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4EAT reverse direction for Vanagon

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...OK, theoretically, you could build some gearcases on the outside of the transmission. but then you'll be shifting the axle centerline one way or another.

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I finally decided to put the central engine in my Vw t2 Pickup with automatic box really is not what I wanted, because the engine really looks beautiful in the tail of the truck .. :wacko:  :wacko:  :wacko:  :wacko:

 

As if they were built for each other :D

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Hi,

my name is Thilo and I'm from Germany. I want to transplant a MY'97 EJ25 DOHC with 4EAT from a Legacy into a VW Type 2 motorhome (Karmann Gipsy). I'm experienced with the original VW manual transmissions / gear ratios and plan the manufacture of a reversed R&P that should be able to serve in a 2,5 ton vehicle at moderate engine speeds providing a top speed of max. 120kph / 75mph. The intended cruising speed would be around 100kph / 65mph.

Here my questions now:

Where do I get some drawings /geometrial data of the 4EAT differential to get basic dimensions to forward to my gearmaker for discussion?

Can anyone tell me about the gear ratio configuration of a TZ102Z3CAR-DJ and the differential drive ratio?
Edit: OK, that's answered by forum search. It should be 4,444 44/9. To achieve the above weight and cruise speed with the gears, the R&P ratio should be in the range of 5,8 to 6,3. Such ratios are available in the VW transmissions.

How can/should I block(?) the original SBR rear drive transmission outlet shaft to have the full torque on the front differential (that will become the reversed rear differential on the VW Motorhome)?

Thank you for helping me, I wll keep you updated on my findings.

Thilo

Edited by WackyDoka
added information, corrected ratio

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I don't know about specs for grinding a new gear.

I do know that the rear output hydraulic drum and output can be removed.  And the case end plugged.  very easy.  It's not a differential so no worry, all the power will go just to the front R+P (rear for VW)  

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Actually now that I think a little more.......

The tail output shaft and drum WILL need to be in place  (*unless you get the 2wd rear case parts FROM 90-94 FWD 4EAT*)

The reason being that the main output shaft is held laterally in the case by a roller thrust bearing against the tailshaft drum, held in the rear case.

BUT.......one could take out the plates from the transfer pack, and just put the dummy drum back in, plug the end of the case.

Honestly, I'd try to find a FWD 4EAT and just use that.  lighter by 10kg at least.

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OK, update: Reverse R&P is not possible due to geometry of differential housing and ex-centric position of pinion shaft after looking more detailed to the FSM of the '97 Legacy 4EAT.

Alternative: Change to reverse rotation in reduction gear at opposite end of transmission by changing 1:1 ratio to a 1:1.3 ratio and using an additional gear wheel to reverse - this will be the plan to discuss with my gear maker. by this I will achieve a ~ 6.x ratio using the 4.44 R&P setup.

Anyone has experience with such a modification to the 4 EAT?

Edited by WackyDoka
formatting

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Well,
due to the torque output from the EJ25, in this heavy vehicle, the VW transaxle (currently 4spd Manual) might not last long as it was only designed for a torque of up to max. 180-200 Nm. Therefore I try to use the full EJ25 + 4EAT powertrain setup that has to be reversed in output rotation due to rear engine Installation (engine behind transaxle

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1 hour ago, WackyDoka said:

Well,
due to the torque output from the EJ25, in this heavy vehicle, the VW transaxle (currently 4spd Manual) might not last long as it was only designed for a torque of up to max. 180-200 Nm. Therefore I try to use the full EJ25 + 4EAT powertrain setup that has to be reversed in output rotation due to rear engine Installation (engine behind transaxle

Well then, wouldn't it be wiser to invest in a heavier duty auto transaxle such as Porche 911 Cayenne or a HD race 4 spd manual transaxle?

https://ranchotransaxles.com/pbs-transaxles/

Scroll down - they manufacture transaxles with Subaru bellhousings.

Monies invested in special purpose R&P for 4EAT could be spent on HD race transaxle already available.

As has already been stated in this thread, reverse driving a FWD R&P doesn't last.

Edited by czny

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15 hours ago, czny said:

..... As has already been stated in this thread, reverse driving a FWD R&P doesn't last.

Sure, that is why I thought it might be a good idea to reverse the rotation by changing the reduction gear of the 4EAT.

Installing an adiitional gear wheel for reverse and thus change to reverse rotation from 1:1 ratio to a 1:1.3 ratio. The new reduction gear would consist of a 37 tooth, a 25 tooth for reverse and a 47 tooth on the pinion shaft. An additional small shaft and bearing would need to be installed for the 25 tooth reverse wheel.

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8 hours ago, WackyDoka said:

Sure, that is why I thought it might be a good idea to reverse the rotation by changing the reduction gear of the 4EAT.

Installing an adiitional gear wheel for reverse and thus change to reverse rotation from 1:1 ratio to a 1:1.3 ratio. The new reduction gear would consist of a 37 tooth, a 25 tooth for reverse and a 47 tooth on the pinion shaft. An additional small shaft and bearing would need to be installed for the 25 tooth reverse wheel.

https://www.proformance.com.au/single-post/2014/08/15/COAST-TO-COAST-RUNNING-DIFFS-BACKWARDS-OR-UPSIDE-DOWN

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Another solution for the manual: 

http://subarugears.com/ 

I’m thinking there’s a reason why no one has a reverse cut gear for the auto. Either no one has worked it out (not possible) or there’s a very simple solution that doesn’t require modified parts. 

The reduction gear on hub idea is probably going to be the best option after working out the rear section of the auto box as FerGloyal discusses in previous posts. 

Cheers 

Bennie

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