Divorced tcase and stock rear diffs/cv axles

[SquigSprinter]

Hey folks 

For those of you who have gone down the path of putting a divorced transfer case and using a rear diff (plus fabrication) to serve as a front diff, how well do the diffs and cv axles hold up to the additional low range gearing? For context this is using the newer VA type 2 r160 diffs found in the Ascents and Outback Wilderness (with the 4.44 final drive) and newer style CV axles that don't have the stub out for the inner CV assembly. This would be getting mated to a Subaru dual range with 1.44 reduction

Mostly curious if something like the Suzuki tcase with the extra low range gearing will be too low for the rest of drivetrain. If you've done this mod before, how well did the rest of the drivetrain hold up?

[el_freddo]

I have not done this and those that did this years ago are most likely long gone from the forum. 

One of the biggest factors is your driving style and mechanical sympathy. 

With a dual range gearbox and the dual range divorced transfer case and the addition of 4.44:1 diffs, you could run larger tyres and crawl really slowly - best of both worlds. 

What vehicle are you putting all of this into? If a vehicle with an AWD, you’ll need to weld the centre diff. Being a 1.44:1 low range it’s either an MY chassis or the sf forester (but I didn’t think you guys got the dual range gearbox from factory in the states). 

[SquigSprinter]

Aye the welded center diff would be required in my case (this is a 23 Crosstrek with the dr 5mt swapped in, it has the viscous coupling center diff and came with 4.44 final drive stock)

If I go with the Samurai tcase I plan to upsized tires to 31s to take advantage of the hi range reduction

I know the older stub style cvs tended to explode from too much torque, this would be using newer style Subaru CV axles. I mostly want to avoid getting all of this low gearing in place and then start popping diffs/CV axles.

[el_freddo]

That sounds awesome. What size lift will you run in the cross trek? 

Should be an interesting and capable vehicle!

[SquigSprinter]

I'd try 6 inches first (Raceworks coilovers can get me to that height without top hat spacers). Between that and 31s I would hope to regain the clearance lost from the front diff getting mounted.

We'll see how the fab goes in the front, my plan is to order a rear subframe and cut/modify it to incorporate in front control arm mounts and build up the front subframe from this

[el_freddo]

Wouldn’t it be easier to get another front subframe and build the diff mounts to that? 

My thinking is you’ll need the steering rack lowered as well - and the rear subframe may not sit where you need it to accommodate the suspension pick up points and steering rack mounts. 

The way this was always done in the MY and L series models from the ‘80’s was to use a second engine crossmember. In saying that we don’t have a rear suspension crossmember or subframe as such in these models. 

I’m keen to see how this pans out!

[Numbchux]

Generally the front crossmember is spaced down, and diff mounts fabbed to it (this way suspension and steering mounts are all kept correct), and then motor mounts fabbed above that, usually incorporated into the subframe spacers. Generally the crossmember needs to be spaced down from the body about 8" to provide adequate clearance to the oil pan.

I think all the cars where I'd seen it done still ran the EA81 or EA82 engine, so not much power to speak of. Which probably helps keep the diff alive. And with actual lockers available now, it'd be a lot easier to abuse.

Edited 14 hours ago by Numbchux

[SquigSprinter]

Using an additional engine cross member was my initial plan (this does match what I have seen in the previous tcase builds) , but I wasn't sure I'd be able to extend the steering input shaft (i.e. the part that goes to the u joint) through the additional cross member

 

To handle the steering adjustment I was thinking of extending the tie rod ends and leaving the steering rack where it is. I'll have to see how extreme the angle becomes with this approach

 

The front control arms have two mounting points that I am planning to drop down off of the fabricated portion of the front subframe. Depending on the trickiness of relocating the front control arm mounting point I may end up cutting/using a portion of a front cross member anyway (the bottom half)

 

Reusing the rear subframe will provide a start to integrating the equivalent of "frame rails" to mount the t case to. Between mounting this front subframe (with rail supporting the tcase) to the original control arm mounting points, the transmission cradle mounting points, and eventually the rear subframe I hope to provide enough support 

 

The 2.0 in the Crosstrek doesn't make a crazy amount of torque but I am concerned with the larger gear ratios still blowing components up.