Building a AWD OFF-ROAD gearbox...., diff lock vs DCCD

AndrewT · Post by **AndrewT** » Fri May 27, 2011 8:54 am

You could have just repaired your L gearbox - it's a very very good condition one (from what I hear), just needs those rear gears replaced with some from a donor box. Should do that really and sell it as a good L box. Get your 1.5 low range gears from some other shitty L box.
I wouldn't have sold all my stuff before actually deciding on what path to take with the project but hey :P

If your final drive ratio is a low number (3.7, 3.9) then the car will feel less powerful to drive, you will need to slip the clutch more offroad but on very long trips you might get better overall economy as less engine revs per wheel revs. Having big tyres amplifies all these effects too.

If your final drive ratio is a higher number like 4.1 or even 4.444 then you will get better accelleration, the car will feel more poky, but the revs will be higher on the highway - Having big tyres lessens all these effects, and therefore should balance it out a bit and make the car feel more normal.

discopotato03 · Post by **discopotato03** » Fri May 27, 2011 9:23 am

I think AT is right , AWD is nice everywhere but if your bent is off road you will save megga bux just using a part time L DR 4WD gearbox . They're like rings , everybody has one and they work . The carby DR boxes have closer ratios and I think all came with the lower LR gears .
Also if you find and convert an AWD L box good luck finding spares if you break it . With a conventional box , out over the shoulder and in with a good 2nd handee .

I wouldn't even bother with the DCCD thing because its more expensive to set up and doesn't offer much off road .
Remember locked center diff vs PT box in 4WD , whats the difference - nothing except a MUCH lighter wallet .

I'm guessing once you raise a L Series its a bit diabolical on the road and not the sort of thing thats going to like being thrown about so AWD on the street may not do much anyway .

Your money your call .

Gannon · Post by **Gannon** » Fri May 27, 2011 9:55 am

To gain the best highway economy, aim for revs what the car originally did at 100km/h, lower revs doesnt always mean better economy.
FHI chose the final ratio and 5th gear to maximise Specific Fuel Consumption. This is the RPM where the engine makes enough power to maintain a specific speed, (100km/h) but at the lowest possible fuel consumption.

This graph gives you an idea of SFC, but isn't typical of Subaru

guyph_01 · Post by **guyph_01** » Fri May 27, 2011 10:00 am

Ahhhh, you guys all have good points and its making my life really hard to decide. thx for all of your input. Made my life harder to decide. I sold all my stuff as i badly needed the money plus i'd already made up my mind about the AWD:)

But I made my decision:) Some 'Andrew' are not going to like it, some 'H-Top' are:)

I've had the 3.7 D/R part time 4wd and i'd love to change. From legacytt post showthread.php?t=18284&highlight=DCCD It has been done and tested. And to all those offroad lifted Liberties with open diffs, 'ScubyRoo,yarney,d_generate'impreza', Bumpty and many more that are doing quite well offroad, i don't see why the DCCD will be worst?

My old ratio was 3.7 with the big 225/75/15.

So i'm going for a 3.9 ratio gen1 D/R AWD liberty box, with a DCCD and with hopefully the L low range:)

I'd prefer 4.11 but that will just get cost higher:(

AndrewT · Post by **AndrewT** » Fri May 27, 2011 10:58 am

haha nah I love it. I'm sure that ratio will be okay. The EJ25 should have the balls to still drive really well on-road and the L series low range should be good offroad.
Will be awesome to see this gearbox configuration come to fruition, there's just no way in hell I'd do it unless I had money to burn

YouTube · Post by **El_Freddo** » Fri May 27, 2011 11:43 am

If you're after 4.11 keep an eye out on the wrx forums - they pop up from time to time

As for the L series gearbox and the adaptor plate issues - Ruby Scoo has a standard PT 4wd L series gearbox behind the EJ without adaptor plate or EA flywheel. She's all EJ in the clutch department. All you do is swap the front half casings with as set from an EJ that is also dual range

Piece of piss and works a treat! But you'll still be stuck with 3.7 or 3.9 diff ratios with out some serious modification...

Anyway, sounds like you're on to a winning combination - at least you know where you want to go with it which is always easier than making it up as you go!

Cheers

Bennie

guyph_01 · Post by **guyph_01** » Fri May 27, 2011 11:50 am

AndrewT wrote: there's just no way in hell I'd do it unless I had money to burn

Don't say things like that:( thats a big mood hope killer!

guyph_01 · Post by **guyph_01** » Fri May 27, 2011 12:02 pm

Also,

Just for general knowledge:D

What would i need to convert the 3.9 D/R lib gearbox to 4.11??

And will it be easy to change the ratio? As in do i need to just replacing the crown from 3.9 to 4.11??

Post by **TOONGA** » Fri May 27, 2011 12:20 pm

Guy as I understand it you need the crown and pinion from the 4.11 as the pinion gear on the 3.9 has a different cut to match the 3.9 crown

TOONGA

Gannon · Post by **Gannon** » Fri May 27, 2011 1:19 pm

Do you have any figures on the holding torque of the DCCD transfer clutches?
They cannot provide a positive lock like a mechanical coupling can. Id expect it to have a similar holding torque as a later 4sp auto with its MPT coupling.

Id hate to see you fry the clutches on a DCCD

guyph_01 · Post by **guyph_01** » Fri May 27, 2011 1:24 pm

Anyone have torque figures??? Would be good to know:)

vincentvega · Post by **vincentvega** » Fri May 27, 2011 1:27 pm

they are way tougher than a MPT coupling.

If you want to compare them with autos they are more like a VTD rear end

Gannon · Post by **Gannon** » Fri May 27, 2011 2:11 pm

vincentvega wrote: If you want to compare them with autos they are more like a VTD rear end

Sorry, typo.

The difference is that DCCD uses an electromagnetic clutch and VTD uses a hydraulic clutch.

guyph_01 · Post by **guyph_01** » Fri May 27, 2011 3:44 pm

Ok.

Now, this question goes to all you gearbox master minds:)

What would it take to change that gearbox ratio to 4.11?

Do i just swap the crown and pinion and everything else will bolt/slide back on including the L low range?

Or is there more to it?

Thx

Gannon · Post by **Gannon** » Fri May 27, 2011 4:06 pm

A lot of earlier gearboxes that were 3.7 and 3.9 wont fit the larger 4.11 or 4.44 crown wheel. I have a feeling you will have to grind down some of the internal ribs to make it fit (i think)

guyph_01 · Post by **guyph_01** » Fri May 27, 2011 4:15 pm

Or get an outback gearbox:(

Well its just its easy enought i'll try to convert it, but if it's not than i'll see how the 3.9 goes:)

Post by **TOONGA** » Fri May 27, 2011 4:55 pm

Guy my brumby has a 3.9 single range AWD liberty box in it and Ive not been able to bog it (yet) I use 215 /65/ 14 tyres and haven't had a problem.

TOONGA

guyph_01 · Post by **guyph_01** » Fri May 27, 2011 5:01 pm

Yeah, I would be happy with 3.9 but everyone says 4.11 is better. So i though while the box is apart might as well put 4.11 in it if its not to hard:) I already have a 4.11 rear diff ready to go in.

RSR 555 · Post by **RSR 555** » Fri May 27, 2011 5:46 pm

Does anyone else have a sore head??

guyph_01 · Post by **guyph_01** » Fri May 27, 2011 5:59 pm

Arwwww:(