meltdown

I just purchased a 1996 F-150XLT 4X4 with AT and 136K miles. The truck vibrates under aload at speeds of 35,45, and 55mph . I had the tires rotated and balanced, Drive shaft balanaced, replaced all shocks, and Front rotors. Does anyone know what this vibration could be?
Tail shaft?
Front Wheel bearings?
Torque converter?
Transmission or transmission fluid?

Butchart

You might want to check the yoke that slides into the rear of the transmission, if the bushing inside is worn this can cause the yoke to vibrate at the U joint. Also check your universal joints for any movement.

meltdown

Thanks Butchart for the reply....Is the Yoke an easy install? whats involved?

Butchart

Sorry I didn't get back to you sooner. Grab hold of the yoke at the universal joint, thats right behind the tranny and try to move it up and down and sideways etc., if it has a lot of loose or sloppy play (there will be some minor movement) in it the bushing needs to be replaced on the tail housing of the tranny where the yoke slides in. To remove the yoke, undo the rear U joint and pull the whole driveshaft out. If your not sure have a mechanic check it for you for loose play.
It just occured to me, you say you had the tires rotated and balanced etc. Tires can also be out of round and this will cause vibration too even though they balance out on a tire balancer, I've actually had this happen to me. To check that out, just jack the vehicle up enough so the wheel is just off the ground and rotate it by hand and see if it rubs on the ground in one spot when rotated.

meltdown

["I've actually had this happen to me. To check that out, just jack the vehicle up enough so the wheel is just off the ground and rotate it by hand and see if it rubs on the ground in one spot when rotated."[/quote]
Butchart,
Thanks for getting back to me.....Since I wrote to you last I repalced the following; Inner and outer front wheel bearings. Left radius shaft bushing and replaced the tail shaft with a new one and it still Vibrates at 35 & 45. The weird thing about the whole thing is that it does not vibrate all the time. I will try the wheel thing next.

Butchart

Ok, appreciate if you let me know how you make out.

meltdown

Butchart, Just to let you know that my brother Joe and his Automotive colleagues has solved the Vibration issue with my truck. After the countless hours of trying to figure this out the following was done. We placed my truck on a computerized Dyno that test everything you could imagine under the hood and everything turned out perfect. <so this ruled out injectors etc.> Next, we had a transmission expert test drive the truck. After their findings this is what he recommended. Drain the transmission and the torque converter of its fluid. Next replace the transmission filter, replace pan gasket, fill the transmission with 12qts of Mercon V <Synthetic blend> and one transmission additive called Lube guard. Take it for a spin and BAM! Vibration Gone. This truck rides so smooth it's unbelievable. Thanks for all your help!

Butchart

Glad to hear you solved your problem. Thats a new one to me and a lot of other backyard mechanics I bet, draining oil and changing filters etc. Good for you.

karmachris1

I had the same problem and took it to a fellow who promptly plugged my EGR valve and it stopped. He said that the air ports on my manifold were clogged causing it not to "breathe" properly. You also probably have "services engine light" on? Good luck.