"Thunk" in four-wheel drive

[Jim-ME]

All Series ring and pinions should be the same ratio or atleast that is what I have been lead to believe.

[luangwablondes]

Series landies have wind up problems when locked in 4 wheel drive. My understanding -- this is from the village idiot- but on his 5th series landy- is that the front and rear ratios are not equal. So when on 'hard pavement' you should be in 2wd. I put in Range Rover difs and it seemed to resolve the problems of the gear wind up. But on the other hand, I usually caught my 'mistake' within the 1st hundred metres, so what do I know. When you feel that thunk a couple times, you can be sure you also put alot of stresses on the gearbox.

[LaneRover]

Even if the ratios are exactly the same, on a hard surface you get wind up when you turn because at that point the wheels in front are going a different distance than the wheels in back. Even slight turns will do this.

Brent

[Tim Smith]

I'd like to just note that I was getting the thunk on a very very snowy day. Partially in a slide the whole way. The thing that had me concerned was that it would occur pretty regularly within a few hundred feet of the last one.

That's why I thought it was due to the slightly different ratio's from front to back. If it happened randomly or if I wasn't in a slip and slide then I would have concluded that it was just wind up from turns or road crowning.

Not sure if that makes it any clearer...

[LaneRover]

Ahh yes, getting back to the actual problem!!

If you were slipping and sliding most of the time the diffs could be different ratios and you probably wouldn't have gotten the 'thunk'. As to what could cause that every hundred or so this is the only idea I have.

Any chance that there is something wrong with the front ring and pinion that takes a bit to line up, thus giving you that thunk? Something like 1 tooth from each being missing and unless they are at the samepoint under pressure the teeth on either side 'deal with it' while when they come together the pinion gear slips a notch thus creating the thunk? This would explain why it would only happen under load and only when in 4wheel drive with front hubs locked. It may seem like it was coming from the transfer case because that is what is dealing with the shock of the 'thunk'.

Try jacking up the front of your rover and spinning stuff by hand slowly to see if there is a 'click' or skip that you can feel.

I guess in theory the same thing could be happening inside the transfer case but you can easily pop the cover or drain pan and see if there are any toothless gears in there.

Brent