D2's have a ZF Heavy Duty German Trans. They are quite robust and have very few issues if properly maintained. This includes fluid and filter changes every 30K if used offroad. If left to sit for many days the converter can drain down and cause a lose of drive until filled up. If you are getting a delayed engagement every time, you need to check the fluid level and condition. No dipstick, lift and Computer needed.

 

So, to check this I need to take it to a shop? Is this something any old shop can do, or will I need to take my favorite body part in and give it to the dealer?

 

I dont know if disco I's are the same, but even at 120,000 miles, there is no 2 second and then thump. Its a little slow, and reverse clunks, but i never need to hit the gas and feel a thump the get it into gear, it just quietly slides right in.

Also, mine has a dipstick, so maybe i have a different tranny...

 

I check the trans level myself every 15k miles or so, and have done the trans filter change, drain and refil a couple times without any problems, but it always ends up being a greasy job.If you want I can post the instructions on how to do it - there is specific procedure to follow, and the tranny must be at the right temp range. The specific procedure for measuring the oil level is the main reason trans manufacturers went away from a dipstick. People would check the level themselves, at the wrong temp, etc and would top-off when not needed or even drain oil when it wasn't overfilled. Not having a dipstick discourages the average car owner from trying to check the level and they are more likely to take the car into a shop.
Piotr