With the driving I've been doing lately, I've been considering switching to a full-time 4wd with locking center diff. I've been doing a LOT (sometimes 50 miles/day, 5 days a week) of gravel and dirt roads, too loose for 2wd, too solid for 4wd. I've been searching the forums for information about these transmissions, and the posts I've found mostly seem to be from people who have never seen one, as most of the information is directly contradictory... so I'm hoping to get some solid answers.

What I want: 5spd full-time 4wd with locking center diff, 1.59:1 low range, 3.9:1 final, widest 1st-5th ratio possible. I'm in the US.

Some posts say only the RX had full-time with locking center diff, some say also the XT6, while others say any ea82 turbo might have one. How to identify them is utterly unclear, either from looking at the transmission or at the interior of the vehicle, with no one apparently ever having actually seen one or otherwise giving a useful description. Some posts say they only came with 3.7 final, others say half of them are 3.9. Most say they have a poor (1.19, 1.2, etc) low range, but some say the 1.59 is a direct swap, some day it's not, some say you need au-only gears, and one even says 4spd parts fit, while I'm rather sure they do not. Some posts say that if you get a 3.7 you can swap the 3.9 pinion from an EJ box in, others say you can't, while some say you need XT(6?) parts. Some say it's a mechanical shifter, others say it's electric. el_freddo has a post saying nothing swaps without welding, but his posts are specific to a dual-range EJ tranny that's not available in the US, while I'd be using EA82 parts. Some posts say I'd need three transmissions, an RX, an XT6, and a non-turbo dual range.

My current 5spd dual-range is in need of a rebuild (multiple bad bearings, input shaft wobbles an eighth inch, something clunks like a rod knock when in neutral, 5th->R lockout sometimes requires going all the way to the left then back to get to 4th, selector sometimes jams, synchros aren't the greatest, leaks from every single seal top and bottom and back and front...), so I wouldn't feel bad using it as a parts donor for the low range gears.

I've tried doing a couple searches, and couldn't find anything available that looked like a full-time box. But, I don't know. car-part.com lists the full-time separately and says there's two available, but I think it's just lumping all ea82 transmissions together.

So... What parts do I actually need? How do I identify them, either looking at the transmission or at the car it's in? Are they even available at all?

Edited Thursday at 04:27 AM4 days by bushytails

I'm not here to answer your questions, because I don't have the answers. I know you're in for quite a bit of searching and just as much work, but I can offer some help potentially finding parts.

I know for certain my parts guy has a fulltime 4WD Turbo wagon. Problem is that I'm 99% sure it's a 4 speed auto. But the next time I'm over there (probably early June) I can take a look at all the cars he has and see what's available. He's trying to get rid of the parts and would like to know the parts are actually being used.

Good luck though, if you can source everything it'd be a trick piece of kit!

:]

Definitely don't want an auto. lol. 5spd dual range for sure...

I'm at the point where the more forum posts I read, the less I know, due to conflicting information...

What you could do is look for options package pamphlets on eBay or the like. They may provide some insight as to what was offered from the factory. Could also get some RX and XT informational pamphlets. Just an idea.

Rob Allen may offer some insight.

Wizard of the RX ;)

G’day @bushytails

The L series AWD locking centre diff gearbox came in the RXII coupe, some XT4s and JDM GT wagons. I’m unsure about the XT6 - we didn’t get them here, infact all of these models except the XT4 were personal imports.

How to tell them visually apart from the single range PT4wd gearbox with the vacuum actuator to engage the rear drive:

• this PT4wd single range gearbox’s lever to engage the rear drive is arm above the pivot point.

• The AWD locking centre diff gearbox is the opposite - the arm is below the pivot point for the locking centre diff engagement. I believe the dual range version will have the rods passing through the rear housing like the DR PT4wd gearbox.

The AWD gearbox comes in single and dual range. Pick the one you want as it’s not easy for you to swap it to dual range without another dual range AWD gearbox (EA or EJ).

The 3.9 ratio is out there from what I’ve heard, it’s hard to find. Mine was a 3.7 ratio.

All of these dual range AWD boxes are 1.19:1 low range. The 1.59:1 transfers in without any issues, it’s a direct swap - need a donor NA dual range PT4wd gearbox.

The EJ AWD gearbox pinion shafts are too short. I heard of a bloke that modified two of them to make one pinion shaft for the L AWD locking centre diff gearbox to get 4.44:1 diff ratio - to do this with the good L series low range requires the crown wheel to be shaved to clear the low range selector ring and gearset. I have not seen pics or videos of this done (the double EJ pinion shaft to make one L series AWD pinion shaft).

From my understanding, L series PT4wd gearbox internals do not swap over to the AWD version, other than the low range. Everything will physically fit but it’ll become a part time box that requires the part time rear housing as well.

My gearbox is made of EJ parts (drive gears and front cases) and the L series AWD bits for the locking centre diff and 1.59:1 low range.

Ultimately if you’re on dirt that’s somewhat loose, you want to lock your centre diff, especially if EJ’d as it’s very easy to be spinning the front wheels faster than the rear, over working the centre diff that will lead to its destruction. You could be better off sticking with the PT4wd dual range box, the AWD is only worth it on solid surfaces.

^ PT4wd in the foreground, AWD in the background, you can see the locking lever on the side here with the pivot point above the arm.

I don’t have any better pics than the above sorry.

I believe the dual range AWD gearbox is fitted with the same rod looking setup in the background of the gearbox as the PT4wd gearbox. My dual range AWD gearbox is built from a single range box originally, so my rear housing lacks the rods that I believe pass through the rear housing for the low range dedents/position retainer setup.

Make sure you get the vacuum actuator and it works, plus the matching vacuum switch solenoids too, or have access to them. The single range PT4wd gearbox units work fine with the AWD box ;)

I hope this helps.

Edited Friday at 10:52 AM3 days by el_freddo
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I found a pic of a ft dr... it has both a vacuum pod cable and a manual lever.

19 hours ago, bushytails said:

I found a pic of a ft dr... it has both a vacuum pod cable and a manual lever.

That’s the one!

The harder part might be finding more than just a pic of one... and then figuring out how to get 3.9...

Finding one is the challenge - and one without a shagged centre diff.

Finding a 3.9 is the unicorn. Hence why my box was put together with a modified pinion shaft for 4.111:1 diff ratio.

From memory a 27 tooth speedo drive pulls the speedo back in perfectly with 27 inch diameter tyres. Again, from memory this came from an early Liberty gearbox - a gen 1 series 1.

Need to find a suitable locking AWD gearbox first…

A couple forum posts I read said the XT6 came with a single-range locking center diff box with 3.9, and if you can find one of those too, you can make a dual-range 3.9 box, and have a spare center diff. I wonder if you even need an RX box or if you can mix-and-match a single-range full-time with a part-time dual-range front half...

You need to study the pinion shaft setup as this is the key to a conversion like that.

If the PT4wd gearbox has a pinion shaft that floats on the pinion shaft and is independent of it, then they’re interchangeable.

I haven’t fully investigated this but I believe the PT4wd’s pinion shaft is press fitted with the lower gearset. This is why you can use an EJ gearbox to make a dual range AWD locking centre diff gearbox that mates directly to the EJ engine (like I did).

The nasty way to make a single range AWD LCD gearbox dual range is to find an RX turbo PT4wd gearbox with the same gear ratios, pinch the upper gearsets with the dual range setup and fit it with the lower gearset from the AWD LCD gearbox.

^ insert potential gear whining followed by potential early retirement of one of those gearsets. But you’d have a dual range LCD AWD gearbox..!

I've played with these, swapped gearing, diffs, etc. many many times over the decades (I've posted a lot of it here, search for my posts. Although most of the photos are probably gone). I have a little information in the Retrofitting FAQ.

Here's a "quick" overview.

RX is the ONLY EA-series transmission with dual range and FT4WD. It is also the only one in the US Market. I have heard of an EJ series dual range and FT4WD (with locking, not AWD) overseas, but I'm really not sure. Also would create it's own headaches with an EA engine (I assume that is what you're running just from context)

RX has 3.7 axle ratios, 1.19 low range and .871 5th gear

Non-RX EA82t FT4WD ('87.5+) cars are single range, 3.7 and .871

XT6 has 3.9 axles, no low range and .780 5th.

PT4WD D/R 5 speeds are 3.9 axle gears, 1.59 low and .780 5th (I believe '85-'87 turbo PT4WD cars are the same, but I'm not positive).

14 hours ago, bushytails said:

A couple forum posts I read said the XT6 came with a single-range locking center diff box with 3.9, and if you can find one of those too, you can make a dual-range 3.9 box, and have a spare center diff. I wonder if you even need an RX box or if you can mix-and-match a single-range full-time with a part-time dual-range front half...

Might be possible, but the lower transmission gearshaft is different between part-time and full-time 4WD (FT is 2 piece with a pinion gear running inside of the transmission output shaft, PT has the pinion gear one and the same with the output shaft.

The the low range gearset is part of the input shaft. You can swap gear ratios, but you have to start with a dual range input shaft and case.

So without actually having an RX transmission to start with, you'd be using the input shaft from a PT4WD DR and the output shaft from the XT6. Since the drive gears for 1st, 2nd and reverse are part of the input shaft, you'd have to use the PT4WD driven gears on the FT4WD output shaft. I wouldn't bet that that would be interchangeable, but maybe.

The center diff housing from the XT6 will not have provision for the low range linkage. Not a huge hurtle, but something that has to be addressed nonetheless.

IMO, if the gravel is loose enough that you're spinning a front tire in FWD, than it's loose enough to run 4WD. I had an '86 wagon that was stock except the EJ22 and rear discs, I used 4WD when the ground was damp otherwise it would just spin away everything. Also, keep in mind, when the center diff is unlocked on a FT4WD, you have zero traction devices. If you hit the throttle hard in a turn, you will still spin up the front tire just like you would in FWD. I was so disappointed with the RX box in my Loyale. Even that tired non-turbo EJ22 could smoke the inside front tire coming out of a turn on dry pavement, and I was running 215/45r17x8+48s with High Performance All Seasons and EJ knuckles for better Akermann angle and camber.

On my '88 XT6, I dropped phase 1 EJ internals into the XT6 front case halves. Better gearing (4.111 axle gears, but .738 5th, so lower rpm on the highway), and the center LSD is light years better than the open FT4WD.

I had started combining all of this to make a dual range with 4.444 axle ratios, 1.59 low range, EJ AWD center diff, and a clutch-type front LSD, but that particular front LSD does not clear the low range set. I ended up scrapping the whole project. The front LSD might find it's way into the split-case 6 speed destined for my H6 Baja project, though....

Experiment if you like, but I think you'll be very sad with the results, especially considering the amount of work to get there. It'd be so much easier to EJ swap, then you have the torque where you don't need the low range, and viscous center diff.