Converting to a plated front diff I spent a lot of time worrying about running the same oil in the plate diff and gearbox.. as they share the fluids in the evo 4-9. This is not a worry in the usual grN use case, as they run dogboxes, but with a synchro box I was worried about having to use LS oil in the plate diff and non LS oil in the gearbox, as well as having to deal with possible metal shavings from the plate diiff ending up in the gearbox. Having worked on evo X gearbox and transfer and seeing that the X runs the transfer box fluid in the front diff I got the idea to convert my spare transfer box into a plate diff only setup, converted tooiling the front diff from the transfer box instead of the gearbox... After spending some time thinking about it, I finally paid for and ordered the special tooling and the production of the seals necessary..

So, how is it done on the X? X doesnt have the oil channel from the gearbox into the transfer box, for front diff oiling. This is probably done because of the SST box, that uses ATF inside. Transfer box is slightly larger, with larger bearings, larger front diff and larger diff housing. It also doesnt seem to have any forced internal oil circulation for the ACD clutch pack or front diff. At least looks so..



This is the ACD actuator plate in the X transfer box.. It sits between the ring and pinion part of the transferbox and the ACD clutch pack section. I marked the ports that let the oil trough.





The outer front diff case, that holds the ring gear has two holes in it.. so that the oil from the front diff can go into the ring gear section, that holds most of the oil.



Since the outer diff casing is used to transfer power to the rear (and to the ACD clutch pack) it is connected to the central diff by the usual hollow tube. To seal the oil from coming out it has a oil seal inside, that seals the outer diff casing and the front diff.




Front torsen diff has a little plug in the driver side output gear, and the output gear on that side runs trough a small oil seal between the front diff casing and the output gear.



Here you can see the small oil seal inside the front diff housing.

As a result, X transferbox and front diff share the same oil.

 

How is it done in the standard setup on e4-9

Oil in the gearbox is lifted by the large output gear and thrown trough that little hole in the gearbox straight into the input port on the transferbox.


The main transferbox case has just a straight hole that takes that oil to the central part of the transfercase with the ACD actuator


On the backside of the actuator plate you can see the 4 holes. Top one is the straight hole that transfers gearbox oil further. The next lower one, drilled at an angle, takes oil thrown by the transferbox ring gear and sends it into a channel in the right/passenger side transfer box cover.
Lower 2 angled holes are also connected to 2 lower channels in the right/pass side cover. I presume the lower ports are used totake oiil back from the ACD pack, and the top port feeds oil to it... but I might be mistaken and all 3 might take oil to the acd pack with the return coming trough the central bearing.


On the righ/pass side cover you can see the oil channels. The top left and bottom two end up right in the ACD clutch pack space. The top right channel is the one connected to the gearbox oil feed and ends up right at the end of the right/pass side cover.




The oil feed at the end of the cover flows directly into the nose of the hollow shaft that is also a outher cover of the ACD pack... Trough the hollow shaft, along the right side output shaft, the oil flows into the front diff. Since the front diff is in a sealed container, the oil will flow out trough the hollow input shafts that connect it to the gearbox..



So oil from the gearbox gets into this output shaft with 4 small holes on the end..

 

So, how to mod.. I got a hold of a ralliart plate diff and its specific outer housing.. Outer housing is the same as OE but inside has different plain bearings for the diff due to its different diimensions with respect to OE torsen... otherwise it is the same..




First problem was sealing the front diff and outer diff housing. X has nice oil seals but it also has larger housing that has space for it.. I measured the space available and decided I need 2 seals.. similar to the ones on the X
There needs to be a seal between the front diff and the outer housing, on the gearbox side. There is just a bit of space there. Also, I need a small seal around the output shaft but that is a simple rubber spacer that goes just behind the input teeth on the diff input and seals around the outout shaft... It will sit where the inside arrow is.



The more complex seal siths behind the gearbox side plain bearing and seals around the nose of the front diff.





It will be more clear when I get the seals made. They are making the tooling now.

These two seals will block the oil from coming back into the gearbox. THey do not need to seal perfectly... a bit of mixing is ok, but since there is little pressure it shouldnt be a problem.

Next, I will need to drill some holes into the front diff outer casing, so that the oil flows back into the ring and pinion compartment.

Oil input from the gearbox will be blocked.

Some drilling next...




I need to drill a hole that mimics the hole on the left at the place of the right arrow. That will connect to the oil channel previously used to feed the gearbox oil to the front diff. This way I will have oil from the transfer box ring gear "pumped" to the right side of the transferbox and it will flow inside the front diff, as per OE, just using transferbox oil this time.




Also, on the 4-9 there is a seal on the ACD pack input that seals the acd pack oil from getting into the front diff. I will take it out, just like it is on the X.
And that should be it..

 

This seems like something worth getting Jon @ TRE involved in potentially. If you can figure it out yourself I think that would be super cool but I dont see many being willing to dive into that themselves to replicate. But if Jon did the conversion and blessed it, then we'd all probably make the switch in our next rebuilds.

 

well, the info will be shared as I do it. I have talked to cliveW in the UK. He works magic on evo gearboxes and he told me he did similar mods to some of them to help people running sprint evos with plate diffs and normal gearboxes.. If the seals work it shouldnt be a problem. It could possibly be done as a simpler mod, with less drilling of the transferbox.. but I wanted to retain the OE oiling features.

 

One more thing.. There is a east european company making replacement plates for the RS rear diff and ACD too... they say the plates have more friction but I have no first hand experience. A friend of mine uses their diff in his race bmw... Works fine..

https://racingdiffs.com/products/mitsubishi-lancer-evo

 

100% this. would ping Jon@TRE (very difficult task on its own) and he had a workable solution, my trans/tcase would be making its way back to him

 

So the seal maker came trough... They fit fine and nicely seal the transfer input from the gearbox side... now off to clean everything and drill some holes..