Squealing When in Neutral

[Built6spdMCSS]

Have you tried spinning the input shaft of the Transmission by hand to see how tight it is? If the squeal is the same when in neutral and in gear, and only changing when the Clutch goes in, I'm leaning toward the Input & Mainshaft being too tight and it's loading the bearings.

I know you said it's in neutral, the "being driven down the road" part makes me think you had it in gear, or is that rolling in neutral at speed and it's still making noise.

Is this something that started randomly or when you put the Transmission back in the car?

 

[Full Garage]

Built6spdMCSS - I did check that and in fact the input shaft is a bit loose, ~0.004" of radial play, which could be a problem. Although the shop that rebuilt the transmission said it wasn't a problem (perhaps some/ alot of BS there?).

The squeal occurs in neutral and any gear. If i depress the clutch pedal the noise stops. So if I'm driving down the road, at speed in 4th, and I hear the noise, all I have to do to get it to stop squealing is just lightly rest my foot on the clutch pedal. Thanks.

 

[Full Garage]

Built6spdMCSS - now that you asked the question, I'm thinking it started after the transmission was rebuilt, but I'm not sure. I'll have to go back through my notes and see if I wrote something down.

 

[pagrunt]

Do you have the correct matched throw out bearing for the pressure plate? Other thing would be the imput shaft bearing. Could even be a lack of of the right grease in the throw out bearing's groove.

 

[Full Garage]

pagrunt - the first 2 clutch assemblies I installed were a matched set from the manufacturer. When I installed the 3rd clutch assembly I substituted in the recommended SKF throw out bearing. I suppose there could have been mismatched parts, but the o.d., width and i.d. all fit the clutch fork and bearing retainer.

Regarding the grease, I know that I put a very light coat of hi-temp brake grease on the bearing retainer, not sure if thats the correct stuff.

The input shaft bearing was replaced during the rebuild, but I'm becoming suspicious of it. Thanks.

 

[Built6spdMCSS]

Built6spdMCSS - I did check that and in fact the input shaft is a bit loose, ~0.004" of radial play, which could be a problem. Although the shop that rebuilt the transmission said it wasn't a problem (perhaps some/ alot of BS there?).

I do all mine at .000" or a hair preload if brand new bearings. .004" lash is not drastic enough to cause an issue.

The squeal occurs in neutral and any gear. If i depress the clutch pedal the noise stops. So if I'm driving down the road, at speed in 4th, and I hear the noise, all I have to do to get it to stop squealing is just lightly rest my foot on the clutch pedal. Thanks.

Does that have a steel sleeve on the front that sits around the input shaft? Makes me think the throwout bearing is scuffing that somehow.

 

[Full Garage]

Built6spdMCSS - yes, my transmission has the bearing retainer that sits around the input shaft. From the description in the factory service manual the o.d. of the part that surrounds the input shaft is the guide surface for the throw out bearing. When I reassembled everything the last time I applied a very light coating of high temp brake grease to that surface, and slid the throw out bearing back and forth across the surface to make sure there was no binding or dry spots.

I'm not sure about other designs, but the inner race of this throw out bearing doesn't rotate; its held stationary by the clutch release fork. The outer race has the contact surface that touches the release fingers on the pressure plate. You could be right about the t.o. bearing "scuffing" on that surface. But maybe not from rotation, but from sliding forwards and backwards along that surface. That might explain why a light touch on the clutch pedal makes the noise go away. A new avenue to investigate. Thanks!

 

[Built6spdMCSS]

Given the noise changes when moving the Clutch Pedal it's going to be something in that equation of things relates to the Bearing or Fork. Definitely an odd one.

Pull-type Clutch Pressure Plate?

 

[Full Garage]

Since I've replaced the clutch assembly 3 times I think its a safe bet that its not the primary culprit. Definitely a head scratcher, that's for sure.

Was in the shop a few minutes ago playing with the clutch actuation rod, springs, clutch fork trying to get some sort of squeak; nothing. Wondering if the vibration from the engine running sets up a harmonic resonance in the clutch linkage? Part of my refurbishment of the car included adding an adjustable clutch actuation rod between the Z-bar and the clutch fork. That's the only non-stock part in the system that I can thunk of. Time for more head scratching.

 

[Full Garage]

Built6spdMCSS - I'm not sure I understand what you mean by a pull type pressure plate. I believe the one in the car is a diaphragm design.