I have a T-5 , 3:42's, and a ~25.5 tire. Right now after having a friend pace me I'm exactly 10 mph over. So my speedometer will say 30, but I'm really going 40 mph. I am trying to get the gear #'s from the previous owner, but I was wondering if anyone could figure out the right gears I need just from that information? I understand that there is a way to calculate it by counting the teeth on the output shaft or something similar to that and looking at the speedometer gears that are in there, but I really do not have any free time right now.

Here's a calculator on TCI's page. Don't see why it wouldn't work for a T5.

You should be able to tell how many teeth the output shaft has by it's color. (I know, ya gotta do SOME work )

Thanks, I found the page with the calculator.

hehe...oops! I really meant to attach the link

...but I guess you found it.

Would it help that I had a 700r4 and 2:73's, and now I have a T-5 and 3:42's? Heh, I really need to change them but I honestly do not have more than 10 minutes to spare anytime soon. I was, and still kinda am away this weekend or I could have looked. Figures.

I recently swapped the auto in my 3.42 geared 86 IROC to a t5. My tires are the stock 245/50/16's (which are similar in height to yours.) You need the 7 tooth drive gear usually dark purplish blue) -- this is the ring that slides over the output shaft. Then in the speedometer housing (what the cable screws to) you need a 19 tooth driven gear (natural or whitish tan color.) My trans had the right drive gear, but I had a hard time finding the 19 tooth driven gear. After calling around and asking for this gear for a T5 from a thousand tranny shops and GM dealers (and having no luck), I found out that some autos came with the same style driven gear (some TH350's and TH200's.) I found mine at a local drivetrain supplier, called Axiom. Its on Irving Blvd in Dallas TX. It was only 10 bucks. I could get the phone number if ya wanna order one from them. My speedo is pretty close, I might be travelling a lil faster than the speedo shows.

Thanks. I think a local shop by me can get them, but if not I'll pm you.