Custom 3.9 RX FT Trans Question

[Crazyeights]

I built a FT 4WD RX trans with 3.9 gearing from a core XT6 trans and 23 spline stubs so it will fit in my '83 EA81 wagon. So far I have about 1500 miles on it and it works great, no noise, no metal on the drain plug, ect. I took great care in setting it up properly.

 

I REALLY miss the 1.59 low range from my old D/R. Can I gut the 1.59 low range section from a P-A-P D/R and swap them in to my current trans config? Yes I know it's a lot of labor but it might be worth it. It's seems like it would be a good combination.

 

What do you think?

[ruparts]

I built a FT 4WD RX trans with 3.9 gearing from a core XT6 trans and 23 spline stubs so it will fit in my '83 EA81 wagon. So far I have about 1500 miles on it and it works great, no noise, no metal on the drain plug, ect. I took great care in setting it up properly.

 

I REALLY miss the 1.59 low range from my old D/R. Can I gut the 1.59 low range section from a P-A-P D/R and swap them in to my current trans config? Yes I know it's a lot of labor but it might be worth it. It's seems like it would be a good combination.

 

What do you think?

Hi,

is the trans you modified a dual range case??? i want to ask more about just what you did.

you have to use a d/r case to have a d/r , not sure if the 1-5 main gear set and shaft is the same for the d/r and the fulltime. i think the main shaft is different where it fits up to the d/r gear set . the xt6 trans has a slightly higher ratio on all the 1-5 gears which is slightly different from the 1-5 ratios on the 4-cyl fulltime trans. i had been wanting to convert a RX close ratio d/r trans with 3.7 front diff , and use a xt6 1-5 gear set in it. after looking at the parts book the pieces look like you can't connect fulltime parts in a d/r case or d/r parts in a fulltime case. the parts look different where the front of the main shaft gearset fits up to the d/r gears.

if anyone else has more actual hands on, i also would like to learn more on what will or will not fit together.

[Crazyeights]

I bought a low mileage used FT 4WD 3.7 ratio Dual/Range trans with a center locking diff and changed the final drive (ring and pinion) to 3.9 using a gear set from an XT6 trans. You must take care setting up pinion depth, backlash, end play, ect. I also opted to remove the 25 spline stubs for the front axles and replace them with a 23 spline set from a single range push button core at the local P-A-P. Now my stock EA81 axles fit right in.

 

The RX trans does indeed have the 2 piece input shaft just like the D/R part time trans does. I was just wondering if I could use the 1.59 Aux trans (low range) in my current set up.

 

I wasn't sure this was going to work so I didn't try it the first time I had the case split. This combination turned out so nice though, it would be nice to have the slightly lower low range set.

 

We just had some snow in the PNW and with the custom trans and the LSD in the rear it tracks incredibly well:grin:

 

This trans build wasn't all my idea, thanks to those that helped privately with ideas, you know who you are:banana:

[MSSLGECKO]

I want this transmission. The best gear shift out there is the 1.59 D/R down shift in second gear (on snow of course). I used to have a BRAT w/only rear axles installed using a custom trim piece to prevent shifting into 2WD inadvertently; the quick throw b/w Hi & Lo ranges was phenomenal.

 

The fact is that having that 'halving' effect of the 1.59 Lo range allows you to put your (low hp/tq) engine in the power band at any speed. I like it most for the 2nd Hi to 2nd Lo shift, it gives the lower-speed torque like first gear w/o out the hesitation from the 1st gear synchros.

 

 

Build me one?? (I like the 23-spline mod, EA81 FTW!)

[Crazyeights]

Yes, it is a SWEET combination. Each low range gear right now is roughly half way in between the 5 high ones. Like a passing gear if that makes sense). If I build another one with the lower low range I'll probably start with a different R/X box so I can leave this one together. I only had 53k on it when I got it (before I modded it) and I think it's the only 5MT trans I've ever had with good first gear synchros:grin:

Edited November 26, 2010 by Crazyeights

[Gloyale]

The 1.59 gearset will swap right in.

 

Requires alot of disassembly of the upper shaft though.

 

Hope you got a press.

[Crazyeights]

Great info, Thanks!

[ruparts]

hi,

ok , so you used the rx case and d/r gear set, and the 3.9 diff from the xt6 trans,, is that correct ? but did you use the 1-5 gears from the xt6 trans , or the 1-5 gears from the rx ?

thanks

[Crazyeights]

1-5 gears are from the RX (closer ratio I think than the XT6). The final drive ring and pinion are from the XT6 (was 3.7 before). The current low range is stock RX - not as low as the 1.59 in the D/R part time trans. That is why I was wondering if I could swap in the 1.59 front section. This would be the ultimate combination for me, but It's really sweet now as it is. The car is street driven mostly and has 15" pugs/tires on it with an SJR 4" lift.

[ruparts]

hi,

ok ,, i was trying to find out if the 1-5 gears from the xt6 trans will fit up in a dual range case to the front hi/lo gears ,, i don't think they will , but still have not found out "for sure" . i have a regular d/r trans from a wagon , and what i wanted to do was put xt6 1-5 gears in it , they are a different ratio each, i would use all of them but i wanted to know if they will "fit" in the dual range transmission first.

the parts book shows single range and dual range (1-5) gears look different at the front where the dual range input set go together with the mainshaft set. what you gonna do with the xt6 leftovers?

thanks

Edited November 28, 2010 by ruparts

[Crazyeights]

Not sure yet what to do with the left over XT6 gear set. Might put a 3.7 XT6 box back together as a spare or put it behind a "Franken" in a Bad A** street Hatch.

Edited November 28, 2010 by Crazyeights