I'm going to swap in a 140 speedo cluster into my GTA that has the 120. When I do the swap, will there be any calibration needed or will the 140 work just fine? I ask because I have a 2.73 rear and 140's usually work with a 3.23 or simlilar gear...

 

im guessing you are the same 92GTA over on hoodscoop.com? i am mattp over there...
on to your question, i have a 145 speedo in my IROC and it also has 2.77 gears in the BW 9bolt. i hope this helps some. at worse, youll need to get a speedo gear from GM.

 

Yup, that's me. I'm 92GTA everywhere.

So you did the swap and didn't have to change the gear? Cool.....

 

no , no swap. stock 145 speedo with 2.77 gears...
the only thing ive really done to the car is to put in a t56, nothin else. i was just giving you that example to show that 145 speedo might (should) work with 2.73 gears.
any thought to going to some steeper gears? say maybe 3.42 or 3.73?

 

I'm already ahead of you. I'm installing a rebuilt tranny and a brand new posi with 3.42 gears in about 3 weeks. I of course know I have to change the driven gear in the tranny for the 3.42's but I just wanted to make sure I didn't have to change the speedo gear too.

Thanks!