We’ve been living dangerously with Project Magneto, our 10R80-equipped 2018 Mustang GT ever since we put on the meaty Mickey Thompson ET Street R 305 drag radials. Even with the Steeda Stop the Hop Kit, the sticky tires tested the viability of the factory aluminum center section and Traction-Lok differential on mid-10-second passes. With the intention of cranking up the boost even further, we searched for a budget S550 rearend upgrade.
Since the manual-transmission cars came with iron Super 8.8 center sections, and better still – the Performance Pack cars also came with Torsen differentials – picking up a used center section from a wrecked vehicle was the obvious path. I found a Mustang recycler within 30 minutes of home that was selling one for $550. It had only slightly fewer miles than my stock one, but thankfully the Torsen diff is a gear-type, so it doesn’t wear out like the Traction-Loc clutch-type.
All our used Performance Pack S550 rearend needed was a ring and pinion swap, some fresh seals and bearings, and fresh fluid. Though 3.55:1 may not seem like a lot of gear, the VMP blower and 10-speed combination warrants a max of 3.31s or you risk going into an Overdrive gear at wide-open throttle (delivering a quick death to a 10R80 automatic). Since 3.31:1 gears are OEM Ford ratio, I found a Ford dealer online and ordered an install kit from Ford Performance (who also sells brand-new, complete 3.55 Performance Pack rearends separately).
Ulterior Motives
If there was one complaint with driving Project Magneto on the street, it was the noticeable NVH introduced by the differential bushing insert kit. It funneled gear noise straight into the cabin. Since that aluminum diff was living on a hope and a prayer, I was OK with it for a while. However, with the piece of mind of an iron diff I decided it was time to quiet this thing down a little and would sacrifice a little performance to swap in some urethane. Steeda had sent the urethane insert along with the Delrin version as part of the kit, with the warning that unlike the cradle lock-outs, these would increase NVH.
Although I endeavored to work with the best rearend guy I could find in the Charlotte area to swap the gears, I didn’t want to leave anything to chance, so I also had the ring and pinion micropolished. Micropolishing not only extends the life of the hardware and and enhances durability, but it also increases oil retention on the teeth of the gear, leading to smoother…
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