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V-Spec Diff Swap 4Wd Problem

Pezhead
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Pezhead Grand Master

Pezhead

Posted
Posted

Hi guys,

I'm having a problem after switching the diff on my R33 GTR v-spec to an r32 GTR non-vspec diff with carbonetic LSD center. The preload stays on for too long after an initial start. Then after a few seconds the ABS/4wd/LSD light comes on.

The A-LSD lines from the pump have been blocked off. The system has been bled. The shop has checked all 4 wheel sensors and they are sending pulses. Diff ratios checked and number of "cogs" on the rear ABS same between old and new stud shafts.

Has anyone had a similar issue when swapping the diff and center? Do I need to swap to a non-vspec Attesa computer?

I'm stumped.

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https://www.sau.com.au/forums/topic/451895-v-spec-diff-swap-4wd-problem/
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XKLABA
XKLABA

Ok so the sensors came in today and it works perfectly The issue I found is the A-LSD ABS sensor locator mounts vertically where the non A-LSD locator mounts horizontally which means it turns the se

Pezhead
Pezhead

Michael, looks like I owe you a round. I rotated the sensors and ran around the block where the error used to show in first 100 meters. Now I need to change the connector on the old sensors and the

XKLABA
XKLABA

Your most welcome mate, we'll talk about that round later The R34 GT-T ones I got bolted straight in and pluged up no wuckers $45 delivered off eBay Will look for new ones now I know it works

Duncan Grand Master

Duncan

Posted
Posted

Isn't the problem simply that 33 vspec had an active diff, and all the other diffs are normal? Surely the issue relates to whatever wiring differences there are in making the diff "active". Or is the only difference at the diff the hydraulic lines?

Pezhead Grand Master

Pezhead

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That's part of what I wanted to know. Do I have to find a R33 non-vspec Attesa computer? The only wiring on the rear diff was the ABS sensors and we left those in place.

I thought that the Attesa computer would just send signals to the pump (that's blocked off) and that would be it. The sensors in the diff are the same. So it is just the mechanical A-LSD is shunt off.

GTSBoy Grand Master

GTSBoy

Posted
Posted

I would suggest that it is failing the startup tests where it is probably cycling the A-LSD solenoid and not seeing the result it expects (probably a pressure change or something else that it can monitor). Then it says "My solenoid is borked" or something and faults out.

Take it to a mechanic and put a code scanner on it. You will be able to interrogate all the CUs on the car, find the fault code.

GTSBoy Grand Master

GTSBoy

Posted
Posted

I'm running an Autronic computer so no ODBII fault diagnostic. Where is the "light" on the Attesa computer under the parcel shelf. I looked for it but didn't see any LED lights.

Doesn't matter. Has nothing to do with the ECU. Plug a decent code scanner into the Consult port and you will be able to see all CUs that are connected to that bus. ABS, TCS, Auto, ECU, ATTESA, HICAS, whatever is there.

Pezhead Grand Master

Pezhead

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I haven't used Consult, I thought it was on the stock ECU.

Now there isn't a bleed plug on the diff - since it is replaced with a non A-LSD R32 unit. The bleed for the Attessa is on the rear of the trans. What bleed plug are you referring? Is there an electronic bit there?

I had Award diff do the work. Terry said that they've done a fair few of these conversions but never run into this issue. It has us both scratching our heads a bit.

XKLABA Grand Master

XKLABA

Posted
Posted

you can not bleed the A-LSD if there isn't one, but the ATTESA has to be bled after removing the diff, the A-LSD also has it own light so the ATTESA one coming on means the issue is the ATTESA and the bleed plug for both is, oh shit you have a 33, I think it is behind the fuse box lid under the steering wheel, white plug with one wire in and one out wraped in foam tape

GTSBoy Grand Master

GTSBoy

Posted
Posted

I haven't used Consult, I thought it was on the stock ECU.

Consult is Nissan's equivalent of OBDII. It's a bus that connects to all the CUs. I hooked one up to my car and saw the TCU and the HICAS as well as the ECU. Could pull codes from all of them (and both the TCU and HCU were full of them because of what had been done to those systems!)

Pezhead Grand Master

Pezhead

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Hmm, so do I bleed the system from the one bleed nipple off the back of the transmission? I've done it before with unplugging the bleed wire option. So I'll need to see how they blocked the A-LSD and see if I can somehow bleed the blocked line.

XKLABA Grand Master

XKLABA

Posted
Posted

Nah nah sorry no, they use the same wire plug to activate the pump for both ATTESA and A-LSD, but bleed nipple I two spots, one on transfer case and one on top of diff, plus one at pump for the gravity feed to the pump, it's the wire plug used for bleeding that I was talking about, check it is connected

XKLABA Grand Master

XKLABA

Posted
Posted

It has the ATTESA pro with the faster ECU, the hydraulic pump that controls the 4WD also controls the A-LSD which is hydraulically activated, same pump different valve so realisticly it shouldn't unless the pump is unplugged which is why I thought it might be electrical, since it is reading something on the dash then the pump is plugged in, maybe the pressure sensor ?

I am about to do this myself and would really like to know the outcome

Pezhead Grand Master

Pezhead

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So here is the really strange thing. I bled the system but fluid does just keep coming out without the system even on. And the weird bit is that the front shaft is engaged all the time. Seems like my transfer case is locked on. I had this problem when I first rebuilt it, but another shop determined that the case was put together incorrectly and fixed it.

It was working fine immediately after the diff change cause I pulled the front drive shaft to drive it to the tuner immediately after. But when I was going to put the shaft back in after the tune was the first I noticed it.

Any ideas?

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