transmition modification

[scottiescottiescottie]

Hey guys,

clubsub has not been alot of help in the past but here goes...

iv got a TV752VB4AA trans and want to put in a mechanical LSD front diff then attach the DCCD center. It all bolts in mechanically but I want to know if there is anything that I need to do to make this work?

ie rear diff? does the front LSD from an STI change the ratios? I wouldnt have thought so since it uses the same crown wheel. The trans is normally 4.1 so does the front/center diff change modify that at all?

are there any problematic issues here?

thanks.

[jacsmiley]

i wouldnt see a problem but there is still a bit of grey area as to what youre asking about the STI lsd.

dont worry bout the dccd that should be sweet.

youre just swapping the open center of the front diff to an lsd unit right?

using the original crown wheel etc?? if it doesnt change the ratio from 4.1 and youre running a 4.1 rear diff then you should be sweet. make sure the sti unit came out of a g/box that was 4.1 it may be a R160 crown wheel but it could be a 4.444. make sure the lsd have an identical crown wheel

do you have a dccd?

[scottiescottiescottie]

Yea I put the crown wheel on to suit the box its going into. Now to find out what my rear diff ratio is!

[madmike]

As per first reply..

Dccd. Not a problem.

As for the lsd swap. If the ratio of the new lsd matches your rear diff i see no problem..

Sounds like a good project to me.

[kamineko]

the ratio is irrelevant in the front as he mentioned he is just swapping the differential, you will need to have the backlash reset though

I assume your swapping the whole dccd transfer case onto the back of your current gearbox? the torque split should be the only the only difference. ratios won't change

rear diff is also irrelevant, if it is matched to the gearbox.

as an aside, prepare to have an interesting car. mechanical fronts can be a little crazy with your dccd wound up, expect heavy understeer but fantastic exit grip

mechanical ABS is also fun

[scottiescottiescottie]

 kamineko'] prepare to have an interesting car. mechanical fronts can be a little crazy with your dccd wound up, expect heavy understeer but fantastic exit grip...

mechanical ABS is also fun

the DCCD will be auto controlled by this...

http://dccdpro.com/zcart/index.php?main_page=product_info&cPath=1&products_id=2

mechanical ABS???

[quote name='kamineko said:

you will need to have the backlash reset though

hmmm do you mean the shims at the end of the box where the transfer case bolts up? I didnt "reset" it but just tapped it down. Will this be bad? it shifts fine by hand?

[kamineko]

 scottiescottiescottie']

the DCCD will be auto controlled by this...

http://dccdpro.com/zcart/index.php?main_page=product_info&cPath=1&products_id=2

should help a lot with the understeer. have not used one before though, so not entirely sure how they react

mechanical ABS???

lsd's lock up in relation to the difference in axle speeds, so if your brakes try to snatch the front left, the lsd will bind up and the remaining grip on the front right will act apon the front left, forcing it to turn again (if the grip exceeds the braking force in the first place. probably better to say the diff uses its available binding force to bring the axel speeds back to equilibrium)

if you exceed the grip on both front wheels, both will snatch, then the difference between front/rear will cause the centre diff to bind, forcing the rear wheels that still have grip to turn the fronts

huuur explaining diffs. in essence, running high dccd lock with mech front/rear is fantastic for braking until you exceed your overall adhesion and all four wheels lock up at once, quite suddenly in my experience

[quote name='kamineko said:

you will need to have the backlash reset though/quote]

hmmm do you mean the shims at the end of the box where the transfer case bolts up? I didnt "reset" it but just tapped it down. Will this be bad? it shifts fine by hand?

as you have described, the pinion is in the same place in relation to the case. but since you have changed the differential, the position of the crown may have changed in relation to the case and pinion. you can re-position the diff by adjusting the diff bearing races (for lack of a better term i can think of) but its not really a DIY job.

best to read the transmission service manual for an accurate description of the shims and backlash adjustment

[subieboy]

 kamineko said:

in essence, running high dccd lock with mech front/rear is fantastic for braking until you exceed your overall adhesion and all four wheels lock up at once, quite suddenly in my experience

Hehehhe seen funny video's in past of this...

Can't imagine it being fun if at speed tho...

[scottiescottiescottie]

Thanks for all the help all! great info. The box is built now (not to hard actually) and I am looking forward to seeing how she handles once the car is up and running :~)

im in CHCH so might see some of you at the track one day.