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Transmission noise. Help please.


faber
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Noise is a grinding noise especially loud on deceleration in 3rd, 4th and 5th gears. Slow transitions from acceleration to off the gas and the grinding noise pops up and is louder at higher revs. Happens in all gears but more noticeable in higher gears.

Have had the car up on a lift to check. guibo is good. support bearing is good. sound appears to be coming from the tranny, not drive shaft or diff.

Problem is I just replaced the previous 5 spd with another used one for this reason, and the sounds are identical.

Any ideas? after tranny no 2, I'm almost willing to pay big money for a rebuild.

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If it sounds identical, the trani may not be the problem.

What is age and condition of:

Pilot bearing, clutch and disk, TO bearing, center bearing, also motor and trany mounts and diff and mounts?

Is drive shaft aligned proper, and was center bearing pre-loaded?

also is it noisy when coasting in neutral with/without clutch depressed?

i know this sounds like a lot of stuff but thats the way it goes, also you sure on the Grinding noise and not a Howl?

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Here is an easy way to determine if its the tranny or rear end. When decelerating push in the clutch, if the noise stops its the tranny. i have this identical problem right now. I am not sure if its the TO bearing, pilot or maybe both. A tranny shop told me if the tranny is noisy on decel it is the bearings in the rear of the tranny

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Guest Anonymous

Just replaced my 4sp due to bearing noise. It was the input or layshaft bearing. It was kind of a 'howl'. If yours is really grinding ... metal on metal sound I'd really stop driving it and look for a kaput bearing. The grinding sound could come from wheel bearings. The bearings in the trailing arms make grinding sounds when they wear out. You'd probably feel a bad front bearing in the steering wheel. Then determine if the exhaust pipe is rubbing against the output flange of the differential. This makes a grinding noise as the flange rubs the pipe ... very metallic as well. The TOB makes a grinding noise when it is worn out. But usually quiets down when you press the clutch pedal. The pilot bearing is usually a small bearing and the shaft is supported by the clutch plate. I'd guess that the sound it makes when destroyed is quieter than most of the other bearings. The center bearing on my car was bad, I drove for months before I noticed that it needed replacing. Not enough noise from it to get me to get under the car and look.

Sometimes it is difficult to hear where the noise is coming from when you are in the car. Get a friend to listen from outside the car when you are on the street driving past. If it is really a metal on metal grinding sound, you're probably due for a bearing replacement at the trailing arm.

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Throwout bearing makes noise when the clutch is pressed, because it is being pushed against the pressure plate and it moving. When the clutch pedal is released, it's not spinning, not the other way around.

The best way I've been able to describe diff noise is like a train rolling down the tracks. Granted they've all be Dana or Chrysler corporate axles, but they should sound similar. Louder on accel would be a front pinion bearing (closest to the gear), louder on coast would be a worn rear pinion bearing, and all the time would lead me more towards pinion bearing. If it's affected by speed, I would look more towards diff, center bearing, and wheel bearings. If it changes with RPM, but not speed, I'd look towards the tranny.

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I would put the car up on some sturdy jack stands (or a lift), disconnect the driveshaft from the transmission then start the engine with a helper inside to pinpoint the noise. A long handled screwdriver, stethoscope or long pipe held up to your ear (be careful!) will help if pressed against the transmission.

The pilot bearing, throw-out bearing, transmission bearings, guibo, driveshaft nose centering pieces, center support bearing, U-joints, exhaust, rear differential all could be suspect. Using a process of elimination should help.

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Based on your description I would lean toward the pilot bearing.

Earl

74 02Lux

02 M Roadster

72 Volvo 1800ES

Just for information, SKIPSFCR's shop just replacaed the clutch in my tii, and the pilot bearing was frozen. A sure test of this bearing is to come to a complete stop from driving, and go immediately to reverse. If it grinds, then the pilot bearing is bad. Now mine goes into reverse smoothly with no grinding at all.

I have (somewhat) the same growl when decelerating in first and second. I was hoping that the replacement of the clutch, pressure plate, pilot and throw-out bearing, along with resurfacing the flywheel would fix the noise, but it's still there.

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Thanks for the ideas. I will try a process of elimination again. Wheel bearings are good. In neutral either coasting or stopped, with clutch in or out, there is no noise. It is RPM dependent not speed dependent, as it happens at all speeds. It is a grinding, growling noise, not whining or howling. It only happens in gear. The exhaust is clear from the driveshaft and differential.

I will change the diff oil to see if it makes any difference.

Is it possible for me to replace the transmission bearings that are suspect?

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If it was me, I'd change the diff and the center bearing.

But only because I have a stash of center bearings.

It really does sound like the diff, from your description,

and the fact that it didn't change at all when you changed transmissions.

Can you 'tune' the noise with the throttle when you're coasting down?

That's a sure sign it's diff or trans- and again, we're pretty sure it's not the trans.

. In neutral either coasting or stopped, with clutch in or out, there is no noise. It is RPM dependent not speed dependent, as it happens at all speeds.

Ok, now you've lost me. So it growls at a frequency tied to the engine, not the wheels? If that's the case, it's the input or countershaft in the trans.

If it growls at a frequency tied to the wheels (higher frequency the faster you go)

then it's output shaft, driveshaft, or diff.

Oh, cripes, pull your driveshaft and check all the u- joints again for

a stiffie. That'll make a racket. And sometimes they only do it under

certain loads.

And yes, you can change bearings in the trans- but getting it apart

and back together is a bit of a pain.

hth,

t

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  • 6 years later...

I have been chasing a noise in my 74 and spending way too much money.

Mine sounds and feels like a propeller noise especially when decelerating  lugging slow in 3rd gear.

I changed the guibo, center brg, and now driveshaft .

Runs smoother but still has a hump hump sound in 3rd .

ANY IDEARS ???

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