Excel 3.55 thick-gear ring and pinion set in 8620 steel for the GM 7.5 and 7.625 inch 10-bolt rear axle, replacing GM 10035674 and G875355X.
Most GM 7.5 and 7.625 inch 10-bolt rear ends left the factory with lazy highway ratios. Owners of G-body Monte Carlos and Cutlasses, third-gen Camaros and Firebirds, S-10 and S-15 pickups and similar cars usually come looking for a 3.55 for one of two reasons: the old gears have started to whine, or the car feels flat off the line after a tire, engine or transmission change. The Excel from Richmond GM75355TK is a 3.55 set built for that axle, and the TK suffix is the detail that matters most.
The pinion turns the ring gear, which is bolted to the carrier with ten bolts, and the ratio between their tooth counts sets how many times the driveshaft turns per wheel turn. Summit Racing's spec sheet lists this set at 39 ring teeth and 11 pinion teeth, a 7.5 inch ring gear, a 27-spline pinion with a 1.438 inch pinion shaft and standard rotation. GM 7.5 carriers come in two series split by ratio. Deeper ratios have a smaller pinion head, so they normally use a carrier with a thicker ring gear mounting flange. A thick-gear set moves the extra material into the ring gear instead, which is how this 3.55 bolts onto the 3.08-and-down carrier. That can save buying a second carrier, or a new limited slip, just to change ratio.
First confirm you have a 7.5 or 7.625 inch axle and not an 8.5 or 8.6. Measure the ring gear or read the axle code on the right tube. Next confirm your current ratio from the code or by counting driveshaft turns per tire turn. Most important, confirm your carrier series. This thick gear fits the carrier used with 3.08 and numerically lower ratios. If your axle has already been geared 3.23 or deeper, it has the other carrier and needs a standard set such as the Motive GM 7.5 3.73 set. Our GM 7.5 and 7.625 10-bolt problems guide covers the common failures and what a rebuild involves.
The listing places this set in the GM 7.5 and 7.625 inch 10-bolt rear axle and shows it replacing GM 10035674 and the G875355X aftermarket number. That axle went under a long list of 1970s through 1990s GM cars and light trucks, including Buick Apollo, Century and Regal, the G-body Monte Carlo and Cutlass, Camaro and Firebird, and S-10 and S-15 pickups. GM changed bearings and details over that span, so match your axle code, carrier and ratio, or send us the year, model and VIN and we will check it before it ships. More drivetrain parts are in our hard parts section.
This is the gear set only, with no bearings, shims, crush sleeve or seal, so plan on a bearing kit such as the Excel GM 7.5 differential bearing kit or a complete USA Standard 1982-1999 GM 7.5 overhaul kit. Revolution Gear and Axle's setup chart gives these GM 7.5-7.6 starting points: 0.035 in starting pinion depth, 12-15 in-lb pinion bearing preload, 0.006-0.010 in backlash, 65 ft-lb on the ring gear bolts and 60 ft-lb on the bearing caps. Remove the C-clips and axles before pulling the carrier, keep the carrier shims sorted left and right, and start pinion depth with the original shim. Crush the new sleeve in small steps and stop as soon as preload is in range. Check the pattern with marking compound, then fill with 75W-90 gear oil, adding friction modifier for a factory clutch-type limited slip. Go easy for the first few hundred miles, avoid towing or hard launches, and change the oil after break-in.
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| Replaces | |
| Axle | |
| Ratio | |
| Ring gear | |
| Material | |
| Weight |
Doing this repair right usually means replacing these at the same time. Same transmission, ships together.
Probably not without a carrier change. This thick gear fits the carrier used with 3.08 and lower ratios. A 3.42 axle normally has the deeper-ratio carrier, which takes a standard 3.55 set.
Both have ten cover bolts, but the 7.5 ring gear measures about 7.5 inches and the cover is smaller. The axle code stamped on the passenger side tube also identifies it.
New pinion and carrier bearings, races, shims, crush sleeve, pinion seal and ring gear bolts from an install or overhaul kit, plus marking compound and 75W-90 gear oil.
Yes. Changing ratio changes the driveshaft speed per mile, so a mechanical speedometer needs a different driven gear and an electronic one needs recalibration.
It marks the thick ring gear version. Summit's data describes it as a thick gear for use with the 3.08 or numerically lower ratio carrier.
