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Front diff interchangeability: The true answer


WJM
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From what I can see from pulling apart a couple of subie gearboxes it would be super easy.

 

Unbolt the back plate form the rear of the gearbox.

Unbolt the center diff housing, I needed a little force to get the diff splines off.

Split the gearbox casing apart.

Pull the front diff out.

Unbolt the crown gear/ring gear off the diff.

Bolt the LSD unit to the ring gear.

Play around with shimming for a few hours. (I'm sure you can look on google for "how to shim an LSD")

and then do the reverse of what I said above.

I may of missed something, like maybe putting the stubs on the LSD unit if it doesn't already have them, but I'm sure any one could be able to figure out what needs to be done. Just mostly circlips holding things together in there by the looks of it.

 

Like WJM says, it's easy. And if aren't sure you can do it, maybe you shouldn't.

 

Yeah...something like that.

 

Trans out.

Shifter union (the piece on the shifter arm).

Transfer case, remove center diff and transfer shaft.

Extension case w/shifter arm.

4 bolts on rear pinion bearing.

all small and large main case bolts

lay on LH side...aka the LH side of the trans facing down.

remove RH side of case.

remove mainshaft

remove driven/pinion shaft.

remove front diff.

remove crown gear.

install crown gear on new LSD.

Install new bearings on LSD

install LSD into main case.

install pinion/driven shaft.

install 2 of the 4 bolts into the LH side of the rear pinion bearing at FSM TQ (21 ftlbs IIRC)

Check and adjust gear backlash.

At this point, once the backlast is done, assembly-installation is the reverse of uninstall/dissasembly.

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Now, with 100% more developed suspension, the 2 new diffs, and ATLEAST 300 at the wheels...I am sure that I'll be able to outrun anything in the $40,000 to $80,000 range on a road course. :burnout:
And look much better (just my opinion on new car styling)
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Even before all the intensive suspension work on my RX...and definatly before the diffs were a though...I had no problems running down stock STi's/EVOs/WRX's...even lightly to moderately modded ones. When it came to ones with high HP levels, I could only keep up in areas that the larger turbos could not get to full boost, at that point I was all over them and either passing to letting them get some distance.

 

Will, I know you are a spectacular driver, and couldn't some of this ^^ be attributed to you being a good driver and them being only mediocre? You also may not like the WRX very much, but in my Dad's stock 02, I can keep pace with those funny little "performance cars" with the blue and white emblems on the hood and those awesome tires from Indiana... I like the WRX just fine. :headbang:

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Well...I cannot give my driving too much credit...I'll get a whole bunch of :rolleyes: :rolleyes: :rolleyes: :rolleyes: from people. ;)

 

But yes, *MOST* of the people I've beaten were mediocre...however, I have kept pace with, and outrun some very good drivers.

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  • 2 months later...

After reading all of the posts, I am still a little confused. All I need to know, is if it is possable to turn my 1985 GL wagon D/R 5speed 3.9 non LSD into a 4.11 or 4.44 LSD. I already know it is possable for the rear diff. If it is possable for the front, can you tell me what parts I will need and from what model of Sub., and what years.

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After reading all of the posts, I am still a little confused. All I need to know, is if it is possable to turn my 1985 GL wagon D/R 5speed 3.9 non LSD into a 4.11 or 4.44 LSD. I already know it is possable for the rear diff. If it is possable for the front, can you tell me what parts I will need and from what model of Sub., and what years.
The 80's wagons never came in 4.11 or 4.44. So you would have to use the gearset, pinion shaft, rear casing, center differential, etc out of a AWD car with the ratio you want. Then use the front LSD of your choice with the AWD's crown wheel and install all that into your EA's gearbox casing.

 

Of cause, this gets to a point where because you didn't get AWD EJ dual range transmissions. So using the gearset out of a EJ box in a EA box might be interesting. You would need to make sure 1st through to 4th are the same ratios in both boxes. or you would have to lose the dual range.

 

Just as a note that most people don't know, the pinion gear is part of the pinion shaft and is not interchangable. So if you want another raito, you must change the pinion shaft. And seems the pinionshafts in the 5sp EA box only came in 3.7 and 3.9, that's all you can have in a PT4WD box without changing the PT to FT/AWD.

 

Short answer, possible, but not for the light hearted mechanic.

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You can't go lower than 3.90 in an EA82 d/r or s/r 4WD (part time) box without a lot of custom machine work. Even though a 4.10 or 4.44 ring gear would go in, as Phizinza notes the pinion gear is machined as part of the pinion shaft, which is different between the 4WD and AWD gearboxes and can't be swapped. And you can't use a 3.90 pinion with a 4.10 or 4.44 ring gear.

 

EA82 AWD boxes (RX, ect) are a different story, they can be dropped to 4.10 using Legacy parts (I've heard, never done it, but others here have).

 

Andy

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The 4WD turbo boxes are plug and play with the EJ 5MTs.

 

However, in North America, there are no Dual Range EJ transmissions.

 

Aparently in Europe, it seems that the D/R was standard in foresters...every one that I came across has D/R.

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Um yeah you can get AWD dual range transmisions, nearly all outback manuals have them

I ment "you" as in "americans" I have a Liberty D/R box casing now, so I know that they exist.

 

EA82 AWD boxes (RX, ect) are a different story, they can be dropped to 4.10 using Legacy parts (I've heard, never done it, but others here have).

The one person I know of here that has that setup (beefaru?) has the EJ center diff, front diff, pinion and casing. So really it isn't an EA82 AWD box, it's a blend of Leg parts as well.

I done the opersite, look at my thread in the Retrofit forum.

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Well...I cannot give my driving too much credit...I'll get a whole bunch of :rolleyes: :rolleyes: :rolleyes: :rolleyes: from people. ;)

 

But yes, *MOST* of the people I've beaten were mediocre...however, I have kept pace with, and outrun some very good drivers.

:rolleyes: :rolleyes:

 

 

 

:-p

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yep, axle ratio is dependant on what center diff you use. if you're using a PT center, you have to use a 3.7 or 3.9 pinion from a PT box. if you're using a FT center, you have to use a 3.7 or 3.9 (XT6) pinion from a FT box. if you're using an EJ center, you have to use an EJ pinion (3.9, 4.111, 4.444, etc.)

 

no mixing and matching without severe modification.

 

BUT, the point of THIS thread, is that you can put any 5MT front diff carrier into any other 5MT case, i.e. a front LSD for a WRX 5MT into an RX 5MT.

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You are forgetting 3.70 from an EJ. USDM WRX's are 3.70 in the front. The rear output has a reduction that makes it a 1.1:1 thus the rear diff is 3.545.

 

that's why I put etc. for the EJs....I couldn't remember all the combinations.

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  • 4 weeks later...

the PG's have a decent bit of initial, but its a weak 2 way in reality.

 

I didnt like it on the back of the WRX I had. However, the one in the front was a PG rip off, but about 5x more preload, and it work pretty well....but it would eventually tear up the spider gears and spew metal all inside the transmission, ruining everything.

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thanks will, that just reinforces my wanting to get a real lsd for my car when i get it back to life.

 

 

the PG's have a decent bit of initial, but its a weak 2 way in reality.

 

I didnt like it on the back of the WRX I had. However, the one in the front was a PG rip off, but about 5x more preload, and it work pretty well....but it would eventually tear up the spider gears and spew metal all inside the transmission, ruining everything.

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  • 9 months later...

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