mbintx

Yesterday I took the 964 (1989 C4) for its first (and probably last) track day. Just wanted to get a sense of what the car would do when pushed to 8/10ths or so, and needed a safe environment to do so. Anyway...after coming off the track after the second 20-minute session, I heard a new noise coming from the rear. Driving around in the grid, I determined it only happened when I was turning to the right or left, at slow speeds. Once the wheels went straight, the noise went away. It sounded like a slight dragging/clacking, definitely from the rear. Skipped my last session, drove 50 miles home without noise or incident.

This morning, I drove to a nearby parking lot to do a bit more investigating. Well, the noise is gone (at least for now). So of course I'm wondering what happened yesterday at the track. Friends there (non-Porsche guys) seemed to think it was the rear diff. Could I have overheated the diff in 15-20 minutes of semi-aggressive track time? Anyone ever encounter this? Or have thoughts on what else it could possibly be?

TIA!

Steve Weiner-Rennsport Systems

Do you have an aftermarket LSD in your car?

Vandit

It's a 1989 Carrera 4.

mbintx

99% sure I don't.

Earlydays

Probably not it, but I've experience a strange noise when turning at slow speed and it was low power steering fluid.....

Earlydays

PS - How was the car at 8/10ths.?

tjb616

It does sound like you are describing an LSD noise as Steve suggested. Otherwise, I'd say check your axles shafts first.

mbintx

That's my inclination as well. Need to have my mechanic inspect it.

mbintx

Noise was definitely at the rear.

mbintx

Actually quite easy to drive. A bit understeery in the tighter turns, but less so in the faster sweepers. Once you're properly turned in, you can just put the foot down and hammer through. You have to do something VERY deliberate to get the rear end to step out.

I'm sure it would be even better if all of the rubber bits in the suspension were upgraded from OEM. But for a 28 yr.-old car, I was impressed. The Bilsteins and semi-sticky rubber did a fine job. The weak spot was the brakes. Newer pads and SS brake lines would certainly help there.

Foxman

Are you running with LS 90 gear oil? https://rennlist.com/forums/964-foru...ial-noise.html

Earlydays

When the fluid is low the noise is in the rear coming from the pump......