I put a diff speedo in my 69 charger now it shows im going faster than i am.At 35 it shows 55 at 70 it shows 105.I did find out the mtr and trans came out of a 67 polaras could it be the gear in the trans at the cable hook up?Are the mtr and trans still basicly the same?

Kinda confusing question. Did the old speedo read right or is this a new build? Probably the speedo pinion needs to be corrected for tire height and rear end gearing.

same trans and engine but as mentioned, you need to find the right color pinion gear in the trans (where the other end of your speedo cable goes). Have to measure your tire height and your gear ratio and it will give you a tooth number/color and thats what you install...Here is a chart on the subject. I don't care for JIMs auto parts...and please do not buy from them, but it was the only chart I could find



http://www.jimsautoparts.com/transmission_parts.htm

The archives has a page on the subject with current part numbers that might still be available from the dealer.

http://www.moparts.org/Tech/Archive/auto/12.html

Check your tire diameter here:

http://www.discounttiredirect.com/direct/brochure/info/tmpInfoTireMath.jsp

Will tire size alone make it go up to 35mph faster?But i think the trans gear(at end speedo cable)is the problem.The car has not been on hwy for over 28 years.The speedo did not work in it so i bought a cluster rebuilt and installed it and im trying to get the bugs out now.I am green so wish me luck.