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4EAT reverse direction for Vanagon


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I'm going to put a 4EAT into my Vanagon. It already has an EJ25 engine, so with the 4EAT no adapter plate is needed. I plan to use a 4.44:1 R&P. The gearing with this should be pretty close to ideal I hope, and I think with the EJ25 I'll be able to hold 65 MPH in 4th (around 2600 RPM) with the torque converter locked up.


To reverse the R&P direction (as the Vanagon is rear engined) I plan to replace the reduction gearset with a chain. I'm currently investigating chains that will work, although it's hard to find real spec's. Currently the top contender is the Morse Hy-Vo chain which is used in a lot of 4WD transfer cases. However the widest chain I can easily fit would be 1", and I'm unsure if this can handle the power. The Jeep YJ transfer case chain is 1" (to drive the front wheels) so maybe 1" will be sufficient.


A few things I'll need to figure out is how to mount the new sprockets to the old shafts. I'm considering machining (or wire EDM) the old gears into hubs, and then shrink fit and weld the new sprockets on. I'm unsure if I'll need to re-heat treat the sprocket teeth, but I'll check the hardness after the welding. The bearing structure and the parking pawl system complicate things here, but I think this is doable.


Any ideas about chains or fabricating sprockets would be great!

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Wouldn't the R&P still be driving in reverse all the time? The gears really weren't designed to do that - you would be running on the coasting side of the diff gears which is significantly weaker and in a vehicle that's a lot heavier....


The front diff on my t-case lifted hatch is an R-160 that's been turned around and used in the front. It ate itself once and had to be replaced already. R&P chewed up pretty good and that one isn't even used to drive the car except when 4WD is engaged.


I wouldn't expect it to last very long in that scenario. All the transaxle conversions I've seen have swapped the R&P for a reverse drive set that has the proper cut and/or flips the ring to the other side of the pinion.



Edited by GeneralDisorder
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I've read that the R&P in the 4EAT already uses the "coast" side of the R&P gears for "drive", so maybe it will make it slightly stronger to reverse it? I need to check this out.


There is no reverse R&P set available for the 4EAT that I know of. I even have a spare 5MT in the shed but I've decided on the 4EAT. Smallcar has mentioned working on a reversed chain drive, and the guy in Australia is working on something too, but there is nothing available now and no ETA.


A belt isn't strong enough, but yes I have seen aircraft that use the Hy-Vo chains.


Here is an aircraft gear maker mentioning the issues with Hy-Vo chains, but still says they are a viable solution.


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I have another thought as well. What about making an external input shaft to the pinion gear? This would allow an external t-case with two driveshafts between the tranny and the t-case. The t-case will drive the pinion with an internal chain, along with the possibility for low range and 4WD to the front.


I know the t-cased lifted Subies use a front diff under the existing one, right? But being able to utilize the existing diff inside the 4EAT would open up some possibilities.

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  • 7 months later...

can you not do flip the diff over like is done on manual subaru transmissions for use in beetles and kombi's?


Like this

4eat ring gear rides to the far right side, pinion shaft off center.


Hmmmmm..... Perhaps a 5spd diff carrier, with the centerd ring could be mounted with the ring to the other side???? I doubt it would work but hey. At least worth a look.

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maybe re-work the inside of those old gear-hub reducers from the 70s to reverse direction at the wheel?


problem is, probably not a good ratio for driving on the road.

The gear hub reduction boxes would work well, but they were all swing axle design on the US models, so the transmission is the pivot point of the rear suspension. Brazilian bus's used an IRS reduction box that had a U joint half shaft running to it.


Here's a swingaxle one with a CV axle modified to fit: http://www.mudtrials.org/thetrialscar41.htm


The gear reduction on the later ones was 1.26:1

Combine that with the steep overdrive of 0.69 in a 4eat with an avalable 3.9 final drive and you end up with 2700 rpms at 65mph on 205/75r15 tires which should be close to a stock bus size. That's a livable cruising RPM.


Looked up stock bay window bus tires. They are 185/80r14's which puts 65mph at 2900 rpms. Still OK for highway use especially as that's what a stock 2003 Outback 5spd is turning at the same speed.

Edited by WoodsWagon
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  • 3 months later...
  • 4 weeks later...
  • 1 year later...
  • 1 year later...
Hi, I'm looking for exactly the same solution, but I think this topic died ...


At least I wanted to be the only one in the world with rear engine and automatic .. haha


:(  :(  :(  :(  :(  :(  :(  :(  :(  :(  :(  :(  :(  :(  :(  :(  :(  :(
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I love to see people thinking outside the box, and doing cool swaps with Suby engines and trannies. But in this case, it just will not work unless you can come up with a reverse ring and pinion. That means you, or someone else has to make one. There is no other way around it. If you try to drive the standard rotation gears backwards, they will die. Simple as that.

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