Speedogear Question

[vintovka]

Closing in on finishing my project. One issue is that the original 54 speedometer runs 10 MPH too slow at all speeds. The 700R4 tranny has a 40 tooth driven gear in the original 1984 aluminum housing. My studies so far indicates a 36 tooth gear in one of those plastic housings may be the answer, Before i spend anymore $$$ on this i request any suggestions from you experts.

[mr48chev]

10 mph or 10 percent slow? If the drive and driven gears are wrong it should be a certain percentage off across the whole range.

Here is one page I use a lot. http://www.tciauto.com/tc/speedometer-gear-calculator/ Scroll down to the 700R4 section

This one is another go to but their instructions to jack the car up and turn the rear wheels to calculate the gear ratio is pretty shade tree. That may or may not give an accurate reading and is inaccurate more often than not.

[vintovka]

Thanks.. !0 MPH too slow. I used the page and came up with the 36 tooth idea. From what I have read the 36 tooth driven gear should work with the original drive gear. The other issue is the plastic housing can only be used with 34-39 and the aluminum one for 40 plus. Correct or incorrect?

[_Ogre]

if it's reading 10mph slow at all speeds you need to bend the needle 10mph down
if it's reading 10% off: 9 at 10, 27 at 30, 54 at 60; then regearing it will work

reading 10mph slow at all speeds will not be fixed by gearing