Have a RAm Van 250 extended body, actually a RoadTrek conversion, 318ci, think an A588 tranny w/ auto overdrive. Developing a bad rumble, off throttle, downhill. Immediately suspected ujoints so checked them.Found that the tailshaft spline appears to be very loose, ujoints OK. Is there a design feature that make the fe. spline softer to accomatate wear? Do I have to pull the O/D and housing or just replace the ujoint yoke? Appreciate anything you can feed me.

Thanks, Jack

 

Ive not heard of the slip yoke on any dodge having a problem of the type you describe.
When you attempt to turn the driveshaft, you could also be turning the entire output shaft on the transmission, and instead the play may be there. I'm not sure what you mean by very loose, there is some play in the output on my TF A727 but it doesnt seem to be more than 3-4 degrees of rotation. I checked this recently after I broke the driveshaft on my RC, and it has the same A727 transmission my van did.

Instead of being only off throttle, you may want to try neutral and off throttle on a smooth road. to see if your problem is hapening farther up the drive line. When you are off throttle, the transmission is still engauged and you could be experienceing engine brakeing.

 

Immobilized the tailshaft and the play is definitely in the spline, a little torque wise but quite a bit as in side to side slop. Not elsewhere in the drive train. Is there a bushing somewhere inside the tailshaft housing? Do not have a breakdown of the tranny handy.