Have researched this problem on the forum ( and others with little help so far).
Situation: 2005 Ranger XLT, std cab, long bed, 3.0, Auto, 2wd., 50K. Vibration apparently from rear at 60mph to 75mph, strongest at 70mph. Had worn tires and did mostly local in city driving so any vibration was attributed to old tires. Replaced tires with new Starfire SF340's. The shop took it for a test drive after and noted the highway vibration (felt in floor and caused seats to shake). Brought it back in and checked tire balance again and also driveshaft. Balance was good, u-joints were tight. Replaced u-joints but had no improvement. Put vehicle on lift (axle supported) and test ran. Vibration very apparent. Had driveshaft professionally balanced. vibration remained, but somewhat improved. Removed driveshaft and tested - no vibration. Determined rear axle/diff was potentially the problem. Replace rear axle assembly with good salvage yard part - vibration still there. Test ran without wheels and tires and brake drums - vibration still there, (does vary at times, sometimes goes away for no reason, i.e. no changes with gear, or engine rpm. Checked even by turning off engine in neutral and coasting). Tried test run on lift with wheels suspended, vibration still there, but reduced. All repairs done at the shop I work at by technicians with over 20yrs experience. They are at a loss except try a different trans. Trans shifts properly, has no slip or noise. Expensive guess!. Any thoughts? Any help out there?

 

Did you replace the whole rear end or just the chunk and axels ?? Did you change the yoke bearing ??? Do you have a very slightly bent axel ??? Sounds like it is in the rear end itself !!!

 

If you have a multi-piece drive shaft, with a center support bearing, you can get the drive shaft 'out of phase', and it will vibrate.
Given that it has had the vibration 'forever' as far as you are concerned, the shaft has been balanced, the joints replaced, there's not much left.
Have you grabbed the yoke at the rear of the transmission tail housing? Try to move it up and down. If you get any wobble, besides just a slight amount of movement, the tail housing bushing may be toast. You can drive the old one further in, and it will ride on the transmission output shaft with no problem, and press (thump thump..thump) a new bushing in place. Make sure to lube the yoke spline internally so it will move on the output shaft as the length varies(rear axle & suspension movement varies the dimension).
Some drive shafts are sensitive to clocking of the yokes, front and rear. If you rotate one yoke 180 on replacement of the 'cross' & bearings, it can cause vibration. Similarly, if you do the same with the CV joints used in some multi-piece drive shafts, it can cause vibration, as can a bad, or worn center support bushing. In addition the center support can have failed 'rubber' isolaters that allow too much movement, and then lead to vibration.
Things to do, if the driveshaft runs true, no wobble, and after checking the tailhousing bushing and the center support(if equipped) are to try re-clocking the yokes.
I would also measure runout at both ends of the shaft. I don't know the spec, but it should run pretty close to true.
tom

 

Did not think about it being the tail end of the trans,, good idea Tomw

 

Replaced complete rear axle assembly. Are you referring to the yoke bearing as the one at the pinion shaft or the trans tail shaft?

 

I was referring to the yoke bearing at the pinion shaft and I think Tomw is referring to the yoke bushing at trans tail shaft which sounds like a good place to have a look at to me !! You should carefully read Tom's post again,, he is pretty good at troubleshooting these old trucks !!!!

 

It has a one piece driveshaft. I cannot determine when the vibration actually started as most of my driving is local in town and doesn't include speeds higher than 45-50. The last previous highway speed trip was 3-4 months ago and any vibration was attributed to worn tires. There is a very small amount of movement of the driveshaft at the tailshaft housing. With the driveshaft removed, I can move the output shaft a small amount which I am told is acceptable and cannot see the bushing to tell if it is worn. If I understand you correctly, I can simply drive the old bushing further into the tail shaft housing and then install a new bushing afterwards? The service proceedure shows using a special tool to remove the old bushing. Is that necessary?

 

I did not replace the pinion shaft bearing. No play or noise noted on either the original axle housing or the replacement.

 

I was wondering where your from and if you still have old rear end,,,, I think I might have a bent axle housing and looking for a close by cheap replacement,,,have not checked local yards yet except to get a price .. After just carefully rereading Tom's post again I do believe he said the old bushing can be driven in and a new one tapped in behind it (thump,, thump ,,thump ) but if your not feeling a lot of play I am not sure if that is your trouble,,, do you have any wobble at the tail shaft of trans with the drive shaft yoke slid in ????? Or should I say will the drive shaft wobble at tail of trans when it is slid in ???? Sounds like you have replaced everything almost ,,, HHMMMMM very puzzling problem !!!!!!!!!!!!!!

 

I am from Ohio and unfortunately I must return my old axle assembly to the salvage yard due to a core charge. I do feel uncomfortable with driving the old bushing farther into the tail shaft housing and having it bounce around loose, but if that can help I am willing to try. Bushings are cheap either from Ford or Ebay. I just wish I could find the specs for run-out of the d/s front yoke in the tail shaft housing. We don't get many late model Rangers in the shop for service/repair to compare.

 

If you want, you can add some bags of sand to carry around. Say 100-150 pounds. That will change the 'at rest' angle of the drive shaft U-joint yokes.
If you have standard cross-type U-joints, they will vibrate if the angle is too sharp. That is the reason for CV joints. Take a look and I think you can find a good explanation on youtube. The 'cross' must wiggle back and forth as the shaft rotates, and can set up vibration. Adding the weight will bring the angle(if your truck bed rides 'high') down to lessen the joint angle. OTOH, if your springs are worn, the angle may be to sharp in the other direction. I remember seeing videos where a tool was set against the driveshaft to measure the angle the shaft was 'seeing', and whether it was outside limits of a plain u-joint to handle.
If you have little movement of the yoke in the tail shaft bushing, don't bother replacing it. There is always a slight bit of movement. You would know if it was bad as it would be obvious movement rather than 'subtle'. Have you looked at the yoke bushing wear area and checked for scoring? Have you lubed the inside spline of the yoke? A dry spline will not move as readily in response to rear axle motion and will give a 'lurch' effect as it torques up and releases.
I would think the driveline guys that balanced your shaft would know if the yoke runout was within reasonable tolerance.
The only reason a differential or 'pumpkin' could affect balance was if the nose bearing was bad, and allowed the differential input shaft to wobble. Was yours loose? I did not get why it was replaced.
tom