I bought a 92 VX with 100,000 miles a year and half ago... I just had the transmission replaced with a new rebuild and they put in a DX tranny; even after checking the VIN. Now the "shift-up" light goes on in 5th which it never did before.
Anyone have any idea why this would happen?

 

5th gear on DX has shorter gear ratio then the VX

?????

 

I don't wish to seem ungrateful for your response nor do I want anyone to get the wrong impression but your reply is just a statement of fact; not an explanation in any way.
I thought about this over the last week and the answer is: because the DX tranny has a lower overall ratio (shorter?) which you derive by multiplying the final and the individual gear ratios...and because the ECU compares engine speed with car speed it "thinks" it is in 4th gear. The overall ratio of 4th in the VX (2.77) is nearly the same as 5th in the DX (2.73), thus the shift up light. I find myself constantly trying to shift up because of the "feel" of the RPM vs. speed.