What's wrong with my speedo?

[Jim R.]

My 65 speedo, when driven normal works good ,but when you stomp on it the needle falls to zero then slowly starts to catch up. (4spd car) any idea's

[Tom D.]

Re: What's wrong with my speedo?

Interesting. How much HP and how long does the lag last?

[Bill I.]

Re: What's wrong with my speedo?

Jim, I thought about this for a long time, since I've never heard of this problem. It's got to be stress on the cable under acceleration. Have you checked both connections, tranny & head? Sure hope you get some good input on this one. Bill.

[Jim R.]

Re: What's wrong with my speedo?

my car is a 365hp ,yes i have checked both ends (connections) they seem to be good and have a new speedo gear in the tranny. also the gear for the speedo ,trip odom is new. the lag last for 1 second or so

[Louis T.]

Re: What's wrong with my speedo?

Hi Jim,



Good luck!

Louis

https://www.forums.ncrs.org/showthre...+lube&uid=7826

[Roger O.]

Re: What's wrong with my speedo?

If the fitting that holds the gear in the trans is aluminum you should get the steel one. The aluminum fittings get loose and allow the the driven gear to get away from the drive gear. (The weight of the cable on the fitting becomes an issue.)You can prove this by temporarily pulling up on the cable using a bungee and then driving the car.

[Jim R.]

Re: What's wrong with my speedo?

Thank's I will try these things and see what happens.

[Michael W.]

Re: What's wrong with my speedo?

The driving gear on the trans out put shaft may be slipping.

[Wayne M.]

Re: What's wrong with my speedo?

The driving gear on the trans out put shaft may be slipping.

All good suggestions above. further to M.W.'s thought, did you use another STEEL drive gear on the output shaft ? ie. not the plastic with the retention pin.

Have you removed the plastic speedo driven gear to examine for center tooth wear (indicating mis-matched gear sets -- driven for 3.08 to 3.55 being used on a smaller diameter steel drive gear intended for 3.70 and 4.11 ?)

What was there before the change ? What was your aim in changing -- was it because of a change in final drive (diff ratio) ?