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Old 07-21-2021, 03:24 PM
John V. John V. is offline
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Default '74 Muncie 4 spd Details

Been trying to scrounge up some info on these late production Muncie 4 speeds on the '70-'73 Firebird forum, thought I'd come here to see if the '74 guys can offer any additional info.

Here is the original thread I started.
https://forums.maxperformanceinc.com...d.php?t=851688

I was initially trying to figure out if I had the "correct" side cover for my early production '73 TA. I was advised it should be casting 335308.

I have figured out quite a bit, no thanks to the widely published info on the 'net about the 335308 Side Cover. I even contacted Paul Cangialosi from 5speeds.com who wrote a book on rebuilding and modifying the Muncie published in 2014. It contains all kinds of p/n info and pix. But he had no idea about the early production '73 Pontiac side cover design and seemed uninterested in learning what I had uncovered about the 335308 casting.

His book may even be the source for the incorrect info about the 335308 that has been spewed by numerous other Muncie "expert" sources and websites.

All of these references claim that the 335308 is a LONG shifter shaft boss cover. They further claim that "some" of them were cast with a 1-2 switch boss but that it was "never" drilled and tapped.

None of these claims appears to be correct.

Mr. Cangialosi's book confirms the existence of a 3952642 side cover, saying it is rarer than others and that it is a LONG boss cover, with a switch boss only on the 3-4. He doesn't identify the application(s) of this cover.

Released at the same time was the 3952648 side cover, it being the SHORT boss design, also with a switch boss only on the 3-4.

What I have determined is that all 335308 side covers have a switch boss on the 3-4 which was always drilled and tapped. But all of them also have a switch boss on the 1-2 which was always drilled and tapped for the early production '73 Pontiacs but was not drilled and tapped for some applications.

The 335308 also has the same boss dimension as the 3952648 side cover and should properly be identified as a SHORT shifter shaft boss cover.

For applications needing only the 3-4 switch boss, the 335308 side cover was interchangeable with the 3952648.

If you go by all the published references, you would believe the 3952642 was interchangeable with the 335308 but strictly speaking, you would be wrong.

This is critical because in production, a side cover with the SHORT bosses was assembled with specific short Shifter Shafts which would NOT work with a LONG boss cover. The specific Shifter Shafts used with the LONG boss cover are claimed by some references to not work with a SHORT boss cover. But apparently this is also incorrect. GM eventually discontinued servicing the short Shifter Shafts and only the long Shifter Shafts were available.

The short Shifter Shafts carried various p/ns including 3950308 which were used with the '69 side cover 3950306, this was the first that featured lever tabs secured by bolts instead of nuts. It was a SHORT Shifter Shaft boss design but had no switch bosses. Then there were the 3952651 Shifter Shafts which I believe were also short design. At the same time, the 3952649 Shifter Shafts were released, I believe these were long design and originally used with the 3952642 side cover. Eventually GM discontinued the 3950308 and 3952651 Shifter Shafts and specified the 3952649 Shifter Shafts for all Muncie 4 speed applications. It is obvious that a short Shifter Shaft could not work with a long boss cover. Less obvious that a long Shifter Shaft could be used with a short boss cover. But given the supersedures, I conclude that the 3952649 Shifter Shaft must be the long design.

But the main problem with the published references is the failure to recognize that early production '73 Pontiacs made use of the 1-2 switch boss for the p/n 490751 TCS switch that was part of Pontiac's ill-fated early '73 design TCS/EGR emissions system.

Prior to the EPA demanding Pontiac redesign the '73 TCS/EGR system, Pontiac Muncie 4 speeds used the 335308 side cover and BOTH the 1-2 and 3-4 switch bosses were drilled and tapped. Pontiac installed a thin head plug in the 3-4 switch boss, they had no use for it. The aforementioned TCS switch opened when the trans was shifted from 1st to 2nd gear (the infamous Time Delay Relay controlled the system approx. 30 secs on the 400, 50 secs on the 455 after the shift to 2nd).

When Pontiac redesigned the system beginning for cars produced on March 15, 1973, the design moved the TCS switch (new p/n 494366) to the 3-4 shifter boss.

Since it appears no other manufacturer made use of the 1-2 switch boss, Muncie could have reverted to the 3952648 side cover that had been used thru '72.

Instead, it looks like they continued to use the 335308, but they may have stopped drilling and tapping the 1-2 switch boss.

I am trying to collect as much evidence as I can to determine if this is what was done. Alternately, Muncie could have continued to supply Pontiac with 4 speeds with the TCS switch and plug positions swapped.

And it is also possible that Muncie recognized that the late production '73 and '74 Pontiac Muncie 4 speeds could make use of the 3952648 side cover and installed that instead.

It is entirely possible that a mix of these side cover choices was employed by Muncie during '73 and '74 production.

So I'm asking anybody with a '73 or '74 Muncie 4 speed to provide the side cover casting no. and the Muncie serial no. date code (example P3S02A) and partial VIN stamp (example 23N118765) as stamped on the Main Case.

Also add any comments as to how likely the trans is "original" or "rebuilt/pieced together" to give me some sense as to how likely the side cover is original to the Main Case.

Finally, if you can provide a pic showing the date coding on the side cover casting that would be great. Early 335308 castings had two 1/2" dia. circles that provide cast date info, later ones transitioned to a larger circle with a year (73 or 74 in a small center circle) surrounded by 12 pie shaped segments with dots in some or all of the segments.

The Following User Says Thank You to John V. For This Useful Post:
  #2  
Old 07-24-2021, 02:12 AM
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Formulabruce Formulabruce is offline
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I can get you that info. My Buddy has a 1974 factory Formula 400 4 speed. I have seen the trans a few times as we put a flywheel and clutch in it. I didnt take pics but verified its originality, and the hack job the factory did on the now all automatic floor pans to make it a 4 speed.
This car is the last day/ week of Muncies in Birds in 1974. It is its original M20
He has been driving this car a lot. when he is by next Ill pop it up on the lift for some detailed pics.

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Old 07-24-2021, 10:01 AM
John V. John V. is offline
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Thanks. that would be awesome to include.

Thought there'd be more 4 spd response here and in the '73-'77 A body forum where I also started a thread. Seems 4 spds were really scarce at the end of the Muncie 4 spd production era.

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Old 07-26-2021, 02:37 PM
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I'll get those pics this week, I believe his trans was built in 1974.

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Old 07-26-2021, 03:59 PM
poncho-mike poncho-mike is online now
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I have a 1974 SD455 4-spd T/A, and it has a Borg Warner ST-10. I bought the car back in the early to mid-1980s, and it was 100% numbers matching. I confirmed the VIN was stamped into the tranny case, and I questioned why it was not a Muncie.

A few years later, High Performance Pontiac came out with a "Numbers Matching" series, and it noted all 1974 SD455 4-spds were built with ST-10s. My car was built in July 1974, and I don't remember if HPP said whether all 4-spd cars changed to ST-10s or just the SD cars. BTW, there was some odd stuff going on in the late 1974s. I have another late build 1974 455 T/A automatic that the engine code wasn't listed, and it had HEI. The late cars changed from points to HEI (except the SD). At some point, I ran across a 1974 supplement to the shop manual and it listed the engine code for my standard 455 T/A with an HEI.

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Old 07-27-2021, 10:38 PM
John V. John V. is offline
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I don't have any knowledge of the '74 SD tranny usage. If all the '74 SD 4 spds got the B-W, then apparently none of them were built before January or maybe even February based on what I understand that B-W didn't start supplying the ST-10 to GM until after Dec and Muncie stopped assembling their 4 spd by the end of Dec.

The non-SD 4 spds definitely started getting the ST-10 in '74. But according to info I've learned elsewhere, these builds all got the Muncie until about Feb and a few continued to get the Muncie even after the ST-10 entered into the production stream, as late as March or April builds at Norwood from what the Z28 guys have documented. The Muncie trannies themselves in those builds however were all assembled prior to January '74 but the partial VIN stampings tell us when the car was built. I've posted some data in the '70-'73 forum thread.

Best guess, the Final Plants had Muncie 4 spds that remained in inventory after the B-Ws started showing up and they got installed in builds rather than becoming Service trannies or being trashed.

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Old 08-06-2021, 02:32 PM
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My buddies car is a Late April Formula 4 speed.
Vin is on the trans, and so is the P code marking the Muncie m20 as a Sept '73 built transmission. This tranny sat around a while. This car was ordered but have Not seen a '74 any later than this car with a Muncie M20 factory installed.

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Old 08-06-2021, 05:31 PM
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Muncie # P4P25A.
Cowl Tag = 04C W66
Main case of trans = 3925661
Side cover = 3952648
Vin 144152

On a side note, this car was ordered in Texas, But
Was ordered with RPO K05, probably because owner was being transfered to Michigan.

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Last edited by Formulabruce; 08-06-2021 at 05:44 PM.
  #9  
Old 08-07-2021, 10:13 AM
'ol Pinion head 'ol Pinion head is offline
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Here's detail on a Dec 14th, 73 assembled M20.
Was in my rack, not out of a '74 T/A that I've parted.

P4M14A
Main case of trans = 3925661
Side cover = 3952648
VIN 24N103817

Anyone have a need for this M20 to date a '74 Formula or T/A, let me know.

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Old 10-22-2021, 01:29 PM
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Quote:
Originally Posted by Formulabruce View Post
Muncie # P4P25A.
Cowl Tag = 04C W66
Main case of trans = 3925661
Side cover = 3952648
Vin 144152

On a side note, this car was ordered in Texas, But
Was ordered with RPO K05, probably because owner was being transfered to Michigan.
Pics. Second is casting on side cover.
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  #11  
Old 10-24-2021, 11:15 PM
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3tas4me 3tas4me is offline
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John,
My ‘74 T/A is a January build that has the Muncie. When I get the car home this week, I will get a pic with the info. Trans is original to the car with almost a zero chance of there being any replaced parts. I do know the side cover is a 335308 casting.

I also have a Muncie from a 1973 Grand Am. I will get that info for you as well.

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Old 10-25-2021, 01:55 PM
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Here are the pics from the Grand Am Muncie. This one is the 335308 side cover.
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