My speedo works fine until I hit 25 or 30, then howls and bounces around.

Any input??

 

what truck? what transmission? on my stock 49 F-1 the cable comes directly up from the rear of the tranny and has to take a right hand turn. make sure that turn is a gentle as possible. it may help to unhook the speedo cable from back of speedo, wipe it clean, lube it up good with spray graphite and put it back. make sure it's firmly seated in speedo when reconnected. mine is now working ok now minor jitters at a couple of speeds. dick r

 

r_reed nailed it. You need to pull out the cable from the housing, clean it up, and re-install it. At the dealership I used to use top just push the cable into a tube of Lubriplate Engine Assembly Lube (white lube) and then re-install it.

Good luck
Bobby

 

Typical. After many years, these old things get a little gummed up. I had that issue with the fire trucks speedo. I found that if i reached behind the dash, and lossened the grip on the cable nut, it would quit bouncing, and get back to normal. What it is, is it starts to bind. Take the cable off, and clean it out real good. You can usually get a solvent to run through it. After that, soak the cabe in a lubricant. Let it run through the housing and all over the cable. Make sure the speedo unit is clean, and apply something like lithium grease, or a graphite lube. It should be ok after that, and provide amny miles of trouble free operation. Most of these speedos get screwed up by bad cables. They get stripped out and froze up. Moisture builds in the cable, and takes them out pretty good. The first sign, is the jumping around, and noisy operation.