I bought a 1988 F-150, 4x4, reg cab, long box, t-18 4 speed manual trans almost 2 years ago now and have been having drive-line problems since i got it. I was leaving the pharmacy one day and got on it kinda hard to cross 3 lanes of traffic and the engine essentially free rev'd as it got over 2200 RPM i assumed the clutch was worn and slipping (truck has 100k and was used as a farm truck last 6 years) i replaced the original 10.5 clutch with an 11" got the bolt kit turned the flywheel new pilot bearing, and release bearing. put it all together and still had the problem. the clutch i replaced didn't seem worn excessively or burnt either..flywheel didn't look abnormal either. i then put a new slave cylinder and clutch master cylinder on it. Also the previous owner had a bungie from the fork going forward to around the motor mount, he said it was just to stop a squeak. Am i supposed to have a clutch return spring from the fork to somewhere? and if so, where would it go? does anyone have any ideas on the free rev or slipping i'm getting. it does it when trying to go up the ridge on the interstate here..I've replaced everything i can think of and am out of ideas...HELP lol

 

There should be a spring to keep the clutch fork "returned".

What you describe can only be the clutch slipping.

IF it were a broken crank, your engine would have self destructed long ago.

IF it were in the transmission, your trans would have locked up or split open long ago.

IF it were in the differential, your rear axle would have locked up or broken open long ago.

At the very least, early in any of those situations, the noise, vibration and parts breakage, etc would have been intolerable.

What brand clutch did you go with?

 

I got a clutch pressure plate throw out bearing pilot bearing and slave cyl. From Felton's in town when I was a tech at Kenworth we go all our clutches from them they are very reputable..I think it is a luk, I couldn't think of anything other then clutch either dug out the old pressure plate evidently tossed the old disc it didn't look special though