I'm not so sure it's in the trans, Bill.... If it does it without even letting up on the clutch, the only thing turning is the flywheel and pressure plate. You might have a pilot bearing issue, a clutch disc/assembly issue, or possibly even a bent input shaft (unlikely, I think)

I've put probably a hundred of these together, and never heard of anything like that... My best guess is a bad clutch disc.....

 

Sorry I haven't responded. Been driving to the Niagara Falls show. I'll try to answer the questions, as best I can. I appreciate all the comments. As soon as I get home from the Ohio show, in mid August, the trans is coming out. I think I have located another trans (thanks Tom Rightler) I can stick in the car temporally. If another trans eliminates the problem, then at least I know it's in the trans. If not I'll look at the flywheel clutch etc.



Dave, the pilot bushing is new. I can't imagine anything being wrong with it at this point, but I will check it out when I pull the trans. I won't have time ti pull the trans before Ohio. I'm thinking maybe you could sit in the driver seat and feel the vibration, in Ohio, and see what you think.

I don't know that it's a clutch if it only does it in 4th and 2nd gear. I would think it's inside the tranny but I haven't rebuilt a bunch either so it's only a guess.

I would think it would shake all the time if it were a flywheel/pressure plate out of balance??

I'm going with the majority here, and say it's PROBABLY not in the tranny.

Without actually seeing/being in the car, it's nearly impossible to say what the problem's source is. But, if this happens when it is just sitting still, ESPECIALLY with the clutch depressed (which means the disc is not engaged), I almost gotta believe the pilot bushing/bearing is REAL bad!

I know what your saying Tom. It's hard to describe the vibration, but if you were sitting in the seat you would feel it big time. Again, I will look at the pilot bushing, but it is brand new, with virtually 0 miles on it.

Bill,what kind of clutch/pressure plate are you using?

It's brand new Centerforce 2 clutch, pressure plate, and throw out bearing.

I'm wondering if it could be one or both of the shift forks (the fork that moves the syncros)? Maybe for some reason it doesn't come completely free an the sticking is causing it to move around. The next point is make sure you shift linkage is adjested correctly. You could be holding a bit in gear and not completely out. I have see some so bad you can't pull them out of gear when misadjusted.

I'm real sure the shifter/adjuster rod are right. I double checked them with a 1/4 rod going thru the Hurst shifter, and all the rods are adjusted correctly. I've done this a million times. I'm sure it's right but will check it again. The forks are new too. It was part of the rebuild, but I'll look at them again to, when I pull the trans.

Bill, when you pull the trans look at the bearing retainer on the front of the trans to see if it is scarred up. I had one that the throw out bearing was digging into the bearing retainer when the clutch was depressed. I was using a new throw out bearing but it had a very sharp edge on the front where it slid back and forth causing it to dig in. I finally found it when I bought a new trans and could see the gouges when I pulled the trans again. The bad bearing was a TRW, I replaced it with a cheap Chinese one from Auto Zone and havent had any problems.
Ron

I'll look at this too Ron. The bearing retainer is also new, so if it's scratched at all, I'll see it.

 

I don't know that it's a clutch if it only does it in 4th and 2nd gear. I would think it's inside the tranny but I haven't rebuilt a bunch either so it's only a guess.

 

Bill,
It is possibly the wrong flywheel. A 396 engine will use a neutral balance flywheel. The 454 and 400 small block each has it's own. If you got one of these by mistake it will shake quite noticeable.
fasteddies68

 

Bill, I have rebuilt my M21 (and others) twice over the years by just buying a rebuild kit with no problems. Did you use a bearing or brass pilot bearing? I agree with others in that I can not image anything in the trans causing the shaking in only certain gears. If you want to practice rebuilding a trans I have a spare 67 M20 that needs to be rebuilt.

 

I'm going with the majority here, and say it's PROBABLY not in the tranny.

Without actually seeing/being in the car, it's nearly impossible to say what the problem's source is. But, if this happens when it is just sitting still, ESPECIALLY with the clutch depressed (which means the disc is not engaged), I almost gotta believe the pilot bushing/bearing is REAL bad!

Not many of you have been building manual trannys as long as I have (45+yrs).

 

Not many of you have been building manual trannys as long as I have (45+yrs).

Just beyond cool that we have resources like you here. :hurray::thumbsup: You've been rebuilding manual transmissions for 12 years longer than I have been alive. I dont mean that in a bad way - AT ALL - rather thats just way beyond cool that the experience, ages, etc on TC spans so far and is as deep as it is.

 

Bill,what kind of clutch/pressure plate are you using?

 

Hey Tom! How's it feel to be a resource!

 

Ummmmmmmmmmmmmmmm, not much feeling!

 

I'm wondering if it could be one or both of the shift forks (the fork that moves the syncros)? Maybe for some reason it doesn't come completely free an the sticking is causing it to move around. The next point is make sure you shift linkage is adjested correctly. You could be holding a bit in gear and not completely out. I have see some so bad you can't pull them out of gear when misadjusted.

 

Bill, when you pull the trans look at the bearing retainer on the front of the trans to see if it is scarred up. I had one that the throw out bearing was digging into the bearing retainer when the clutch was depressed. I was using a new throw out bearing but it had a very sharp edge on the front where it slid back and forth causing it to dig in. I finally found it when I bought a new trans and could see the gouges when I pulled the trans again. The bad bearing was a TRW, I replaced it with a cheap Chinese one from Auto Zone and havent had any problems.
Ron

 

I had a vibration problem when I first swapped the muncie into my chevelle. It was actually worse in 1st and second, but it was always there. Turns out my brand new daiken flywheel, which I bought for a 454. It had the balance boss cast into it. So I figured it was the right one was the culprit. I found a stock 454 flywheel swapped it in just to see if it made any difference and what a difference! IF your pulling the tranny anyway. why not support the oil pan and fire off the motor without the trans installed and see if you can feel any vibration. jim

 

EXCELLENT advice!!!!!!!!!!!!!!!!!!!!!!!! :thumbsup:

 

I would take a real hard look at the pilot bearing. Make sure it is the right size, or if you are re-using it, make sure it is not worn. The last clutch I changed had a full 1/8" slop between the input shaft and the bearing. Unless your clutch pressure plate is bolted on wrong, that's most likely where the vibration is coming from.

Tom

 

Bill,

There could be a number of possibilites but all the advice the guys have posted are on track. For what it's worth, I would like to share a simular problem I delt with 2 years ago

My son had a friend who sent his M20 to a professional shop to have it rebuilt. Upon installing he encountered the same situation as you. He asked if I could fix his problem after putting about 100 miles on it. I am not an expert by no means ( by trade) but have assembled and sold over 200 Muncies on ebay and private customers with no returns!

I took his trans out and found the input bronze bushing worn out which was new at time of rebuilt. I disassembled the Muncie and found the front snap ring at front of main shaft, had slipped. The input gear was swapped at the shop for one that had excessive wear where main shaft mates into input grear.

I had to replace the main shaft and input gear. The tail housing bushing was worn out as well Muncie was assembled and installed with no vibrations except over 60 mph. Had drive shaft balanced upon noticing what appeared to be a small wieght missing. Problem soved!!

Now this was work done at a professional shop ( automatic trans) Not to many old school guys left that give a darn or just out to shaft somebody

 

Hey Bill, any updates on this problem???

 

Yeah Bill...after our discussion on this issue at the CanAm show, I'm curious if you've found a solution yet.

 

Are you sure that the shifter is not hitting the crossmember while shifting it into 4th or 2nd? Both rods and the shifter lugs would be moving in a forward motion for these gears. I have seen extra long shifter lugs combined with the low 1 1/2" trans mount cause this.

As others have stated, when the clutch pedal is dressed to the floor, you are disconnecting the transmission from the engine. The gears would not spinning and no noises would be heard.

It sounds like an interference issue with the shifter or something forward the transmission. Something inside the bellhousing. To check the shifter, have someone shift it through the gears while you are underneath checking the shifter for proper operation.

If the Philly guy was Ed H. you can bet that your transmission was done correctly.

 

Re: Muncie rebuild disaster - BOTTOM LINE!

BOTTOM LINE....

Understand how things work. If you have the transmission in gear and the clutch pedal is down. The transmission is not turning. NOTHING in the gear box is turning because simply everything is locked to your rear wheels and the car is not moving.

What is happening is things are rotating AROUND your transmission input shaft because the input is locked stationary. So what can give you a vibration such as this?

Is your bellhousing fully flush to the block? Is it aligned and dialed in?