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AWD d/r trans rebuild?


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I figured while i got the engine out maybe i could pull the trans again and clean it up a bit. It's a dual range awd with 3.7 gears from an 87 rx turbo. There are two issues with it i was hoping to address and maybe someone here can point me in the right direction. The first is it didn't go into any gears very smoothly, like you had to get the road speed and engine speed lined up pretty close or it wouldn't really shift into gear. As you can imagine this made for some difficulty when bombing up a hill and needing to drop a gear really quick. The second is I don't feel the low range is low enough. I've seen threads that people swapped in a lower low range gear set just wanted to know what specifically i can pull that from to have the lowest possible low range.

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You can replace the synchros but is isn't exactly trivial. The type and weight of gear oil greatly affects shifts as well. Also, if the problem happens in all gears, is the clutch properly adjusted and working? Pilot bearing not hanging up?  You can also swap in the low range set from a regular dual range for a 1.59 low. It's a fair amount of work and requires gutting a D/R trans to do it. I have built several hybrid 5mt trans. My current RX trans (now behind an EJ22E) has a 3.9 ring and pinion set from an XT6 trans, center locking differential, small spline stubs, etc. I can help if you are serious send a PM. I am also looking for another RX trans if you know of one.

 

As you can imagine this made for some difficulty when bombing up a hill and needing to drop a gear really quick.

 

The older Subaru EA series transmissions just DO NOT shift that quickly ^^^^^.  I feel when I drive that I really need to allow the proper time between shifts.  IMO shift slowly and then put the hammer down.

 

Happy Holidays,

 

-Jeff

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If it's grabbing at very very bottom of the pedal, it can sometimes not be disengaging the clutch fully leading to either consistent or occasional difficulty changing gears. As far as where it grabs however, I don't think that matters. Adjust it to wherever you like it, though if it's too close to the top I can see it beginning to slip as it wears and having to adjust more often.

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if memory serves me correctly it engaged about 1/3 the way up from the floor. I believe its the syncros because the transmission is a low mile (around 80k) trans but it had been sitting for a number of years. When I first installed it I ran it with some cheaper synthetic oil for about 500 miles and then drained it and put in the fancy subaru oil, didn't make a difference.  I'm definitely serious about doing it but I would like to assemble a parts list ahead of time and have been having trouble finding anything beyond basic seals. I dont want to gut it and find out I cant get parts for it basically 

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I just installed a 1985 turbo D/R 5 speed in my 1984 wagon, it also has 3.70 gears and feels like it is too high geared, but it shifts good. I split the trans case and changed the axel stubs to 23 spline ones, replaced the front bearing and all of the seals. Never had done a Subaru trans before but it wasn't all that difficult to do, the hard part was installing the tail section back in place as I dropped the little screw that locks the shift rods together, it took 4 tries to get it back on. Get all of the seals and other parts first as you won't have all the parts just setting around.

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When you pull the box apart if there is no visible damage to the syncro's a trick I have used successfully in the past with Rally cars is to glass bead the syncro cones, Tape up the gear and glass bead the matching syncro hub on the gear.

 

Often what happens is the surface gets a Polished finish and they do not brake the gear efficiently enough to synchronise properly, Quite a common issue on Honda gearboxes in Civics, Especially if very high quality synthetics are used too early in their life, Just like piston rings gearboxes need to bed in to work best.

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Subaru still has all parts and diagrams for these transmissions on its Subaru parts web site. Might want to check that out. You can still even but a whole brand new transmission, but it'll set you back about 1800 if I remember correctly lol

 

Got a link to this parts site?  I need some rear housing seals, and since I don't have a factory Australian delivered VIN with this gearbox I'm finding it near impossible to get the bits I need for my build.

 

Thanks for the tips ill have to research the glass beads in not familiar with them. Anyone know what gear/ gears I would need to lower my low range? I'm going to pick n pull tomorrow. Pictures would be very helpful thanks

 

You need an NA PT4wd gearbox from the L series.  MPFI will have the 25 spline diff output stubs and the carb'd units will have the smaller 23 splined output stubs.

 

If you're really serious about a lower final drive you can have the pinion shaft cut and shut.  Not ideal but it's a solution to the 3.9/3.7:1 ratios that are currently on offer.  I've gone 4.111:1 with 27 inch diameter tyres and love it.  I'd love to go to 4.44:1 but it's a cost thing :(

 

Cheers

 

Bennie

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  • 3 weeks later...

Check the "roll-pin" where the shifter arm meets the transmission input shaft. If it has slack, then it needs to be changed. These were "wear" items and destroyed too many trannys. A stainless steel bolt with "shoulder" (304ss) should be sufficient.

 

These trans had such close tolerences internally, a "sloppy" roll-pin would eat up gears and syncros. Witnesses it too many times out West years ago. Holla /pm if you need any technical assistance.

Rock on and GL(good-luck)!

Stay thirsty.

Edited by flatfourx4
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