Speedometer is out by 20KM/h

[Stryker_78]

I installed a new rear-end in my '78 this past summer(late). I was running a 3:08 rear-end but have stepped up to a 3:55 rear-end. But I now have a problem with the speedometer. I have been told that I need a cheap $15.00 part to match the rear-end up with the speedometer. Does anyone know what the part is called and where it has to go?
I am on the metric system so don't mind the 20KM/h.
Thanks.

I think what you are looking for is a new speedometer gear that goes in the transmission. You would need to match up your tranny with the rearend. In one of my manuals (think it's the AIM) is a chart for '75 that shows the different tranny gears available and how they relate.

[Stryker_78]

I believe you are correct. I remember someone mentioning that to me. Is it a long process to change out? Is it very difficult?
Thanks for the reply Ken.

[barrier5]

Go to your local Chevy dealer,tell them the rear end ratio and which trany you have and they should be able to set you up with the right gear.There all color coded for the number of teeth they have,I'm not sure if theres a difference between gears for metric and speedos set up to read by miles.
As for changing the gear,it"s pretty basic,just follow the cable into the trans,pull one bolt and a Uclip I believe.You will lose some fluid so have a catchpan handy.........

[Stryker_78]

Thanks for the tip Barrier. I appreciate it. I will look into it once I return home from the "war" I am serving on a destroyer in the Arabian Sea, counting the months till I get back home to my car... Oh yeah, and my wife..
Thanks again.

[barrier5]

Best wishes to you and your shipmates.....

[78SilvAnniv]

My local GM dealer told me they do not stock parts for my older vette.

The parts manager told me he orders all parts for older vettes through Ecklers, Mid-America and Corvette Central.

I'd give them a try first. If your GM dealership is ordering from those supply houses, chances are you can purchase it directly, and without the dealer mark up in price!
Silver

[barrier5]

Items such as speedometer gears are best gotten through GM or a good trans.man as there are so many different combinations.Four speeds are different from automatics and can even have more then one size because of cases from year to year.Also gears where not designed for Corvette alone,but across the board tobe used in all GM cars and light trucks.A friend of mine has a 66 that came with a M22 and 410 rearend but was changed to a 3.08 gear and M20 or M21 internals in the M22 case(still haven't got that one to read right yet).So trying to order one mail without knowing the exact size and number of teeth can get pretty tricky.........

[Stryker_78]

Thanks for the help everyone.