Have 1989 F150, 300 six,M5OD tranny,2wd, 155,000 miles. Just recently developed a vibration when accelerating. Say I'm moving at a steady 45 mph, give it alittle gas and the vib. occurs. Slack off the gas it goes away. Does this in all gears. U-joints seem tight, but are probably original. Changed tranny fluid last nite and it was 2 qts. low and probably original also. Also have a click sound sometimes when the clutch is let out, and this has become more frequent also. Any ideas out there? Thanks.

 

Couple of things. First, do you have any trouble getting it into low gear or reverse? That can sometimes be a sign of a clutch going south. Could also be a weak pressure plate with that kind of mileage. Second, you say the u-joints seem tight. With that kind of mileage if they are orginal you should probably change them on principle. I don't think it sounds like a u joint although a bad u joint can do all kinds of crazy things. I would have a look at the clutch through the inspection cover (although I'm not sure what you can see... its been a while since i had mine).

Maybe that will get you started.

 

Don't have any problem with shifting,low or reverse gears. Talking to some other friends, they suggested this might be a problem with the throwout bearing. I have had a squalling noise coming from somewhere if truck sits for any length of time. Noise lessens when clutch is depressed. Clicking sound also when clutch is let out sometimes. This has gotten worse.
Can clutch or bearing cause vibration/rumble when accelerating? Clutch might be original, and I was gonna replace this anyway. Anyway to know if its a 10"or11" clutch without pulling the tranny? Gonna go out and put it up on stands and run it to see if I can see/hear anything.
Thanks a bunch.

 

Put rear of truck on stands tonite and ran it in 2nd. gear,with wife giving it some throttle. Crawled underneath to have a listen and sound is coming from trans., sounded pretty bad(loud chunkin noise,definitly what ever it is, is causing vibration. Any ideas?

 

Bad bearing in the trans. Probably the input bearing, thats what went on mine.
Alan

 

Well changed u- joints tonite and truck runs smoother than a baby's ***. Could'nt find any play in joints but when I removed them they were nothing but pieces of bearings and dry rusty dust. Thanks for the input! Happy Thanksgiving!