Slack..

[welder79]

When replacing my u-joints recently I noticed that when I grabbed the driveshft in hand and rocked it back and forth that there seemd to be some slop in either the rearend or the transmission or both. When I take off from a standstill I feel a little bump. Could this be transmission mount? I know it could probably be many different things so where should I start?

[m35a2]

Find out which end the slack is in but it sounds like a Worn Pinion bearing on your rear end.Get under there and twist the shaft,See if there is any in and out movement of the Pinion.The Brick had a very worn 8.8 and the sucker would move out a quarter inch.Just about to let go on that truck.Ring and Pinion looked like little Razor blades.

[typefour]

My f350 had the pinion yoke splines just about gone, would not have been fun on the 1200 mile camping trip we planned.
Real common on the 10.25 rear because it uses a crush sleeve then gets loose on decel, the ring gear trys to pull the pinion toward it. I machined a solid spacer to make it preload like a Dana 60.

[welder79]

So how can I tell what rear end I have?

[tim94f250]

You can check the sticker on the drivers door jamb. It will have an "axle" on the sticker. It will have a number or letter and number beneath it. Tell us the numbers and we can tell you what axle you have. Or, check the rear axle cover. It should have a metal tag bolted to the cover. Tell us all the info on that tag.

[welder79]

Axle code 39

[pnose]

Should be a 10.25 ford sterling,with 3.55 gearing,open diff.