I was having tons of problems with my convertible's NA speedometer. It would bounce at low speeds, cruise control was jerky due to speedometer, and finally the needle just broke off.

So I removed the NA speedometer and replaced it with a TII speedometer from a yard pull that I made this fall and it has worked beautifully. No more bouncing, I have a smooth cruise control, now I can see how fast I'm going, and I can pretend that my car's capable of 160mph. Can't say if the TII is a better quality model or if it just wasn't as beat. Either way, it works!

I was able to adjust the mileage by carefully separating the scrolling numbered wheels of the odometer - keep in mind that there are small blue gears between the scrolls. Don't worry if one falls out or you lose it cos you can just pull another from the broken speedometer - just takes a little patience and some steady hands. And I adjusted the mileage on the hidden odometer (probably serves as a check?) that's visible once the speedometer is removed. Now the speeds will match once I swap in the TII drive-train.

Thought I would post as an FYI in case it's helpful to anybody.....