gcfcos

Hi all. Just wondering if anyone has ever modified the mt75 4x4
Cossie gearbox to just run rwd before? Had the front prop off just to try it, would drive just about to pull away but then nothing, just like clutch slipping. Maybe the transfer chain could be removed but thought I'd ask if anyone's done it before. Cheers

gcfcos

Anyone?

gcfcos

I've heard from a couple of people it can be done?

dojj

iTrader: (3)

do you want the long technical explanation or the short mechanical version?

the short version is no you can't, because it won't work

if you want the long technical one you'll have to wait for me to type it out

gcfcos

Lol cheers mate

dojj

iTrader: (3)

long version:

inside the transfer box there is a diff, but this diff is mounted sideways and the input goes in one way and the output's go the other ways

so for starters the output shaft length from the gearbox is longer than the 2wd version and the case is a different shape so you can't just swap out parts

so now the output from the gearbox goes into this diff, in the middle and, through the wonders of gearing, it turns the output shaft of the box in the same way that you would use one of your wheels to spin up your own rear diff

this, as you would expect, then turns the wheel on the other side of the car 180 degrees to the input AND turns the diff crown wheel

the difference in a sideways diff is that the crown wheel doesn't turn a pinion shaft at 90 degrees, but rather the crown wheel turns a chain which then offsets the output to further outside the gearbox (which is why it's got a hole about 14 inches further outside the gearbox to drive the front diff)

this then all sounds brilliant, but as soon as you remove the front prop, all the turning from your output shaft is now going in the direction of least resistance, exactly like an open diff if you were to remove one of the driveshafts

but you have a viscous coupling in your box, which limits the amount of slip, which is why you call them "limited slip differentials"

so essentially by removing the front prop, you are loading up the centre viscous to max to drive the rear prop and this will overheat it and burn it out in a matter of minutes

when the front prop is connected, all the wheels are spinning at the same speed and so there is no requirements to load up the viscous and so it doesn't wear out

phew

i could go into this deeper with diagrams and stuff but i'll only do that if you want it explained further

dojj

iTrader: (3)

there you go, easy

gcfcos

Lol cheers mate. My mate said he removed the front prop on his xr4x4 and had instant rear wheel drive (he's a mechanic like myself) but think he was telling me proper porkies and when I removed my front prop she hardly moved so thought yeah he's proper full of shit lol

dojj

iTrader: (3)

if there was a way to make the centre viscous part of the diff solid then yes, it would work that way and be fine because it would then be 100% locked 100% of the time

you'd still only be getting 66% of the torque going to the rear wheels though, so if you want to detune your car thats the perfect way to achieve it

Marc sierra

iTrader: (1)

Why doing it the difficult way? There are lots of rwd MT75 gearboxes that are on the 2.0 DOHC. I think they have less strong bearings, but the V6 MT75 rwd box has the same bearings as the 4x4 cossie box, so I guess it should be possible to use these bearings in the 4 cilinder rwd MT75 which would be usable on a cossie.

RIB1122

iTrader: (2)

I love reading stuff like this! All 2wd and 4wd have the same bearings in the main box!!!

The internet is full of SH@£

gcfcos

Think ill just wait untill my gearbox gives up and convert it to proper 2wd with a t5 box then