AWD trans in FWD application

[Morphius]

Story goes.... I'm going to put a GGSX trans I have behind my second 4D68T engine I picked up for my mirage. I already know about welding the VC, VCE, or center diff mods. I intend to go the route of putting a VCE or weld up a shot VC I already have. What is done about the output shaft running to the T-case. Is it removed and hole plugged? Is it just left in place? Shaft hanging out there in the wind?


Please, I'm only looking for input from those that have run this setup. And run it daily, not for dyno only. I read a number of the threads posted here and other places and no one makes mention about doing it permenatly and what's done about the t-case output shaft.

Thanks.

 

[JackM]

You can use the same seal/plug used for the balance shaft ellimination when plugging off the hole in the trans once you remove the output shaft. You can also leave out the VCU.

Jack

 

[Morphius]

You can use the same seal/plug used for the balance shaft ellimination when plugging off the hole in the trans once you remove the output shaft. You can also leave out the VCU.

Jack

Aren't the side gears in the center diff supported by the output shaft to the tcase? If I pull it, what's to keep the side gears in place (or pinion shaft for that matter)? I haven't pulled it apart to look yet, but looking at all the exploded views in the service manuals it appears the gears run on that shaft. I can see there are some thrust bearings, but I question how well they pilot the diff side gears.

Second, simply removing the VC isn't going to work. At that point, how does the power transfer through? The side gear needs to be coupled to the output gear via the VCE or else you mearly overrun one set of side gears. ( ie open diff with one wheel off the ground)

 

[SBR Joe]

As long as you weld the center diff you will be fine. It wouldnt hurt to put an LSD in there also with the short gearing of an AWD otherwise tire spin will be exceptionally ferocious... As far as the shaft for the t case you can just let it ride, it wont hurt anything.

Joe

 

[JackM]

Aren't the side gears in the center diff supported by the output shaft to the tcase?

No, if you have spider gears in there, which you won't if it is welded, they are held in place by a cross-shaft, not the output shaft.

If I pull it, what's to keep the side gears in place (or pinion shaft for that matter)? I haven't pulled it apart to look yet, but looking at all the exploded views in the service manuals it appears the gears run on that shaft. I can see there are some thrust bearings, but I question how well they pilot the diff side gears.

If you are going to run this car FWD you have to weld the center diff, so you won't have any of those parts anyway.

Second, simply removing the VC isn't going to work. At that point, how does the power transfer through? The side gear needs to be coupled to the output gear via the VCE or else you mearly overrun one set of side gears. ( ie open diff with one wheel off the ground)

Yes it will. You don't need the VCU with a welded center and no output shaft. It is a useless part at that point. When you weld the lower housing pinion gear to the diff, that's all you need as that lower gear is what will transfer the power to the front wheels. Everything else at that point will be for the rear wheels, which you are taking out.

Jack

 

[Morphius]

No, if you have spider gears in there, which you won't if it is welded, they are held in place by a cross-shaft, not the output shaft.

I don't want to weld the center diff. I'd like to be able to use it in stock condition if needed in the future.

If you are going to run this car FWD you have to weld the center diff, so you won't have any of those parts anyway.

I thought one could run in FWD mode by welding the VCU or putting in a VCE?

Yes it will. You don't need the VCU with a welded center and no output shaft. It is a useless part at that point. When you weld the lower housing pinion gear to the diff, that's all you need as that lower gear is what will transfer the power to the front wheels. Everything else at that point will be for the rear wheels, which you are taking out.

I'm away on vacation, so I don't have my manuals in front of me, but I recall, according to the exploded views, there were two gears that ride on the output shaft that runs to the tcase. Is this right? Again, I want to steer clear of welding the center diff.

 

[Morphius]

As long as you weld the center diff you will be fine. It wouldnt hurt to put an LSD in there also with the short gearing of an AWD otherwise tire spin will be exceptionally ferocious... As far as the shaft for the t case you can just let it ride, it wont hurt anything.

Joe

As I outlined to Jack, I don't want to weld the center diff. This trans is from a galant GSX which at 3K rpms, gives me 90mph, vs 70mph for a DSM. Perfect for the 4d68T!!

 

[Rabbi]

this would be nice to get some indepth info on...as the 2G GST trannys are impossible to find, and theres about a 500 dollar price difference in the gst vs gsx trannys.

 

[GRNDSM]

As I outlined to Jack, I don't want to weld the center diff. This trans is from a galant GSX which at 3K rpms, gives me 90mph, vs 70mph for a DSM. Perfect for the 4d68T!!

Does it do that through the diff ratio, 5th gear or both?

I would also suspect that GGSX tranny would be similar to 90 DSM tranny (in terms of crappy synchros), so I am not sure just how well it will shift (unless you upgrade it to the newer components).

Lastly, how much torque are you thinking on putting down? VCE style center diff lockers can only be used on "lower" torque car. Otherwise, you can just snap the center diff splined shaft on which VCE mounts and cause quite some damage to your car...

 

[MidShipCivic]

I'd like some input on this as well I have a 97 fwd TSI with a bad transmission and I want to convert it to AWD later , but I thought about this because the output shaft for the T-case would have no load and spin faster than the front wheels the VC would try to lock it together, but I don't see this hurting anything.

 

[Morphius]

Does it do that through the diff ratio, 5th gear or both?

It does it through the diff ratio.

I would also suspect that GGSX tranny would be similar to 90 DSM tranny (in terms of crappy synchros), so I am not sure just how well it will shift (unless you upgrade it to the newer components).

I'm not sure, as I have yet to open it up, but I'd guess the same. This is going in a mirage I have, which is and will continue to be my comuter car. Finally bought a house and until our powertrain facility relocates to Pontiac, I have a 204 mi. round trip to work every day. I spend 4 hours of my day driving to work. Picked the house location due to the final location I'll be in.

Lastly, how much torque are you thinking on putting down? VCE style center diff lockers can only be used on "lower" torque car. Otherwise, you can just snap the center diff splined shaft on which VCE mounts and cause quite some damage to your car...

The stock motor,if I recall is rated around 150 ft lbs and 95 hp. I've got a crap load of parts for upgrades from turbos, intercoolers, injectors, and injection pumps. Although, this will likely stay stock to keep it reliable. I think I should be OK with a VCE setup.