4wd + mot

New owner, please excuse my ignorance but what happens with permanent 4 wheel drive when the mot man drops two wheels on the brake rollers and the other two wheels cant rotate? will it damage the transmission, or do I have to take it to a garage that deals with 4 x 4s

They can't be tested on a 2 wheel rolling road - much vehicle lurching and confused expressions from testers when they try it (which one set of NCT testers did to mine as I was frantically banging on the window to tell them not to!). When they check the database it will tell them not to do it.
Judging on what went on though I doubt they would do a whole pile of damage, at least no more than you would do off road.

Permanent 4 wheel drive cars should not be brake tested on the rollers, it should be done using a Tapley meter and a road test.

If they're doing it any other way then they're not following the MOT tester guidelines, and they're breaking the law.

The guidelines state: 'Under NO circumstances must a vehicle equipped with permanent four wheel drive,Limited Slip differentials or belt driven transmissions be brake roller tested'

Totally agree with Jon, over the last 8 years I've had 4 RRC's MOT'd using the old fashioned Tapley method by my local tester who has a single axle roller system. I think they enjoy the break from the workshop for a few minutes!

Many Thanks, Will ask the m o t man when I take it.

Be insistent, they'll maybe try and say, "it's ok for the time it's on". Even if they disable the transfer box temporarily it's still a no-no as there is still a limited slip diff which can't be disabled unless its done permanently by seizure!

hippolover said:

Be insistent, they'll maybe try and say, "it's ok for the time it's on". Even if they disable the transfer box temporarily it's still a no-no as there is still a limited slip diff which can't be disabled unless its done permanently by seizure!

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deffo back this up. Had the M.o.t guy over the counter after I TOLD HIM and LEFT A NOTE IN THE CAR REFF THE 4X4 system in the Quattro.....funny old thing the useless cluster-**** did what i told him not to do:mil90:

i allus ask wen i tek mine in,jus t mek sure thi not gonna put it on the rollers.

Can't you insert fuse 11 putting the gearbox in transfer neutral??? Leaving it to free wheel?? Paul

c099895 said:

Can't you insert fuse 11 putting the gearbox in transfer neutral??? Leaving it to free wheel?? Paul

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Ahh, NO!

thats just a trick to make sure the transfer box stays in neutral. The front and back axle are still inextricably mechanically linked and effectively locked together by the Viscous Coupling. The only way to put a P38 (or any Rangie with a VC centre diff) on a two wheel rolling road is to remove a driveshaft.

The only way to put a P38 (or any Rangie with a VC centre diff) on a two wheel rolling road is to remove a driveshaft.[/quote]

What about a RRC fitted with the earlier LT230T box?

Kwikfit idiots stood there head scratchin before i told them it was permanent. then they came back with a two page long list! so i took it down the road an it passed straight away!

Just a quick follow up, took it to my local m o t place, when testing a 4 wd one roller turns forwards and the other roller turns backwards, providing both rollers turn at the same speed the propshafts dont move. (because of the diff)
The only thing they couldnt test was the hand brake, because its on the transmission, they test that with a tapley meter.

hazlington said:

Just a quick follow up, took it to my local m o t place, when testing a 4 wd one roller turns forwards and the other roller turns backwards, providing both rollers turn at the same speed the propshafts dont move. (because of the diff)
The only thing they couldnt test was the hand brake, because its on the transmission, they test that with a tapley meter.

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I assume you're talking about the rollers on one axle. If so then thats a pretty smart way of doing it. Only concern would be if the brakes work equally effectively going back or forward. Can't think why they would but it might just throw up something odd.