76 4sp shifter problems
09-04-2010, 12:06 AM
#1
Melting Slicks
Thread Starter
76 4sp shifter problems
Need some feedback please.
I had to replace my clutch recently as it was not disengaging. So installed new clutch kit (pilot bushing, pressure plate, and clutch disc).
Had problems with the after market pilot bushing necking down while tapping it in. On the second pilot bushing, when it necked down while tapping it in, I just reamed it out a couple of thousands over the input shaft od. I left about 1/4" exposed same as the original pilot bushing.
Also, 4 sp mated up very tight (I thought), no easy slide in here. All original bell housing and original engine, crank, and 4 sp which worked great before the clutch quit disengaging.
I got the shifter adjusted so that the gates line up and smoothly shifts through all gears with the engine not running.
However, when I crank the engine up, I can not get the shifter into reverse at all (grinds) and 1,2,3, & 4 sometimes hang up. New clutch works great and seems to disengage just fine. I can turn the engine off and put it in reverse and then start the engine again and it will run in reverse fine. While the engine is still running I can also get it in one of the forward gears, but not back into reverse at all as it grinds.
From reading some other posts, I am thinking my pilot bushing is hanging up on the input shaft some kind of way. If the pilot bushing is turning the input shaft, does that match these symptoms? Or does my 4sp need a rebuild (@70K, not likely?). The 4sp turns smoothly on the bench in all gears although the input shaft tip did have some very slight play up and down. I got a third pilot bushing and also a roller pilot bearing from Corvette America, so I am thinking I need to pull it all back apart and change out the pilot again? Thoughts on what the problem is? If necessary install a bushing or roller?
Thanks
I had to replace my clutch recently as it was not disengaging. So installed new clutch kit (pilot bushing, pressure plate, and clutch disc).
Had problems with the after market pilot bushing necking down while tapping it in. On the second pilot bushing, when it necked down while tapping it in, I just reamed it out a couple of thousands over the input shaft od. I left about 1/4" exposed same as the original pilot bushing.
Also, 4 sp mated up very tight (I thought), no easy slide in here. All original bell housing and original engine, crank, and 4 sp which worked great before the clutch quit disengaging.
I got the shifter adjusted so that the gates line up and smoothly shifts through all gears with the engine not running.
However, when I crank the engine up, I can not get the shifter into reverse at all (grinds) and 1,2,3, & 4 sometimes hang up. New clutch works great and seems to disengage just fine. I can turn the engine off and put it in reverse and then start the engine again and it will run in reverse fine. While the engine is still running I can also get it in one of the forward gears, but not back into reverse at all as it grinds.
From reading some other posts, I am thinking my pilot bushing is hanging up on the input shaft some kind of way. If the pilot bushing is turning the input shaft, does that match these symptoms? Or does my 4sp need a rebuild (@70K, not likely?). The 4sp turns smoothly on the bench in all gears although the input shaft tip did have some very slight play up and down. I got a third pilot bushing and also a roller pilot bearing from Corvette America, so I am thinking I need to pull it all back apart and change out the pilot again? Thoughts on what the problem is? If necessary install a bushing or roller?
Thanks
09-04-2010, 12:40 AM
#2
Le Mans Master
There are 2 things- 1, the pilot bushing should be flush with the recess it fits into. 2, there has been a run of semi-junk pilot bushings- one of them a magnet will stick to and the other one won't. I don't recall which one is the good one.
From your description, it really sounds like there's something dragging like the clutch is not releasing.
From your description, it really sounds like there's something dragging like the clutch is not releasing.
09-04-2010, 09:43 AM
#4
Racer
There are 2 things- 1, the pilot bushing should be flush with the recess it fits into. 2, there has been a run of semi-junk pilot bushings- one of them a magnet will stick to and the other one won't. I don't recall which one is the good one.
From your description, it really sounds like there's something dragging like the clutch is not releasing.
From your description, it really sounds like there's something dragging like the clutch is not releasing.
The pilot bushing may be binding up just enough to spin the input shaft to grind the gears , but not enough to put enough force on it to lock it up ??
Did you grease the pilot bearing & shaft ?
The pilot bushings I have used were brass/bronze material ? I think that anything with a hard metallic material would tend to gall/lock.
also you said the 4sp did not mate all the way up , it could be hitting the face of the pilot bushing on the input shaft ? I would have seated the bushing flush or deeper
Last edited by Rmorgan&11; 09-04-2010 at 09:46 AM.
09-04-2010, 10:42 AM
#5
Melting Slicks
Thread Starter
Thanks for the help.
The original pilot bushing was exposed 1/4" and the 4sp worked fine so I put it back like the original. I will put the next one in flush as you all suggest.
I think you do not want the cheap chi com bushings with ferrous contaminates which you can detect with a magnet per another post. I did not check the previous one, but I would think Corvette America has good ones and I will check before installing with a magnet.
How to check if the clutch is disengaging completely? Might could do this with the 4sp out, insert alignment tool and have my better half push in the clutch and see if it spins free???
So the input shaft should not be spinning while shifting if working properly? Anyway to check this? either with engine running or not???
I did put a few drops of oil on the bushing before installing the 4sp, thought you are not supposed to grease it?
4sp mated up ok but pretty tight to get in, not an easy slide in. I did not draw it up with the bolts which I thought was a no no.
Much thanks for the help!
I think I will install another pilot (bushing or roller bearing?)and try to make sure the clutch is disengaging 100%. More ideas on what to check are welcome. Thanks again!
I think you do not want the cheap chi com bushings with ferrous contaminates which you can detect with a magnet per another post. I did not check the previous one, but I would think Corvette America has good ones and I will check before installing with a magnet.
How to check if the clutch is disengaging completely? Might could do this with the 4sp out, insert alignment tool and have my better half push in the clutch and see if it spins free???
So the input shaft should not be spinning while shifting if working properly? Anyway to check this? either with engine running or not???
I did put a few drops of oil on the bushing before installing the 4sp, thought you are not supposed to grease it?
4sp mated up ok but pretty tight to get in, not an easy slide in. I did not draw it up with the bolts which I thought was a no no.
Much thanks for the help!
I think I will install another pilot (bushing or roller bearing?)and try to make sure the clutch is disengaging 100%. More ideas on what to check are welcome. Thanks again!
Last edited by 20mercury; 09-04-2010 at 10:48 AM.
09-04-2010, 12:02 PM
#6
Le Mans Master
If your pilot shaft is long enough that would work.
I'm not a real fan of the roller bearings, not sure why, but I'm not. Maybe it's just another place for something to fail?
During shifting on the road, the disc and input still spin, but there's no torque load, and you should be able to stop it. It does slow down when the synchro's in the trans apply a load to the input side.
Getting into reverse with a Muncie has always been a thing. No real fix, other than go into 1st and then reverse. Into first, stops the input and then right to reverse.
Just as a test before you rip it out, adjust the clutch so there's NO freeplay and try it. If that works, then look at all the linkage for movement where there shouldn't be any- frame and engine sides of the Z-bar, wear in a rod end, that kind of stuff.
If you're like me, pulling the trans is the last resort. It's not a real problem, I just never thought it was that much fun.
I'm not a real fan of the roller bearings, not sure why, but I'm not. Maybe it's just another place for something to fail?
During shifting on the road, the disc and input still spin, but there's no torque load, and you should be able to stop it. It does slow down when the synchro's in the trans apply a load to the input side.
Getting into reverse with a Muncie has always been a thing. No real fix, other than go into 1st and then reverse. Into first, stops the input and then right to reverse.
Just as a test before you rip it out, adjust the clutch so there's NO freeplay and try it. If that works, then look at all the linkage for movement where there shouldn't be any- frame and engine sides of the Z-bar, wear in a rod end, that kind of stuff.
If you're like me, pulling the trans is the last resort. It's not a real problem, I just never thought it was that much fun.
09-04-2010, 11:33 PM
#7
Melting Slicks
There was a post not long ago with similar symtoms. I believe the OP had installed his shift arms (that attach to the tranny) upside down (pointing down instead of up). He said it was shifting fine with the engine off then once the engine was running, nothing but a lot of grinding.
Possibility?
Possibility?
09-06-2010, 05:12 PM
#8
Melting Slicks
Thread Starter
Thanks for the advice.
I installed the shift arms just like the AIM picture. I would think the AIM dwg is correct. Thanks for the idea.
And I will play with the clutch disengagement again as you suggest before taking the 4sp out again. Although, I must admit I am getting pretty good at it
Also, would like to practice on something else for a change!
Thanks again for the advice and help!
And I will play with the clutch disengagement again as you suggest before taking the 4sp out again. Although, I must admit I am getting pretty good at it
Also, would like to practice on something else for a change!Thanks again for the advice and help!
09-07-2010, 06:19 PM
#9
Melting Slicks
Thread Starter
Much thanks for all of the help on the Corvette Forum!
Much thanks for all of the help on the Corvette Forum!!!
I played with the clutch pedal rod adjustment today and got the clutch to disengage a little more and it fixed my grinding going into reverse!
Thanks for the help again.
(Out of curiosity, can you damage the clutch fingers if you put too much disengagement in the adjustment? I set mine 2 or 3 flats at a time until the grinding just went away. And it seems like you need to depress the clutch a little more for reverse than for the other gears?)
I played with the clutch pedal rod adjustment today and got the clutch to disengage a little more and it fixed my grinding going into reverse!
Thanks for the help again.
(Out of curiosity, can you damage the clutch fingers if you put too much disengagement in the adjustment? I set mine 2 or 3 flats at a time until the grinding just went away. And it seems like you need to depress the clutch a little more for reverse than for the other gears?)
