I just bought a 1984 F-150 Stepside. It’s got a 302 with a 4 spd manual tranny. Heard a clunk from the rear when I was slowing down so I figured my first project would be u-joints. Advance listed both my u-joints as being brute force brand model 4800BF so I picked both up and went to work. Replaced the front without a problem. Didn’t have such luck with the rear. The 4800BF did not fit into the yolk in the driveshaft. The caps were the right size but after removing the caps I could not fit the joint into the yolk. Also, the length of the joint fit into the differential but the caps were too small. Upon inspecting the old joint, it was not square, cap to cap the dimensions are 3-5/8 in on the differential side and 3-1/4 in on he drive shaft side. The caps from a 4800BF joint fit in the shaft and the caps from a 4900BF fit in the differential. The rear appears to be a Ford 9in (The guts come out the front). I brought the u-joints to every auto parts store around and they could not find a matching one in any of their books. They could not even find the joint that was in there, which was actually a little short on the differential side. Has anyone experienced this before or have any ideas? Thanks!

 

Sounds like a conversion joint. Is the rear axle stock? I can't remember when Ford stopped putting the 9" in trucks. Using a conversion joint is very common when swapping in a different axle and the joints are different.

This link should help you figure out what you need. Just measure what was in it and find the correct joint.
http://www.actionmachineinc.com/ujoi...ringguide.aspx

For example you can have a 1330/1350 joint to convert the stock drive shaft to the non-stock axle yoke.

Hope that helps

 

thanks! i finally got a change to measure up my joints and emailed the dimensions to Action Machine. i finally identified the rear and it is a Ford 9in out of a 1980-82 F-150, 31 spline. Their 1330 special matches my rear and the 1310 matches my driveshaft so hopefully they carry one that is a combination of the two.