5 replies to this topic

[wisky9er]

can some one tell me why I keep breaking u joints? I just bought new yokes;rear axel ,and xfer case but the u joint at the rear axel keeps breaking.
I get a bit of a vibration around 60 when iam just crusing, than when i let off i get a clunck from the rear axel.

[a1bummer]

To much of an angle in the driveline maybe. Pinion angle to be more precise. Clunk sounds like diff or u-joint related. Loose lug bolts would make it sound like that too. Are the pinion bearings properly shimmed?

[wisky9er]

To much of an angle in the driveline maybe. Pinion angle to be more precise. Clunk sounds like diff or u-joint related. Loose lug bolts would make it sound like that too. Are the pinion bearings properly shimmed?

[wisky9er]

I dont know, right now I am just trying to get the truck to me. I am stationed in Ft. Irwin and my truck is at home in WI. I do know that it had bad tires on it. they had knots on the side walls. everyone knows what I am talking about. I am just trying to get r done piece by piece.

[1978 F150 4x4 Toploader Swap]

My brother's '79 bronco was breaking u-joints left and right. It has a 429CJ out of a 1970 mustang in it. We thought maybe it was too much motor for the drive train, then we thought it was bad motor mounts (shotty swap kit). It turned out in the end to be a cracked leaf spring. We checked the leafs numerous times before but you couldn't tell that it was broken until the spring was unbolted and half a leaf fell out. Ever since he changed the rear leafs he hasn't broke another u-joint. Hope this helps.

- Brandon U. from Pittsburgh, PA
1978 F-150 4x4 with a 351m (for now) and a 4-speed toploader out of a 68 torino (extremely rare custom swap). Lots of other custom work done.

[jake_262]

can some one tell me why I keep breaking u joints? I just bought new yokes;rear axel ,and xfer case but the u joint at the rear axel keeps breaking.
I get a bit of a vibration around 60 when iam just crusing, than when i let off i get a clunck from the rear axel.

you said you bought a new rear axle, if you had a single cab truck, and got an axle off of an extended cab, or crew cab, or visa versa, chances are thats where your angles got off. that would cause vibration at higher speeds, and u-bolt failure. you would need to take your driveshaft off and put a degree finder on the rear end (take the u-bolts out of the yoke and place it flat on the yoke) then do the same at the end of your tranny or transfer yoke. the degrees should be the same, (or within variation recomended by the manufacture,) just oppisite ( meaning if you set the degree finder on the rear end straight up and down, then on the tranny, or transfer case, you would turn the degree finder upside down) hope this helps good luck