400hp944

OK - I've searched for half an hour with no luck, so here goes.

I have a "rattle" only when decelerating. Mostly between 3000 rpm and 1500 rpm. The sound is similar to what a throwout bearing makes when it going bad. It's not the bearing - it's new. I'm pretty sure it's something in the tranny. The sound comes from the rear of the car. It's got over 100K miles so it could be time for a rebuild.

Question: Would changing the oil and going to something thicker help? How about an additive of some sort?

Thanks for the help!

Jeremy Himsel

My experience has been that these transmissions are inherently loud on decel. IMHO, second only to a Tremec 3550. Couple that with 100K of loosening up and it’s not surprising that you’re hearing some noise. Some cars are a bit worse then others but in the last 10 years I've yet to see a relationship between the noise generated on decel and transmission failures. A close friend of mine had had his 951 for about 6 years now and inside the car it’s pretty quiet but driving behind him you can clearly hear the transmission on decal. Swapping the fluid from Swepco and Mobile1 to Redline or Amsoil seems to help.

On a related note, I had a failure of the input shaft bearing and the transmission was one of the quietest 951's I heard. Didn't make a sound until it completely failed.

mylesfast

i recently had some similar problems, replacing the trans fluid with fresh swepco worked, as long as the tranny hasn't been abused they should last more closer to the 200k range

Cory9584

my old 951 used to do that, I always figured it had something to do with the torque tube bearings.

TurboTommy

My previous 951 had a tranny noise as well, but mostly at very low load constant throttle. On decel there's sort of a negative or opposite load and it didn't rattle then.
Also, it seems the regular diffs are noisier than the LSD for some reason.

JustinL

The day my transmission stops making noise is the day that I'll stop the car to go collect it from the side of the road. It's just like oil... it leaks to let you know there's some left in there!

All joking aside, my 951S is pretty quiet, but the n/a has been making the identical noise you describe since I bought it in 1999 150,000 miles ago.

400hp944

Well, I feel a little better knowing it's not just my car. My last P-Car was an 89 S2 which I raced for about 5 years. It never made this noise.

Any Suggestions about an oil "upgrade"? A few above^^^ have mentiond Swepco, Amsoil and Redline. Any thoughts on this?

mylesfast

I stand corrected adding swepco didn't fix this problem. I get poor acelearation between 2- 3k and massive rear end shudder/ vibration
I been searching, I think this is something to do with the torque tube bearings

Tom M'Guinn

I tried Amsoil, which did help quiet it a little bit. When I switched engines, it got progressively louder (on decel just like you describe) then eventually blew up with a spectacular screetching sound under WOT in 2nd gear. Go figure, I guess they weren't built for 500 ft lbs of torque. The low mile replacement I plugged in makes exactly the same noise...

JohnKoaWood

I would go for the one of the three you can readily get, I can get Redline localy, but order Swepco... Have had good experiences with the Swepco, but past history has shown me all three you list are good lubes for the transmission...

Recently I put Valvoline SYNPower in My 951, it took care of noise and my 1-2 syncro quit acting badly.... I will see how long it lasts before I swap it out to Swepco...

Cory9584

I'm about to find out how noisy my transmission really is on tuesday when my solid mount comes in

400hp944

Well, my clutch master just took a dump! Good time to put it up on jack stands and change the fluid.
Gotta remove my MAF, Injectors and fuel controller because I just ordered my Vitesse setup. Hope to see that next week.
She's going to be down for a while, so good time to do it.
Can't wait to report on the new Vitesse goodies. Until then...

Jeremy Himsel

I swap out the swepco. If it's a street and some track car I run Amsoil, if it's a track and some street car I run Redline.

Keithr726

Mine made a lot of noise, switched to redline 75w90ns and that helped slightly with noise but mostly with cold shifting. From my experience I've decided that it just must be a flaw in the design because every 944 I've ever driven or gone for a ride in has made this noise.

buxton

My non lsd transmission makes a similar noise on deceleration between 2500 rpm and 1800 rpm. I am confident that it is a TT bearing. Does it make the same sound when the clutch is depressed and coasting? Do you get any noise with the car parked and rev the motor with the clutch in? or out?