Another problem with my '88 B250 is a bouncing speedometer. I have at different times replaced the speed sensor, the speedometer and the internal cable (not the sheathing) of the cable running from the speed sensor to the cruise control servo, which I also replaced a few weeks ago. I have bypassed the servo and the bouncing was reduced, but not eliminated. I would replace the other cables (from the tranny to the speed sensor and from the servo to the speedometer) but cannot find them. Any help here as to cause and finding parts would be appreciated.

BTW, in refurbishing my van, I need to do something with the rust on the roof. Never did understand why they depressed the strengthening for the roof instead of raising them. This only serves to collect water as it has no way to drain. Anyway, I found a rust inhibitor I think will be great and will share the results when I get it done. Its called "rust bullet" if anyone wants to look into it and can be found here http://www.rustbullet.com/Products/A...Automotive.htm.

 

A bouncing speedo is cause by the cable(s) not turning smoothly, your problem lies there. Just replacing the cable insert won't always fix the problem. There can be crud built up inside the sheath that his causing a drag on the insert and the erratic movement.

 

The routing of the speedo cable sheath can cause a lot of bouncing too. Mine was really bad when I first got it, and found that the previous owner had used a zip tie to hold it out of the way for doing something else. This created a large kink in the line.

I removed, relubed and re routed it with minimal smooth bends and the bouncing dissappeared at speeds above 15 mph.