[John V.]

Does anybody have an early production '73 Muncie Side Cover?

Shouldn't it be drilled and tapped for a TCS mounted on the 1-2 Shift Lever Boss?

Some time back I was advised that I needed a 335308 Side Cover. And sure enough, the '76 Firebird MPC shows 335308 for the '73 FC or UA code trans.

As best I can tell, the UA is the code for the early production M20 (the FC presumably is the early '73 M21?).

The MPC lists p/n 3977618 for the '71-'74 4 spd codes WD and WK. It also seems likely that 3977618 was a superseding Service Replacement p/n for the pre-'73 applications, not the original p/n side cover used in actual production. And my reference shows the '73 WD as the late production '73 M20 code. This side cover should be drilled and tapped for the TCS on the 3-4 Shift Lever Boss.

So I purchased a 335308 side cover awhile ago. I have not installed it yet so I just left it on the shelf when I received it, assuming it was what I needed. But today I wanted to check the TCS switch that was included with it to confirm it was the early TCS p/n 490751.

To my dismay, the switch is actually the late production TCS 494366. And worse, I realized that the 3-4 boss is drilled and tapped for the switch, the 1-2 Shift Lever Boss includes a boss for a TCS switch but it isn't drilled and tapped.

I'm bummed and confused (dazed and confused?).

My suspicion is that Pontiac was using the 335308 early year drilled and tapped by Muncie for a TCS on the 1-2 Shift Lever Boss.

When Pontiac redesigned the EGR/TCS at mid year, they needed the 3-4 Shift Lever Boss to be drilled and tapped for the late year TCS.

Did Muncie in their apparent infinite wisdom continue to use the 335308 casting and simply revise the machining?

Surely, when drilled and tapped for TCS on the 3-4 Boss, a distinct p/n was issued by Muncie.

The MPC shows p/n 3977618 for '74 Muncies which of course were only installed part year before stopping production altogether in favor of the Borg Warner trans. I'm suspicious that p/n 3977618 did not use a distinct casting, perhaps it also used the 335308 but was drilled and tapped for the TCS on the 3-4 boss.

I have searched for an actual side cover casting showing p/n 3977618 and have yet to find one.

I suppose the distinct p/n made it possible to eliminate any confusion for Service Replacement even while the p/n on the casting was the same for both designs.

What I'm hoping is that somebody has an early production '73 side cover showing p/n 335308 and can confirm that it is drilled and tapped for the TCS on the 1-2 boss.

I'd also like to know if the TCS boss on the 3-4 Shift Lever Boss is there but NOT drilled.

It would also be useful if somebody here could confirm that an original '74 Muncie Side Cover was produced using the 335308 casting (p/n cast on the cover).

If anybody actually has a side cover showing the p/n 3977618 "as cast", that would also be of interest but for now, I'm doubting such an animal exists.

Appreciate any input here.

['ol Pinion head]

'74 Muncies had side covers with a boss on 3/4 & on 1/2, have a '74. will ck tomorrow to see if I have an early '73 Muncie, have several extra big output shaft Muncies in the rack.

[John V.]

Roger, would be great if you do have an early '73 Pontiac Muncie to check.

Attached are pix of my 335308 side cover.

You will see it has both bosses, only the 3-4 boss is drilled and tapped.

A number of references say that "some" 335308 side covers have a boss on the 1-2 but not machined in addition to having the 3-4 TCS boss.

I am convinced this claim is "wrong" on 2 counts.

First, I believe ALL 335308 side covers will have the 1-2 TCS boss in addition to the 3-4 TCS boss. And 2nd, some of them will be drilled and tapped on the 1-2 boss for a TCS, at the very least, the early '73 Pontiac application.

I believe the references have overlooked this application because it is rare.

There was no reason to have the 335308 casting if it only had a TCS boss on the 3-4. Reason being, the p/n 3952642 has the same "long" style Shift Lever Bosses as the 335308.

But it ONLY has a TCS boss on the 3-4.

I believe Muncie was compelled to issue the 335308 side cover for the early '73 Pontiac application. The p/n itself is possibly an Olds engineering p/n which leads me to think perhaps Olds also used it with the 1-2 TCS boss?

Irrespective of that speculation, by virtue of providing both 1-2 and 3-4 TCS bosses, Muncie could use the same casting for either the 1-2 application or the 3-4 application. And the p/n 3977618 was issued by Muncie for a casting 335308 side cover that was machined for the 3-4 TCS switch.

That is what allowed the 3977618 side cover to supersede the 3952642 side cover for earlier applications that originally had the 3952642 side cover.

Until I get more evidence, the above remains my speculation but it certainly fits the evidence I have found so far.

Still hoping that some others here have original '73 and '74 4 speeds that can check the side covers. For '73, early and late examples will be of interest as I expect them to all have used the 335308 casting. Will be surprised if the late '73s and the '74s used the 3952642 instead.

[camerjeff]

I will try to remember to crawl under my October 72 Built 73 Lemans wagon and get a picture of the side cover for you. I seem to remember just one TCS hole drilled and tapped, but I can not remember if it is the 1-2 or the 3-4.

['ol Pinion head]

John, here's what I have on '73 & 74 Muncies.

P3R17A (Oct 17th) No partial VIN, no CTC or CC1 case, etc. Factory worker just missed stamping it.
Side cover: 335308, has original TCS switches on both bosses.
Original Lisle drain fittings, original bolts, & stamped steel locks on frt bearing retainer

P3B13B
Side cover: "764", TCS switch on 3/4 only.
Original partial VIN stamped out of late April built '73 BG M21 TransAm
Original Lisle drain fittings, original bolts & stamped steel locks on frt bearing retainer

P4M14A partial VIN 24N103817
Side cover: "764"
Original Lisle drain fittings, original bolts, & stamped steel locks on frt bearing retainer

have another big output shaft M20 setting in solvent tank. Was painted Chevy orange, can't decode it yet. I believe another '73 issue.. Side cover bolts are hardware store issue.

['ol Pinion head]

Made a mistake, on all the '73 & 74 Muncie 4spds I looked at today with single boss side covers & a TCS switch on 3/4, the last three digits of the casting number was "648" (not "764").

Have not pulled out all of the big output shaft Muncie 4spds I have, but know I have a '74 M20 with a two boss side cover. Not owning the car it came out of from day 1, that side cover may have been swapped on it at some time.

[John V.]

Roger, I'll add my '73 Muncie to the list but before I do, I wanted to confirm something,

Are you saying that the one you checked with the 335308 side cover has BOTH TCS bosses drilled and tapped and a switch installed in each?

['ol Pinion head]

Yes, the Oct 17, 72 dated '73 M20 has its original TCS switches on both bosses of the "308" side cover.

[John V.]

Another question, how many terminals are on each Switch?

Although all the references say "some" 335308 covers have the 1-2 switch boss, they also say it was never machined.

But some of the references also claim that the 335308 switch boss is for a Neutral Safety Switch.

Pontiac put the Neutral Safety Switch on the clutch pedal so that you had to press the clutch in to close the switch and start the car.

But if other Divs. mounted a Neutral Safety Switch on the trans, I'm not sure how they would set it up.

I'm thinking the switches in your 335308 might offer a clue if one or both of them have 2 terminals instead of one.?

I can't think of a reason to provide 2 TCS switches. Perhaps one was part of the Neutral Safety Switch. But seems to me, they would also need a switch for Reverse. And assuming they also had TCS, it starts getting pretty complicated.

But for sure, we now have evidence of a 335308 that was drilled and tapped at BOTH switch bosses. More on that in a follow up post.

[John V.]

Not sure why I hadn't thought to check the 4 spd section of the '73 Pontiac Service Manual previously.

But I have found a couple paragraphs and an illustration that show how the '73 side cover was set up for early production.

The illustration shows that BOTH the 1-2 and the 3-4 switch bosses were drilled and tapped. The 3-4 had a plug in it and the TCS mounted as expected on the 1-2.

With the late production redesign, Pontiac only needed Muncie to provide the drilled and tapped 3-4. Pontiac could have simply continued to use the same 335308 and just swapped positions of the plug and switch (though the switch itself may have needed to be different).

Or they could have used the 3952848 cover as they had used thru '72. I now have some evidence that at least some of the late '73 builds continued to get the 335308. And Roger has provided data on a late '73 Pontiac Muncie that got the 3952648 along with a '74 Pontiac Muncie. So perhaps Muncie used them interchangeably after the redesign.

I 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. His book is among the many references that claim the 335308 has the LONG bosses and some were cast with the 1-2 switch boss but it was never machined. His book also noted that the 335308 had a "neutral safety switch and TCS switch" but doesn't make it clear how it could have used both switches on a single 3-4 switch boss.

He was unaware that Pontiac used the 1-2 switch boss for their '73 early production TCS switch location. I am still hoping he can help me understand whether the 335308 is truly a LONG boss type cover or SHORT boss same as the 3952648.

I sure can't detect any dimensional difference in the Shifter Shaft bosses between the 335308 and 3952648 covers I have in my possession.

I did learn from his book that the 3952642 cover really does exist. He had a pic of one in the book and described it as the first long boss cover. He also mentioned that it is more rare than other covers though he made no mention of the application(s) for it.

Roger if you can post pix of your side covers, I m trying to see what I can learn from the date "circles".

[John V.]

Jeff, hope you will still check your '73 for me, I'll keep reminding you on this thread! Seems like evidence will be difficult to collect. So I hope you'll come thru with yours.

Need the '71 & '72 4 spd owners to help out here too.

I will regurgitate what Roger posted along with the correction made and I've added some comments just to trigger more discussion. I will add my '73 Muncie to the list as well.

Mine came out of a '73 Corvette and was believed original to that car. The owner was swapping in a 5 or 6 speed and had no use for it.

I'm not conversant with what might look untouched vs. not so I'll just list the pertinent nos. There is no metal p/n tag present which I would think could help as the presence or lack of the original p/n tag is some evidence to support whether the side cover was original to that trans..

On the one I have in particular, the date coding on the side cover makes me think it might not be original to the trans. Until I can collect additional side cover date info, I can't really say one way or the other and I have no idea if the Corvette crowd would know what side cover is "correct" for a '73.

'73 Corvette
P3S02A (Model Year 1973, Assembled November 2, '72, M20 gears)
Partial VIN stamp: 13S407205 (Pretty early build, '73 Corvette VINs ranged 400001 thru 434464)
Side Cover: 3952648

'73 Muncie (application unknown)
P3R17A (Oct 17th) No partial VIN, no CTC or CC1 case, etc. Factory worker just missed stamping it.
Side cover: 335308, has original TCS switches on both bosses.
Original Lisle drain fittings, original bolts, & stamped steel locks on frt bearing retainer

'73 Trans AM (out of a late production TA though with a Feb 13 Trans Assembly date, how could Muncie know Pontiac wouldn't need the 335308 cover for an early production build)? Was Pontiac already ordering Muncie's at that point for the redesigned late production?)
P3B13B
Side cover: 3952648, TCS switch on 3/4 only.
Original partial VIN stamped out of late April built '73 BG M21 Trans Am
Original Lisle drain fittings, original bolts & stamped steel locks on frt bearing retainer

'74 Firebird
P4M14A partial VIN 24N103817
Side cover: 3952648
Original Lisle drain fittings, original bolts, & stamped steel locks on frt bearing retainer

['ol Pinion head]

Originally Posted by John V.

Another question, how many terminals are on each Switch?....

ONE terminal on each TCS switch.

['ol Pinion head]

John, on '71's & '72 Pontiac application Muncie 4spds, I'll have to ck castings on original side covers on my examples. All of the '71 & 72 Pontiac application Muncies that I have, & have had, follow the following TCS switch usage:

-'71 side cover has the boss on 3/4 (front).
-Only 400 engine equipped Muncie 4 spds (M20 & M22) had a TCS switch (single flat blade)
-Original side covers on '71 455 HO M22 cars have a thin hex headed plug that is tightened into the 3/4 boss. Have owned three '71 LS5 M22 cars, & all of their M22's side covers were that way.

Believe all '72 usage Muncie 4 spds have a TCS switch on the 3/4 boss. That's what I've seen, & have on several original '72 Muncie 4spds. My '72 T/A is in bodywork phase & i have yet to reinstall the original drivetrain back in it, sorting out the TCS switch/solenoid wiring, hopefully in the next year.

Will get you a few pics tomorrow evening, feel free & PM me a phone number I can text you pics.

[John V.]

IIRC, the '76 Firebird MPC corroborates the lack of TCS on the HO.

I'll PM my number shortly.

There is a restored '74 Camaro M21 trans on ebay.

P4M10B, partial VIN 14N156267 (August 10, 1973 assembly date)
Side Cover: 335308
Has the later cast date marking on the side cover but not a complete pic of it so not sure how it compares with other pix I've been receiving.

Seller says "with correct side cover 335308" but that doesn't necessarily confirm that the trans was restored with its original side cover or if the builder put a 335308 cover on it believing it to be correct.

It does have the TCS on the 3-4.

It looks like early castings of the 335308 have the two 1/2" dia. circles as the date and status markers but at some point, a different larger circle was used with the year in the center. Looks like the 1/2" circles remained on the casting but unused for a time and then began to disappear. I'll need to see a lot more of them though to get any kind of handle on what I'm seeing so far.

Got no reply from Paul Cangialosi about the long vs short boss with respect to the 335308.

Based on what I observed/measured, I am convinced the 335308 is a SHORT boss cover, the published references got it wrong. Unless someone has evidence to the contrary, I am convinced the 3952648 is interchangeable with the 335308 for all applications that only required the 3-4 TCS location and there is no different in the length of the Shifter Shaft bosses between these two covers.

Roger, the 335308 you have with 2 switches installed seems odd. I cannot think of any application that would make use of 2 TCS switches. And if one was used as a Neutral Safety Switch (it's just a switch so wouldn't necessarily be used in the TCS circuit), I can't understand how it could be used for that purpose by itself. I think it is more probable that somebody added a 2nd switch to match to their application, for example, an early Pontiac trans with a 1-2 TCS switch subbed into a '74 application that needed a 3-4 TCS.

Even possible that this trans was OE in a late production Pontiac that was still in inventory when the March 15 redesign went into production. Pontiac could have added the 3-4 switch and just left the 1-2 switch in the side cover, but not connected.

All to say, I can't think of an application that would make use of switches on both the 1-2 and the 3-4. Maybe somebody has encountered such a thing? But given that the Muncie experts (folks that are probably most familiar with Chevy applications of the Muncie) seem to be unaware of the 1-2 boss ever being drilled and tapped, I'm guessing the only application that ever needed the 1-2 boss drilled and tapped was the early '73 Pontiac.

[John V.]

Was pointed to a thread on nastyz28.com which discussed some late installations of the Muncie after the B-W had already entered into production.

I'll list some of the data from the trannies posted there.

'74 Camaro
P4R23B (Assembled October 23, '73, M21 gears)
Partial VIN stamp: 14N192910 (Full disclosure, there is a 2nd partial VIN that was X'd out and this VIN stamped. There is reason to believe the X'd out VIN was done by the factory, not certain why it happened. But the Camaro with VIN sequence N192910 was built in April, some time after the B-W entered production. The Camaro this was original to was not in existence. Apparently the X'd out VIN was not especially unusual, see next listing.)
Side Cover: Not stated

'74 Camaro
P4R24B (Assembled October 24, '73, M21 gears)
Partial VIN stamp: 14N179503 (Full disclosure, there is a 2nd partial VIN that was X'd out and this VIN stamped. There is reason to believe the X'd out VIN was done by the factory, not certain why it happened. But the Camaro with VIN sequence N179503 was built in March, some time after the B-W entered production. Apparently the X'd out VIN was not especially unusual.)
Side Cover: 335308

'74 Camaro
P4R24B (Assembled October 24, '73, M21 gears)
Partial VIN stamp: 14N136413 (Full disclosure, there is a 2nd partial VIN that was X'd out and this VIN stamped. There is reason to believe the X'd out VIN was done by the factory, not certain why it happened. But the Camaro with VIN sequence N136413 was built in December, before the B-W entered production. Apparently the X'd out VIN was not especially unusual.)
Side Cover: Not stated

'74 Camaro
P4S05B (Assembled November 5, '73, M21 gears)
Partial VIN stamp: 14N128324 (The Camaro with VIN sequence N128324 was built in November, before the B-W entered production.)
Side Cover: Not stated

I found it interesting that 2 of the above Muncies went into Camaros that were built after the transition to the B-W had begun.

The trans assembly date stampings for all 4 of the above are also pretty late. In the same thread it was indicated that Muncie 4 spd trans assembly production ended prior to January '74 so Oct and Nov '73 Trans Assembly date codes would be approaching the end. And the thread also indicated that initial B-W installs may have begun in February '74. So the data also shows that Norwood didn't completely stop installing the Muncie at that same moment. Perhaps they had a glut of M21 Muncies so continued to use them up on Z28s and TAs? Perhaps they even had M20 Muncies still to use up. And this was just Norwood, other Final Assembly Plants may have also been using up the Muncies they had on hand and phased in the B-W as the inventories were depleted. Whatever the case, I now have some inkling about the use of the Muncie during the transition to the B-W during the '74 Model Year.

It does seem that the 335308 side cover was the predominant, if not exclusive, side cover on the last of the Muncies assembled in October and November '73 for '74 builds.

Since I don't have much in the way of cast dates from the 335308 side covers themselves, can't say when they were being cast. So far, the latest trans with a 3952648 side cover was assembled on a '74 trans dated August 14, '73. For now, I'll simply guess that around that time Muncie may have been running low on 3952648 side covers and likely were only casting the 335308 covers as they could be used to service any '73 or '74 application and for that matter any '69 up application, just needed to plug any unused switch bosses.

Clearly, the 335308 was being cast at the start of the '73 Model Year since Pontiac could not have used the 3952648 for early builds as it lacked the necessary 1-2 switch boss. Less clear is whether they continued to cast the 3952648 or were simply using up inventory of them that were carried over at the close of '72 Model Year production. No doubt the '72 strike could have left Muncie with a larger than usual supply of unused 3952648 side covers with no reason not to use them except for early '73 Pontiac applications. A study of cast date marks on both side covers might help to answer that question.

Here's a few other bits of data I've received:

'73 Firebird
P3R17A (Assembled October 17, '72, M20 gears)
Partial VIN stamp: 23NXXXXXX (VIN not provided.)
Side Cover: 335308

'74 Firebird
P3E22A (Assembled May 22, '73, M20 gears)
Partial VIN stamp: 24NXXXXXX (VIN not provided but note, this Muncie was expected to be installed in a '73 Firebird but instead was carried over and wound up original to a '74 Firebird.)
Side Cover: 335308

'74 Firebird
P4R10A (Assembled October 10, '73, M20 gears)
Partial VIN stamp: 24NXXXXXX (VIN not provided.)
Side Cover: 335308

'74 Camaro
P4R09B (Assembled October 9, '73, M21 gears)
Partial VIN stamp: 14NXXXXXX (VIN not provided.)
Side Cover: 335308

['ol Pinion head]

'73 M20 pictures on the way.

only '74 Muncie I currently have is partially disassembled, sending pics. the chevy orange fine spline M20 its a CT (counter transmission), so not really of any relevance to the discussion.

[Formulabruce]

My buddies '74 Formula Muncie info. Ordered car.
Have Not seen a later Muncie Bird, have any of you?

['ol Pinion head]

Bruce, I have not. Sent some pics to John V, hopefully he will post them.