ModenaTwinTurbo

iTrader: (1)

ok this image shows whats going on with the red evo. which is the car i'm fixing, this car will light up the front tires when you just roll into boost. when going in a figure 8 it doesnt BIND AT ALL. when going in circles to the left, to the right, in reverse with respect; it also does not BIND. however i do suspect something in the transfer case to be either SHEERED OFF or broken, due to erratic drivetrain noises.

now i had this car up in the air by the PASSENGER SIDE. while in neutral when you spun the rear tire FORWARD the front tire would spin BACKWARDS. as if it had a completely OPEN differential in the center. this along with the total and complete roast of the front tires when rolling into boost leads me to believe the viscous coupling unit has failed.




i also took another friends evo this is the yellow one and i put it up in the air by the driver side, this one has a good transfer case. while in neutral when you spin the rear tire FORWARD the front tire would spin FORWARD. given the fact that this car has not ever presented any of the above stated symptoms i am trusting that this is how the VCU is supposed to behave.


does this all make sense?
have any of you had similar problems?
if so what were the causes?
any pics?
any corrections?

to the mods i hope you dont mind me also posting this on a higher volume section.


thanks in advance.
Eddie Rosado

ModenaTwinTurbo

iTrader: (1)

by the way this is an 03, so theres no ACD.


Eddie Rosado

Cirrusly Evolvd

iTrader: (44)

That's the odd thing about AWD vehicles. They will react differently when you have some wheels on the ground. Jack both cars with a body lift and then spin the wheels. A viscous differential requires heat generated by friction to thicken the fluid and grab so when you spin the front tires by hand you won't be creating enough heat/friction to turn the driveshaft. When you turn one of your wheels, the opposite side should turn the opposite direction. This is normal as there is no friction created to lock up the diff and transfer the torque.

ModenaTwinTurbo

iTrader: (1)

no way man that thing shouldnt be acting COMPLETELY open. have you ever tried to turn a VCU in your hand. its pretty hard to do it.


in my description the car that was "partially locked" was the yellow car, that car has not run in over a year. the red car which is the one with the "open" center diff, i had just run it in multiple figure 8's in the parking lot, and in circles going left, and going right. so if anything the one with the warm fluid inside was going to be the red car, of course not enough to do that COMPLETE 50/50 lock up, but nothing like the yellow car that hasnt moved in over a year.


Eddie Rosado

ModenaTwinTurbo

iTrader: (1)

remember the yellow car was up in the air in the same way by its side. and it spun both tires in the SAME dirrection.


Eddie Rosado

Cirrusly Evolvd

iTrader: (44)

You got me man...I'm just speaking from how my Evo8 works, stock and with my rebuilt trans, transfer case and upgraded helical diff.

ModenaTwinTurbo

iTrader: (1)

where is the helical diff? the front diff? or the center diff?


Eddie Rosado

Cirrusly Evolvd

iTrader: (44)

The rear is a helical style and if you have an Evo RS the front is also. I upgraded my front to the Mitsu Ralliart Helical

ModenaTwinTurbo

iTrader: (1)

i c

Eddie Rosado

robi

iTrader: (24)

rear = clutch type front= helical....Ive done this befor when you take the front dif out of the ring gear carrier I'll bet the input splined shaft to the front dif is sheared off....(one of the 3 ways I broke front difs befor putting in the quaife)

ModenaTwinTurbo

iTrader: (1)

ok robi i get what your saying but why isnt the front tire staying still when i move the rear one? if there wasnt any splines it wouldnt move. hmm i guess it could if its just a partial sheer. i c, i'll look into that for sure i might be tearing the tc 2moro.


Eddie Rosado

dsycks

iTrader: (10)

Is it true that the RS has a helical Rear? I thought it was a clutch type as Robi points out.

Cirrusly Evolvd

iTrader: (44)

Whoops....guess that's what I get for typing while intoxicated LOL

ModenaTwinTurbo

iTrader: (1)

LOL TUI



Eddie Rosado

robi

iTrader: (24)

the crack all the way around the hollow input "spud" doesn't rotate freely due to the rough nature of the break...when the car sees enough tourque diferential to spin the shave despite the resistance provided by the rough surfaces then you hear all kinds of fun noises....which go away again when the torque is weak (like when tires are off the ground...