I have a 93 integra rs with a ys1 transmission which is done for because it was run with no trans fluid, but I wanted to know if anyone knows if you can take the internals out of a 90-91 integra s1 tranny and put them in the ys1 tranny? Is there any difference between the trannies I heard something about the splines for the clutch disc are different.

 

No it will not work because the 90-91 trannies have smaller shaft sizes along with the smaller sized clutch splines. You could either use the gear sets from a 92-01 tranny or swap the whole thing for a 90-91 tranny and use a clutch for a 90-91 tranny.