing an updated model so I looked more closely at Torsen.

[Torsen Traction]


There are several different Torsen differentials that work with the GM 7.625" rear end found in the 4th generation F-Body. The first is the OEM Torsen T-2. That was the stock unit when my car was built. Next is the aftermarket T-2 (also known as the heavy-duty T2) which is similar in operation and performance to the OEM version but stronger. The last application is the T-2R Racemaster which was first offered in 2001.

[Label] [T-2R]

The T-2R has a higher bias than the T-2 (4 to 1 vs. 2 to 1) which supports operation with even lower torque inputs. This seemed like the way to go so I ordered one from Reider Racing (who are the sole distributor of Torsen products in the US). The part number is GM7/ZT28HB which decodes to GM 7.5, Zexel Torsen, 28 spline, 3-series carrier (3.23 and numerically higher ratio) and high bias.

[exploded view]

[General Motors]


My SS is a M6 and came with 3.42 gears. I had been toying with the idea of trying something lower; 3.73 seemed like a good compromise between 3.42 and 4.10. There are tons of brands available including Motive Gear, Precision Gear, Richmond Gear, Superior Axle & Gear and Strange Engineering.

[Label] [Gear set]

In the end I went with genuine GM Performance gears (GM 14091497). GM switched from forged steel to austempered ductile iron (ADI) in 1977. The main motivation was cheaper production costs but these gears are also quieter and lighter.



The install kit I bought from Randy's Ring & Pinion came with Timken bearings. They were made in the USA; the Timkens I removed from the original pinion were made in Canada.

[Inner pinion bearing] [Bearing set]

I also picked up a spare (non-Timken) inner pinion cone from the local parts house. I used a Dremel tool to clearance it so it would fit loosely on the pinion. This made setting the pinion depth easier because it wasn't necessary to press the bearing on/off to change pinion shims.

[TA Performance]

Rear end girdle

I used TA Performance rear end girdle. It's stronger than the AAM cover that was part of my SLP Auburn upfit option and also provides supports for the main caps. It comes with allen head bolts, washers and a nice gasket that looks the same as the factory part (GM 26016661). The one advantage the AMM cover had is that it has a cooling channel built in; oil flung from the ring gear enters it and exits on the carrier bearings.

[Rear end girdle] [Rear end girdle]

I wanted to install an Auto Meter replacement 250° F electric temperature sender (2258) in the cover (using a brass 3/8" to 1/8" reducer) for use with my oil temperature gauge but the sway bar is too close. Instead, I installed the sender in the oil fill hole (using a brass 1/2" to 1/8" reducer).

Installation notes


The combination of the Torsen Racemaster and 3.73 gears are pretty amazing. My SS hooks up great coming out of a turn or from a standstill and reminds me of how the Auburn felt when it was still working properly. However I probably shouldn't discount the contribution my recently upgraded torque arm and shocks make to the overall package.

This upgrade was a lot work and I spent a lot of money on parts but I learned a lot and I couldn't be happier with the end result.

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[SS #670 Gear ratio calculator]
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[SS #670 Oil report]
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[Craig's home page]

[SS #670 The Super Sport Owners Association]
[SS #670 Miscellaneous]
[SS #670 EMail Craig]
[SS #670 Mods: Sway bars]
[SS #670 Mods: Shocks and struts]
[SS #670 Mods: Springs]
[SS #670 Mods: Panhard bar]
[SS #670 Mods: Lower control arms]
[SS #670 Mods: Subframe connectors]
[SS #670 Mods: Adjustable torque arm]
[SS #670 Mods: Differential]
[SS #670 Mods: ZR1 wheels]
[SS #670 Mods: Shock tower brace]
[SS #670 Mods: Brakes]
[SS #670 Mods: Hurst billet plus shifter]
[SS #670 Mods: Heel/Toe throttle extension plate]
[SS #670 Mods: Driveshaft safety loop]
[SS #670 Mods: Radiator]
[SS #670 Mods: Oil cooler]
[SS #670 Mods: Clutch]
[SS #670 Mods: Differential vent tube]
[SS #670 Mods: Shift light]
[SS #670 Mods: Air box lid]
[SS #670 Mods: Polyurethane bushings]
[SS #670 Mods: Auto Meter gauge pod]
[SS #670 Mods: Disable CAGS]
[SS #670 Mods: Disable daytime running lights]

[SS #670 Mods: EFILive]
[SS #670 Mods: LS1-edit]
[SS #670 Mods: Battery]
[SS #670 Mods: Valentine One remote display]
[SS #670 Mods: Headlights]
[SS #670 Mods: iPod integration]
[SS #670 Mods: LEDs]
[SS #670 Mods: Cellular phone]
[SS #670 Mods: Zaino Bros' show car polish]

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Craig Leres