transmission identification

ok, so i have a hydro trans but the vin tag is gone. i am trying to find out the type of trans i have. at 55mph in 5th, it reads right at 3000-3100. in 5th at 80mph it shows 4000-4100rpms. what trans would i have? i have checked all over but cannot find out for sure what trans i have

I’m not good with ID’ing these trannys. Gearing sounds the same/similar to my S80. It has an LSD and came with my OBD1 B18c (P72).

Open it and count the gear teeth, otherwise you’re shooting in the dark and doing a ‘best guess’.

But you can use a transmission calculator, that may help in trying to ‘guess’ at which trans you have. ZealAutoWerks.com has a nice one. Pick a tranny from the drop-down menu, find a certain MPH in a certain gear at a certain RPM (as you’ve listed here) and see which trans matches.

according to that calculator, i could possibly have a 98-01 ITR Trans, or a 99-00 SI trans. Both are very very close to what mine pulls at. thanks for that link