Muncie 4-sp synchro rings; early/later design

[Wayne M.]

# 3831742 is called out for '63-65 Muncies; # 3880850 for '66-up. Are the two designs operationally interchangeable ? I realize the later # is stronger, but are there use restrictions based on hub (short/long) or slider design ?

If Joe L. is lurking, am curious when GM service stock was no longer available. My 1970 P&A30B still shows the early one (and obviously the 2nd design). But my 1980 Parts Price book shows neither #. Were they superseded ?

[Bob J.]

Re: Muncie 4-sp synchro rings; early/later design

[quote=Wayne Midkiff (3437);340164]# 3831742 is called out for '63-65 Muncies; # 3880850 for '66-up. Are the two designs operationally interchangeable ? I realize the later # is stronger, but are there use restrictions based on hub (short/long) or slider design ?

If Joe L. is lurking, am curious when GM service stock was no longer available. My 1970 P&A30B still shows the early one (and obviously the 2nd design). But my 1980 Parts Price book shows neither #. Were they superseded ?[/quote

Wayne, I think to use the later syncro ring in an early muncie you must use the corresponding syncronizer,so they are not interchangeable. The inner hub in the later syncro is shorter to make up for the thicker ring.
Good luck,Bob

[William C.]

Re: Muncie 4-sp synchro rings; early/later design

Absolutely the rings are not interchangable unless the hubs are interchanged also. The wider hub of the '65 and eralier Muncie will create a bind with the thicker collar of the '66-up design blocker ring and the drag will destroy the blocker ring in no time (Don't ask how I learned this in 1969) The '66-up blocking rings are a good upgrade as long as the entire assembly including the hub is changed as a unit.

[Joe L.]

Re: Muncie 4-sp synchro rings; early/later design

# 3831742 is called out for '63-65 Muncies; # 3880850 for '66-up. Are the two designs operationally interchangeable ? I realize the later # is stronger, but are there use restrictions based on hub (short/long) or slider design ?

If Joe L. is lurking, am curious when GM service stock was no longer available. My 1970 P&A30B still shows the early one (and obviously the 2nd design). But my 1980 Parts Price book shows neither #. Were they superseded ?

Wayne----

I agree with Bill and Bob; the 63-65 synchro rings are not interchangeable with the 66-74.

The 63-65 rings, GM #3831742, were discontinued in December, 1976 and replaced by GM #357225. The latter were discontinued without supercession in January, 1997.

The 66-74 rings, GM #3880850, were discontinued in November, 1976 and replaced by GM #357234. The latter were discontinued without supercession in October, 1991.

Some folks feel that the 3831742 and 3880850 were superior to their respective replacements. I tend tend to agree with that assessment, although the replacements will perform adequately.

[Michael G.]

Re: Muncie 4-sp synchro rings; early/later design

Some folks feel that the 3831742 and 3880850 were superior to their respective replacements. I tend tend to agree with that assessment, although the replacements will perform adequately.

Joe,

Looking at master rebuild kits for my '66 transmission have observed most kits offer brass synco rings. A couple of companies offer bronze. What was the original material syncros were made of in the Muncie? Would the bronze hold up better or is person good to go with brass syncro?

Any one else want to chime in?

[William C.]

Re: Muncie 4-sp synchro rings; early/later design

Originals were brass. I have no experience to comment on the bronze application, and there are different "flavors" of brass. I'd ask myself the question, does the metalurgist working for some aftermarket outfit know more about materials properties and transmission design than the guys who originally designed one of the most successful 4 speed transmissions in automotive history?

[Michael G.]

Re: Muncie 4-sp synchro rings; early/later design

Bill,

What are you trying to say ? Please explain.

[William C.]

Re: Muncie 4-sp synchro rings; early/later design

What I'm trying to say is that the original design was brass and that the people who designed the trans did that for a living, with many thousands of successful results. I don't know who designed the replacement part nor do I have any confidence that they have a half million or so successful applications of their product to demonstrate, so why take the chance?

[Wayne M.]

Re: Muncie 4-sp synchro rings; early/later design

Joe,

Looking at master rebuild kits for my '66 transmission have observed most kits offer brass synco rings. A couple of companies offer bronze. What was the original material syncros were made of in the Muncie? Would the bronze hold up better or is person good to go with brass syncro?

Any one else want to chime in?

Wow -- saw my name and date at the top of this thread and thought I was in a time machine . Tried googling to get the definition of bronze versus brass. Anyway, thought I'd post 4 thumbnails 2 each of the '63-5 '742's, and another two of the '66-up '850's. Notice the higher shoulder on the later design -- requires different hub width as previously mentioned.

I have a dozen of the early type and 10 of the latter -- waiting for if I ever rebuild the 5 trannys I have . A bit of blue/green corrosion on the rings after all these years, but cleans to a brilliant sheen with a little brass polish.

Sorry I can't answer your initial question, but just thought the DB guys would like to see the originals, and the differences.

P.S. Did GM ever issue synchro rings with vertical grooves on the inside, or are those service rings from other suppliers ?

[Michael G.]

Re: Muncie 4-sp synchro rings; early/later design

Thanks for the clarity Wayne....however post is regarding bronze snycros as they compare to brass. Bronze as I understand it has tin incorportated into the mixture giving it additional strength. In saying that does it make for additionally durable syncro....or will brass be sufficient. Thanks.