(WORDS AND PHOTOS BY SCOTT PARKER) – If you didn’t know it already, the bad news about your G-body is that most likely it has one of the worst rear ends GM ever built. Only the Grand National, later T-types, and the Olds 442 were the lucky recipients of GM’s sturdy 8.5-inch 10-bolt. Even the Monte Carlo SS received just a 7.625-inch 10-bolt, a slight upgrade from the original 7.5-incher. And when it comes to rear ends, an inch can make all the difference – a tenth of an inch, not so much. If you’ve got big bucks, you can spring for a 12-bolt, S60, or a 9-inch. But unfortunately I’m not rich, and the market for used 8.5-inch 10-bolts has dried up. Lucky for me, this happened just in time for my 1983 Buick Regal build (aka “G Machine”). The solution: pick up a used Ford 8.8-inch and convert it.
There’s something I’ve always loved about taking a totally pedestrian part with potential, like an 8.8-inch you’d find in a dozen different Ford models, and converting it to work in a high performance application. It really harkens back to the early days hot rodding…before we had so many plug-and-play aftermarket parts. And since we have child labor…I mean a great group of gearhead students at BCIT doing the work on the Buick, it seemed like a great opportunity to explore what it takes to swap in the Ford rear. It was a little bit of an experiment, but thankfully others had done this swap before. The folks at Bulldawg will weld up an 8.8 to match the stock axle’s mounting points, but we liked the idea of doing the work ourselves and using a conversion kit from Baseline Suspension. The upper control arms are the major difference between the two rear ends, so the Baseline kit essentially uses a Mustang UCA and creates a new mounting point on the frame. There is also a major difference in the driveshaft, but we’ll tackle that next time.
For starters, we found a Fox-body Mustang rear end locally, which turned out to be around an inch (total) wider than the G-body. Thankfully a half-inch per side wasn’t enough to throw off our wheel fitment, which would have been an issue with an Explorer or Aerostar rear that are another inch wider. The Crown Vic, Thunderbird, Lincoln Mark VIII, and later style Mustangs are wider still. And if you happen upon a Ranger rear in your travels, don’t bother since the center section is offset. The easiest thing would have been to adapt the drum brakes, get a set of used 4-lug Weld wheels, and go. However, we plan to do some serious road racing and compete in the Ultimate Street Car Series, so that wasn’t going to work. We needed 5×4.75-inch pattern axles, no C-clips (for safety), and mounting provisions for a set of big Wilwood disc brakes. Strange Engineering recommended a set of 28-spline custom axles to work with our stock Traction-Lok and the later style big Ford 9-inch ends (PN H1137).
With that the crew at BCIT started to get to work on installing this rusty rear end into our rusty Buick, in the hopes of one day banging some gears at a road course. Follow along for the details and don’t miss the next installment when we finish off the driveline with a T56 manual transmission!
The down side to using a Fox-body rear is that they never have a performance friendly ratio. Greg Lovell at AntiVenom came to the rescue to tear this 8.8 apart and put in a new set of gears since I’m useless (except when it comes to making corny sexual innuendos). A cutoff wheel and grinder came in handy since this thing was so old and rusty.
We used Ford Racing 3.73 gears and an install kit from Summit Racing. Greg has managed to swap gears in a junkyard before, so in an air-conditioned and fully outfitted shop it was no trouble. Check out that gear mesh! We aren’t expecting any gear whine.
To pull off this swap others have suggested using spherical upper control arm bushings for proper articulation and fitment. We got these from TRZ Motorsports ($110), who used to make a swap kit. We later discovered that with the stock rubber bushings in the 8.8-inch rear, the upper control arms won’t even line up. So these are essential!
Driving out the stock rubber bushings can be a chore – a torch, chisel, and just about anything else you can think of will be needed.
Here are the essentials to the Baseline Suspension kit ($320), which include the 3/16-inch thick zinc-plated Torque box buckets and Mustang-style adjustable upper control arms.
The factory frame pockets had to be modified using large channel locks and a drill. The directions specify which hole to mount the brackets. Once the Baseline pieces were in place, the crew welded them just to be safe.
The directions also specified the length of the control arms. This setup allows adjustability of the instant center that we didn’t have before.
With the rear now located by the control arms, the crew was able to mock up the G-body spring perches for proper location. Since the factory 10-bolt housing was extremely rusted out (this was a 200k mile car from the Northeast), I bought a set of spring perches from DTS.
Thankfully the shocks bolt right up to the rear. We had a set from Detroit Speed on the car already, but they appeared to be too long (we may have to rectify that later). The G-body lower control arms bolted right in, but did require spacers. Baseline sells control arms that are the correct length if you prefer. But, again, we already had aftermarket pieces from DSE and decided to reuse them. The U-bolts on the sway bar were also an easy swap to get in place.
To rectify our mismatched bolt pattern we ordered a set of custom 28-spline axles from Strange Engineering that are much stronger than the factory pieces. A diff was beyond our budget and the stock Traction-Lok was in good shape, so we went with it.
Installing the wheel studs and bearings is a fairly simple operation.
Cutting off the stock ends and welding on the 9-inch ends, though, is a bit of a feat. The welding shop fabricated its own fixture to make sure they’d be straight, however, you can purchase one from Chris Alston’s Chassisworks or pay to have a fab shop do it. I’d recommend the latter unless you plan on doing a bunch of these.
Here are our Wilwood 4-piston rear brakes (PN 140-9219-DR) for the “Big Ford New Style” rear end axle. These bad boys match our front brakes, and have a built-in parking brake.
The 12.88-inch rotors look killer and fit nicely in our 18-inch Grip Equipped forged wheels. Stand by for more with this build as we tackle a manual trans install!
Sources
AntiVenom Racing
813/381-3995
Baseline Suspensions
BCIT
Strange Engineering
847/663-1701
Summit Racing
800/230-3030
TRZ Motorsports
407/933-7385
Wilwood Engineering, Inc.
805/388-1188
new brakes and more gear… fun stuff. Waiting on details for the six speed!
Sweet, thank you for sharing this!
I love seeing elbow grease and junkyard ingenuity in improving a car!
Cool, a bit better than the version of the same story in Car Craft mag & website this month. Those guys at BCIT look pretty handy. I might add that the other reason to not use the Explorer unit (which with it’s 31-spline axles, common 3.73 posi and rear discs would seem like an obvious choice if you were changing the ends/width anyway) is, no mounting ears on the diff casting.
Neat, a lick o paint would have rounded the job off nicely…….
There is definately a great deal to know about this subject.
I like all of the points you made.