60>10: Strange Engineering’s Bulletproof S60 Rear End
Strange Engineering’s bulletproof S60 rear end cures our 10-bolt blues and gets the STI Killer back in action
From the January, 2013 issue of GM High-Tech Performance
By Justin Cesler
Photography by Justin Cesler
This is the article where we tell you that 10-bolt in the STI Killer finally broke and you get to write us letters saying, “we told you so!” And, that’s fine; bring on the mail. Seriously, I like getting mail…send it. Regarding the business at hand, if you recall, the Killer has been running a factory supplied 10-bolt since the beginning (we originally built it in the August 2010 issue) and it’s been stuffed with the best goodies we could find, and even narrowed for our new wheels, for the entirety of the project’s life. But, for all that was great about the little 7.625-inch rear, it eventually did what they all seem to do and managed to chip a couple of teeth off the ring and pinion. Unlike many a 10-bolt of the past, we managed to do this one on a particularly nasty downshift (no brakes into a hairpin at Sebring) and still got lucky enough to take the car to the CHP Nationals and make a couple of passes before the rear said goodbye for good. Physical carnage aside, we never really got to launch the car hard at the track, and we always knew it was just a matter of time before this happened, so there really was no love lost seeing the ol’ rusty 10-bolt head on out the door, even if we knew it meant hearing “I told you so” from every e-thug with an email account.
01. You can’t be out on track slaying imports if you’re broken, and with our 10-bolt down for the count, it was time to step up our game and get serious. What you see here is Strange Engineering’s bolt-in S60 F-body kit, which shipped to us with everything necessary for a complete conversion including a new chrome-moly driveshaft, and 3-quarts of gear oil.
02. Strange designed the...
02. Strange designed the S60 from the ground up to work in a plethora of applications and the cast iron housings were designed perfectly for a torque arm equipped F-body. Inside, the S60 features a massive 9.75-inch ring gear and a Strange Trac helical differential unit bolted in place by upgraded and enlarged main caps. For the Killer, we optioned our S60 with a 4.10:1 ring and pinion, along with 35-spline axles.
03. Large 3.150-inch axle...
03. Large 3.150-inch axle tubes are fully welded to both ends of the S60 for additional strength and the entire unit shipped assembled, which made for a quick and easy install without needing access to a press or any special tools. If you’re looking to save some cash, you can send Strange your stock backing plates and reluctor rings (4-channel) and they’ll assemble them on your S60 free of charge.
04. Along with the cast torque...
04. Along with the cast torque arm provisions, the S60 comes with all of the correct brackets to make everything work in a fourth-gen F-body. Fully welded to the axle tube, you can see the driver’s side suspension mount, which connects any factory or aftermarket Panhard bar, shock, spring, and lower control arm to the housing. Also note the welded sway bar mounts, which are an upgrade from the stock 10-bolt design.
05.0 Pulling the factory...
05.0 Pulling the factory 10-bolt rear is a very simple job and one that can be done by any competent GMHTP reader, although it is heavy and awkward at some points.
But where we’re headed now, we’re not ever going to have to worry about the rear end situation again, thanks to the highly regarded rear end specialists at Strange Engineering. After a quick call to J.C. Cascio at Strange, we were sold on the idea of an S60 for the Killer, even though it seemed a bit like overkill at the start. Up front, the weight seemed tremendous, with the cast iron S60 ringing in at over 200-pounds fully assembled. But, to be fair, that’s only 15-pounds more than a 9-inch, and just 25 more than a 12-bolt, and the advantages really do speak for themselves. First, lets look at the housing itself, which has been cast by Strange specifically for several applications, including the late model F-body. What you get is a bolt-on nodular iron housing with beefy torque arm mounting provisions that was designed “to be more rigid through the use of computer modeling for improved durability and quieter, long-lasting gears.” Inside the S60, Strange offers a variety of differential and ring and pinion options, although we chose to run with the company’s Strange Trac helical differential, 4.10:1 ring and pinion, and 35-spline axles. Unlike a traditional Posi unit, the Strange Trac features six massive pinion gears to control differential action, instead of clutch packs, which can wear out over time, and is positioned as an excellent unit for street/strip, road racing, autocross, and drift cars, which pretty much sums up the Killer in a nutshell. The 4.10:1 ring and pinion matches our old gear ratio, which we loved around Sebring, and the 35-spline axles are an obvious upgrade over the 28-spline units we had before.
05.5 To begin, Kyle Miller...
05.5 To begin, Kyle Miller of AntiVenom unbolted the factory brakes from the backing plate and ziptied the entire assembly to the chassis of the Killer to keep them out of the way and still connected to the factory brake lines.
06. Attached to the factory...
06. Attached to the factory housing is a little bracket that holds the brake lines in place. Kyle removed this bracket from the housing, freed up the remaining lines from the axle tubes, and slid everything up and out of the way. Doing it this way allowed us to keep the brake system sealed, which meant we didn’t have to bleed it later on.
07. Next up, the BMR sway...
07. Next up, the BMR sway bar was dropped out of the way, which required unbolting the factory U-bolts (one on each side of the axle) and the sway bar endlinks. You won’t be reusing the U-bolt mount, but you will need the sway bar bushings, so keep them close for the installation of the S60.
08. With the rear hanging...
08. With the rear hanging by the shocks and lower control arms, Kyle removed the two through bolts from the rear housing and pushed the BMR torque arm out of the way. The torque arm to housing bracket will need to be modified slightly to work with the new rear, but let’s not get ahead of ourselves.
09. If you’re tackling this...
09. If you’re tackling this installation at home, this is the part that sucks. If you’re lucky enough to have a lift and a proper jack, like AntiVenom does, than it’s pretty easy to lower the factory rear out of the way. Of course, don’t forget to disconnect the shocks, LCAs, and Panhard bar first!
10. Out with the old and...
10. Out with the old and in with the new. At 203-pounds, the S60 isn’t a lightweight rear, but sometimes that is the price you pay for such robust performance and reliability. For those watching weight at home, that’s exactly 50-pounds more than the 10-bolt we pulled out (203 vs. 153), so keep that in mind when you’re considering your options.