Transmission Noise, Throwout Bearing, Input shaft Bearing or Pilot bushing?

[lstoltenbe001]

I have a whurring / grinding noise when I depress the clutch which will change with RPM changes. It is more pronounced when it is shifted into a gear, and will get worse when the transmission is at operating temp. I think it has to be either the pilot bushing, throwout bearing or the input shaft bearing as those are the only components moving when the clutch is depressed.

Sounds simple right? let me give you some more background. I have owned the J-10 since 1985. 360, T-18 with the long input shaft, Dana 20 xfer case. After the first engine rebuild in 1985, I went thru about 5 throwout bearings, but the pilot bushing would be messed up as well. We ended up replacing all the 3 parts and this lasted 20 years. This year I went and did another complete engine and transmission rebuild, when I pulled the old transmission the input shaft was so loose, that it had eaten up the input shaft bearing retainer (that the throwout bearing rides on). I replaced the transmission with a re-built transmission from the guys at Novak. I went with new everything, flywheel, centerforce clutch, bearings, bushing. I even measured the runout of the bellhouse, which appeared to be within specs. Now, 3000 or so miles into the rebuild, I have the noise again. Am I missing something?????

Any help would be appreciated.

[75J20]

I would suspect the throw-out bearing but since you replaced everything I'm not 100% sure, could be dumb luck that it went out already.

Do you rest your foot on the pedal while driving....possible you may be and don't realize it....when you're stopped at a light do you leave the clutch pedal depressed waiting for the green light....another possibility is if you greased the pilot bushing, the pilot input shaft is grabbing and not spinnig freely....the bushings are a self-lubricating oil impregranated bronze material(presto-lite) also the pilot should be clean and smooth again with no oil or grease applied.

Unfortunately no matter what it looks like you're going to have to pull the trans to fix. My truck did the same thing when I bought it from the PO and I replaced with a new clutch kit, only cleaned the flywheel and input pilot with some emery paper and installed new bushing without any lube and all is good now.

[drlocke]

Your throwout brg is toast. When you pull the gearbox to replace it check everything from A to Z--including clutch plate fingers, pilot bearing and shaft, tranny input brg. Any slop is NG. Any burr on anything can cause premature wear of that component, triggering wear of other components as everything goes south. Lotta energy in that locality, and things can go to hell quickly.

[lstoltenbe001]

Thanks for the info. Ordered the new throwout bearing tonight. Will pull the transmission this weekend and see what everything looks like.

[75J20]

Let us know what you find.

[Serious Johnson]

...Any slop is NG...

I'm curious as to just how much "slop" is expected on a T-18 (long) input shaft. I've only checked two, and both exhibited quite a bit, though I don't think either was enough to allow contact between the shaft & retainer. In fact that very issue, so unlike other manual trannys I've messed with, almost led me top tear my T-18a down. But a tranny guy took a look and said it felt just fine.

20,000 miles on, and I'm getting pretty much the racket described above. My noise is somewhat intermittent though, and all bad release bearings I've had before have groaned constantly with the pedal in. This one (if that's what it is) displays somewhat randomly, apparently depending on how I hold my tongue as I depress the pedal. Motor & tranny mounts are fine, and linkage seems no more goofy than any other of its type.

My old back has made it known that there are not too many more T-18 R&Rs in its future, so I'd like to go into this next one more or less informed.

S.J.

[JeepinPete]

It doesn't make any sense to be that it would be the throw out bearing. Since the noise changes when you put it in gear, the only thing that changes is the input shaft is now stationary. That means there is movement between it and the pilot bushing. The throw out bearing is spinning regardless of whether the tranny is in gear or not (when the clutch is depressed).

I have to believe that the tranny is not alighned with the engine properly. With most manual trannies, the input bearing and the pilot bushing/bearing are what support the input shaft. If you are wearing out the retainer, then either the input bearing is toast, the pilot bushing is severly worn, or there is a misalignment causing the input shaft to rub against the retainer. And a badly misaligned tranny will cause the throw out bearing to engage the fingers on the pressure plate unevenly, which could very well cause the destruction of the throw out bearing in short order.

One other possibility is the input shaft is bent. I had this happen on a T90 in my old M38A1. I must have bent it while installing it. The only symptom it showed was popping out of third gear for no apparent reason.

[lstoltenbe001]

I'm curious as to just how much "slop" is expected on a T-18 (long) input shaft. I've only checked two, and both exhibited quite a bit, though I don't think either was enough to allow contact between the shaft & retainer. In fact that very issue, so unlike other manual trannys I've messed with, almost led me top tear my T-18a down. But a tranny guy took a look and said it felt just fine.

I've looked at two, the old one I pulled out with a TON of miles on it and the fresh rebuild from Novak. The first one was gone and had eaten up the retainer, pilot bushing, etc (as mentioned above). The fresh rebuild still had play, but not too much. Theoretically, the pilot bushing is supposed to hold it straight.... At least that is my understanding. I will let you know what I find. BTW, the noise is intermittent at this point, I think it depends on how the bearing makes contact with the clutch....

[drlocke]

A bit of longitudinal play is perhaps OK; it's the side to side play that I was thinking of.

[lstoltenbe001]

It was the throwout bearing for sure. Everything else looked good. what was interesting is that the new bearing was actually a little shorter, not sure if this has to do with it going out pre-maturely.....