anyone had issues with active LSD on hub dyno when pulling out the transfer case shaft?

[GD51LA]

long story short i blew my standard gear box, but the way it happened seems odd...

 

first i went for a hub dyno tune in rear wheel drive, so i pull the transfer case shaft out,

when on the dyno the lsd was fighting each other so much so that the car wouldn’t rev smoothly and reading allot less power than it should. i know this because out of the three pulls on the dyno one of them was smooth,

first pull the diff was fighting itself and read 300kw,

second pull the diff worked and read 500kw, third pull 300kw again...

he checked the reading of each hub and the two sides were reading very different power figures??

 

the car always drove fine?? the tuner said the diff is no good, “this normaly happens when a diff is wearing out” one wheel gets more power than the other

 

here are the reasons i don’t believe this too be true.... the diff had new gears and checked recently, the diff guy even said “i tightened it up abit” in other words it should be more “limo” than standard

 

now, is there a way the active lsd works on the dyno?

 

i rang one diff place and he said by you taking out the front shaft your confusing the active lsd pump "it sounds like an active lsd pressure problem, probably caused buy you removing the shaft"

 

the guy that did the diff is pretty good at what he does, i don't think he got it wrong

 

now i'm driving home in rear wheel drive (shaft still out) on low boost and i can feel the reving out pretty slow (it never did this in four wheel drive) so now the diff is fighting itself on the street too (for the first time)

 

i give it a hit in second and the gear box breaks ( mind you the box held 1000hp before that) yet it breaks in rear wheel drive at 65% of that power

 

what you think?

[R.3.2.G.T.R]

TPS has a big input to A-LSD, worth checking TPS signal

[dr phil]

Did you pull the air bleed wire and push the brake pedal 5 times to put the 4wd computer into RWD mode as well as removing the front shaft?

Sounds to me like there was 200kw of power turning into heat somewhere, one rear wheel rotating faster than the other is going to heat up your diff real quick isn’t it?

For me the question is what the 4wd computer was trying to do, when it detects wheel spin it shoves torque to the front (ie locks up centre diff more), hence the question about setting the computer into rwd mode.

I wonder what it does to the A-LSD lock up in this situation, would it go up, or down. As mentioned by R.3.2.G.T.R in normal operation more TPS = more alsd lock up (and more cornering force = more alsd lock up too), but I wonder if it was freaking out and going into a failsafe mode (the centre diff failsafe is 20% lock from memory).

Perhaps you overheated something. Maybe a hub dyno aint so good with A-LSD.

[KiwiRS4T]

Surely there are 4 wheel dynos in Sydney?

[GD51LA]

Did you pull the air bleed wire and push the brake pedal 5 times to put the 4wd computer into RWD mode as well as removing the front shaft?

Sounds to me like there was 200kw of power turning into heat somewhere, one rear wheel rotating faster than the other is going to heat up your diff real quick isn’t it?

For me the question is what the 4wd computer was trying to do, when it detects wheel spin it shoves torque to the front (ie locks up centre diff more), hence the question about setting the computer into rwd mode.

I wonder what it does to the A-LSD lock up in this situation, would it go up, or down. As mentioned by R.3.2.G.T.R in normal operation more TPS = more alsd lock up (and more cornering force = more alsd lock up too), but I wonder if it was freaking out and going into a failsafe mode (the centre diff failsafe is 20% lock from memory).

Perhaps you overheated something. Maybe a hub dyno aint so good with A-LSD.

no i didn’t do that

there was no light on the dash

you think that would have caused it

like i said, the car always drove straight under power

so putting it in RWD mode is a must?

(btw i did see the front torque gauge go too max at times)

[GTSBoy]

7 hours ago, GD51LA said:

(btw i did see the front torque gauge go too max at times)

That is not good.  Transfer case doing horrible things.

[Scott Black]

what broke in the box? 

[dr phil]

I’d say most people on this forum with 500kw have replaced the A-LSD with a normal LSD like nismo etc, and possibly broken gearboxes too.

The thing about the A-LSD is that it locks when commanded to by the attesa ecu, not from torque from the engine like a regular lsd. A-LSD operation also relies on hydraulic actuator lines not leaking, or needing to be bled.

Dunno if you ‘caused it’, but the A-LSD not being locked on hub dyno sounds bad IMHO.