Rabat Matt

Rabat Matt

Member
I put my Disco 1 up on axle stands to check if the Diff Lock was engaging (just bought it and it hasn't been off-road in living memory, and there's no diff-lock warning light, so I was expecting the selector to be seized), but I don't understand what the h*ll is actually going on.

First, there was no evidence of the central diff locking (when I turned the back left side wheel by hand, only the back right turned), so I started the engine.

Then, with the engine running and the gearbox in 1st, in high range the back two wheels and the front left spun. With the same thing but in low range, only the back two wheels spun. There was a very slight tendency of the free-wheeling wheels to spin with the driven wheels, but it was easily stopped by hand.

Thanks in advance to any thoughts on how to go about figuring out what's going on under there.
 
Rabat Matt said:
I put my Disco 1 up on axle stands to check if the Diff Lock was engaging (just bought it and it hasn't been off-road in living memory, and there's no diff-lock warning light, so I was expecting the selector to be seized), but I don't understand what the h*ll is actually going on.

First, there was no evidence of the central diff locking (when I turned the back left side wheel by hand, only the back right turned), so I started the engine.

Then, with the engine running and the gearbox in 1st, in high range the back two wheels and the front left spun. With the same thing but in low range, only the back two wheels spun. There was a very slight tendency of the free-wheeling wheels to spin with the driven wheels, but it was easily stopped by hand.

Thanks in advance to any thoughts on how to go about figuring out what's going on under there.
Click to expand...

You have a tight disc brake on the non spinning wheel.
 
Thanks. That makes good sense. And has the advantage of not needing fixing! I put it up again and spun the wheels - sure enough, the ones with the most resistance (if only by a small margin) were the ones that weren't getting the power.

Thanks again.
 
Rabat Matt said:
I put my Disco 1 up on axle stands to check if the Diff Lock was engaging (just bought it and it hasn't been off-road in living memory, and there's no diff-lock warning light, so I was expecting the selector to be seized), but I don't understand what the h*ll is actually going on.

First, there was no evidence of the central diff locking (when I turned the back left side wheel by hand, only the back right turned), so I started the engine.

Then, with the engine running and the gearbox in 1st, in high range the back two wheels and the front left spun. With the same thing but in low range, only the back two wheels spun. There was a very slight tendency of the free-wheeling wheels to spin with the driven wheels, but it was easily stopped by hand.

Thanks in advance to any thoughts on how to go about figuring out what's going on under there.
Click to expand...
doesnt sound like anything is up
when you turn 1 rear wheel if the rest are off the ground the easiest to turn will ,which was your other side wheel, if you braked that wheel drive would have gone through to the prop and so front ,but it takes more effort as it has to turn crown wheel then pinion
 
Rabat Matt said:
I put my Disco 1 up on axle stands to check if the Diff Lock was engaging
Click to expand...
Easy way to test is, engage centre diff lock, jack up one front wheel only, just clear of the ground, does not matter RH or LH, try to rotate the wheel that is lifted, it should rotate only through a small angle of rotation, (backlash in the transmission components), then stop solid, if it does not stop rotation CDL is not working/engaging.
Do not try running engine and engaging transmission with this test method.
 
At best/worst even with cdl engaged it will only ever be 2 wheel drive, you have open diffs as standard on the axles the only locking diff is the centre one. Do you fully understand the concept?
 
DiscoPol said:
At best/worst even with cdl engaged it will only ever be 2 wheel drive, you have open diffs as standard on the axles the only locking diff is the centre one. Do you fully understand the concept?
Click to expand...

I don't know if he does, but you certainly don't.
 
wammers said:
Don't think there is any need for that. Will you be voting to leave or stay?
Click to expand...
Apologies offered, you are right.

I dont get a vote and quite frankly it doesnt concern me.

now back to the diff question, one locking diff splits the drive 50/50 then the two open diffs under perfect conditions split that accordingly but if the power has an easy route out then it will take it, ergo under the worst case scenario you could easily end up with just two driven wheels, e.g cross axled. Does that sound about right @wammers or am I mistaken?

Please dont try to make an argument out of everything to appease your complex.
 
DiscoPol said:
Apologies offered, you are right.

I dont get a vote and quite frankly it doesnt concern me.

now back to the diff question, one locking diff splits the drive 50/50 then the two open diffs under perfect conditions split that accordingly but if the power has an easy route out then it will take it, ergo under the worst case scenario you could easily end up with just two driven wheels, e.g cross axled. Does that sound about right @wammers or am I mistaken?

Please dont try to make an argument out of everything to appease your complex.
Click to expand...

sounds right to me, and when the TC kicks in the drive goes to the wheels that have got grip :)
 
Oh I think I'm getting it now. Wasn't really the conceptual stuff that was my problem so much as the practise - didn't realize how little resistance was needed to kick the power to the other wheels and leave 1 or 2 just hanging there looking useless.

Definitely not getting any central diff lockup, but I was half expecting that anyway. And there's some good threads on that already.

Thanks to everyone who pitched in with the useful points. Much appreciated.
 
DiscoPol said:
Apologies offered, you are right.

I dont get a vote and quite frankly it doesnt concern me.

now back to the diff question, one locking diff splits the drive 50/50 then the two open diffs under perfect conditions split that accordingly but if the power has an easy route out then it will take it, ergo under the worst case scenario you could easily end up with just two driven wheels, e.g cross axled. Does that sound about right @wammers or am I mistaken?

Please dont try to make an argument out of everything to appease your complex.
Click to expand...

Not trying to make an argument. Best case four wheel drive, worst case two wheels being driven if they completely lose traction. But the others are still connected or the slipping wheels could not spin. But you would have to be in deep doodoo for that to happen. There are few combinations with centre diff locked or unlocked. Of course you can fit locking diffs for serious off roading but they would only be engaged as required in a straight line if you don't want to knacker your transmission. But for general everyday use they are not needed. To get the effect you talk of you would have to have gone somewhere it was best not to have ventured.
 
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