What does a whining 5th gear mean in a 901?

EarlyPorsche · 11-24-2006, 07:22 AM

In fifth, at certain speeds/RPM's I get an annoying whine. The transmission shifts and drives perfectly other than this. Any idea what it could be? I have not changed the fluid in it yet but I will hopefully do that here shortly. I doubt a fluid would change a whining, I was just saying I will change it.

Zeke · 11-24-2006, 07:37 AM

Sounds (no pun intended) like the pinon bearing. I had the same.

Grady Clay · 11-24-2006, 07:49 AM

Generally speaking the whine is a worn ring & pinion gear pair. Of course there are other possibilities.

When you change the transmission lubricant, carefully inspect the magnet on the drain plug. It is worthwhile to remove the shift pivot and inspect inside (it will take a new gasket 901.303.191.01).

A 901 is so easy to work on (even DIY), you should go look inside at your first opportunity.

Best,
Grady

EarlyPorsche · 11-24-2006, 03:36 PM

Now is the installation of a ring and pinion the same as an american car, require fancy backlash and installation. I was guessing pinion bearing too actually. Can I just replace that? The synchro and such are all tight and nice, its shifts really well but I can imagine the last guy just reused a pinion bearing. So just let me know what to do and I'll do it. Also, could it be carrier bearings?

EarlyPorsche · 11-24-2006, 04:15 PM

Wait why would pinion bearing only make noise in 5th?

84toy · 11-24-2006, 04:43 PM

Are you sure it's not coming from the shift shaft? It will transmit noise. Mine sometimes does that because I used bronze bushings instead of plastic. If you push the shifter to one side does it stop?

EarlyPorsche · 11-25-2006, 05:39 PM

No its a speed related 5th gear only whine. Any answers to my new questions above?

Clay Perrine · 11-25-2006, 06:47 PM

There are needle bearings inside of each gear. If it whines in one particular gear and on no other gear, it is probably the needle bearing on that gear.

On a 901, It will require that you tear down the gear stack to replace the needle bearing.

davidtorrey · 11-29-2006, 12:49 PM

Under acceleration my 5th gear whines as well. If it is the needle bearing in fifth gear, does this require removal of both the engine and transmission to fix?

Dave

Clay Perrine · 11-29-2006, 05:26 PM

Quote:

Originally posted by davidtorrey
Under acceleration my 5th gear whines as well. If it is the needle bearing in fifth gear, does this require removal of both the engine and transmission to fix?

Dave

If you are working on a 911, then the answer is yes. On a 914, you can just pull the gear stack.

davidtorrey · 11-30-2006, 05:32 AM

Clay -

Yes, I have a 911. In your opinion how long before I may do other damage by driving in fifth? The whine isn't severe and it is only noticeable under load.

Best regards,
David

Clay Perrine · 11-30-2006, 10:33 AM

Have you changed the gear oil out for swepco? If so, did it help?

If not, change the gear oil out, and see if it makes a difference.

the 901 is faily reliable, but the parts are getting expensive. I would fix it as soon as feasable for you.

davidtorrey · 11-30-2006, 11:56 AM

Clay -

I am not using swepco. I have put my car away for the winter and probably will not get a chance to drive it again until next April. Apparently, there is a chance the change in lubricant might quiet things down? I will give it try. The car and transmission has 150K miles on it and otherwise shifts very nicely.

Thanks for your help.

Dave

quaz · quaz's Garage

When I heard this sound from my car it was caused by this. Pretty much in line with what Grady was saying.

EarlyPorsche · 11-30-2006, 01:46 PM

I cant quite make it out, is the pinion chipped?

Clay Perrine · 11-30-2006, 07:15 PM

Galling on the pinion gear... not a good thing.

It means a new ring and pinion, and a complete reset of the gear stack,. requiring special tools.

I have a 901 that has over 300,000 on it. It doesn't whine a bit. It may be the pinion gear like the picture above, but unless the transmission was run with the oil level very low, it won't gall like that.

The swepco can't hurt, and it may give you another 50k out of the transmission before you have to rebuild it.

dvkk · 12-01-2006, 11:50 PM

If it was a bad R&P or a bad pinion bearing, the noise would be speed related, not isolated to a specific gear. That's because the pinion shaft is turning exactly the same rpm at 70mph in 5th or 4th, or 3rd.....

If you haven't checked the oil recently, it could be running low. I have seen gearboxes that were noisy become quiet with a gear oil change. If you were worrying about the gauling like in the pic of the pinion gear above, make sure you pick a gear oil with a GL-5 rating instead of GL-4. The GL-5 spec calls for a better extreme pressure additive.

quaz · quaz's Garage

Just as a note to my pinion gear above, I really only noticed the whining in 5th. However, it was speed sensitive so the faster I went the louder it got. At 65mph it was quite loud.

The cause was simple, the input shaft seal was leaking something fierce and when I removed the tranny it was very low on fluid. Fortunately that was the only damage.

davidtorrey · 12-02-2006, 03:09 PM

Is Swepco considered to be a GL5 gear lubricant? I haven't used this before, but I have used Redline MTL. I guess the only way I'll know is to pull the transmission to find out for sure whether it is the pinion bearing or 5th gear bearing. From what all of you have said, it is worth trying Swepco first. ]]Thanks to all of you for your information.

Best regards,

David

Charlie V · Charlie V's Garage

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