gear grinding

[William F.]

Having some grinding noises sometimes when I shift my '67 M21 tranny. Seems to happen if I apply pressure to the right on the shifter when upshifting from 2nd to 3rd or downshifting from 4th to 3rd. Is this likely a maladjustment of shift linkage or something wrong with shifter mechanism itself? Would seem unlikely to be an internal trans problem since problem is related to right side pressure on shifter. Problem doesn't occur if I am careful not to put right sidde pressure on shifter when making shifts mentioned.
Thanks

[William C.]

Re: gear grinding

Most likely your pressure is causing two shift levers to attempt to move at the same time. There are spacers in the shifter to prevent this problem, yours could be worn or missing. How much pressure are you exerting to cause this? Is there noticable looseness or "slop" in the shifter?

[William F.]

Re: gear grinding

William C.
Thanks for the reply. I'm only putting the usual right side pressure on the shifter when going grom 2nd to 3r. Not really trying to put any right pressure on shifter when downshifting from 4th back to 3rd-just notice that I have to be careful to go straight up ,avoiding ANY pressureto right on this downshift or I'll get this serious grinding. Where are the spacers in the shifter? Any photo in AIM or in any of the vendors'catalogs-Paragon, Long Is., etc.?

[William F.]

Re: gear grinding

Do you think the "spacers" would be more likely than just shift rod lengths needing adjustment? Why?

[Ken A.]

Re: gear grinding

If you've had "serious" grinding, then it's time for a tranny overhaul.

[William C.]

Re: gear grinding

OK, lets look at how the shifter and the gearchanging activities in the transmission are conducted, specifically in the sidecover where the shifter forks are contained. There is an interlock assembly that consists of two arms and a spring. The arms are constructed in such a manner that if the 1-2- shift arm is being activated, all movement on the 3-4 arm is locked out. Based on your description of the problem, I'd pull the sidecover and check that all springs and the associated parts are there and in good condition. I suspect a broken spring or spring attachment point on the arm. I'm attaching a picture that should make it more clear hor the side cover operates in gear selection (and non selection of multiples). The spring on the top between the two arms causes the arm to lock in place once a gear is selected and at the same time locks out movement of the other gears. You may have a damaged or broken pin on one of the shifter forks causing the interlock to malfunction or a spring problem. NO AMOUNT of side force on the shifter during normal operation should be able to overide this lockout system. This is for a muncie as per your '67 notation, but warners have a conceptually similar feature, although different in its execution.

[John H.]

Re: gear grinding

Here's a photo of that same area.


SideCoverInside.jpg

[William F.]

Re: gear grinding

Thanks for the replys, but:
1. Don't think I need a tranny overhaul since problem is related to shifter position-side force.
2.Concerning parts related to side plate- I can keep grinding from happening by very carefully applying only enough right side pressure on 2nd to 3rd shift to keep it from going back into first and when downshifting from 3rd to 2nd by making sure I push the shift lever straight forward with no right side pressure. Conversely, I can make it grind by applying slight side pressur on these same shifts. Wouldn't this point to some kind of problem external to the tranny itself, such as improper shift rod adjustment or a problem in the shifter mechanism?If I kneew what the problem is, I wouldn't be asking, but those are my thoughts. What would you check with my decription of the problem?
Thanks again

[William C.]

Re: gear grinding

OK, shifter exploded view attached. About the only shifter problem I have ever seen that (might) haqve the effect you are reporting is onece I had a shifter that had a broken weld where the outer case overlapped at the rear and the spot weld was broken. Otherwise there isn't too much to go wrong with the shifter. You have to remove the shifter to pull the trans, so there is no harm in checking it to see if the housing is intact and all the parts are present. It can be "tightened" slightly with a press if things are too loose (rattles) but it is essentially bulletproof otherwise. I still believe you will find your problem inside the sidecover, but it's good to eliminate other possibilities.

[Ray K.]

Re: gear grinding

First -- I would remove the shifter assembly from your 1967 and put it on the workbench, disassemble it and look for anything that appears to be bent, broken, extreme wear, or missing. After correcting anything that you might find in the previous task, I would then re-assembly the shifter unit and lubricate everything in the process.

Second -- Just for giggles -- and if you are ambitious and curious -- I would remove the shifter cover and inspect the cover for cracks or breakage, inspect the shifter interlock levers and spring mechanism, and also inspect the shifter forks.
The forks can be easily removed from the synchronizer shifter collar and examined, look for extensive wear on both the forks and the synchronizer collars. You may need a mirror to assist with looking inside the trans at the syncro units.

Third -- If all the components look okay, re-install the shift forks and shifter cover. Install the shifter assembly and then make sure all the shifters rods are adjusted correctly. Not sure what you might find, but it seems to me that something inside the trans is amiss - concerning the synchronizer shift collars / and or forks.

Ray

[William C.]

Re: gear grinding

I'm with you Ray, in that sequence!

[Domenic T.]

Re: gear grinding

William,
If you remove the side cover take a good look at the syncro. That is what makes the grinding noise as the forward gears never leave the cluster.
The gear itself will look great so look at the syncro that is part of the gear (little dog houses). The brass ring usually survives but the slider and the syncro on the gear are the ones that grind and you may have the beginning of a bad syncro.

DOM

[William C.]

Re: gear grinding

Unfortunately, the little brass unit is the clutch that makes smooth shifting possible, so replacing them requires complete disassembly of the trans, still not likely related to his problem of grinding with pressure on the shifter to the side...

[Domenic T.]

Re: gear grinding

I agree,
But it is always a good idea to look at all the possibilities.

Statistically out of all the trannies that I rebuilt the majority ended up being a syncro problem as 3rd gear is the one that most guys miss when racing.

I sincerly hope it is a shifter problem as the syncro is the worst case.

It never hurts to look, especially if one go's thru the trouble of removing the cover.

DOM