Changing of diff ratio without changing all internals of gearbox

[El_Freddo]

So, this has been continued from the "Ea82 Ft Awd 5mt Info" thread.

What i want to know is: Is it possible to change JUST the Drive gear and Ring gear to change the final ratio?

What i want to do is retain my 1st to 5th and reverse gears and change the diff ratio to 3.9 from 3.7. I'm hoping that the drive gear is pressed or clipped onto the drive shaft (from the gearbox).

My aim is to "investigate" several gearboxes to make up one, AWD box with centre lockable diff running 3.7 internals with 3.9 diffs. The idea of retaining the 3.7 internals and run a larger diff ratio is to have the ability to run a bigger tyre diametre and retain the standard performance and speedo reading (i know you can get a kit to keep speedo true but i want the standard performance too).

The lockable part i want to check out is from the single range Part Time L series box, i'm sure they use the same sort of locking device as the AWD L series boxes do, only difference is that a centre diff is missing. I'm hoping to beable to fix this to the centre diff to have drive to the rear at all times either locked or un-locked.

I could be totally wrong in my thinking, but its something that i really want to check out for myself to see if it works. Some discussion on this has occured on this thread here about building an AWD gearbox using EJ internals.

Phizina has built an EJ box with a lockable centre diff for his brumby (Phizelishus, EJ22 and Tri-Hybred Brumby) but he found an L AWD lockable centre to do it, which is what i'm trying to do but with out finding an L AWD DR box.

Unless someone can tell me i'll have to wait to find out myself (not entirely a bad thing...)

Cheers

[BlackMale]

OK, I am a little confused here so lets have a crack at this…

What i want to do is retain my 1st to 5th and reverse gears and change the diff ratio to 3.9 from 3.7

. To just change the end diff ratio is possible ie go from 3.9 LSD to 3.7 LSD.

AWD box with centre lockable diff running 3.7 internals with 3.9 diffs.

No diff will go bang is my understanding – both box and diff need to be the same ratio.

Or are you wanting to take the 3.7 internals from an AWD and 3.7 or 3.9 internals from a dual range and… nope my brain just exploded in my head attempting to comprehend this post.

Could you reword it? Or is it me? I will attempt to read it again when I have more time (it just seems weird that 1 thread got hits and this 1 has fallen dead).

[Phizinza]

First up the diff ratio:
Simple answer is 'no'
This is because the pinion gear is attached (machined as one) to the pinion shaft. In the FT boxes this is a shaft that runs through the lower gear set's (output gearset) shaft. In the PT boxes this shaft is 1 piece, as in the pinion gear is part of the shaft that holds the gearset, this is because they are normally FWD. So, if you want a different ratio, you need the gears from that box as well.

Second up the PT mod to FT:
I think I'm hearing you correctly wanting to make a PT rear casing run a centre diff?
Well I'll explain how the PT box engages 4WD for you and then how the centre diff locker works in the import L series box.
The 4WD engage system operates using a synchro that is basically the same as all your other gears synchro. What this does is engauges a gear that is attached to your pinion shaft to another gear attached to your propshaft. This is the gear that binds up when in 4WD on road.
The FT centre locking diff engager operates using a dog style cog. This is connected to your pinion shaft (which runs through the gear shaft) and simply slides onto the diff connecting your rear output from the diff to the front pinion shaft. Thus not letting there be a difference between rear and front. In the middle of that dog is the spline that connects the output gearset to the centre differential.

You cannot put a centre diff in a PT box to my knowledge. And you certainly can't put a centre diff on a 1 piece output/pinion shaft.

You can fit the L series centre diff box rear casing and gearsets into a early Liberty box using the lockers rear casing. You can also fit early Liberty gearset and VLSD centre and rear casing on/in a L series FT and PT box. I'm pretty sure you can't fit the VLSD centre in the FT L rear casing.

So, basically.
You pick your centre diff type you want and the box you want it out of, then you have to take the diff ratio, gearset, and rear casing from that box too.
You could even put the PT stuff in a Liberty D/R box if you wished too.
But to have a centre diff, you need the rear casing to go with it. And to have a centre diff lock, you need the centre diff lock casing as well.. Unless you were to spend LOTS of money and maybe make a air locker or auto locker centre diff to fit a EJ box.

Sorry mate, but you'll need that box. There is a place in QLD that sells import ones with low KM for $550. http://www.japparts.com.au/products/gearboxes.html. They quoted me $200 shipping to SA. But I went with the one Rising Sun had.

[Phizinza]

Just remembed... The XT6 AWD came with a single range FT4WD box with centre locking diff and a 3.9 ratio front diff..

But if you thought the FT4WD 3.7 boxes were hard to come by.

[BlackMale]

Yes what he said

That's really what i was going to say ;-p

So at the risk of hijacking this thread what is my L series d/r 3.9 FT AWD out of?

[El_Freddo]

Just remembed... The XT6 AWD came with a single range FT4WD box with centre locking diff and a 3.9 ratio front diff..

But if you thought the FT4WD 3.7 boxes were hard to come by.

I've actually seen the remains of a car that had one of these in it, smelt fresh of a strip job.

Anyways, back to the main topic.


BlackMale:

1st thing i want to do/know is: Can i pull the 3.7 diff out of my gearbox and drop a 3.9 diff in, retaining the 3.7 ratio drive gears (1st -> 5th and reverse). I realise i'll have to change both front and rear diffs to change the ratio in the car. Phizinza has said above that this is not possible without taking the whole 3.9 gearbox internals with the 3.9 diff as the shaft with the pinion gear on it is not a slip on and off application, its cast/ground as a one piece.

2nd thing i wanted to know is: The L series single range-part time 4wd gearboxes have the same extension housing on them as the AWD counterpart, minus the centre diff inside.
I'm wondering if this is able to be used with a centre diff from an EJ AWD gearbox.
Aim here is to modify the centre diff to beable to be locked using this housing that has the locking arm thats operated by vacuum (from the single range L series box - they're the model with the 4wd button on top of the gear selector).
If anyone has an internal photo of the centre diff and locking mechanism, would you please post this as it would be great to see inside one of these, currently i'm using my imagination - could be why i'm way off in my thinking.


Phizinza: The website you gave looks very promising, but i'm wondering if they have mixed up AWD with PT 4WD. I'm going to contact them anyway.

The PT casing i'm talking about is from the L series single range gearbox. I am positive that these rear casings are the same as the AWD L box. This would make sense in production that you have multiple items using the same parts. This is the casing i've been looking at using.

My next move would be to pull one of these gearboxes apart at pick-a-part or somewhere like that to find out what it looks like... Then maybe buy it to see if it will all fit together ($$$ factor kicks in here )


Last thing, and this could be a very nasty suggestion and i think i know what the answer will be:
Can you change the 3.7 crown and centre (if need be) with a 3.9 crown and centre but still run the 3.7 pinion (if its a flat out no i had to ask anyway)?

How many teeth does the:
3.7 pinion have?
3.9 pinion have?

Thanks everyone for your info. More food for thought. Keep the ideas/knowledge flowing, this will keep me occupied for a while

And thanks for reading, i know its long, i've tried my best in words, next time i'll draw it, scan and post as a pic

Cheers

[Phizinza]

2nd thing i wanted to know is: The L series single range-part time 4wd gearboxes have the same extension housing on them as the AWD counterpart, minus the centre diff inside.
I'm wondering if this is able to be used with a centre diff from an EJ AWD gearbox.

I think you'll find this not to be the case. The S/R "extension housing" is the same as the D/R with exception to the 4WD engage selector which is on the side instead of running through the back to front.

Phizinza: The website you gave looks very promising, but i'm wondering if they have mixed up AWD with PT 4WD. I'm going to contact them anyway.

I'm very sure that their "5mt diff lock" L series box is the FT4WD box you will want.

Last thing, and this could be a very nasty suggestion and i think i know what the answer will be:
Can you change the 3.7 crown and centre (if need be) with a 3.9 crown and centre but still run the 3.7 pinion (if its a flat out no i had to ask anyway)?

How many teeth does the:
3.7 pinion have?
3.9 pinion have?

I forgot to look at the difference of the 10 tooth pinion on my Liberty 3.9 box and 3.7 L series box. I'm kickin myself for that now. But I still have a D/R I need to pull apart with a 3.7 diff and the Liberty guts are just sitting there, so when I get around to it I can compare. But the general answer from everyone is "NO."

3.7 uses 37tooth crown and 10tooth pinion,
3.9 uses 39tooth crown and 10tooth pinion,
4.11 uses 39tooth crown and 9tooth pinion.

The WRX's that use a 3.545 rear diff use a 3.7 in the front I believe and use a 1.1 to 1 reduction type thing in the rear after the centre diff.. Kinda interesting really.

Pictures of the box I got from Rising Sun, it's was a standard L series box using the gearset, pinion shaft, crownwheel (still standard 23 tooth spline diff,) and rear casing from a import FT4WD.
http://offroadingsubarus.com/images/ea8 ... bench2.jpg
http://offroadingsubarus.com/images/ea8 ... r_diff.jpg
http://offroadingsubarus.com/images/ea8 ... ngager.jpg
http://offroadingsubarus.com/images/ea8 ... ntview.jpg
http://offroadingsubarus.com/images/ea8 ... ftside.jpg

As far as I can see, the centre VLSD from a EJ box will only fit in the EJ's box casing. BUT, if you just want L series AWD, it's simple as getting a custom gearbox crossmember, Liberty box, Lseries PT box and using the internals from the Liberty box in the Lseries box but keeping the input gears and low range gears. But that's not what you want right? You want a locking centre diff? Well to put a locking device on a EJ centre diff is going to be like fitting a 4.44 crown wheel and pinion to a FT4WD box.. LOTS of fab work. Which needs a machine shop to do.

[El_Freddo]

Thanks for the pics Phizinza. I had a little trouble working out what i was looking at in some of them but i'll spend more time on that later.

I'm very sure that their "5mt diff lock" L series box is the FT4WD box you will want.

I've had a return email from andrew, i've sent one back and now it looks like it will be an email "ping-pong" game, but hopefully something will come of it.

I forgot to look at the difference of the 10 tooth pinion on my Liberty 3.9 box and 3.7 L series box. I'm kickin myself for that now. But I still have a D/R I need to pull apart with a 3.7 diff and the Liberty guts are just sitting there, so when I get around to it I can compare. But the general answer from everyone is "NO."

3.7 uses 37tooth crown and 10tooth pinion,
3.9 uses 39tooth crown and 10tooth pinion,

anyone know the difference in these pinions (physically or how they interact with the ring gear)?

if you just want L series AWD, it's simple as getting a custom gearbox crossmember, Liberty box, Lseries PT box and using the internals from the Liberty box in the Lseries box but keeping the input gears and low range gears.
But that's not what you want right? You want a locking centre diff? Well to put a locking device on a EJ centre diff is going to be like fitting a 4.44 crown wheel and pinion to a FT4WD box.. LOTS of fab work. Which needs a machine shop to do.

You nailed that on the head. I'm after the AWD bit but want the locking centre diff to go with it. I'm guessing that LOTS of fab work in a machine shop will mean lots of money...

Thanks for the input, your last post was very helpful. I'm now keen to know what the difference is in the pinion gears of the 3.7 and 3.9 diffs...

Cheers

[Phizinza]

I'm now keen to know what the difference is in the pinion gears of the 3.7 and 3.9 diffs...

Me too.. But not keen enough to get out there and break open the 3.7 PT D/R box I have sitting there that was out of a mates car...

[El_Freddo]

I'm sure someone out there will have the two diffs to compare...

[El_Freddo]

Phizinza, thanks for the gearbox pics...

I've just spent the last 15 minutes looking at all the pics trying to get my head around it all, its starting to hurt now and i'm at the point where i really need to look at the real thing, put it together, move some parts, pull it apart and check it out that way... I've done all the "theoretical" that i can do without looking at the real thing.

Still keen to know the difference in the 10 toothed pinions of the 3.7 and 3.9 diffs. I've started another thread in subaru chat intitled "3.7 diff and 3.9 diff pinion gear differences (both 10 teeth)".

Trying to hunt one of these AWD L boxes down, jap parts has at this stage gone cold after one email... Geoff's got another idea for now, we'll see how that goes.

Cheers

[El_Freddo]

Phizinza: Is it possible to take the lockable centre diff and slot it onto the back of an EJ gearbox?

Are there any different parts in the L's AWD box that won't allow the lockable centre to work on the back of an EJ box - meaning using all EJ internals with the EA lockable extension housing?

I've had some other thoughts, but not sure where they're going just yet. They involve one of these L AWD boxes and a forester dual range box - as these have a good sized wheel diametre over the L series which is what i'm after (plus a lockable centre).

Things i need to know - will the forester diff fit into an EA casing and will the lockable diff mount directly onto and EJ final shaft allowing it to operate correctly?

Any info would be greatly appreciated.

Cheers