There's nothing like having the confidence of knowing your hot rod's got the strength to handle almost anything you can, or plan, to throw at it. Especially the rearend. If you participate in any kind of straight-line racing, or any kind of racing for that matter, you'll need a set of beefy gears that can hang tough through a long day at the track. Merely bolting on a set of drag tires or slicks can play havoc on a flimsy factory 10-bolt. Add into the equation some VHT, or any other traction enhancer and you're just asking for trouble.
Even on the street, a set of fat, sticky tires coupled with some uneven pavement could result in a ring gear teeth-shattering episode at the hit of the throttle.
Simply put, more traction means more stress on your driveline components.
01 To get started, Mike...
01 To get started, Mike removed the old cover. Be pre-pared with a container underneath to capture the used oil.
One remedy is to ditch the stock 10-bolt and scour the swap meets for a used 12-bolt setup. This could take more time than you're willing to invest, could induce sore feet, and there's a good chance you'll be driving home empty handed. And, if you do happen to find one in good shape, it may be rough on your wallet as well.
Aftermarket companies that offer 12-bolts are an excellent source, as they offer a plethora of high-quality units. But if your racing budget is slightly less than your grocery bills, this route may cost a bit more coin than you're willing to spend on your "little hobby."
For our purposes we'll be upgrading a factory 10-bolt rearend with Moser's 1970-and-later 10-bolt upgrade kit for factory late-model GM passenger cars. It uses an 8.5 diameter ring gear (vs. the 8-7/8-inch 12-bolt) and stronger 30-spline axles (vs. the stock 28-spline) and added a 30-spline posi unit. This is a drag car, so we went with 4.88 gears and a C-clip eliminator kit, which adds safety in the case of a broken axle. If such an accident were to happen with this system, the wheel would remain bolted to the backing plate.
02 Next up was to remove...
02 Next up was to remove the driveshaft by removing the u-bolts from the yoke.
To top things off we added the Moser cast-aluminum performance cover. Not only does it look great, it incorporates preload screws for bearing cap support, added strength and also eliminates deflection.
For this installation, Moser included Richmond gears and a Detroit Truetrac limited slip differential. This will provide us with plenty of strength (about 50 percent over stock components) necessary for our high 10-second 1980 drag Camaro.
We could have gone with a brand new Moser 12-bolt as a legitimate option for even more strength (the housing is stronger than an original factory, and the tubes are welded in a full 360 degrees and are 1/4-inch thick, as opposed to the 1/8-inch thick factory housing), but we wanted to show what's available for a bit less dough. The Moser 10-bolt upgrade costs just about half, give or take, than the complete Moser 12-bolt system, and will provide plenty of strength for our needs.
We enlisted the installation services of Mike Bastio from Toy Shop Transmissions in Pomona, California. Mike informed us that labor for an install like this will vary from shop to shop, but suggested that you put aside another $400 if you have someone else do the work.
Although we'll be using this unit in a drag racing situation, we highly recommend this upgrade for street use as well. With today's high-performance engines making more horsepower than ever before, you can't afford not to pay attention to your assets. So don't take a chance, or you could risk losing your rear ... end.
| Compare The Cost |
| 10-Bolt 8.5-inch Components |
| 30-Spline Custom Alloy Axles | $315.00 |
| Stock Chevy Studs | $17.50 |
| GM Eliminators | $150.00 |
| 4.88 Gears | $175.00 |
| 10-Bolt Cover | $160.00 |
| TrueTrac Posi (30-spline) | $445.00 |
| Setup Kits | $100.00 |
| Total | $1,362.50
+ Shipping |
| |
| 12-Bolt Leaf Spring & Bare |
| Leaf Spring Housing (M/E Ends) | $739.00 |
| M/E Custom Alloy Axles | $315.00 |
| Bearing Package | $100.00 |
| TrueTrac (30-Spline) | $465.00 |
| Moser Pro Street Gears | $155.00 |
| #R12B Setup Kit | $100.00 |
| #PY100 Pinion Yoke - 1350 | $130.00 |
| #7110 Performance Cover | $160.00 |
| Setup Labor | $150.00 |
| Crate Fee | $25.00 |
| Discount For Complete Rear | -$ 75.00 |
| Total | $2,264.00
+ Shipping |
 03 Before removing the bearing...  03 Before removing the bearing caps it's a good idea to put identifying marks on each cap signifying right and left. It's very important these are reinstalled correctly. |  04 Next was to remove the...  04 Next was to remove the center-pin bolt to get the axles out. |  05 Our center-pin bolt was...  05 Our center-pin bolt was broken, so we had to cut the differential pin in order to get the center pin itself out. It isn't entirely uncommon for this to happen, so be prepared. |