About six months ago i got a salvaged transmission from a 99 lesabre, i had to have the buicks VIN programed in in order for it to work.It only have 30,000 miles on it and it works perfectly, but i noticed that while im in overdrive and going at highway speeds my car only runs and 1,500 RPM.Now my dad has a 98 SSE and his runs at 2000 at highway speeds and climbs hills better. Does anybody know what the difference in gear ratios between the buick and the bonny are?

I bet you have the 3.05 gear but the LeSabre transmission has the 2.84 (or 2.86)

That'* my thought, at least.

You will need the code off the original trans, and find out the code for the final drive for the trans in the car now. Newer cars can be checked at the Dealer. Buy i am sure the ones you have wont have it online. I would look into it for you send me the vins from the two cars in a email.Or i know the trans has a code on the metal plate on its back. Let me know, J