SST How It Works, Problems, Upgrades; (All pictures associated on the site it would take too long to copy all of them over) http://www.jackstransmissions.com/pages/sst-how-it-works-problems-upgrades

The dual clutch Getrag TC-SST (Sportronic Shift Transmission) 6-speed, found in the EVO X, is a very compact and complex unit.



To find a unit like this in a car that is not a $100k+ exotic is very cool and us tech geeks love these things! For Mitsubishi to include the option to have them in the X shows how performance oriented the car really is.
Unfortunately, the SST unit is so complicated that very few people know how to repair them. Your average Mitsu tech, who is trained to work on an econo-box, won't have a clue and will just blindly replace the unit without ever cracking it open. On top of that, Getrag is notorious for pushing full replacement of the unit when it has a problem, and will not sell parts only. This is becoming a serious problem for X owners now that their warranties are expiring. I can see why Getrag would do this. Due to the complexity of the unit, as a manufacturer, you don't want your average tech digging into them and try to fix them. In most cases, the unit may not function properly after the inexperienced tech performs repairs and quality is compromised. This is my guess as to how a company can keep quality up and control the repairs to their product to insure proper operation.
Luckily, we can repair these units and also upgrade them! We have access to all parts for repairs (sorry, we can't sell them yet. We can only use them for repairs here) and have a very solid experience with complex units like these due to our willingness to learn how they work and our engineering mentality.
The unit pictured in this article is a unit we tore down and repaired, which had a case leak. The dealer wanted to replace the unit for $12k, but we were able to repair it for a small fraction of that price! This was the perfect unit to take pictures of so we can show how it works, the weak links, and what can be done to increase reliability.
CLUTCH ASSEMBLY:
This picture shows the clutch pack assembly removed from the trans.



The SST uses two wet clutches, which will switch from one to the other, when the trans shifts. While one is engaged, the other will stay disengaged and select the next gear. When the unit changes gear, one clutch will disengage while the other, with the preselected gear, engages. This is a very smooth operation and timed just right to give you the feeling you engaged the next gear without the need to lift the throttle, or any interruption in the vehicles acceleration.
The clutches create friction and clamp down on the disks via hydraulic pressure. The more pressure applied, the less slip and more clamp load
The clutch system is actually very simple in how it works. The system has 4 oil lines from the valve body which control pressure to the disks for clamping load and cooling.
The image below is of the center shaft which feeds the clutches their oil:



Note there are 4 oil channels. The two in the center (2 and 3) are there to distribute oil to the clutches for cooling. The two outer channels (1 and 4) are there to supply pressure to the disks for clamp loading. All 4 of these oil passages are fed from the valve body assembly.

Back side of shaft.

http://cdn.shopify.com/s/files/1/003...rge.JPG?101035

The picture below is of one of the clutch assemblies. Note the holes in the tube which line up with the oil feed channels in the center shaft:



Each channel has 4 holes drilled around the tube to transfer the fluid as efficiently as possible. You can see, just under the orange o-ring, the oil hole for the clutch pressure line. Hydraulic pressure comes through this hole and applies force to the top of the large black seal. The seal then will press down onto the clutch pack assembly and create friction.



Full tech report on site through above link to much to paste here and manipulate to fit

 

Awesome!.. I've been waiting for this! Thanks!

 

This is an awesome contribution. Have you guys also looked into tuning the SST?

 

Subbed. Good info

 

Read the link to your site. I think you are on to something about the excessive friction with normal mode.

I have one question though. Would 15 minutes of city driving really create that much heat? Do you know how long or how aggressive the driving would need to be in normal mode to start heat issues? I have no problem driving around in sport or s-sport if it prolongs clutch life, but I drive so gingerly when I'm in normal.

Thoughts are appreciated.

 

You can easily log odd and even clutch temperatures via Evoscan... so you don't have to guess...

Rich

 

I was not aware. I dont think I want to invest in tatrix just for that though. Already have an AP.

Any idea what value is too hot?

 

Subscribed...

 

Sub'ed.

 

In for more

 

Subscribed.
Great info!

 

Here is what it looks like inside

 

This is out of an R32. I am in vw trans tranning now. the Evo uses the same trans from the same manufacture.

 

I'm pretty sure the VAG cars use a BorgWarner dual clutch transmission, whereas our trannies are from Getrag, who also supplies BMW with the DCT.