Porsche 964 C4 Troubleshooting

This 964 came back in after it’s new battery due to some front end noise that the owner noticed after he had new tires installed. Likely the noise has been there since he just bought the car, and he just noticed it after the tires were installed. We did swap wheels to rule out anything with a possible bad tire.

While I had it in there air inspecting for any signs of rubbing, I noticed we had some inner tire rub. I cleaned and painted the metal so it was no longer exposed. Our issues rears it’s head when driving and applying the brakes hard, we get a grinding from the front end. It comes and goes, which is very odd, and probably why it wasn’t noticed earlier. But….this rub is obviously occurring under turning, so not our immediate issue.

With the 964 C4, troubleshooting front differential problems is always a bear. It is hard to pinpoint the noise, but it sure seems center front of the car. So I started poking around some more. When I turned the key on, I noticed something was missing. The front diff light is not lit up! I pulled the gauge cluster to find the bulb missing…..great. Looks like someone knew about this issue. (notice the parking brake light is also burned out). After installing a new bulb, of course now we have a diff light that stays on with the car running.

I wanted to rule out simple things like calipers sticking, pads binding up, etc, so I pulled the front brakes apart to find Pagid Orange racing brake pads (same in the rear), so this car has obviously been driven hard on the track. I cleaned up the pad mounting areas and installed some street pads.

There was a lot of build up in the pad grooves, but I’m not convinced that is it at all.

While in the air, we found another torn CV boot, so time for all 4.

Pretty well completely shot.

After getting the rear axles done, I wanted to swap the diff and transaxle fluids for fresh fluid in case we had something binding due to that. There was swepco in the units, so that was removed and replaced with some good old fashion mobile 1

Pumping in the new fluids. Stay tuned as we continue to dive into this beast. We have a leaking longitudinal slave cylinder to the front diff that we need to replace, and that may be why the diff light is on.

964C4Front DifferentialNoisePorsche

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