4wd system help

[plkettle]

Hi All,

Please can someone give me an overview of how the 32GTR's 4wd system works ?

I think my 4wd pump has died whilst driving and caused my transfer box to let go ?

Can anyone tell me how the system works so i can figure out what has caused this and how best to fix it ?

Thanks,
Pete

[kismetcapitan]

what are your symptoms? The ATTESA system is pretty simple. On the electronic side, there are speed sensors at each wheel (that must have correct torque and clearances) and the G-sensor under the center console. Those five sensors go to the ECU. The ECU controls the pump to engage the center clutch plates.

My right (or left) front sensor is acting up, or wasn't reinstalled correctly. If I'm at a complete stop, and then turn the wheel completely to the right, when I start moving, the ATTESA engages. This is something very undesirable when parking, and even worse, it does it even when I reverse - the ATTESA engages the fronts ONLY in the forwards direction!!

It's slowly going away so maybe it's working itself out. I hope.

btw Pete, I have FINALLY gotten 100% satisfaction with my fuel system. Twin Bosch 044s, making a holy racket of sucking and humming in the boot, but I get absolutely no pressure dropoff at 6 bars fuel rail pressure. I realize my problems were due to the fact that Jap pumps engage their relief valve at 5 bars. I never ran lean, but it's a beautiful thing to watch my fuel pressure do exactly what it's supposed to do - stay rock stable in relation to manifold pressure! One 044 would maybe have covered things, but I'm glad I did two - I can flow 300lph at my highest rail pressures!

[plkettle]

its a strange one toby,

previously the 4wd used to come on very occasionally from hard launches but after an engine restart always went off again and stayed of for weeks without issue.

A few days ago i was driving along (quickly ) the 4wd light came on so i though its just gone into RWD and carried on at speed...

as i approached a junction i gradually slowed right down and as i turned off right - (slowly in 2nd gear) there was a massive crunch and lots of knocking noises coming from the car.

I thought oh **** the big ends have gone in the bottom end.

However upon idling the car i realised that if i depress the clutch the knocking completely dissappears ?? so i slowly move the car forwards and there is metal ratting around for sure somewhere and the car jams up (only moving at 1mph) as though something has locked up the wheels

I can get into all gears fine and im not sure its the gearbox as the car was not under pressure at the time and I was only turning slowly when it let go (plus the 4wd light wouldnt damage the box and is too much of a coincidence to be a different issue)

so im thinking front diff or transfer box ?

- probably the transfer box due to the 4wd light not having any connection to the front diff (or at least i dont think it does)

I have done some searches too and cant find any cases at all on here where the transfer box has gone with similar noises etc so im now not sure....

I know the best way to tell is to just drain each of the oils and the one with the metal pieces in it will be the culprit but until i get it to a ramp where i can do that im just trying to work out what the likely issue is and what i need to buy 2nd hand to fix it

[kismetcapitan]

sounds like the transfer box. As the center "diff" is a clutch and not an actual differential, if the clutch plates engage when front and rear wheels speeds are way out, the clutch plates can bind up and break. IIRC, there's a lot of them and each one is pretty small, so if they shattered they'd make plenty of racket.

Good thing though is that AFAIK that system isn't connected to anything else so metal bits can't get into anything else.

I've never heard of the transfer box dying either, but I guess there's always a first. Seems to me that if the front diff went, it wouldn't jam up like that, but I could be wrong.

The 4WD light definitely only is connected with either sensor failure or ATTESA hydraulic problems.

[MIKEGTR]

sounds like a diff problem to me