vibration between 40 and 50 mph

[towtruckerfour]

Hi guys. In my 70F100 I have a 4 speed manual. I had to replace the differential seal since it was leaking a little. After I put it back together, it now has a vibration between 40 and 50 mph. I tried rotating the driveshaft a few splines and it got a little better. It has a two piece driveshaft and the truck is a 1/2 ton. Anyone have any other thoughts on what it could be? Thanks for the help

[ScreaminZ]

Are the yokes on the ends of the driveshaft in phase? If not, that could be the problem. If so, might try rotating 180 degrees.

[fordman]

all yokes must line up as well as the weights should line up. thats probably where the problem is.

[averagef250]

Don't look at any weights on the DS. They don't matter. The U-joints in any driveline absolutely have to be in phase.

[towtruckerfour]

Thanks for the help. I'll take a look at it this weekend and hopefully fix it. The vibration is quite annoying.

[binder56jd]

????

please to define "in phase"????

does this mean yokes aligned or 180 in opposition??

old dfer's want to know

[fordman]

in phase means lined up. to match all the way up to and including the seconed driveshaft. so both shafts are lined up in line with the rear yoke.

[averagef250]

A two piece driveline has 3 U-joints. One piece of the driveline is solid, the phase cannot be changed. The side with the slip yoke in it can be clocked or "phased" wrong if you take it apart (modern ones are keyed so they cannot be assembled wrong). The yoke ends of each individual driveline section must be in the same plane. In a two piece driveline, the planes of the two driveline's yoke ends will be 90 degrees from each other.

[willowbilly3]

????

please to define "in phase"????

does this mean yokes aligned or 180 in opposition??

old dfer's want to know

Timed is what old timers called it where I came from, in phase, same thing, all u-joints in the same plane.

[FORDification]

Just for the visual:

[towtruckerfour]

Thanks for the diagram Keith. I will check it out tomorrow and see how I have it put together. Thanks for the help guys. You guys are the best for info.