: Still a tranny noise, but nothing else...

Cadillac Giovanni
10-16-08, 05:11 PM
I was having some transmission noise recently, and decided to change my fluid, although I did it about a year and a half ago, I figured it couldn't hurt.

I changed the fluid and filter and everything seemed fine. No metal flakes in the pan, just a very slight build up of sludge in the bottom. I put everything back together, and the noise is still there, however the transmission shifts fine into all gears, no slips or shudders.

The noise itself is a rotational moan that is only apparent after the shift into second, and once I speed up beyond 30-35, it stops. It will also make a different noise with a very specific position on the accelerator pedal, just a slight touch will cause a constant whine. If I release the pedal, or push it down more, it goes away.

I'm just stumped. I'm no transmission specialist, and I have no idea what's going on. I'm reluctant that a trip to a shop may only result in them trying to push me into getting a rebuild.

Any thoughts?

10-17-08, 07:04 PM
Hi, I had a similar problem on my '78 Fleetwood, there was no problems shifting or anything like that, it would just whine, but when I got above 30-35 mph it would go away. Most people thought it was the pump, or a blocked filter but it turned out to be the torque converter. A couple of questions; Does the car have as much power as it should? Does it whine louder and more high pitched if you floor it? Does it whine in Park and Neutral, or just the driving gears?

10-17-08, 08:52 PM
Its the rear differential. Mine does the same thing and I had my tranny rebuilt and they said it was the rear diff. so I looked it up in the service manual and sure enough it discribes our problem to a tee. Around 30-35 miles an hour and eventually you will here it when its in 3rd with just a light touch on the gas. Take it to a shop and tell them you think the rear end is whinning. They might even let you listen.

Cadillac Giovanni
10-18-08, 03:04 AM
Hmm, thanks for the input.

I was listening to the noises some more. It also moans rather loudly as I slow down, just before it shifts down to first, that's when it's loudest. Power-wise, the car seems normals. Flooring it, or otherwise creating heavy torque situations, seems to actually quiet things down. It whines loudest during slow acceleration. As far as I can tell it does not make any noise in park or neutral. When I'm driving and I slip it into N,the noise stops.

I had suspected at one point it was the differential, but it's hard to hear where the noise is coming from while I'm driving.

10-18-08, 08:37 AM
yea, the book says the sound will be there while coasting down. Not braking but just coasting(no gas, no brake) at certain speeds.

The service manual:
Gear noise is normally a whine type noise and is usually audible from 20-55mph under four driving conditions:
1. Drive - Acceleration or heavy pull
2. Road Load - Car driving load or constant speed
3. Float - Using enough throttle to keep the car from driving the engine, car slows down gradually engine still pulls slightly
4. Coast - Throttle closed and car in gear. Gear noise most frequently has periods where noise is more prominant, usually 30-40mph and 50-55mph.

I hear mine the best floating at 30-35mph and coasting down. I love this manual, every single little thing is in here.

Cadillac Giovanni
10-18-08, 01:32 PM
Definitely a great manual, I picked one up myself a couple of years ago. I never thought to check if it was a differential problem.

I'll have to check to see if it makes the noise while coasting around 30, I don't usually coast around that speed.