Had my 98 D1 for 2 years and I suppose it's always done it but I am running out of things to fix now haha, yeah right...

When I select reverse there is a fairly heavy clunk and the truck gives a little lurch. Revs at idle are at 750rpm. Can I adjust this out somehow?
Thanks

 

Leave the idle alone. When was the last time you inspected and greased both drive shafts u-joints? Does your rear shaft have the rubber roto-flex ring, if so are there cracks between the 6 bolts?

 

I wasn't meaning can I adjust the idle, I was meaning is there an adjustment for the tranny?

I thought of the rotoflex but I changed that in another vehicle with the same problem and it didn't make the slightest bit of difference.

 

Update, I shoulda checked this first but IMHO the oil level is too high. Tranny fluid was replaced about 10k miles ago and I just checked it according to RAVE procedure, cold fluid, engine running in neutral and it is about 1-1.5" above the max mark. Could this be the cause?

 

Not good to have it that high but I doubt it is causing the problem.
So back to my original reply, answer my questions regarding your u-joints, service on them and go visually inspect this rotoflex, I am not interested in what happened on another vehicle but this one.

 

Some clunking in the driveline is normal especially in the mornings. Be sure to check your ujoints though.

 

I just noticed that it doesn't do it from cold just when it been run for a bit.
Also it "feels" more like the clunk is coming from directly under the gearshift rather than the rear diff.
I'll check the U joints for a nipple but I don't know if they have them on the 98. They would be greased by the shop when the oil change is done right?
I'll look for the Rotoflex and report back.

 

Mine does the exact same thing.
Only when hot never when cold.

Drain out some of your trans fluid level and let us know what happens.

 

Spike, I would like to get the fluid level correct to begin with so my question is can I just loosen the drain plug and let it trickle out or will nothing come out until the plug is all the way out?

 

Yes you should be able to just loosen it and let it dribble.
It might go slow so bring a drink with you.

If you remove the plug completely it will drain out faster than you want and she will be empty before you can get the plug back in.