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human compass Fri Sep 22, 2017 11:05 am

I'm going to be going down the syncro conversion hole using a subi gears 5 spd with a pelequin. what are the groups thoughts on a subi front diff with pelequin vs a syncro front diff with pelequin?

any advantage to the suby front? I have easy access to a syncro non locking front diff and the suby front diff will be a bit of a pain to fit, but I'm willing to consider it if there is a significant benefit.

This rig will not be a hard core 4wd but rather an overlander designed for snow and overall drivability in mild/moderately rough conditions. setting it up for a south america tour.

thanks in advance

(PS please lets not get into lockers and low gear debate, I know the trade off im making)

raoul mitgong Fri Sep 22, 2017 11:26 am

I think that the only subi tranny option is currently 2wd. Could be wrong.
-d

snwbrdr435 Fri Sep 22, 2017 12:03 pm

raoul mitgong wrote: I think that the only subi tranny option is currently 2wd. Could be wrong.
-d

Wrong, subaru gears has an AWD setup now. Need to fabricate your own mounts though.

alaskadan Fri Sep 22, 2017 1:19 pm

Thats awesome! The last time i read up on this they didnt have the front trans plate that now moves the out put shaft downward so it clears everything. The real question is does it work on a suby trans with high and low range?

raoul mitgong Fri Sep 22, 2017 2:35 pm

snwbrdr435 wrote: raoul mitgong wrote: I think that the only subi tranny option is currently 2wd. Could be wrong.
-d

Wrong, subaru gears has an AWD setup now. Need to fabricate your own mounts though.

Never been happier to be wrong.

-d

Pcforno Fri Sep 22, 2017 2:36 pm

I would figure out which engine you're planning on using, along with what size tires, then look at the subarugears ratios and RPMs, then decide which R an P ratio you need. Why limit yourself to 4.86 if that's not the gearing that's ideal for you? In addition, don't most subaru rear diffs employ a LSD? You'd be killing two birds with one stone that way...

gears Fri Sep 22, 2017 2:50 pm

Why would you put a TBD in the front diff? Assuming a VC is used, a TBD will do nothing in the front, only in the rear.

Pcforno Fri Sep 22, 2017 3:47 pm

Yes gears - I'm confused by the post as well - subaru typically uses a center diff with a VC to allow continual front/rear power that locks via VC with large slip. There were lots of other subaru transmissions that handled front/rear slip in ways other than a VC, such as a center Torsen and hydraulic clutch packs, but these usually came on VDC packages that required computer control.

Subaru utilizes a clutch pack on the rear diff (now the front diff where the OP wants to use) so there's no need for a peloquin. Some rear diffs didn't have a clutch pack and you could order aftermarket ones, but it would be simpler to source an OEM subaru with a clutch pack then to install an aftermarket one.

So I'm confused buy the question as well.
Perhaps the OP could clarify for us?

11BC2 Fri Sep 22, 2017 5:36 pm

Pcforno wrote: ... In addition, don't most subaru rear diffs employ a LSD? .

No, they don't. Most R160 rear diffs are an open differential design, but cusco makes a great LSD replacement unit:
http://www.cusco.co.jp/en/catalog/pdf_catalogue_lsd.html

The larger R180 diffs, found in STi variants, have an lsd from the factory.

Pcforno Fri Sep 22, 2017 5:57 pm

Just did some reading on this - all the higher end models had LSD, including Impreza, forester, legacy, and legacy outbacks, not just wrx stis...

D Clymer Fri Sep 22, 2017 9:46 pm

I would go with the stock Syncro front differential with a solid shaft in place of the viscous coupling. There are three advantages to using the stock VW front diff.

1. You can use 4.86:1 gears. With a Subaru front, the lowest you can go is 4.44:1. Considering a Subaru trans has a taller first gear than the VW trans, that's just not low enough.

2. The VW diff has a speedometer drive gear. With the Subaru you'd have to go with a GPS speedometer, or an electronic speedometer driven off of the Subaru transmission VSS.

3. The VW diff works perfectly with the stock front drive axles. No worries about custom axles and whether or not they are truly the right length.

There's only one advantage to using the Subaru rear diff up front and that's price. If you have a Syncro roller with no drivetrain, it's tempting to get a $200 Subaru R160 off of eBay rather than pay $700 to $1000 for one of the rare VW Syncro front diffs. But if you already have a working Syncro, I'd say it's a no brainer to use the original front diff.

Dave

11BC2 Sat Sep 23, 2017 6:35 am

Pcforno wrote: Just did some reading on this - all the higher end models had LSD, including Impreza, forester, legacy, and legacy outbacks, not just wrx stis...

Reading tells you one thing, working on these cars daily, tells me something else.

Plain Jane impreza, forester, legacy models are open diff.
Most outback sport impreza, outback legacy, wrx, forester xt, and legacy gt models are open diff.
If car came with the "winter package", which was found on mostly wrx wagons, it left Japan with an led.
Most legacy based models use a Subaru, and not an FHI R160, rear diff.

Easiest way to verify a diff is to remove the fill and drain plugs, shine a light in, and look at the carrier.
Either way, non Sti factory lsd units are "meh" at best.

Pcforno Sat Sep 23, 2017 7:01 am

Good to know for the OP then! If going the subaru route get a STi rear diff? Or are the aftermarket kits even better?

gears Sat Sep 23, 2017 7:54 am

I think it's important to note that in VW Speak, a "Rear Diff" is what's in the transaxle.

In the original Subaru layout, a "Rear Diff" is what's in the separate differential unit, NOT what's in the transaxle.

So, some readers may be confused unless we take pains to "Differentiate" ;^)

human compass Sat Sep 23, 2017 8:32 pm

awesome discussion! thank you all!

so I already have a NA 2.5 suby installed. I'll be putting in a 5 spd suby tranny with a TBD.

what I'm hearing is that if I put in a suby diff, I need to make sure it has a LSD installed, its cheaper, I'll need custom drive shafts, I wont be able to gear the tranny as low.

Any advantage to using the suby diff? I cant see one (aside from cost).

thanks!

human compass Sat Sep 23, 2017 8:34 pm

also, anyone know or have thoughts on how drivability would be with a 5 speed suby with a TBD linked to a syncro front diff with a TBD (non locking)?

11BC2 Sun Sep 24, 2017 5:25 pm

gears wrote: I think it's important to note that in VW Speak, a "Rear Diff" is what's in the transaxle.

In the original Subaru layout, a "Rear Diff" is what's in the separate differential unit, NOT what's in the transaxle.

So, some readers may be confused unless we take pains to "Differentiate" ;^)

Excellent points! In the future, I'll try better in translating Subaru-ese into VWese.

Some other information:
R180 diffs are stronger than the smaller r160 units.
R180 units usually only come in 2 ratios: 3.54 and 3.90. This is based on USDM production.
R160 can be had in 4.11, 4.44, 3.54, 3.90, again, based on USDM production.
Make sure the diff in the trans, or rear diff in vwese, matches the front, or rear diff in Subaru-ese.

human compass Sun Sep 24, 2017 6:22 pm

alaskadan wrote: Thats awesome! The last time i read up on this they didnt have the front trans plate that now moves the out put shaft downward so it clears everything. The real question is does it work on a suby trans with high and low range?

from my understanding, no. attempts to convert these transmissions have resulted in the case being too thing

D Clymer Sun Sep 24, 2017 8:15 pm

human compass wrote: awesome discussion! thank you all!

so I already have a NA 2.5 suby installed. I'll be putting in a 5 spd suby tranny with a TBD.

what I'm hearing is that if I put in a suby diff, I need to make sure it has a LSD installed, its cheaper, I'll need custom drive shafts, I wont be able to gear the tranny as low.

Any advantage to using the suby diff? I cant see one (aside from cost).

thanks!

You don't need to have an LSD in the transplanted (Subaru rear) differential mounted up front in a Syncro. That would just enhance the traction even more. With a TBD between the rear wheels, and the Subaru center differential, you are going to have excellent abilities already.

Yes, it would be cheaper to acquire a Subaru R160 than a stock Syncro front diff, but then you have to factor in the time that would be needed to mock-up the Subaru diff up front, make custom mounts, and order custom axles.

The lowest final drive you can use if you go with the Subaru diff up front is 4.44:1. If you use the stock Vanagon Syncro front diff, you can use 4.86:1. A Subaru 5 speed has a taller 1st gear than a stock Vanagon transmission - 3.54:1 compared to 3.78:1 for the VW trans. For that reason, I don't think a final drive taller than 4.86:1 makes sense.

There is no advantage to using the Subaru diff up front, other than saving a little bit of money.

Dave

human compass Sun Sep 24, 2017 8:17 pm

thanks Dave,

Do the suby transmissions all have a center diff? sorry if this is a dumb question



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