1969 Muncie restoration

[RPOZ11]

Thought I would start this one...

I am in the process to do 2 rebuilds of M20 transmissions.

I am looking at the bolts for the front retainer, side cover, speedo tab bolt, and the bolts for the rear tail housing.

I looked at the transmission mount bolts that I have and they are TR bolts.

The speedo bolt at the tab is an "L".

So far, I have some SBC & TR tail housing bolts.

Can you guys offer up what I need to be correct for my M20's???

[68camaroz28]

I'm not sure you have anything to do as everything you mentioned I believe are bolt suppliers that GM used so they would/could be correct. I've got mixes quite a few places. Did not go out and check our M21's to compare but nothing you mentioned seemed out of line.

[RPOZ11]

Well, so far... my walk has determined some of these Bolts.

RSC , RBW , TR Bolts on the tailshaft housing.
The Tailshaft housing has 3 larger diameter bolts on the at 5, 6, and the 7 o'clock positions.

SBC , RSC , and TR for the side cover bolts.

TR ( for now ) for the front retainer.

RBW and L for the speedo gear tab.

Now, I just had my 1969 M20 rebuilt for my coupe.
Everything we had for it was TR bolts and the speedo gear tab was an RBW bolt.

The Drain Plug is a W.

I pulled out my PaceCar's M20 and I have a Metal ID tag of 3950356.

Would like to ask others here to contribute to this thread to gauge any variances across the years.

[RPOZ11]

Been doing several things to get my M20's correct.

However, I do have 2 questions...

1 : How do we decipher the clock date time stamping on these?

2 : I am at the pointe of trying to decide which side ciover that I have should be correct for a January - March Van Nuys build.

I have 2 here with different font sizes.

The first image has much less casting flash cracks vs. the second one.

What are the differences between the 2 castings and why???

Here are the 2 that I have to select from :

[68camaroz28]

What are the date codes on the cover (cast in ciircular area)? That would or should assist you in determining which one to use.

[RPOZ11]

Well, That is exactly what is desired in establishing this here.
Looking for input from knowledgable people who can contribute to this thread regarding the details of restoration, assembly, and defining the minute points of these Muncies.
I see fonts present on what I have as core side covers.
4/7
1/6

[KurtS]

The variation in the side covers could be just from die variation.

[RPOZ11]

Was there only one factory casting for the Muncie assembly division, or

Is there any timeline as to when the changes took place?

Van Nuys vs. Norwood?

[KurtS]

Only one plant.
Muncie did their own castings in-house. That's a diecast part, vs the sand casting of the main case. Question is - is it even a time-based change?

[RPOZ11]

So would either side cover pass a judge's inspection?

Any commentary on the casting times in front of the caster part number?

[RPOZ11]

Here is my M20 rebuilt.

[RPOZ11]

Found another shot of my M20.

Having some stands made out of aluminum.
Hope to have those posted soon.

[RPOZ11]

Hey all...

I just built up my 3'rd M20.

I purchased this unit decribed as being rebuilt by a very reputible rebuilder.

I found many used & damaged items inside when we popped the side cover open and after initial teardown.
Needless to say, I was not very happy!  
The rebuild cost me, but after proper inspection and replacing with new parts,
I now have a really sweet M20.


Bad parts :
Cluster shaft badly pitted and worn
Countershaft Roller Spacer/Washers for some reason were indented by the roller bearings
Synchros were used
Clutch Hubs were both bad
Speedo Plastic gears were worn and broken
Maindrive Bearing was used
Worn engagement teeth
Reverse, 3'rd, and 4'th had damages to the actual teeth tips
Tail Housing threads had helicoils; typical
Main Case ended up being OK after many hours of detailing


1'st and 2'nd gear both were OK, oddly.
I ended up replacing all of the above parts with brand new pieces.
Some Italian, some typical rebuild parts.

I am going to post up a few images of the 3'rd gear and 4'th / Input shaft.
Someone before me owning this M20 ground down some of the engagement teeth.
Interestingly..
Both engagement ground locations were at 6 & 12 o'clock postions.
I ended up replacing both with Italian Gears.

Can you folks tell me why someone did this to these gears?




















The M20 completed; sorry for the fuzzy image.