Im finally putting the 4x4 drive shaft in my 86 F150. I bought the truck with it uninstalled laying in the beds toolbox haha need new u joints question is which way does it go short end to the front or back????

 

The slip joint goes toward the transfer case.

 

It actually isn't all that important, and it will work either way (unless one end of the driveshaft has a CV joint, but yours doesn't). However Dave is right, that the slip joint end was up by the transfer case when it was new, and is probably the best way to do it.

One theory is that the slip joint end is more fragile than the other end, and it's better protected up by the transfer case. I'm not sure if I buy that because I think some Bronco rear driveshafts have the slip joint at the axle end, and they have a CV joint at the transfer case end so they can't be reversed.

Another thought I have is that the slip joint seal slips against the driveshaft so it isn't actually "sealed." Having the slip joint end pointing forward might make it more likely for debris to get driven up into the slip joint than if it's pointed back. But I don't think that theory completely holds water either because I think most pickups came with the slip joint in the rear axle pointing to the front (that is, back when pickups had slip joints rather than slip yokes).

So I don't know why (or even if) it matters at all. But "everyone" (including the factory) puts front driveshafts on with the slip joint toward the transfer case, so that's probably the best way to go.

 

I don't know if Ford always had them, or started using them a certain year, but boots over the joints help keep the dirt out. I have used those colored shock absorber boots with tie wraps with some success.

 

sweet thanks yall now i just gotta get the rear shaft repaired haha

 

Depending on what you're doing, a drive shaft repair can get expensive.
I'm selling a good set of front /rear drive shafts off a 1986 F150 4x4,
but live around 3 hours away from you in Canada.

They're yours at no cost if you want to pick them up.

 

Mookie thats awesome turns out i dont have to get it rebuilt just gonna replace the ujoints but id love to have a pair just in case ill have to find a way north of the border here soon then.

 

I removed my Kijiji ad and set them aside for you, but its better that you wait til early Spring to pick them up.
I live on a lake where, this time of year, snowstorms are mean, unpredictable, and driving can be very nasty.
If I don't hear from you again by mid March I'll relist the ad. ...sound good?

 

Replacing u-joints is pretty simple (in a pinch you can do it beside the road with a hammer and c-clamp). But I would get it balanced afterwards, especially since you don't really know the history of the shaft.

If you use greaseable u-joints with the fittings in the valley of the yoke, for best strength install them so the fitting is under compression when driving forward.
Personally I use u-joints with the zerk in the end cap so I don't have to think about it.
Grease them at least whenever you change your oil (more often if you do a lot of wading or driving in mud.
You should see new grease coming from around all 4 seals when you grease it.

 

There are 2 schools of thought on that. One is to pump in enough new grease to purge the old grease like Rovernut says. The other is to just put in enough new grease that you see the seats START to bulge, but not enough to push any grease out of the seals. Supposedly that keeps the seal (more) intact so you're less likely to get crud into the U-joint.

I'm not sure which of those methods is best for normal use, but for extreme use (frequent water or mud) I'd DEFINITELY go with Rovernut's method. I'd basically figure that I was guaranteed to get crud past the seals no matter what, so I'd try to clean them out whenever I greased them.

 

The "just enough" school of thought comes from the myth that you can blow u-joint seals, probably started by people who don't really understand u-joint seal design.
They are actually designed for you to purge the old grease and crud. On the rare occasion I've had one pop off it's trivial to use my finger to press it back in to place.

On a humorous note:
There was one person on another forum who just couldn't accept the fact of how u-joint seals are designed, even after I posted a link to Spicer's u-joint maintenance web page.
So I did an annotated screen shot. Kept insisting he learned the correct way to do it in the Army.
I thought about naming the file "u-joint_lubrication_for_idiots.jpg" but thought better of it. LOL



Actually the above reminds me of something I think a lot of people overlook, greasing new u-joints before you install them. The grease shipped in them is more a rust inhibitor than a lubricant.

 

Good to know. Thanks