Fixing our Cayman’s gearbox for thousands less than the dealer quote

Our Cayman had a bad transmission–fifth and sixth gear simply not home.

The dealer quote to fix? About $15,000.

Yes, three zeroes to the right of the comma.

This little issue torpedoed the selling price of the Cayman, allowing me to pick it up for $15,000, about half of what it should have fetched.

[$15,000 Porsche: Are we stupid, or the smartest bargain hunters you know?]

But now what?

I finally tore the broken transmission out of the Cayman–now my Cayman–and, after splitting open the case, figured out why my car is missing fifth and sixth gear: The dowel pin holding that shift fork to the rail simply wasn’t, and instead sat against the magnet in the bottom of the transmission’s sump.

Photography Credits: Tom Suddard

What I did is impossible, per Porsche, as the transmission is a non-serviceable part. The only way to fix my car is a brand-new transmission from the factory, hence that $15,000 or so quote from the dealer.

Clearly we need to get the folks in Stuttgart reading Grassroots Motorsports, because I fixed my car for just $61.05.

How? By replacing that dowel pin with a new one.

Rather than go to a Porsche dealer for that part, I instead went to McMaster-Carr, the world’s greatest online hardware store. For $12.90, I bought a pack of 25 alloy steel dowel pins, 6mm in diameter and 24mm long. These are slightly larger in diameter than the pin I removed.

I also spent $21.79 on a bottle of Loctite 603, otherwise known as a “high locking strength retaining compound for oily close-fit parts.”

My plan? From the factory, the car’s brass shift forks retained their loose-fitting dowel pins with peened edges. I’d replace the dowel pin with a slightly oversized one for a tighter fit, then glue it in place with the Loctite before peening the fork again. And just to be safe, I’d also glue and re-peen every other pin in the transmission, because I don’t want to do this job twice.

And, well, my plan worked–if anything, it was easier than I thought, and it took about 15 minutes from opening the McMaster box to having a transmission that felt as good as new–a disassembled transmission, that is.

Photography Credit: Tom Suddard

See, I still needed to put the case halves back together, which presented the next problem: Porsche doesn’t seem to have used a gasket, sealant, or anything else between the aluminum halves.

Instead, there were nearly microscopic knurls on each surface, which I learned were designed to crush and seal upon the first assembly. Reassembling the transmission dry was a recipe for leaks, but adding a gasket or traditional gasket maker would add a bunch of space between the halves, landing bearings and shafts halfway seated into the tail-end of the transmission and likely causing problems down the road.

Photography Credit: Tom Suddard

Fortunately, this problem has been solved before: Motorcycle engines are often designed as two case halves that bolt together to form an assembly with both leaks to seal and tolerances to hit, and there are special sealants designed for them.

So, I decided to treat the Cayman’s transmission just like a motorcycle case and used Permatex Motoseal to seal it up. (At $14.99, this tube was the second-most expensive part of the fix). Motoseal looks a bit like traditional gasket maker but is nearly as thin as water, meaning it seals while allowing a tight fit between parts.

All that remained was reinstalling the transmission, which only took a few hours. (Did I mention how easy this car is to work on?)

I had spare transmission fluid on the shelf, meaning you’ll need to budget another $20 or so to replicate this fix at home, then turned to the Cayman’s clutch.

Photography Credit: Tom Suddard

And, well, I completely blew through my $60 repair budget. The car’s original clutch looked good enough, sure, but I just couldn’t stomach removing and reinstalling the transmission on a car with 70,000 miles–a car that would see track use–without changing the clutch.

The original dual-mass flywheel felt perfectly fine, so I bolted on a new OEM clutch and pressure plate on and reinstalled the transmission. Why not go with a fancy aftermarket lightweight flywheel and a stronger clutch? Here’s why: I intend to mostly street-drive this Porsche and didn’t want the make the NVH compromises that come with deleting the stock dual-mass flywheel. Summit Racing Equipment had the best price on the OEM Sachs clutch kit, charging $482.39 after I used a 10% off coupon. (Thank you, SCCA membership.)

Photography Credit: Tom Suddard

Okay, so I lied: This is really a $563 repair if you change the clutch while you’re in there. But that’s still an absolute bargain, because after driving the Cayman out of the garage….

IT HAD ALL SIX GEARS. And fifth and sixth weren’t just present. They were perfect! Engagement felt like a brand-new car, the synchros were healthy, and my Cayman honestly drove like a new car.

Photography Credit: Chris Tropea

Notice it’s been a few weeks since my last update on our car? That’s because all of this honestly felt too good to be true, so I put a few hundred city miles (and one track day) on the car before taking this editorial victory lap, just to make sure I’d really, truly fixed it. Heck, it doesn’t even leak–that Motoseal worked perfectly.

What’s this about a track day? Yes, I’ve already baselined my newest project car. I’ll cover that in the next installment.