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Where to find GM 3 speed info?

sled_dog

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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.
 

thatK30guy

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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

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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
 

leadfoot067

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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

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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

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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.
 
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