924S Growling Rear

[Moonranch01]

I am the new owner of a 87 924S with 69K. Strong, clean car.

There is a noise in the rear that I initiallly thought was a throaty exhaust growl or vibration noise. Listening more it sounds more mechanical in rear end.

Clues:
Transmission smooth shifting, all gears good. no leaks, no vibration.

Clutch firm, no slip, no noise.

Sound is louder with speed.

Does not vary with steering l/r vs straight line driving. does not sound like grating brake/bearing noise.

Brakes firm, straight, quiet.

Are there suspect or historical problem areas in this model and vintage that might cause this noise?

Is servicing this model advisable with other than the Porsche shop (very nice, scary expensive...)? Next stop would be trusted local professional service shop.

Welcome any suggestions as I hope this is the beginning of a long and happy relationship.

Thanks,
Bob

[John_AZ]

Originally Posted by Moonranch01

I am the new owner of a 87 924S with 69K. Strong, clean car.
There is a noise in the rear that I initiallly thought was a throaty exhaust growl or vibration noise. Listening more it sounds more mechanical in rear end.
Clues:
Transmission smooth shifting, all gears good. no leaks, no vibration.
Clutch firm, no slip, no noise.
Sound is louder with speed.
Does not vary with steering l/r vs straight line driving. does not sound like grating brake/bearing noise.
Brakes firm, straight, quiet.
Are there suspect or historical problem areas in this model and vintage that might cause this noise?
Is servicing this model advisable with other than the Porsche shop (very nice, scary expensive...)? Next stop would be trusted local professional service shop.
Welcome any suggestions as I hope this is the beginning of a long and happy relationship.
Thanks,
Bob

Hello Bob,
I appears you have a very well maintained 1987 924S.
Did you get any service records, a pre-inspection report PPI, or any shoe box of receipts when you picked up the car?

I will eliminate the small resonator behind the main muffler since you do not think it is exhaust related.

That leaves two areas. A bad/failing rear wheel bearing or CV joints that need servicing.
Begin by checking the transmission fluid and change. Ask what members advise for current fluid.
Repack CV joints. Dirty and messy. Get CV grease in tubes, special stuff.
When you have cleaned joint but before repacking, check for bearing wear inside joint.
Rear wheel bearing replacement is not impossible for a new owner but you do need to do your homework.

If you take it to a shop, many do not work on our cars even import shops, expect to pay in labor what your car cost you in a few visits. The Board can help you DIY.

Good luck and ask more questions.

John_AZ
1987 924S + 1988 924S

[Moonranch01]

Thanks John,

I appreciate the suggestions.

Against my better judgment, I did buy this car without seeing the service records and have yet to get my hands on much. Coming as a 'certified used car' from what I believe to be a reputable, dealer I assumed that had been taken care of...will ask for details again. Sometimes my optimistic side takes over when I feel the car is right. The fluid was on my check this first list and that makes sense.

I will dig into it and see what we find. Just got the front calipers on my 67 Volvo 122S back in service, so looking for another good reason to spend some time in the garage...better now than January if you live in MN!

thanks again.
Bob

[John_AZ]

Bob,

Transmission fluid. Short version. 924S originally needed GL4 rated fluid-Porsche says GL5 is now OK. Be careful what you grab for at store. Your dealer and mechanics may suggest brand. Here is a page from www.clarks-garage.com on transmission fluid change:
http://www.clarks-garage.com/shop-manual/trans-06.htm.

Reading it will begin the confusion of current fluid to use. IMO, especiall in MN, go with some type of synthetic. Redline MT90 is often chosen. Get over internet or local dealer near you-check web.

John_AZ

[Moonranch01]

Thanks again for the excellent direction.

Off on a fluid quest.

Happiness is a well lubed German...

Thanks,
Bob

[Rasta Monsta]

I put Valvoline Synth 80-90w in the wife's S. Made a huge difference in shifting.

DEFINITELY follow Clark's caution about the fill plug. Having these suckers seized in place seems common.

[rickharrison]

I use Swepco 201.

Order yourself 2 new drain/fill plugs, and the proper 17mm allen head tool for lossening them. Put anti-seize on the threads too.

Could also be pinion bearing noise...they get older and sloppier and the growling comes from the ring and pinion "knashing" together. Good fluid can help.

Don't drop the clutch and launch the car, and drive on.

FYI...A rebuilt tranny is @ $2500-$3000 depending on where you go.

[JonA]

Check the cheesehead bolts that hold the cv joints together. They are prone to loosening. It may be that simple.
If the cv joints are bad you can buy rebuilt driveshafts with both joints for short money and it makes for a pretty easy repair.
If you get that far the wheel bearings can be replaced with only a little more work. But you gotta do the heat/chill thing to get the new bearings in. Read Clark's Garage for all the details.
At 90,000 mi I had to do all those things to my 924s

Jon

[ERAU944]

start with easiest first. try the CV axles repack/swith sides. unfortunately it sounds an awful lot like the rear wheel bearing on my '85.5 when it went. no fun. no fun at all.