Replacement / Repair Of Vspec Diff

[paulr33]

hey gang,

my gtst has the a-lsd vspec diff. its shagged and basically single spins most of the time.

the slip light comes on and the electronic side appears to do its thing.

it has locked mech previously (burnout photos) so it did work at some stage.

its at a place being disected as we speak but i am not sure what to do.

he suggested a kaz centre to replaice it. has anyone been down a similar path?

can it be fixed? they arent sure if its viscous with pump or mech gears diff.

for simplicity i would rather keep it the same cogs and centre (but have it work)

can i just replace the inner cogs inside it (if thats whats dead)?

[Cubes]

Its easy enough for them to rip the center out and check if its visc or mech.

Another option if your not so keen on a clunking and bucking mech. (subjective) is a s/h GTR center, they are a mech clutch lsd but not as harsh as an aftermarket lsd, if I were to go down this route I would have it shimmed lightly to ensure its relatively tight.

[paulr33]

ah good point, didnt think of the gtr centre

so is it the same viscous centre as the stock gtr

and it just has elec controlled pump to turn it on?

cos ive looked underneath and its got the finned cover

then it has some hydraulic shit and a pump near the ass end

[Coupe-This]

who wants a loose lsd?

tighten the bastard up mine feels like a locker sometimes skipping the back wheels, thats where its at ...

paul you should be able to reco the gear thats in there although waiting for parts may be a pain in the ass, i havent heard anything about kaaz centers ... i think its kaaz anyways ... g/luck with whichever route u take ... cheaper option would to be reco i rekn, but i dunno ...

[paulr33]

hey

can i go shorter gears

like 4.3

[paulr33]

gonna get them to open it and find out whats inside

and then they will let me know whats busted

i could be a simple thing like the pump

or it could be the cogs are facked

either way im not buying a new centre bugger that

given that i wont be driving the car next year ish

not worth it. worst case if they cant reco it

ill get a 2nd hand gtr diff. i just found that auto diff is 4.3

could i change to that for some more punch

or is it too short

[Cubes]

If its a visc. lsd then its just worn and really not much you can do to repair it.

If its a mech clutch type lsd then the clutchs are worn.

If a gear was busted it would be clunk, clunk, clunk.

I don't know what the idea behind the active lsd's are, is it a form of traction control or does it lock the diff upon acceleration?

EDIT: All I could find was... # Active LSD system splits the torque between the rear wheels.

[paulr33]

it looks at the abs sensors, when it detects wheel spin (slip light comes on) it turns on a hydraulic pump to make it lock. so it sounds like it just pumps in viscous fluid

ive had the fluid changed, that didnt help. had a look and poke around, traced the hydraulic lines and found a pump. unplugged it, started car and a-lsd fail would come on.

so it sounds like its the pump for it. the idea is to split torque (that i can think of) but as far as i can see it just does a diff lock. i cant see how it can throw power to one wheel but not the other.

[MANWHORE]

Paul33

I will be watching this thread very very very very closely.

You know i'm very itnerested in the A-lsd, and it is very much an uncharted territory here on sau.

As far as i'm aware, it is a mechanical diff which is activated using the oil pump.

Have you tried bleeding the fluid? Some say that it's supposed to use attessa fluid - that is, nissan special pas fluid.

I would be very much interested to hear what happens.

[MANWHORE]

gtr stock diff is a waste of money. People charge around 600 for the diff alone.

I was told that you still need the shafts and everythingbecause it has a different pattern.

Furthermore, the gtr diff is second hand. It'll probably be in the same condition as yours.

A brand new kaaz/nismo/cusco can be had for around the 1100 mark. Straight fit in.

I know which one i'd choose.

But the A-lsd is supposed to be superior to the standard gtr diff anyways, because it was in the v-spec.

So, I'd be interested to know how much it is to reco the v-spec unit.

[paulr33]

had a chat with the diff centre place today. the diff is out of the car.

the centre is still in tact. they havent opened it yet.

the diff housing has an oil feed that goes in the right side, runs around, then pops up and relinks to the right side of the diff. so as you said, its an oil feed.

they are going to open the centre up and see whats inside and find outs busted.

he has said i can have a kaaz centre for 1500 then another 150 odd to swap it (if its fits) then the original 350 to put it all back in. so im looking at 2 grand. i said im not prepared to spend that. i was originally quoted 350 to open it up and find out whats wrong inside. he will proceed to open the centre (included in the price) and let me know whats the next step.

he said i can get a 2nd centre from somewhere else providing it fits but he cant guarantee it will be any better or work better than what i have. he also said it could die anytime as well being 2nd hand. if they change to a kaaz centre they will block off the oil feeds, which will most likely mean the pump wont work and ill have a-lsd errors on the dash all time (which would suck).

more to come when i check up on tuesday, after they've opened the centre

[Beer Baron]

standard GTR diff is mechanical clutch plate type diff, NOT a viscous diff. I have NFI what an A/LSD is, but I would say it's mech too, with pressure from the pump altering the preload on the plates.

[paulr33]

thanks bb. the a-lsd is the diff in the vspec gtr.

i think its the similar type but instead of mech locking it uses a pump to pump oil into the housing. it looks at the abs speed sensors to detect wheelspin on each wheel then locks when it see's wheelspin

[Coupe-This]

heh paul, if thats the reason, well the pump highly likely isnt priming enough pressure into the diff housing/centre to lock the axles (sorry i dont understand how these diffs work properly)

but if thats the case, take off the pump, and see if it can flow a constant pressure, it may heat up and fail ...

just an idea ...

yes paul you can change the ratios pretty easily in most diffs, not sure about yours ... depends what ratios are actually availible ... it will decrease top speed and fuel economy though, better low down rpm and torque tho ... will be hard to launch

[Syphon]

Paul, possibly you could also shoot Nismogirl a PM as I am certain she had the A-LSD diff in her 33 rebuilt, she might be able to give you some sort of information and costs etc..... just a suggestion

[paulr33]

i will accept donations or contributions towards my new diff

[Rowdyr32]

Did you try bleeding the oil pressure line to the diff? I heard this is a problem on some gtrs with the altezza. The transfer case doesn't have enough pressure on it to lock it up tight enought.

[paulr33]

interesting point gareth. i had the fluid changed some time ago, 8 months ish.

im not even sure what fluid was put in. ive got the guy disecting the centre and ill find out tuesday. it certainly could be pump and pressure related. how would i go about tetsting/checking

[abcent]

if you wanna know about the kaaz 1.5ways talk to Al, i think he just had his installed not that long ago. As for the Nismo 2 way, I have one, and love it sure you get a bit of diff chatter on slow tight turns...but doesnt bother me. Makes the car very predictable an controlable when traction is lost.

but yeah, is a very expensive way to go, very glad mine had it fitted when I bought it 5 years ago

good luck Paul

[paulr33]

hi all,

just got the report back from the diff place. there is nothing wrong with the diff. the center is fine, no damage, no metal shavings, no signs of fatigue or mechanical problems. the diff like gareth said (and they've realised now) is pressure controlled by an oil pump.

he said the next step i should do is test out the oil pump and oil feed. he said u could even just run an override switch to the oil pump power to make it lock on demand. so anyway ill get the car back tomorrow and the same 350 price. he said they will clean it up and change the oil and do some final testing but he said its likely the pump isnt providing enough pressure, or could have even ceased up. ill probably speak to dr drift and get him to help me debug whats wrong with the pump. an override switch would be ace