output shaft play?

[steadyhand]

I know very little about transmissions so keep this in mind.

I have a 99 Mountaineer, 5.0, 2WD auto. I have been chasing a thump sound that occurs when I come to a complete stop too fast and when I take off. I have replaced so many parts already. I used some Teflon (XG?) grease from the Ford dealership to put in the slip yoke. I am not sure if I put enough in the yoke, but what I did use didn't seem to make any difference.

While I had the drive shaft off I noticed the transmission output shaft moved when I pulled out the yoke. By that I mean it can literally be wiggled side to side quite a bit. I can't move it enough to touch it to the tail shaft housing, but it seems like a whole lot to me. I have rebuilt an 8.8 rear end before so I have a basic idea what tolerance something is simply by how much it gives.

Is the tailshaft suppose to move and if so how much? The movement would be determined in thousandths of an inch, right? If so there is something obviously wrong here. My output shaft moves like it is attached to a knuckle inside the transmission.

 

[deweyville65]

My bet is on the front u-joint, or more likely the slip joint of the drive shaft seizing, causing the noise and wearing the bushing on the output shaft. I don't know how much play is allowable, but anything over about .020 would be cause for replacement to me. I am sure there is a Ford mechanic on here with the exact info.

 

[steadyhand]

I replaced the U-joints already. I also have all new shocks, inner and outer tie rods, ball joints (upper and lower), bushings in the front and rear (except leaf spring bushings). I recently put new rotors and pads on the front and back. I also have a new transmission mount.



Btw, I just noticed the transmission is now shifting hard into reverse. It was not doing this before I added the slip yoke grease. It shifted fine through all gears and still does except when I shift into reverse it jerks hard and it sounds like you can hear the linkage clanking. I have no clue how adding slip yoke grease would cause this but I just did this today and now it's shifting harder to reverse. Leads me to think it might be related.

I also guarantee the output shaft moves much more than .020 with the drive shaft out.

 

[steadyhand]

Well I tore into the differential today. I found the traction lok has 3 broken tabs on the discs and the rest look bent or scarred on the outside edges, like they were slamming back and forth. I'm wondering if this could be the cause for the thumping sound I'm getting in the rear. Maybe the discs are slipping. I'm going to order some new carbon fiber discs so unfortunately it is going to take me a day or two before I can finish this. I thought I was going to get them locally, but it turns out no one has the discs. They expect me to order the entire traction lok.

I also found that the pinion preload is only about 5 inch lbs. Of course these are old bearings. There is no side to side movement to the pinion and no dragging noise to the pinion bearings so I'm guessing there is no problem there.