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Monte Makeover (Part 5): The Accidental Rear-Axle Upgrade

Editor’s Note: Perhaps the only things Travis Jones loves more than his 1986 Monte Carlo SS are autocross courses and a good challenge. That’s why Travis is on a mission to transform his Monte Carlo from an underpowered, ill-handling daily driver to an Autocross hero. A self-described “GM guy through-and-through,” Travis is a regular on the site OppositeLock, has documented his project on his Instagram page (@sslow6.0), and will give us a first-person account of his build here as a guest writer.

Travis has owned the Monte Carlo since high school. Although he’s thought about selling it from time-to-time, Travis has held on to it for sentimental reasons, even though the car has often sat idle. After his girlfriend inspired him to try Autocross for the first time, Travis started to look at the Monte in a whole different way.

“I became obsessed with taking a 1980s boat and making it handle,” Travis said.

In part 5 of his Monte Makeover series, he takes on an unexpected rear-axle upgrade:

In the last article, I wrapped up my LS swap and took the car to the track and a friend’s chassis dyno. It ran a 13.27 at 107 miles-per-hour and put down 352 horsepower and 375 ft.-lbs. of torque. I was now ready to enter my first local Autocross event with the newly LS-swapped Monte.

Overall, I was happy with the improved throttle response of the fuel-injected LS showed on the Autocross versus my carbureted 350. Here’s a video I made of some of my best runs that day with an overlay from the Microsquirt Datalog.

My performance was good for second in my class!

I was feeling good about the car, the engine swap — and the transmission even stayed together! I was excited for the next event, so I registered for an SCCA autocross event with the Saginaw Valley Region at NEXTEER (formerly GM Saginaw Steering in Saginaw, MI). During the two-hour trek to the event, I was cruising at a steady 70-75 mph when my tach and speedo suddenly started rising together.

I looked behind me expecting to see smoke or a trail of transmission fluid. Instead I saw sparks… and my passenger-side wheel and axle slowly passing me!

(Image/Travis Jones)

Thankfully, traffic was light, and no one got hit by my wheel and axle. I was safe, and the car didn’t sustain any body damage. Looking back on it, I didn’t feel fear in that moment. Just embarrassed. But once I was onto the side of the shoulder and realized how bad all of this could have been, I about had a heart attack.

I grabbed my axle and wheel, called AAA roadside assistance, and had the driver take my car to my parent’s house outside of Lapeer, MI.

From there, my dad and I got to work.

We dropped the whole rear axle and started disassembly, or post-mortem rather.
We popped the cover and what looked like liquid anti-seize started pouring out…
What was interesting was that at first glance, the carrier, the ring and pinion all looked just fine.
Upon further inspection, the spider gears were all chewed up.
And the clutch spring plate was broken.
Based on what I could tell from the carnage, and my understanding of the factory Auburn style posi-traction unit, I think that the cone clutch had worn down so much that the splined spider gears on the axles had clearanced enough material from the carrier itself that there was end play which caused the C-clip to drop out, and the axle to exit the housing.
So if you have an old factory Posi, make sure you pop it open and check for end play on the spiders. It’s a potentially dangerous situation so stay on top of it.
Amazingly, the only real damage done to the car was this. This is the shock mount that was dragging on the pavement and sending all those sparks. I welded a piece of flat plate over it, and called it good enough.

About two weeks prior to the wheel-off incident, I scored a complete 2002 Camaro SS rear end for $80 off Craigslist. A guy was upgrading to a Strange S60 and had no use for it. I pulled the Zexel Torsen diff, and the F-body LS1 disc brakes.

My plan was to rebuild the rear axle using the Torsen diff. My dad dropped me and the axle housing off at my house and I ordered the parts that I’d need to fix it.

I had the axle rebuilt at Ring and Pinion of Oakland, MI. Normally I would have done it myself, but I wanted them to check the straightness of the housing and correct it if necessary.

I had my dad pick me and the rear end up, and we took it back to his house to install it under the car. It went back together in a snap.
Unfortunately I was in a time crunch. My wife and I were about to close on our house, and I needed to get the car back together ASAP, so I just stuck it back together with the stock drum brakes.
I put the car back together, wondering how the new fully functional torsen differential would help the car around the corners. I signed up for an autocross event at Michigan International Speedway with the Detroit Region SCCA to find out.

Overall, I was pretty happy with the diff and how it put the power down from a standstill. However, around tight corners, it was still lifting the inside wheels and spinning. Unlike a locking rear differential, a torsen diff or a Detroit TruTrac require both wheels to have at least some resistance for the torque basing to work. If you lift a wheel, it acts like an open diff and the wheel without traction just spins.

To fix the inside tire lifting problem, more drastic measures would be required — drastic measures like a Ford 8.8 and a three-link.

But first, I wanted a bigger cam, new valve springs, and a custom exhaust to make power

Because more power always solves every problem, right?

We’ll find out in Part 6.

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2 Comments

  1. Scot Galvin says:

    Like your car and where can I find part 1 thru 4 of your buildup?

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