84_Carrera

So, this is a relatively new whine... almost sounds like a rear wheel bearing whine, but only occurs in 5th gear. Doesn't seem to be RPM-specific.

What else do I need to add to the "fix it" list when the trans comes out for 1-2 blocking replacement, etc.?

Approx. 83k miles, '84 915 trans, original, running Swepco 201 now, due for fluid swap to be sure.

Peter Zimmermann

Hi Fred: Your symptom is one that's unusual enough that it's a tough one to pin down without driving the car. Let me ask, when you're cruising at about 75 mph you hear the whine, but that whine goes away if you (1) shift into neutral, or (2) down shift to 4th and hold your speed steady? If yes, does your car have a history of being driven in 5th gear at speeds below 50 mph?

FYI: Rear wheel bearings growl when they fail, that is most likely not your problem. Oh, are you sure that your trans fluid level is correct?

84_Carrera

Pete -
exactly the symptoms. At first I thought it was an alternator whine through a speaker, etc., from the pitch. It's very hard for me to direction-find () sounds, as I have 2 different frequency hearing losses in both sides from childhood (spinal meningitis when I was 2). Since I only heard it while rolling, I figured it might be rear bearings as I'd done the fronts. Then I narrowed it down to only in 5th, constant speed, shifting from 5th to 4th... no whine.

I usually try to keep the 10 mph per gear as a MINIMUM rpm, keeping 5th for 60+ cruising. I haven't checked the fluid level yet, but that's on my list... gotta get me some more 201 on order. Last time I changed it was a couple of years ago / 25k miles.

Peter Zimmermann

OK, it's unusual to hear a 5th gear whine in a 915, especially at your low mileage. Usually 5th gear noise is a result of lugging, driving the car frequently in 5th at low speeds (below 50 mph). When that happens, what I call "chatter" marks (straight, evenly-spaced lines) appear on the inside of the gear where it contacts the needle bearing. This can produce a whine, but usually requires fairly advanced wear. Hopefully you can see those marks, which are deep enough to easily feel as you move a fingernail across them, on the gear pictured (which is a throw-away). Of course, the noise can also be caused by wear on the gear teeth, although that's very rare.

BlackPearl

Peter: What about ring-and-pinion gear aging, R&P indexing off by worn final drive thrust bearings, or poor/absent lubrication of R&P?

Just curious. My old 944 trans R&P whined like a lonely dog, but that's the nature of those 944 trans boxes, no?

GothingNC

One of the Fixen Der Porsche articles it metions that 5th gear whine can be casued by low fluid since the gear sits is higher up in the transmission then the others.

John

Peter Zimmermann

BlackPearl: Because of the low miles on the car/trans I seriously doubt if there is any wear at all on the R&P. The carrier bearings are extremely durable, usually only replaced during a rebuild. If some of their pre-load goes away during use, from case stretch, etc., it's never really enough to affect the diff settings enough to cause noise. In addition to that, 5th gear is farthest away from the R&P, so if the noise was diff related it would more easily be heard in 4th gear, which is right next to the differential.

John: Actually, 5th gear sits on the same plane as the other gears, but it's isolated with reverse inside the trans end cover. For some reason, when the fluid is low, it has a hard time finding it's way into the 5/R area - that's why I asked in post #2 if the fluid level was OK. FYI, regarding the gears, each gear set is comprised of two gears; one is fixed in position by splines, it's mate rides on a needle cage bearing. The bearing supported gear of 3rd and 4th speeds are actually the gears that ride higher inside the trans than the others (1st, 2nd, 5th), and rely on oil being splashed around for their lubrication.

porsche930dude

when i first drove my car when i purchased it it made a loud whine in 5th on the highway and cleared up after about 15 or 20 minutes i never really knew why it did that but havnt ever heard it again. It had been sitting for quite a while before i bought it

Mike Murphy

First thing I would do is change the trans & diff fluid. You might be running low or the oil could be old.