photos by: the author
With Over 700 hp Planned for Project Redrum, the OEM 10-Bolt Just Won’t Cut It
Some say we’re crazy and others think we should have focused our efforts elsewhere, but when it comes to our ’84 Trans Am, Project Redrum, we’re simply head over heels in love. With a ratty paint finish and a factory drive line that’s best reserved for the scrap heap, on the face of it, they’re probably right.
However, our inner gearhead persuaded us otherwise, and we ultimately elected on going with a large-bore LS3, 6-speed transmission and ultimately, boost. Now anyone who’s ever had the opportunity to infuse real power numbers into an early third-gen F-body will tell you, the factory 10-bolt rear ends can’t handle huge amounts of power and torque.
Typically, the 300 horsepower level is their breaking point, literally, and considering a 416 LS3 with boost is quite capable of making a bit more than that, it was obvious that we’d have to seriously step it up out back. Enter Strange Engineering.
Providing us with multiple ways to fortify the driven axles, Strange’s own Glenn Cope suggested their Dana-based S60 for our build. It’s available as a bolt-in piece, that’s capable of handling just about as much power and abuse as we can throw at it.
Generally, most enthusiasts wait until their rearend actually grenades before they upgrade, but we know better — and chose to rather save ourselves the embarrassment and inconvenience.
Of course, we wanted to ensure we were ordering the right combination of parts, and we felt uncomfortable relying on the old driveshaft. In addition, the design of the S60 differed quite a bit from the old 10-bolt, meaning that the OEM driveshaft was too long for the OEM 5-speed that was still in place during the time of the install.
Here’s what Redrum looked like underneath when we first picked it up — clean, save for the suspension, rearend and exhaust. The good news is, we’re throwing everything covered in rust into the scrap pile. The stock 10-bolt being among them.
Before we could even get into removing the factory rearend, we first had to pull the exhaust, sway bar, lower control arms and Panhard bar. Being the Southwest car that it is, the parts came off fairly easily. All it took was some elbow grease, WD40 and a power drill.
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- Once we had everything loose, we had to lower the car on the lift so we could get the old 10-bolt onto the jack stands for final removal.
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- Popping open the rear hatch, removing the rear interior panels and pulling back the carpet revealed the nuts the held the rear shocks in place.
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- Since we’re pulling out the tired old shocks, anyway. we went ahead and pulled them to install the the Strange S60 and QA1 coil-overs.
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- The final bolts holding the rearend other than the Panhard bar bolts that were the only things holding it into place.
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- The bolts are out, and so was the decrepit 10-bolt. With it, will be the old drum brakes — they won’t be going back on as we have Baer disc brakes going on all four corners.
Our S60 rearend was built exclusively for our project car, so we spec’d 3.73 gears to give us the right combination of acceleration, top end and streetability. We could have just as easily went with a 4.10 gear set, but considering our engine displacement and low-end torque from the blower, it didn’t make much sense to do so.
In addition, this car will be on road courses and small autocross tracks alike, as well as the occasional jaunt on the dragstrip, so we’re looking for that perfect balance in off-the-line acceleration.
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- Our S60 was equipped with 35-spline axles. We plan on going with Baer rear disc brakes in Redrum so caliber mounts were implemented into the rear axle as well. Unfortunaltey, the kit does not allow for factory ’82-92 rear disc brakes, so you’l have to spec them in pre-’81 style or ’93-02 style.
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- Strange ships their rearends empty, however, they include three quarts of synthetic Lucas Oil 85w-140 differential fluid. It’s a formulation that’s designed for high performance and racing applications.
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- I suppose you can technically say that we still have a 10-bolt, but that would be an insult to the high-quality hardware that Strange implements into each of their S60 rear axles. Helical Gar Differential is also installed oil our unit. The black powdrercoat is an additional option, but being as how we plan on using tis car at the track, drag strip and on the street (in the Midwest, no less we went ahead and ordered the powder coat.
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- Strange also included a set of polyurethane bushing sway bar end links. These will not only help improve handling a bit, but will also help the sway bar keep the wheels to the pavement on launch.
Strange S60 1982-92 F-body Features:Ā
- S60 housing with F-Body mounts installed ā H60GFME
- 35 spline Alloy Axle Package ā P3502 / P3504
- 4 3/4ā³ bolt circle
- Choice of wheel stud kit ā A1035 / A1025 / A1026
- 35-spline helical gear differential ā D3523 / D3533 / D3534
- Selection of gear ratio (3.54 / 3.73 / 4.10 / 4.30 / 4.56 / 4.88 / 5.13 / 5.38)
- S-Series pinion yoke ā U1600
- Pinion yoke u-bolt kit ā U1610
- Dana / Spicer steel cover ā D3505
- Extended sway bar link kit
- Lucas oil package
- Fully-crated ā No extra charge
This was quite an exciting moment for us, after a few months of it collecting dust in the box (being sidelined by other projects, our ’84 Trans Am was finally getting a rear end worthy of our soon-to-be 700+ horsepower powerplant. Installing the S60 was much like removing the old 10-bolt, essentially reversing the steps. However, we won’t be reinstalling the 33-year old stock suspension or exhaust. If you pay close attention to the rear wheel wells, you can get a glimpse of the QA1 coil-overs. A complete BMR Suspension system would also go in place, but we’ll delve more into that at a later date. We’ll give you a quick sneak peek below, though.
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- Once we had the rear end solidly in place, we were able to pull the drain/fill plug for filling It removes easily, with an Allen head socket. The good folks at Strange were also kind enough to use white thread locker in advance, so you shouldn’t ever have to worry about it seizing inside the threading.
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- There’s no real science behind filling up your rear diff; basically you’ll know when it’s full as the access will begin to leak out of the fill hole. You can pour it directly in with the nipple on the Lucas Oil bottle, or you can use a hose which wasn’t really necessary in our situation, as the hole was easily accessible.
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- We installed the driveshaft from Strange to be able to move the car around while we waited our upcoming 6-speed transmission conversion. We will have to remove it at a later date to shorten for the trans swap, though it worked wonderfully for our stock 5-speed.
Here’s the final product of the S60 installation. As you can see, there’s quite a lot of BMR Suspension hardware underneath there, be we’ll focus more on that at a later time in a separate segment. The great news is, we can now take great confidence ion knowing that our new rear axle will be able to handle as much action as we can throw at it, without leaving us broken down and stranded, either on a highway or on a race track. It’s certainly an investment for sure, but one that will save you plenty of time and headache later down the road.
Rick Seitz is the owner and founder of GMEFI Magazine, and has a true love and passion for all vehicles. When he isnāt tuning, testing, or competing with the brandās current crop of project vehicles, heās busy tinkering and planning the next modifications for his own cars.
