1997 Discovery 1.
My front drive shaft appears to be making a loud clank/clunk every time I shift into drive or reverse. I had a good look at and you can see the rear drive line is almost stationary when shifting, but the front shaft looks like its moving 20 or 30 degrees when shifting from park to drive or reverse.

Should the front drive line be pretty tight like the rear drive line?

The U-joints appear to be solid I cannot find any slippage there.
Could it be in the Diff or T-Case?

I'm a newbie at the Rover and just trying to figure this truck out.

I have replaced all t-case and diff fluid with Disco mike recommended 15w140
which has worked well. But I'm still getting the clunk.

 

Man, I'd change them ASAP. Cheap insurance if your a diyer.

 

You should raise the front wheels off the ground to check the front u-joints. Or remove the shaft and check for slop. Cheap as they are if in doubt, change them out.

 

It could also just be plain old gear lash.
Mine is worse if one of my tires is softer than another.
Mine has been doing it since the day I bought her in '07.
New u-joints made no difference for me, but that is where I would start, $10 each, you need four.

 

I,ll go with the u joints first and report back. Talked to a local shop and said it could be the input Flange on the diff. Ever heard of those splines going bad?
Trying to find one may be chore.

I put the truck in neutral and diff-lock neutral( chock the tires!) and tried rotating the front drive line only got about 20 degrees out of it before it would not rotate any more. I assume thats normal or should I get a full rotation out of it?

 

It is a full time 4x4, both prop shafts are connected all the time.
Replace your u-joints, if that does not cure it you can either continue to chase a red herring or you can live with it.
Yes you can find the input flange, or you can buy a new diff for about $1,000, or you can buy a used one for $50.
Or you can just live with it.
I have chosen to live with my clunk, going on 70,000 miles with it now.

 

Be especially careful with the front driveshaft. If it breaks free it can knock a hole in your transmission case. Then you're talking about some SERIOUS repairs. As previously mentioned, U-joints are less than $20 apiece and can easily be changed in your driveway on a Saturday afternoon. New transmission... not so much.

 

That is only a problem with the DII because it has the double cardon joint on the t-case end.
With the DI if the u-joints seizes completely you will get a vibration that makes it undrivable and it will also have a severe squeak.

 

Thanks for the good advice. I spent this morning trouble shooting the problem a little more and it almost seems the hard shift is coming from the t-case or tranny and causing the backlash in the front diff. Had a reliable friend check the u joints and said they look fine. I recently changed the T-case and Tranny fluid and added a lucas additive to the tranny. The clunk soften for about an hour and then back to clunk again.

On a positive note I did reanimate my dead Tachometer by cutting off the bad lead wire to the Alternator and installing new blade connector. Works good now!

 

Don't sound like a noob to me.......