I have an 84 firebird s/e with a 305 5-speed,2:90 first gear, 3:73 non-posi rear and an 85mph speedo. About a year ago i had to chang the tranny because i was having problems with it and the only tranny i could get quick to replace it was out of an 89 formula 5-speed, thats the only info i have from the donor car. My old tranny had a mechanical speedodometer while the donor tranny from the 89 had an electric.. So i couldnt swap out the speedo gears. Now my speedo reads about 20-25mph to much (e.g. driving 30mph speedo reads about 60mph).

My question is, does anyone know how to calabrate this new set up so i can figure out what speedo gear i need? Or know the ratio of and 89 t-5 out of a formula?

New set up:
85 mph speed-o
T-5 out of an 89 Fromula
3:73 rear. Thanks~Vinny

 

Yes you can swap out the speedo gears. The speedo gears from your 84 non-world class tranny and the 89 world class transmission are interchangeable. Whatever speedo gears you had in your old tranny, put both of them in your new tranny.
An 89 manual trans car would have either 3.08 rear end or 3.45 rear end.

 

Kev, I tried that, trust me. That was my first move.
The housing for the mechanical and electric speedo's were diffrent and the gears wouldnt swap.

 

I find that amazing. Are you sure its a T5? I've swapped speedo gears between NWC and WC T5's, and from cable and electronic speedos several times.

 

Yes, mine was an orginal 1984 T-5. As for the other, the info i provided is all i know. I used to have an 88 formula and the new T-5 looked just like the one in my 88. I know, i dont understand why they wouldnt swap. I cant remember exactly because it was a long time ago when i did the swap and someone stole my old orginal T-5 so i cant go back and look. even if they did swap, the speedo's are diffrent.

Thanks ~Vinny

 

I think I have what you need for the speedometer (cable driven) what is your e-mail? I will send pictures of what you need

 

My email is xvin99@aol.com

Thanks for your help but Just so you know my speedo is hooked up and working. My problem is that i have the wrong speedo gear. Let me see the pic though. Thanks ~Vinny

 

I hope the picture I sent of the gears helps... I did not send a picture of the sender (bullet looking thing in the trans) because you said yours was working and I assume you would already have this then. just the wrong gear

 

hey thanks for the picture but it was very blurry. The first one on the left, cable gear, is the one i have, same color as well. Im not sure about the other one though. i never checked. In fact, i didnt know that i would have to chang that one as well. I thought i would just have to find the right gear for the speedo.

Thanks ~Vinny