Transmission Overdrive not working.(Digital Dash) I replaced my speedometer cable and it works up to 40 MPH and then goes back to 0.

[mbarnett]

I replaced my speedometer cable on my 1987 Buick turbo Limited. Now the speedometer works up until 40 mph then goes back to 0 mph. I also noticed that the transmission will not shift into overdrive after replacing the cable. This car has the original digital dash cluster. Can anyone tell me what could be the problem?

 

[pacecarta]

did it work before cable change (assume speedo cable) or was change to try to fix this issue with speedometer dropout
might want to make sure the cable is properly installed to back of cluster

that said overdrive (4th gear ) doesnt care about speedometer but lockup does
the speedometer vss output needs 47mph for lockup (you can check this with a scanmaster on MPH settting)
if you dont have a scanmaster you should get one
vss below that lockup wont happen .. if cable is good it could be a bad cluster , casperselectronics.com repairs them

if speedo is dropping out because cable at cluster end isnt spinning could be the driven gear in trans but could also be the governer gear and that has effect on the shift but in that case it wouldnt be only od issue , it would be an issue for all gears

 

[mbarnett]

Yes, the overdrive did work before the speedometer cable broke. After the speedometer cable repair, I did noticed the overdrive kick in, but only once. That is when I noticed the speedometer went to 0. Now when I drive the car, the speedometer works up until around 30 to 40 mph, then it goes to 0 again.