There is a "thunk" noise when i let off the gas then tap right back on to it. not something I do too much, but i would like to make sure something isnt broken, or about to break. I looked at some threads and read that it might be my U joint. I went under to check and there's no play in the shaft or anything. it all seems very tight. might it be something else? or is there something I'm missing?

Thanks!

 

Even if there is no play in the driveshaft if it does not have zerks on the UJ's it needs to be rebuilt. Even if it is not the problem, it needs to be rebuilt. Even if someone tells you it is fine, it needs to be rebuilt. Got the idea? The DII driveshaft did not come with greasable UJ's so due to their location they get hot, the grease dries out, they fail, and usually take out your transmission with it. Ouch! $2000+ fix on the tranny, $200 fix for the driveshaft. Now as to the "thunk", could be the driveshaft but it could be other things. Does it do it when you turn? Does it do it when you brake? Is there anything unusual about the way it shifts? Is there any vibration when driving at certain speeds? Give us some more details to try to pinpoint where the sound is coming from and go from there.

 

If you are describing what I think you're describing, its totally normal. Every DII I have ever driven does it. I asked this question when I first starting looking at them a few years ago and I was assured its just "one of those sounds" you'll have to get used to.

However, like Discomedic said, it would be a good idea to check if your driveshaft has been replaced with greasable U-joints. That is a MUST if you're a new disco owner. If you're lucky, it may have been done already.

 

This is also true. I forgot to mention that. Sorry, got off on the UJ soapbox and I forgot to mention that mine has a slight clunk normally. But you want to make sure it's not any of the common problem areas also. If you check everything and its still there it may just be the normal drive train "slop" that disco's have.

 

Yea i have the same thing, sounds alarming, but probably just some backlash somewhere.

 

There is a fair amount of backlash/play in the driveline especially when you get up over 100k miles. So it's normal for a thunk after sitting all night and shifting into reverse from park. The thunk is also there if you take your foot off the gas then gun it and also from shifting from 1st to second. Rebuild your driveshaft anyways if it has not been done.

 

The "thunk" is only while driving if i step on the gas quickly. it does not do it when i turn or break. everything seems very normal with the exception of the "thunk" and sometimes a little bump when i qickly step on the gas. It sounds like its coming from the rear driveshaft area. Maybe it's normal then?

Either way, what about the driveshaft needs to be rebuilt? do i have to replace it completely or just make it a greaseable u joint? I think I may have seen kits but I thought they had to do with the rotoflex joint.

Thanks!

 

The front driveshaft on a DII has three UJ's, one at the t-case end, and a double cardon joint at the front (the diff end). The double cardon has 2 UJ's and a centering ball. You need to replace all three UJ's and the centering ball. Look in the how-to and write-ups sticky at the top of the page. There is a great write-up there that will tell you exactly what to do and the part names and numbers. Unless there is actually damage to the driveshaft you shouldn't need to replace it. Some guys replace it with a Tom Woods driveshaft but if you are not doing a lot of heavy duty off-roading you are better off sticking with the factory driveshaft. Be aware that after a rebuild it is a possibility that you will need to have it rebalanced by a shop. If you rebuild it yourself it is fairly cheap, a shop is a little more expensive but it all depends on you, your mechanic skills, and your budget. It can be a bit of a pita to do yourself but there is some satisfaction to doing it yourself. BTW the flex disk you referenced is part of the rear driveshaft.

 

mine does it to, make sure you change the tranny fluid, that seems to make it quiet down.

 

Dido on what everyone else has mentioned. I have found a major source of the clunk. While inspecting a used locking CDL transfer case I purchased to install on my 2003 Discovery with only 18,500 miles on it. I locked and unlocked the tranfer case. Twisting the output shafts by hand where the propshafts install revealed 2.5 inches of play in the gears. This was all while it was unlocked. This simulated going from reverse to drive. I guess there a lot of gears in there that all have to sync-up when changing from Forward to Reverse. That is what I assume from looking inside with the large inspection plate removed.