Correct 1970 M21 Side cover and shift forks

[rjohns]

Is casting # 3831707 correct side cover for 1970 M21 Muncie 4 speed?

Also,are correct shift forks the ones that accomodate bolt to hold on shifter fork arm for 70 GS 455 /Stage 1 car as opposed to shift forks that protrude out of side cover needing just a nut to attach shift arm?

Feedback appreciated

[1972 Stage 1]

Rich,

I believe the correct side cover is # 3952648, and it has the TSC switch.

From what I was told by a Muncie re-builder, 1970 transmissions required three bolts (therefore no nuts) to connect the levers to the fork arms.

[JDB]

Side Cover
<TABLE cellSpacing=4 cellPadding=4 width="90&#37;" align=center bgColor=#cccccc border=0><TBODY><TR><TD>3831707</TD><TD>1963-1965 Early side cover stud type shift shafts</TD></TR><TR><TD>3884685</TD><TD>Cover issued with "584" tail stud type shift shafts</TD></TR><TR><TD>3950306</TD><TD>Short boss with bolt on type shift shafts - no switches</TD></TR><TR><TD>3952642</TD><TD>Long boss bolt on type w/ TCS switch on 3-4</TD></TR><TR><TD>3952648</TD><TD>Short boss bolt on type w/ TCS switch on 3-4

</TD></TR><TR><TD>335308</TD><TD>Long boss bolt on type with neutral safety switch. Some have a boss for the switch that is cast but not machined on 1-2.</TD></TR></TBODY></TABLE>


http://www.5speeds.com/casting.html

[flynbuick]

http://www.buickperformance.com/JLore.htm

Scroll down a few pics to see the correct one on our 70 GSX. Yes it has the switch.

[rjohns]

Thanks everyone
My trans is correct however side cover and forks are not.
Anyone have a 3952648 side cover and correct forks for 70 M21 Muncie trans for 1970 BBB 4 speed application?
Let me know
Thanks

[1972 Stage 1]

Rich,

Call Kajun Jon at 254-694-6600, or visit www.kajunjon.com. Tell him I referred you - he's rebuilding a few Muncie's for me.

He has the covers in stock at $50 each. It may not have the correct single terminal TSC switch, but they may be available new???

[flynbuick]

Rich,

It may not have the correct single terminal TSC switch, but they may be available new???

I doi not think so. I had to find NOS and it was not easy. If someone knows of these been available new I would love to know. Everytime I have seen that said they had the wrong switch in mind.

[rjohns]

Thanks James I will give them a call.
Does any one have a close up pic of sidecover showing TSC switch?
Also what is the TSC switch's function/purpose?

[flynbuick]

It has a detent ball on the end that threads into the case. When depressed it activates an internal electric switch. The switch is connected through a plug to the wiring harness to the vacuum solenoid mounted at the carb. The solenoid is connected to the distrbutor vacuum advance via a vacuum line. If I remember correctly when you go to 4 th gear the ball is depressed and it sends a signal to change the ignition advance.

[rjohns]

That makes sense Jim
Do you have a closeup pic of side cover and or switch?
Thanks Rich

[flynbuick]

Here is a sample

[1972 Stage 1]

Rich,

Here are some close up pics. Used TSC switches like this one sometimes have a broken terminal, but as long as the plastic retainer is intact, your wiring harness will still snap onto it and it will look fine, but obviously not work. Some of the other types of switches have two terminals, but do not have the plastic retainer for your original harness. Hope this helps.

[rjohns]

Wow Jim and James
Thank you very much for taking the time to post pics of the correct side cover showing switch.
This is a very unique side cover ,now I know what to chase down
Thanks again guys!:beer

[JDB]

Rich,

You can still get the switch from AC Delco.

AC Delco # D6404 GM # 3996286

[1972 Stage 1]

Rich,

You can still get the switch from AC Delco.

AC Delco # D6404 GM # 3996286
Great info! Thanks, JDB! :TU:

[flynbuick]

That would not be the original part number but there could have been a number change. Someone else showed me a Delco unit some time ago and I compared it to the NOS unit. It was different but I cannot remember the details. The one you show appears to be shaped like the one in James cover. It would be good if it will work or is the same.


see 1970 Assembly Manual page 7-9.1

9799850 switch assembly (This is the NOS unit I used In out 4 speed GSX)

3906462 gasket

[JDB]

That would not be the original part number but there could have been a number change. Someone else showed me a Delco unit some time ago and I compared it to the NOS unit. It was different but I cannot remember the details. The one you show appears to be shaped like the one in James cover. It would be good if it will work or is the same.

Jim,

Like AC Delco # D6403


<TABLE width=700 border=0><FORM onsubmit="return validateForm()" action=ViewPartImage.jsp><TBODY><TR><TD align=middle></TD></TR><TR><TD></TD></TR>
<TR><TD align=middle>http://198.208.187.182/servlet/com.entigo.acdelcocatalog.servlet.ProcessImageServ let?languagecd=EN&countrycd=US&user=InternetUser&mfgname=&prodlinecd=&acpartnbr=D6403</TD></TR>
</TBODY></FORM></TABLE>

[TXGS]

thanks for sharing this info.:beer

[flynbuick]

No, the 6403 does not have the spade terminal as is required. The 6404 does have the correct terminal. I would examine it for the depth of the detent ball into the case which is critcal and whether the switch is normally open or closed as is required.

[1972 Stage 1]

I can't verify that the switch/terminal in my picture above is correct. It's what came in a transmission I acquired.

My new M&H wiring harness for a manual trans has different plug that will not work with either switch JDB posted since it requires two terminals (looks just like the TH400 detent plug). So, either M&H mislabeled my wiring harness, or the correct TSC switch should have two flat terminals that form into a "T".

Who has an original manual trans wiring harness to verify the TSC plug type?

[flynbuick]

I did and I remember one spade. Mine was broken off also. Are you sure the plug you are looking at was not intended for the carb solenoid?

[1972 Stage 1]

If it's one spade, then M&H mis-labeled my harness. This looks like an automatic detent plug on my harness. I do remember seeing two spade TSC switches, but don't recall the position of the terminals and thought they used a different type plug.

[JDB]

Photos M&H 4 speed harness

[1972 Stage 1]

Photos M&H 4 speed harness
Looks like my harness is labeled wrong and going back. It also has the A/C compressor plug on it and it's labeled correctly with M&H part # 36256 for a non-air 4 speed. :rant:

So the correct appearing switch is the single spade Delco D6404, GM 3996286 pictured above.

Thanks for the help. This is the type of info that makes this board great. :beer

[flynbuick]

We bought new harnesses from M & H and they got it correct. Must be a mistake on the one they sent you. I bet they do not get many calls for these but they tell me they work from the factory blueprints.

[JDB]

That would not be the original part number but there could have been a number change. Someone else showed me a Delco unit some time ago and I compared it to the NOS unit. It was different but I cannot remember the details. The one you show appears to be shaped like the one in James cover. It would be good if it will work or is the same.


see 1970 Assembly Manual page 7-9.1

9799850 switch assembly (This is the NOS unit I used In out 4 speed GSX)

3906462 gasket

Jim,

I found the differents in # 3996286 (Left in photo) & broken # 9799850 (Right in photo).

Also posted photos of wire harness connected to TSC switch.

[flynbuick]

Yes I see you did. I am glad my memory had not totally failed me. The stock wiring boot will not fit flush on the 6404 but it looks like the distance the detent ball penetrates into the trans may be the same. If the switch being normally opened or closed is the same it will work.


Did you measure the penetration depth? From the pic they look the same but there is nothing like having it in your hand.

[rjohns]

Rich,

You can still get the switch from AC Delco.

AC Delco # D6404 GM # 3996286

Thanks JDB
I will order one on Monday:TU:

[PaulGS]

The same switch with the stud pin connector instead of a spade connector is part # 3996286.

[1972 Stage 1]

I tried ordering GM #'s 3996286 and 9799850, as well as Delco D-6404, but it has been discontinued.

Does anyone have a source for ordering one of these TSC switches?

Thanks.

[TXGS]

I tried ordering GM #'s 3996286 and 9799850, as well as Delco D-6404, but it has been discontinued.

Same here.

I tried a local shop that carries AC delco and the part number is good however they do not have any in inventory and are not able to get them.

[PaulGS]

I have the switch with the stud pin connector - part # 3996286.

NOS with the original box.

$50 shipped.

PM me if interested.

[rjohns]

Sent you PM

[rjohns]

Looking to purchase Cast # 3952648 side cover with shift forks,anyone have one?
Let me know
Thanks Rich