"In this Special Series, I document my various experiences with DCT leaks, failing clutches, and their solutions, including the GTS Motorsport Oil Pan Kits. 

In this entry, the loaner DCT got on its worse behaviour and pissed itself nearly dry. We try fixing her up by fitting the prototype main oil pan from the GTS DCT Motorsport Oil Pan Kits."
- Matt

The DCT's worst behaviours.

No matter the error codes from the loaner DCT we fitted in the previous entry, I needed a car to haul me around for the next few weeks. I set the drivelogic to D1 as it uses the least fluid pressure to operate the clutches. 

On a 300km highway trip, I experienced issues that were significantly worst the the initial clutch slipping issues at part throttle of the original DCT.

I sustained major stalling issues at highway speeds as I attempted take over manoeuvers. The transmission would trigger pressure and temperature codes with an orange COG. It would refuse to shift any gears, idling in neutral, even at highway speeds. 

Furthermore, the 1st and 2nd gear whines at high RPMs I first heard on the initial test drive became progressively louder. 

I had to stop, and restart the car 4x times on this 300km trip. 

Symptoms of dehydration. 

I had noticed obvious signs of leakage having parked the car for extended period of time during the last 3 weeks.  There was dripping fluids visible anywhere I would park and the leaking fluid would also leave an oil film of the trunk. 

The worst came after a spirited drive upon parking at the gas station. A cloud of blue smoke engulfed the car. The fluid was dripping on the hot exhaust system. 

I got the car back to Phil's after a trip to the beach and we put the car on the lift. 

As expected, the transmission undertray was covered in fluids, inside and out. 

The original Genuine BMW plastic pan on this DCT was wet. It was one of the worst looking unit the guys had seen. 

How low can it go?

Let's do an exercise in napkin mathematics: the standard DCT will hold around 9 liters / 2.4 gallons of fluid. The pan holds a little less, roughly 7 liters / 1.8 gallons. The M18 drain plug is roughly 0.7 inches in diameter.

The gravity flow rate for this diameter is very roughly 11 gallons per minute depending on fluid temperature. A standard flush should take roughly 10 seconds. 

We drained the pan under 3 seconds. How many fluids was in the transmission?

In times of needs [...] prototype!

I've had the prototype billet DCT pan sitting on my shelf for close to 9 months. The project had been delayed due to focus on other CNC machining projects, amongst other things. 

I was awaiting updated pan bolts and a new drain plug to test. 

Genuine BMW bolts cannot be reused on this unit. 

A quick fit. 

The installation process for the pan is the same as described in the second Build Journal entry of this Special Series here. There are a few elements that need to be transferred from the original pan. 

This entire service shouldn't take more than 2 hours. 

The magnet needs to be transferred over. The original plastic screw does not fit here. A new bolt is provided along with a washer.

Do not over torque this as you risk breaking the magnet :) We used the magnet from my original transmission. 

The original pick up on the loaner DCT had a slight crack. We opted not to fit the extender this time around. We would wait for the subsequent DCT and order a new pump just in case. 

The prototype's drain plug was fitted and torqued to spec. It made use of an aluminum washer. 

The seal was created with high temperature silicone, aka "gasket maker". 

You have a short window to seal the pan to the transmission upon applying the silicone. Read the instructions on the tube!

AH! This being a prototype, we had little things to adjust on the fly. The supplied bolts were a had a few millimetres that needed to be shaved off. 

We quickly bolted in the pan to secure the seal. 

Every bolt was torqued to specifications provided by BMW's technical bulletins.  

The GTS fill. 

At the core of the GTS fill is the mysterious banjo bolt. It's a little trick that allows you to augment the pan's fill without having to tilt the car. I previously documented the GTS banjo bolt features, installation and the uprated filing procedures for the enlarged pan here. I skip the filling details in the current entry. 

The banjo bolts moved the fill point higher than the original fill plug, allowing the extra fluid. 

We fitted the Banjo bolt to the fill plug by the passenger side of the transmission. One washer per side is required for a proper seal. 

I had previously used LiquiMoly's 8100 DCT fluid. This time around, we went with Motul's. I don't have a preference here, we just used what we had around. Motul does tend to blend great oils. 

We first filled to room temperature until it leaks from the GTS bolt, and then proceeded with the ISTA filling protocol. The car was started up, RPMS were raised to 2,000 RPM until we reached the target fluid temperature. We filled it again until it leaked and that was it. 

The undertray was cleaned and put back on. It clears the lower hanging pan with ease. 

It fixed my issues. 

I had grown accustomed to some part of the DCT's degradation: the stiffened chassis, including the recent polyurethane differential bushings, led me to wrongly assume the DCT's behaviour were normal. 

The new pan and proper fluid fill fixed everything. I was able to remember how a properly functioning DCT feels: it's smooth, fast and extremely efficient - with a few well placed torque bumps. 

It's even better with GTS software, a lightweight flywheel, a carbon driveshaft and stiffer rear end bushings: it's telepathic. 

[...] for a short while. 

Over the next week, I experienced fluid leaks again. My trunk was once more getting stained with fluid residue, accruing dirt and grim. I was carrying a bottle of degreaser to keep the car clean - it was a ridiculous affair. 

Having not performed a complete DCT service as on the original DCT-001, I defaulted to the usual culprits of the mechantronic O-ring or the side pan gaskets. 

I was wrong, and I was in for a surprise.  

The side pan's gasket was dry, along with the upper channels towards the mechatronic harness. 

It turned out the aluminum washer used on the drain plug didn't seal correctly. It had been a concern Phil pointed out the original installation. He prefers the original copper crush washer design from BMW. 

We replaced the washer, properly torqued the drain plug, and refilled the transmission. 

My latest failures would turn out to be useful experiences for final design revisions. 

Up next: I document the complete, production version of the GTS DCT Motorsport Oil Pan Kits.

The S65 gets fully dropped, and we swap the loaner DCT-002 for the replacement DCT-003.