Project Ron Burgundy: Rear End Considerations

Project Ron Burgundy, our S10 time attack build and official LS1tech.com project vehicle, is here with another update. Right now it’s engine is getting put together along with the front end from QA1. However, while we are still waiting for the final word on tires we decided to look at what we would need to make the OE Wheels Corvette Stingray wheels work and one of the things we had to decide on is related to the rear end. The question at hand: Should we go Ford 8.8 or GM 8.5 10-bolt?

So, let’s get you familiarized once again with Project Ron Burgundy. It’s a 1995 Chevrolet S10 that we’re doing a LS2-based LH6 swap with to go time attack (time trial for the SCCA and NASA folks) and autocross racing in. The front end is getting the QA1 S10 Race Front Suspension – of which we’ll have an install video soon – along with using a 4L60E automatic transmission to be different and give a slightly less expensive option to the T56, maybe.

The wheels we’ll be using are the OE Wheels, LLC Corvette C7 Stingray reproduction wheels. These will be 17×9.5 front and 18×10.5 rear and…

They will also be Corvette-spec backspacing. That’s a problem. Corvettes can fit massive wheels, but use particularly specific offsets that are a bit different than what would be used with most other vehicles. Corvette wheels use a numerically high offset, and may be marked as “+60,” while typically a rear-wheel drive car with wide wheels and tires would use a numerically lower offset to push the wheels further outboard. What this means is that the wheels will sit too far inside the wheel well and contact the body and suspension components. Fear not, for we have a plan!

Front End

We will be using a bolt on spacer and Monster Lug Nuts from Wheel Mate to cover the front and give us the spacing we need. Before you panic about using spacers, two things to consider: one, the bearing load will come out the same as a 17×9.5 0-offset wheel and that is the recommended offset for a 9.5-inch wide wheel on the S10. Two, having worked with Wheel Mate before on a Time Attack/Pikes Peak car, these spacers are proven safe provided you install them correctly. This means checking the torque of the lug nuts after about one-hundred miles of installation – and yes, that means taking the wheels off and on and re-inspecting them after one-hundred miles. Anyhow, enough of the rant.

Rear End

The rear, however, presents an interesting option. I could do spacers on the stock rear end and, again, it’d be fine. However, the GM 7.625 in this S10 doesn’t exactly hold a great reputation for strength. I could install parts into it and make it stronger, have a limited-slip differential, and convert to a disc brake system but that can come out to be pretty expensive and it’s still a 7.625 10-bolt rear end. I’m not exactly for that but there are a couple of options out there for me.

Keeping it in the Family – The GM 8.5 10-Bolt

The GM 8.5 10-bolt from the Blazer is a huge step up from the 7.625 that’s currently in Ron. It would come with disc brakes, potentially a factory locker, and would be fifty-nine-inches wide (hub face to hub face) while still bolting up to the S10 spring-under rear suspension design and mean that I would only need a half-inch spacer. However, it’s also a strangely an expensive axle to find. Another option that would probably easier to find cheaper would be the 8.5 from the four-wheel-drive S10 as it’s also but it would still be drum brake and it may also not have a locker for its price. If I can find a ZR2 rear-end, that would be great but it would probably be a little too wide as it’s sixty-three-inches wide WMS to WMS. However, any modifications needed to be done – from ring gears to axles – will all be more expensive in comparison to the Ford 8.8.

Hatfields helping the McCoys – The Ford 8.8-inch

Yes, it is a serious consideration as it has a lot going for it. Provided I find one from a 1995 to 2002 Ford Explorer, it will be fifty-nine-and-half-inches wide hub face to hub face, meaning no spacer would be required. It also comes with a factory locker, but that one sucks as most factory ones do that weren’t Detroit lockers or a real clutch-type LSD. It also comes with factory disc brakes along with 31-spline axles with three-and-quarter-inch axle tubes. Not only could you find it in 3.55:1 to 4.10:1 from the factory but you can also find nearly any ring and pinon combination in the junkyard for stupid cheap to brand new for relatively cheap and still high quality. The complete axle itself is cheap to find and plentiful when compared to the 8.5 GM along with being a little stronger with an 8.8-inch ring gear.

However, there would be a catch, a few, actually. First, the Explorer axle would be five-by-four-and-half wheel bolt pattern. I would need to convert the axles or buy a pair in the five-by-four-and-three-quarter wheel bolt pattern. That would also mean drilling the brake discs for this bolt pattern as well. Second, the axle pinion is offset. This isn’t a big issue with a two-piece driveshaft like the S10 has. Third, I would have to get a conversion U-joint or modify the aluminum one from the Explorer. Finally, I would have to modify the spring perches by elongating the holes for the U-bolts towards each outside corner. This also isn’t a huge deal as the amount needed is very small and covered by using a washer on the nut.

Or, I could go really crazy and go with a Ford 9-Inch. What to do, what to do? We want to hear from the community: which route would you take and why? Stay tuned for the next episode of Project Ron Burgundy!

Project Ron Burgundy is sponsored by these fine vendors. We thank each and every one of them for their support: