BrandonV

He's not saying that you should replace your rear end gears, but the gears in you speedometer if your going to change it out you need to replace the gears that drive them.

kyleag89

I know what he is talking about. I just don't understand why I would need to change the plastic gear in the trans to match the speedo. I thought the gear in the trans needed to match up with the gear ratio in the rear end. Things like this is what gets confusing and irritates me at the same time.

AdderMk2

you dont change the gears in the speedometer... you change the drive and driven gears that are at the end of the vehicle speed sensor, and in the transmission.

BrandonV

Yeah, I figured they were some where, but i think he was thinking of the gears in the rear end.

Project 5.GO!

They are little cheap plastic gears, they go at the end of the speedo cable where ip plugs into the tranny, no big deal financially. Prolly $10. I think he heard gears and thought big expensive steel gears.

kyleag89

I have the purple gear in my trans now and I have 3.73 posi gears in the rear end. I have the 85mph speedo and I'm pretty sure the speedo is close to accurate. What plastic gear would I need for a 140mph speedo? My 85 is starting to act up(needle bouncing off and on and I have a NEW speedo cable). So I mine as well replace it with the 140 guage..

nitrous_bob

the driven gear(the one on end of cable) should be the same no matter what speedo you use. the drive gear (part of the output shaft on your AOD) is probably an 8t, and incorrect with your purple 21t driven gear. UNLESS YOUR TRANS IS A 7T than it IS correct

you originally asked if you could paste a cover over it and that answer is no

but if you swap the whole speedo..then yes your fine

but you also most likely need to replace the driven gear if it's bouncing because the teeth are all chewed off it

Project 5.GO!

Aren't the speedos always getting that bouncing needle effect anyways? Mine has it only when it's cold outside, and always under 30 mph. I thought I heard discussion on the board a while back that the speedo in the stangs will do that eventually and need to be replaced when it happens. I know I had the cable out of the tranny when I rebuilt it, and the teeth were pristine. I guess the setup is a little different on the AOD.