I have matching numbers 68 RS It has 3 speed saginaw, can i use the 3 speed case and build it ito a 4 speed
thanks in advance

no.
cases are different

You sure about that?

I will know for sure in a little bit b/c I have a car 3.50 ratio 4-speed all cleaned up sitting on the floor just waiting for me to get ambitious and finish pulling my 3-speed out of my beater P/U..

pdq67

Let me know if it works, i'm supposed to talk to guy todat thats done the swap, i'll post if i see working transmission

Saginaw 3 and 4 speeds share the same case, main shaft and tail housings. The input shaft, gears, 1-2 shift fork and side cover are different in the 4 speed.

You can also combine a Saginaw 4 speed with a 3 speed with overdrive for a 4 speed overdrive transmission.

ok well the tranny shop is wrong?
he told me that it cant be done without some machining.
something about the bosses for the secondary shaft.
he also showed me that they are different part numbers.
saginaws are cheap just get a 4 speed and be done with it.
I personally never liked them thats why I got a few M22s stashed away .