Super T10 vs M20/M21

[Shields]

Hey Folks,

As some might remember I swapped in a Super T10 into my truck and I believe it came out of a 78' Trans Am. I am looking to delete the speedo cable but I am having trouble finding a speedometer port plug that is specific to the Super T10. I have found some on Ebay that are specific for a Super T10 but they don't ship to Canada which is a bummer. What I have found is a range of speedometer port plugs for m20/m21 transmissions but I am not sure if they are the same spec as the Super T10.

The item below is a B&M piece and it says it will fit a TH350 and m20 trans, will it fit a Super T10? Will a speedometer port plug for an m21 fit a Super T10?

Thanks in advance for any advice! Cheers

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[77Dmax]

I doubt it will work. All of those transmissions take different speedo gears and have a different size hole. It's aluminum, if you're dead set against a mechanical speedo then pull the tailshaft and have a plug welded in. Or snip the cable and plug the end of it.

 

[Rickf]

Or use JB Weld and a freeze plug.

 

[Ricko1966]

According to Amazon and Ebay the T10 uses the same speedometer bullet as a Muncie or Saginaw so I'd think the block off you found would work or work with minor modification. Edit or lookie what I found.

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found

 

[idahovette]

NO they do NOT have different size speedometer holes, All M20, M21, M22s, are all the same size

 

[Shields]

Thanks to everyone for their input, I am going to order the B&M item that I posted and I will updated this thread with the fitment. Thanks again!

 

[DoubleDingo]

NO they do NOT have different size speedometer holes, All M20, M21, M22s, are all the same size

But is it the same as the Super T10?

 

[idahovette]

I think it is? No reason to change that part of it, same out put as the M22?

 

[vr1967]

If I remember right, the Borg Warner cases are different than the Muncie cases in the tail housings.

M20,M21, & M22 are just option codes for the ratio of transmissions.

My 79 TA factory 400/4 speed had M21 transmission on the build sheet, but had a T10. Bought it from the original owner in the 80s and it was a low mile car when I got it.

 

[Ricko1966]

The M22 also had a stronger input shaft,a 1 inch counter shaft,wider straighter cut gears made of a tougher alloy. I think I'd have bought the plug from post 4 that says it fits T10s.

 

[bucket]

The M22 also had a stronger input shaft,a 1 inch counter shaft,wider straighter cut gears made of a tougher alloy. I think I'd have bought the plug from post 4 that says it fits T10s.

That one you posted states Muncie, T10 and Saginaw too. That leads me to believe that the speedo drive hole is the same size on all of them. Not surprising for GM.

 

[Ricko1966]

That one you posted states Muncie, T10 and Saginaw too. That leads me to believe that the speedo drive hole is the same size on all of them. Not surprising for GM.

I thought the same thing kind of,the one in the post looks like it is rubber and may have more give to fit slightly different bores. IDK. That's my thoughts and concern is that .020 difference in a rubber plug that gives, is a seal,..020 to small on an aluminum plug is a leak. Fingers are crossed for O.P. things will probably be fine. I bet they will be.

 

[bucket]

I thought the same thing kind of,the one in the post looks like it is rubber and may have more give to fit slightly different bores. IDK. That's my thoughts and concern is that .020 difference in a rubber plug that gives, is a seal,..020 to small on an aluminum plug is a leak. Fingers are crossed for O.P. things will probably be fine. I bet they will be.

I thought it was plastic, due to the groove with a separate o-ring in it.

 

[idahovette]

Never have seen anything but a steel "bullet" for the Muncies or the T10s......same as the old Chevy 3 speeds for that matter, same hold down. too

 

[Ricko1966]

I thought it was plastic, due to the groove with a separate o-ring in it.

Good eye,I didn't see the Oring. I thought the plug was rubber.