I just bought an '82 4x4 with super swampers. I'd never had those kind of tires so I thought they were the source of this horrible vibration above 35. I wa headed to the junkyard to find wheels and had just got on the freeway when a loud driveline knocking and clattering ended with a release of all drive power. It turns out that a bad rear u-joint had rattled the bolts loose and dropped the driveshaft. I was able to put it in 4wd and disconnect the driveshaft and front yoke and proceed down the road on my junkyard mission.

Later I installed new u-joints and read in the manual that I'm supposed to make alignment marks on the driveshaft before pulling it. Since I didn't have a chance to do this on the rear, and had removed the front yoke at the splines before reading this, I didn't get to make these marks except at each u-joint. I kind of assumed it was for the purpose of making it easier to line up the rectangular driveshaft yokes without having to pull the yoke off and realign the splines several times when reinstalling the driveshaft.

But then I got to doing that (playing with the splines alignment to get the bolts to line up) when I started playing with the gear lash of the front axle in relation to the gear lash of the rear axle when I got to thinking: do I have to have these two sets of gear lash lined up equally? Is it necessary to have the gear lash tight on front and rear drivelines or else wear and damage could occur? Is it possible to be off by a spline or two and have the gear lash of front and rear axles bucking against each other in a harmful or potentially damaging way when 4wd is engaged if I don't set it up correctly? The most testing I did was driving it half a block in 4wd with no nasty noises so I figure it couldn't be too bad. I thought it would be worth asking. I'm probably overthinking it but I wanted to play it safe since I'm new to 4wd tech.

Once I got that driveshaft lined up I had to call it good because I'd had all I could take struggling under the truck bench pressing that shaft in tight confines. I did notice at some rotations the splines would not always fit back together so I had to rotate some more, round and round I went until I got the bolts in.

 

The front and rear ujoint crosses should be 'in phase' with each other.

Both yokes should be in the same plane, and not X'd with each other.

Google it.

 

X2 this ^^

 

Ok, so the front and rear u-joints on the driveshaft from the tranny to the rear end should be lined up with each other, right? Right now they're crossed up and I need to fix that first thing tomorrow morning.

That may have been the thing that caused the rear u-joint to fail so badly in the first place, maybe someone messed that up before me, who knows?

Now how about the front driveshaft versus the rear? Can there be any play issues between the two that affect 4wd performance/long term wear?

 

As long as the joints on each separate shaft are properly set. All is good.

Even if you wanted to, I don't know how you could make any permanent setting between the front and rear shafts, because the front output is disconnected from the rear output whenever you have selected 2 wheel drive.

 

I just got under the truck and got the rear driveshaft in phase front and back. I did look it up and understand the way it should be.

One thing I did notice though, is that the drive flange from the transmission is a little wiggly. I can jiggle it up and down a bit, and front to back a bit, even though the nut that holds it down is 'staked', or punched at the indentation. My guess is someone didn't tighten it all the way when replacing the rear seal or something. There is a bit of gear oil spray back there, not much but some.

I want to get that corrected as soon as possible. Best case scenario, I get a new seal and stake nut, and it's only because it was loose. Worst case, I'm in for a new transfer case or something like that.

Any advice on a place to get a good price on a rear seal and stake nut?

 

Seal should be available at any parts store.

You can reuse the nut.

Torque spec for transfer case companion flanges is 90-95 fp.

They often loosen on high mileage trucks.

Degrease, use some loctite and restake the nut.

 

Now that I have understood how the rear driveshaft needs to be set up and have set it up accordingly, I see your point. Thanks!

 

The truck was sold to me as having 130,000 miles, and the working odometer displays that mileage (approximately). Does that seem normal for that reported mileage?

 

I guess it depends on the level of use and abuse.
The output flanges on my babied '95 with 112,000 are still tight.
I found the flanges on my '87 to be very loose @ 274,000.
I would'nt be too concerned if I were you.
You may well find that the companion flange @ the differential is somewhat loose too.
It may need a new seal as well.
I torque these a little tighter, as much as 130-140fp.

130,000 seems really low for a 1982 truck. Maybe a carfax would tell a different tale.

 

First thing I did when I got my '82 is get a manual. Has helped me to no end. I know the reason for marking the flanges and yokes is cause at the factory they were finely balanced, not sure if that included the yokes? You should be able to match them again by grease, paint and scratch marks, if lucky, I had to once? The u-joints have to go in so you can have access to zerk fittings or you'll need a needle adapter. If the wheels are off turn the diff yoke and see if you feel roughness from shaft, if so might be a bad front bearing then should replace it then seal. That bearing doesnt get oiled as well as the rest.
FYI, my diff front bearing inner race was spinning on the pinion shaft with slight shaft wear. Rather than leave it or get a new shaft I cleaned it up and had to do a very quick assembly using lock-tite 620 (it sets up quick), it will be hard to remove but might not need to if i watch the fluids.