i swapped out stock motor and tranny for 350/turbo 350. now my speedo doesnt work. 700r4 was mechanical far as i remember so i thought i could just screww it in turbo 350 and should work but it doesnt. any ideas or suggestions would be great. thank you in advance.

 

Did it work before?

Remove the cable from the trans.
Spin the cable counterclockwise repeatedly.

If the speedo looks to be working,
put the rear up on jacks. Have a helper start and put the car in gear.
Is the driven gear spinning?

If no, remove the speedo gear and sleeve to inspect for damage.
Also, see if the speedo gear lines up with the drive gear. Big TH350/700-R4 speedo gears fit the 700-R4 tailhousing. Little TH350 gears are only about 1" diameter.

Pics of what you have would be helpful.