Where to find GM 3 speed info?

[sled_dog]

Dad is swapping the th350 in his circle car for a 3 speed or 4 speed, but we want to figure stuff out like gearing before it goes in. We have them sitting in the garage and the only website I found with transmission codes well none of them match these transmissions! Can anyone help me find info on GM 3 and 4 speed transmissions? The 4 speed is definetally not an M21 or M22.

 

[75-K5]

Did they make a 4 speed Saginaw box? Maybe that's what it is.

 

[big pappa b]

Yes they did

 

[thatK30guy]

The 3 speeds are somewhat a rare variety. I had a parts truck that had the 3 speed and a 205 behind it. I know for fact that some '81-'91 trucks had the 3 speed and 208's behind them. Yep, seen and drove one myself. I've got a 3 speed/205 adaptor in the garage. It don't look anything like the 465/205 adaptor at all. Very different. But both the 3 speed and 465 use the same t-case to interchange between them.

I've got a GM service manual that says something about the 3 speed but don't have it with me right now and it does have some M-code for it. Would need to check. /forums/images/graemlins/whistling.gif

 

[thatK30guy]

I found my service manual (it was buried under some magazines on my desk). It shows 2 different types of 3 speeds.

One is a 76 mm.
The other is a 77 mm.

Thats all the manual shows for 3 speeds. Don't say what M-series tranny it is. /forums/images/graemlins/tongue.gif

 

[pauly383]

Doing an internet search , here some things I found:
Basic reference chart
Refernce with pictures and more scroll down for manual charts and gear ratios
There is more out there. Just got to find it. Hope it helps /forums/images/graemlins/thumb.gif

 

[wicked jester]

Here's a link you can try. I hope it helps you out some.

 

[leadfoot067]

i have a gear ratio chart for saginaw and muncie 3 and 4 speeds....(i used to run circle track)....there will be grooves on the input shaft of the tranny...on the splined part where the clutch normally sits....they have from none to 4 lines on the shaft....figure out the lines and ill tell ya what ratios are in each one /forums/images/graemlins/waytogo.gif

 

[pauly383]

There is no link in your post Wicked Jester. If you scrolled to the bottom of my second one you would see gear ratios for 3 and 4 speeds. I corrected my post to say scroll down. Not too hard now is it. /forums/images/graemlins/waytogo.gif

 

[sled_dog]

didn't see any grooves but hey we just slapped the 3 speed behind the motor and slipped her in. I welded on the Crankcase evac system to the headers and we dropped the motor in. Being the young gun I was the one on my back under the car doing the motor mount bolts. Why is it I am always under mud vehicles? My K5 and this dirt track car? Should have pictures soon, hopefully taking it to the track tomorrow for a shakedown run. Just waiting on the MSD ignition from Summit and need to grab some leaded fuel.