[Half-Inch Stud]

Originally Posted by one70gt37

Well i was fortunate for a while, lol, it worked a little better but is now acting up again, grinding bad going into 4th, we have checked everything out on the outside, linkage bolts, shifter alignment etc,, it's coming back out to see whats wrong s***!. In the meantime i'll put back in my m-20 wide ratio.

This is a replay of a bad dream I had ~22 years ago. Means your back at (my) Post #6.

[Dragncar]

I have a 69 GTO that had a M21 and kept popping out of 1st gear and the linkage would get stuck in second on the 1-2 shift if I banged it hard.
I put a Ford Top Loader in it. Even came up in the right place stock console after some modifying.
You could not tell a thing unless you looked under your car.
Muncies are not all that strong, 65 pounds compered to 115 pounds.
There are some aftermarket Italian "Muncies" that the die hard 4 speed guys use at the track that are real tough.
The Top Loader does not shift as smooth as the Muncie did.
I have a aluminum Borg Warner in my 79 Trans Am and it does not shift as smooth as the Muncie did either. Tough looking tranny though, has a giant output shaft.
But I took it out and put a T350 in the car.

[one70gt37]

Originally Posted by Somanycars

When you get it apart I would look closely at the keys and springs in the hub assembly. maybe binding ?or a 63-65 synchro used with a later model hub.The hub and synchro have to be from the same family.63-65 uses non shouldered brass and 1-1/8 wide hub.66-74 shouldered brass 1 inch hub.You can use either matched assembly in either years of transmission but synchro must match hub.

Thanks again, we will look into that when it's apart on his bench, will let you know what he finds, he's been rebuilding muncies for years, you never know maybe he forgot somthing.

[69Customs]

I can't believe someone else runs a toploader! I thought for a while I was the only one. You know Dragncar a toploader may not shift quite as smooth but they are indestructable and they were used in all the cobra jets and 429 boss. So It must not shift too bad!

[Stuckinda60s]

One possibility I hadn't mentioned, because it's remote, is that there's too much clearance between the main shaft and the input shaft. That could keep the blocking ring from grabbing 4th gear and also keep the slider from full engagement on 4th. That would explain both symptoms as a new blocking ring should keep it from grating. Broken springs/dogs will allow it to grate as well.

[Red Coupe]

Here is the problem that caused my Muncie to pop out of 4th - worn/broken pre-engagemet teeth on the input shaft. As you can see, doesn't take much to cause a problem (like some missed powershifts). Something to look for if you take it apart.

BTW, not that hard a job to do yourself if you are mechanically inclined.