Transmission Shifting Too High

[nascar]

It seems that my transmission, (87) GN, is shifting into OD about 10-15 MPH too early causing the car to bog. Any solutions?

 

[buickboy]

Do not race it in OD. Drive only. ET and MPH will be better.
Mitch

 

[chris718]

if all the shifts are early adjust the tv cable tighter .if its only overdrive you may have to replace the 3/4 shift valve spring w/a stiffer one or one out of another transmission .i have seen this with overheated transmissions that were rebuilt.the overheating baked the tension out of the spring making them softer.