When towing a load at 60+ MPH my truck will vibrate for about 5 seconds and then the vibration will stop for about 5 seconds and then it will repeat until I stop (and when I stop when this is happening it usually dies) has anyone had this happen before? The fuel filter doesn't even have 3k miles on it and the air filter has about the same. It is a '95 12 valve.

 

Best way to find out is to install a fuel pressure gauge even if it's just temporary.
Instructions> http://www.cumminsforum.com/forum/94...-12-valve.html

or you could just replace the overflow valve, $39 from ebay.

 

it is probably drawing air most likely in the fuel heater element or through the o ring in the element housing clean out the screen while you have it off.the o ring gets old and will get hard it might look fine but it wont seal. check any rubber hose connections in the fuel lines.most people buy a new transfer pump only to find the before mentioned was the problem.you can find the screen & o ring kit at genos garage for 7or8 dollars.I cant say for sure this is your problem but is a good place to start.

 

thanks