It depends on the size of the rear tire to make the speedo read correct. What size tire is on the back?
Correct speedo gear for 3.42 rear Maybe someone on the board here can correct me if I am wrong, but I believe with the original tire diameter (26"), you should use the 42 tooth (green) driven gear and housing for a 3.42 gear, if you have the correct 16 tooth steel drive gear that Buick originally used in their TH400 transmissions. I don't know what tire size you are using, but I believe this should put you in the ballpark. Thanks, Ken
I think part of the problem may be that you will also need to know the number of speedo drive teeth on your output shaft as well. With this plus tire height you can use any of the online calculators. There's one on the TCI website: http://www.tciauto.com/tech_info/speedo_gears.htm Devon
this is a stock trans "ba" 455. what was the output shaft teeth?With a stock trans i was looking for the stock teeth on the speedo gear.42 sounds correct
My book says the 1970 BA trans is a GS 455, non-Stage 1, and has a 17 drive gear tooth count (GM gear number 8623312). With this info, knowing the 3.42:1 ratio and 26" tall tires, I calculate you need a driven gear with 45 teeth using the link above. This speedo gear would be GM part 9775187 (light blue). You'll also need the speedo gear sleeve (housing) that has the numbers 40-43 cast on the outside, part number 25512339 which used to be 1362285 if you don't have it already. TCI lists this as compatible with gears 40-45 (I've also seen sleeve 1362293 mentioned for 40-45 teeth). Makes sense to me, I have the same 17 tooth drive gear and for 3.42's I need a 42 tooth driven gear because I'm running a tire 2" taller than yours. Anybody wanna double check my research? Devon
