growling tranny

My 901 transmission has recently developed a strange noise. Sounds like a low pitched rumble that, of course, increases as I pick up speed. Can only hear it in 1st, 2nd and reverse. Don't know if thats because road and exhaust noise drown it out or what. As I come to a stop and dis-engage the clutch I can hear something spinning down in the box for a few seconds then it stops. Just put a new exhaust system on the car so maybe it's a noise that's been there all along and I just couldn't hear it over the engine. Haven't been able to find a competent mechanic here in the Des Moines area since my wrench retired a few months ago, so I don't have anybody I trust to listen to it for me. Any suggestions would be very welcome. Thanks, Marty Scott

Sounds like a rear bearing to me. Probably stops when the car coasts to a stop, right? Search out and read the threads on bearing noise to see if its similar to what you're experiencing. One such thread can be found in a post by rcilurso titled "Rear wheel bearing replacement (long)"
regards,
jlex.

Yeah. Sounds like a wheel bearing, could be front or back. Kind of a rhythmic roar, dependent upon speed only.

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'83 SC

my 901 growls like a hungry bear in first gear and reverse. never heard it in second. i will be replacing the tranny/clutch in april. $$$. also plan to replace all associated parts -coupler, helper spring plate, cable, etc.
bob
'68 911L

Thanks for the responses guys. Drove the car to work today to try and get a better idea of the sound. Seems it only "growls" when there is pressure on the drive train. Press in the clutch and it stops. No noise at all when coasting. Thought maybe input shaft bearings, but it's quiet in neutral with the clutch out. The sound is very pronounced when down shifting thru the lower gears. What do ya think? Marty

Marty,

That sure sounds like a pinion bearing to me! Have you checked the gear oil level in the transaxle lately? It is probably too late for a gear oil change to help the noise, but you never know.

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Warren Hall
1973 911S Targa

Warren, I've only driven the car a couple hundred miles since I first noticed the sound. Last weekend I changed the fluid in the tranny to see if that made any difference. The fluid that I drained looked as clean as the new stuff I was putting in. Didn't seem to have any effect on the noise either. The magnetic plug was pretty well loaded with metallic residue. Is that a really bad thing or sorta normal?
Does this require immediate attention or can I get away with running it a while longer? I don't want to cause any more damage than there already is, but I've been throwing tons of money at this car for a long time and I really would like to drive it around for a while. Can I drop just the transaxle or does the the motor have to come out also to address this?

Marty: when I changed my transaxle fluid last summer (on my '85) there wasn't even a hint of metallic particles in the fluid or on the plug. Something doesn't sound right inside your unit. What year & how many miles on it?
regards,
jlex.

jlex,
The unit is a 901 so it had to have come out of a pre '72 and the mileage is completely unknown. Blew up my original transmission a couple of years ago and bought this one used. My mechanic opened it up and said it looked real good, but of course looking good and being good can be two totally different things. I've put about 10k on it since then with absolutely no problems.
Is the whole thing going to cash out if I keep driving it for a while, or do I need to park it until I come up with the money to fix it? Thanks again for your thoughts. Marty

Marty,

I think fine black residue on the magnet is perfectly normal. I knew a guy that drove a VW Beetle for about two years back in the '70s with a bad pinion bearing, and you could hear him coming for about a half-block away, but it never got any worse! So, I suppose you don't have too much to worry about, as far as daily driving goes. It would/will probably be less expensive to find another 901 than to get that one repaired/rebuilt! I have seen them around for $500, and I doubt if you can get it repaired for less than that. So, you may want to keep an eye open for a used 901. Good luck!

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Warren Hall
1973 911S Targa

Looks like I'll be putting up with the noise for awhile. I've heard that Swepco gear oil has the ability to work miracles on these trannies. Any chance replacing the castrol I just put in might make a difference? Thanks alot for all your input folks. I really appreciate it. Marty

1st and 2nd are on either side of the pinion bearing in the intermediate plate. the mainshaft bearing is above it, and usually is the 1st to go, but maybe not in your case. sorry, but swepco, or anything else won't fix a bad bearing. waste of $30