I have a t89B-1D Borg warner 3 speed transmission mated to a T10 - 7B Tail piece making the transmission a four speed. Driving a 59 Corvette with a fresh 350 and 3.36 rear differential gear ratio. Been only driving it this summer and starting to think the transmission does not help the car much in terms of drivability. seems like really close gear ratios. I searched the web for the t89B transmission and there is little info on it. I am thinking about a 5 speed tremec tkx so I have an overdrive gear for the highway. would really like to know what I currently have for drive ratios but the only information I can find on the t89 is for ford trucks 56-71, Jeeps 1960 to 66 and Studebakers 59-64. I did find one reference to a 1963 Buick leSabre with a t89B - 1d transmission 3 speed. anyone familar with the T89B- 1D transmissions?