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TH350 speedo gear color

30K views 7 replies 7 participants last post by  Restore60s 
#1 ·
Can anyone tell me what color gear (gears) I would need to have my speedometer to read correctly. Have a 77 vette that I just changed the differential gears to 3.55 and would like to change the speedo gears before I put eveything back under car. I had 3.08 gears/ 225/70-15 tires/27.4"dia.and drive gear on transmission is (Green 7T) and driven gear (Red 21 T). With the change to 3.55 gears what gear or gears do I need to change and to what? Thanks jw:confused: :confused: :confused:
 
#4 ·
i bought a trans a few years ago and they told me to yank and reuse my stock speedo gear to get a proper reading and they told me if i had changed rears you can go to a auto dealer and tell them what year+gear ratio and theyll give you the correct speedo gear to give you a correct speedo reading. like- i have a 72 truck with a 373 and theyll give you the corrrect speedo gear.
but if the overall diameter of your tires doesnt equal the original equipment it would be wrong.
 
#7 ·
Through the links and advice you are looking at acheiving a 2.60 gear reduction in the speedometer gears to correct your speedometer.
You can keep the 21 tooth (red) drive gear and switch the driven gear to an 8 tooth (orange) driven gear which will give you a 2.625 ratio.

That little 0.025 ratio difference equates to .7 mile per hour at 65 miles per hour, about as much difference as having brand new tires as compared to a set of tires at the minimum tread wear amount before needing replaced.

If you are in an area similar to mine you might be hard pressed to find the speedometer gear you need, no matter how common it may be. There are online sources for the gear you need, and a simple search will put you in contact with someone who has them.
 
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