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Author Topic: Flip the ring gear in a Subie transaxle?  (Read 8162 times)

Offline ryan

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Flip the ring gear in a Subie transaxle?
« on: July 02, 2005, 10:33:32 PM »
Hello everyone, I'm new to this forum.
Does anyone know if it is possible to flip the the ring gear in an automatic or stick subaru transaxle so with the engine in the rear the wheels will spin forward? I already have the engine it's going into my baja, and I want my next car to be all wheel drive.
« Last Edit: July 05, 2005, 09:26:42 AM by freerock »

Offline freerock

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Re:Flip the ring gear in a Subie transaxle?
« Reply #1 on: July 05, 2005, 09:26:28 AM »
Hi Ryan,

Welcome!

I moved this thread to a new topic.

Not sure about flipping the ring gears in the Subie transaxle, but I do have a transaxle I would be willing to sell very cheap if you are interested it tearing it apart to do some investigation? The trany I have for sale is from a JDM 95 WRX STi Version 2 with about 35K miles on it. The model number is: TY752VB4AA. I'd let it go for $275 bucks in the interest of someone wanting to convert it for use in a rear engine setup (since that sounds like a really cool thing to do), but you would need to pick it up in Bellingham WA for that price.

Kevin
89' Syncro Westy
JDM WRX STi Version 2

Offline Bryan

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Re:Flip the ring gear in a Subie transaxle?
« Reply #2 on: July 20, 2005, 07:35:27 AM »
I've heard about people looking into flipping the ring gear.  Appearently it can't be done, but I don't know why.  Fipping the trans upside down might be an option, but maybe ground clearance would be a problem and shift linkage would be difficult.

Bryan

Offline rick_spiff

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Re: Flip the ring gear in a Subie transaxle?
« Reply #3 on: April 04, 2007, 12:57:57 PM »
Hello!

I've got a '78 bus (not a vanagon, but close) that's getting a JDM WRX engine stuffed in it. I too, strongly considered modifying the WRX transmission, and talked at length about this to a couple of old machinists I know. Here's the breakdown:

1. Flip the ring gear. This requires casting a new aluminum differential section and possibly machining a new R&P carrier (out of chrome-moly steel or something similarly exotic). An adaptor for the axles would be quite easy for a fab shot to work up, however.

2. Flip the whole transmission. At a minimum, you'd have to relocate the drain & fill plugs and the vent line. Then you have to fill the top of the transmission with JB weld or something similar so that when you flip the unit, the gears are still bathed in oil. But then you've reduced the internal case volume, which harms any cooling the oil might do, so you need a cooler/storage tank and pump to move it. In other words, 'yikes!' Ground clearance does not appear to be an issue. Might even improve. Might have to cut into the bus body. Who knows?

In either application, adapting the shift linkage is a walk in the park by comparison. If you're installing a 4WD tranny, you'll want to plug the rear output. Oh yeah, the guys at the machine shop think I'm crazy to try either one.

By the middle of the month, I should have the WRX running gear out and I can look into this in detail. I'm not going to order a pile of parts from KEP if I can just stuff the whole WRX drivetrain into this old bus.

Until then...

Offline Schimke

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Re: Flip the ring gear in a Subie transaxle?
« Reply #4 on: April 07, 2007, 03:14:44 PM »
I too, strongly considered modifying the WRX transmission, and talked at length about this to a couple of old machinists I know.

I don't mean to rain on anyones parade and anyone who knows me know that I like to go about things in my own way.

 I fully support the use of the Subaru gearbox for the engines in the lower horsepower range but for the SVX 3.3, WRX or STi, the 5mt Subaru gearbox just isn't that strong. In fact, with a few upgrades, the Bus gearbox would be a lot stronger. And for the money that it would take to re-engineer the Subaru box to fit, you could easily perform the upgrades to the Bus box.

I have purchased one of the bellhousing adapters from RJES. They allow the use of the Subaru flywheel, pressure plate, throwout bearing and starter. Check out their website for all of the details.

 The reason that I decided to use one of these is because of the clutch issue. I am installing a 2004 STi into my Vanagon and the Kennedy clutches just aren't that great. This bellhousing allows me to keep the STi 240mm clutch. Not only that but the engineering on these bellhousings is excellent. The kit includes everthing that you need for the conversion (not including the clutch parts). They offer two kits, a "N/A" kit for the non turbo push style clutch and a "Turbo" version for the turbo pull type clutches.

Anyway, it just seems to me that the money and time that would go into the engineering involved in making the not-so-strong Subaru gearbox work in a Bus would be better spent on upgrading the stock Bus gearbox and using one of the RJES bellhousings.

Offline rick_spiff

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Re: Flip the ring gear in a Subie transaxle?
« Reply #5 on: April 07, 2007, 08:51:14 PM »
Excellent points. The subaru transmission is by no means indestructable.

After plenty of additional research, I was happy to discover that the VW trans is significantly stronger than I originally thought. Plenty strong enough for my needs anyway. But I'm a born tinkerer.  ::)

I don't have the WRX engine out it, but I did spend a good our looking over the transmission while I was pulling the wiring, and was surprised to see that the entire case is actually cast and machined in two halves, split lengthwise. I'm still interested in doing this, if no other reason than to say I've done it. Mostly because if I do bother with this work, I will be doing it myself, on my own machining equipment. Heh.

Anyway, I will definitely be putting the VW transmission into service. I'm just wondering where I can get a differential with about a 3.6:1 gear ratio (still looking).

Here's to many happy miles with either tranny.

Offline Schimke

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Re: Flip the ring gear in a Subie transaxle?
« Reply #6 on: April 08, 2007, 06:37:11 AM »
But I'm a born tinkerer.......... I'm still interested in doing this, if no other reason than to say I've done it. Mostly because if I do bother with this work, I will be doing it myself, on my own machining equipment. Heh.

Boy, I hear all of that. I'm the same way. Many times people will ask me "Why?" and I always say it's a problem with my genes, I just can't help it.

I plan on putting a 4:14 r&p with a 1.17 3rd and a 0.77 4th in my European 5spd. The 4:14 r&p will make the normally too low 1st gear feel like a standard 4spd 1st.

Keep us updated on your progress.

Offline Bryan

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Re: Flip the ring gear in a Subie transaxle?
« Reply #7 on: April 26, 2007, 11:15:38 AM »
I think the main reason people started investigating subaru transmissions is because they are 5 speed, and relatively new and cheap. 

In the U.S. 5 speed transmissions weren't sold (except for the syncro with the granny gear).  So getting a euro or south african 5speed can be pricey, even though it could be 20 years old.  But a 5 speed would be nice in a turbo van.  I find the 4 speed has too much space between gears for optimum turbo usage  :(  But, that's what my pocket book allowed at the time.

I've been investigating the euro 5 speed option, when I need a rebuild.  Occasionally someone imports one.  But I'm a little nervous buying a used trans from europe that could have problems.  There are some that have these ratios:  4.86 differential with 4.11/2.33/1.476/1.023/0.77, which seem pretty good.  It would be really nice with the RJES bellhousing.

/Bryan

/Bryan

Offline rick_spiff

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Re: Flip the ring gear in a Subie transaxle?
« Reply #8 on: June 26, 2007, 07:13:46 AM »
I have an update on the WRX transmission, now investigating what it will take to fit into my bus. Here's what I know so far:

The tranny I'm dealing with is off a '94 WRX JDM Wagon (GF8 chasis, I believe, EJ20G engine).

The 'transmission' as removed from the car is actually the bell housing, gear carrier (bit with the important parts), front diff, center diff, and nose cone. The bell housing is integrated into the main case, which also holds the front diff and gear carrier (it IS the gear carrier, actually). The main case splits in half down the center, vertically. Onto the back is bolted the center differential in a single casting that also holds the shift rod. The nose cone is integrated onto this piece.

Well, I have a '78 baywindow. Torson bar suspension front and rear. No 4WD, so the center diff can go. The torson bar suspension causes a problem, though: the center diff and the torson tube want to be in the same place. One of them has to go. So, I removed the rear housing to find that suddenly, the input shaft would not drive the front differential, even with the transmission in gear. After some head scratching, I realized that in this full-time 4WD system, all power went directly to the center diff first, then went to the front and rear diffs. No problem. Just lock the output and front wheel drive shafts together, and use the front diff to drive the rear wheels! Genius! Next, I have to remove the center diff from its housing, and cut the housing way down. This housing holds the shift rod, so I don't want to just get rid of it. I kind of like being able to change gears.

The other order of business (which I'll get to this week, hopefully) is to open the transmission and actually flip the ring gear. The case is pretty much symmetrical around the front diff, except for the dip stick (I'll put some pictures up here before long). I don't necessarily need the dip stick, and there's no room to pull it out. Luckily, the hole can be used as a fill port, so that will work out fine. As I stated before, the case is also the gear carrier, so the gearing and shift forks are contained separately from the transmission. The only point of concern is the thrust bearings. Need to find out if they're the same on both sides, or if I just use shims or what.

So far, it looks pretty promising. I'll get some pictures together this week, hopefully, to make some sense of this rambling.

Offline slugmika

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Re: Flip the ring gear in a Subie transaxle?
« Reply #9 on: June 26, 2007, 09:02:20 AM »
Hi
This is really interresting!
I'am going to buy a 2wd legacy which i was thinking to use the gearbox for 914.
That would also be quite easy solution for subaru engine swap for our another vanagon. In that case it needs to be upside down. I'am looking forward to see some pictures of this 4wd gearbox project.

Mika

Offline Schimke

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Re: Flip the ring gear in a Subie transaxle?
« Reply #10 on: June 26, 2007, 08:17:01 PM »
YES! This is really cool. Please, please, please post pictures!

Offline rick_spiff

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Re: Flip the ring gear in a Subie transaxle?
« Reply #11 on: June 28, 2007, 12:11:56 PM »
I'm sick here, but the pics have been taken. I'll be able to upload them this evening.

A tiny update, according to the shop manual, the bearing races are interchangeable to the housing without modification, but they're specific to a certain side of the front differential. This means you just pop out the old ones, and swap sides, then install the differential backwards. I'm doubtful it's really that easy, but I will find out this weekend.

FYI: With this mod you won't need to try and run the trans upside-down, but you would have to open it, put it on a shop press, do some work, and button it back up. Reportedly, this is very difficult to do. Also, I'm not keeping the 4wd capability with this... but it would be easy to do. Heck, the suby rear diff. can be run upside-down with minimal (no?) changes.

Offline rick_spiff

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Re: Flip the ring gear in a Subie transaxle?
« Reply #12 on: June 28, 2007, 10:00:02 PM »
Pictures attached!

Some points of note:

The pic with many red arrows shows the center differential section of the transaxle. The wavering red line is drawn where this housing separates from the front portion. The arrows note the rear drive output, the shift rod, and some sensors I need to transplant.

The second pic should have the splines of the center diff circled. See how there's two sets of concentric splines? The inner set turns the output shaft that's connected to the front wheels. The outer set is connected to the power shaft. The center differential appears to be a clutch type unit, large and heavy. Those bearings sure are smooth!

There is a brief shot of the rear end of the transaxle, minus center differential section, wrapped in plastic. It clears the rear torson tube thing by at least an inch and a half. More than enough room for a cover piece.

Next we've got a tight shot of the splines that attach to the suby's front axles. These are centered on the transmission, and the bearing race retaining hardware is identical on each side. Every bit of info I have says that the differential is centered... good news if you want to flip it!

Finally a money shot. This is pretty close to final install, perhaps an inch low (I was inspected something). Notice that very small lip? That's the only clear visual evidence that this transmission splits in two. Weird. I've never seen a transaxle built like this before.

So, good news so far. This weekend comes the disassembly, more pictures, and hopefully a working transaxle suitable for use in a VW or Porsche. Keep your fingers crossed!

FYI: this setup is going to use the WRX's hydraulic clutch setup, for which there is plenty of room. Non-turbo Impreza models ran with a cable, if I remember right. The hydraulic system fits just fine.
« Last Edit: June 28, 2007, 10:07:32 PM by rick_spiff »

Offline Schimke

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Re: Flip the ring gear in a Subie transaxle?
« Reply #13 on: July 08, 2007, 11:30:00 AM »
More?

Offline rick_spiff

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Re: Flip the ring gear in a Subie transaxle?
« Reply #14 on: July 09, 2007, 06:18:56 AM »
Sorry for the long delay, I've been buried under work. I do have pictures, but not on the computer yet.

The short story: She won't work.

The long story: The pictures will help explain this. The pinion gear meshes with the ring gear out of center. If you extended the shaft of the pinion gear, it would not intersect with the differential housing or drive shafts. Because of this, the teeth on the pinion gear have to be slanted to mesh with the ring gear. If you flip the differential, you'll find the teeth cross. No joy.

The rest of the logistics work perfectly. The races are held in place by adjustable stops, so lash can be set after the transmission is assembled. The bears are identical, so you don't have to swap anything around. One side of the case does have some aluminum fins that have to be cut back slightly (pictures would really help here), but a file, a solid chisel, and some patience (or a dremel) would easily solve that problem. That's it, really. Just a gear-mesh problem, which happens to be the only unsolvable one. I could not find a machine shop that will cut pinion or ring gears for an automotive application, and no companies that sold a modified pinion or ring gear for running this transaxle in reverse.

If only I had a machine shop of my own...

So, I'll come back with pictures so you can see what you're getting into. Pretty interesting tear-down. I do plan on keeping this mess to investigate getting new gears, but I have a schedule to keep, so I'm going to use the VW transaxle in this project.

Until this evening!