I am new to the diesel word and to this forum so any help would be great. I just bought a 1991 d250 with a 5 speed in it. For some reason the speedo just bounces and never stays steady. Where should I start?

 

is it cable driven?

 

Yes it is

 

the cable is probably getting bound up inside the insulation, check lmc truck and see if you can get a new one or you can try and clean it out by pulling it off the truck from both ends and pull the cable out of the insulation spray wd40 or jb80 trough the insulation, then blow all the crap out of it with some compressed air and clean the cable too.

 

also make sure that there are no kinks in your existing cable.

If there are, replace it.

No amount of cleaning or lubrication will compensate for a kinked speedometer cable. Ask me how I know.

 

Thank ya'll for the help I will look into it this weekend and ill let yall know