I've bought a '95 discovery for $300, it took about a month of tinkering and welding to get it to pass state inspection. but now that I'm on the road there's loud clunk from front end and when i''m under neath the truck i can move the front drive shaft like 90 degrees or more. that kind of slack isn't normal is it?

 

Nope. Time for U joints. You can pull off the front shaft, engage the CDL, and drive truck with just two wheel drive until repairs are made. There is a write up in the tech sticky area on front frop shaft rebuild, for a D2, but some of the same parts and methods apply.

BTW, common problem with older Discos is radiators partially clogged, watch temp gauge, should not get over mid point without checking it out. You can get radiator flushed and rodded out for $100 or less U carry in at some small indy rad shops, look for ones that work on farm and construction gear.

 

Worn u-joints don't allow you to rotate the driveshaft 90 degrees. Excessive backlash in the ring and pinion and/or worn bearings in the diff would allow for so much slop.

There is some slop in these drivelines, but 90 degrees sounds like too much. I'll throw out something more common: say, 30-45 degrees.

 

good point - I was thinking the clunk, and of course, Murphys Law says it could be both....

 

Yeah, to much backlash in the drive line.
Remove the front propshaft, turn the pinion flange on the front diff, how much does it move?
Now do the same on the output flange on the t-case.
Do the same for the rear.

Propshaft removal tip, put the transfer case in neutral, chock the wheels, parking brake off, this will allow you to rotate the propshafts 360 degrees so you can reach all of the bolts.

You have options on "fixing" this, like Redline Heavy Shock Proof gear oil.

 

thank you for the redline "fix" tip.
while at work I inspected a little closer and the rotation is only 30 to 40 degrees
and the U-joints are fine and tight. My next inquiry is why is this sloppiness seem to be on both the diff pinion and the T-case??? Is there also a problem in the T-case? Chain tensioner or something
And thanks again for the advice

 

oh and BTW is rebuilding the diff worth it as compared to hiring it out ,or even looking into something like a Detroit locker, i am a new father and kinda broke (stupid hospitals w/all their expensive smarts and stuff) Also is there a source some one can reckomend for a not ruined T-case if that is needed as well
and thank you all again

 

The whole shebang is gears - no chain in the transfer case. So, there's some slop from wear, etc.

To give you an example, under normal circumstances my Disco rolls next to nothing after setting the parking brake (I have a manual trans). The parking brake is on the rear of the t-case, the rear driveshaft bolts to it and connects to the rear - not much room for slop. However, at the moment my rear driveshaft is removed and my CDL engaged so the Disco can be driven. When I set the parking brake, the darn thing rolls a couple of inches until the slop in the driveline (main shaft of t-case through several gears to the front output, then to driveshaft and front ring and pinion (which is a stocker with some slop, since my ARB is out being repaired)) is taken up. Caught me off guard the first time it happened.

If you're particular, you can have the 3rd member checked out and see if there's any play in the bearings and if there's some room to take up some backlash. Though, know that the r-n-p have worn to the current measurements and may whine if messed with (doesn't always happen, but can).

However, there's one other issue (which I can barely recall the detail of - hopefully someone will chime in) which can cause a driveline clunk. The automatic transmission uses an adapter to marry the auto to the transfer case. IIRC sometimes these get damaged or too worn and make the clunk. From what I've read, you hear this when going from park to another gear, or from drive to reverse, etc. (have only owned a manual LR, so I've not experienced it).

 

Like Jimmy said, all gears, slack is normal, clunks are normal.
Worn out gear lube will make it worse, for $30 (Wal-Mart, Tractor Supply) you can buy 2 gal of 85w-140 and change all the gear lubes, both diffs and the t-case, buy a fluid hand pump too.
See what happens then and decide what you want to do.
Dont go to the RedLine unless you are on a last resort.

Also tire PSI makes a difference, if one tire is at 20psi and the others are at 40psi (for example) it will cause a clunk.