Disclaimer, this isn't as impressive as installing an Evo S-AYC in USDM Evo VIII or IX, but it was still a pain in the *** and should be a large performance gain.

Also more pictures can be found at our website.

So how did this story all begin? I guess it was Ebay, that magical world of random crap. While searching for random Evo stuff I found a place in the UK that was selling an Evo X differential. In the posting it mentioned that the differential could be easily installed on any Evo VII-IX with AYC. I hadn’t heard of this possibility before and I instantly wanted to upgrade to this part. Mitsubishi had dramatically improved the design between the VII and X and I felt our rear differential was a weak point in our car’s performance. The only problem was that a used Evo X differential is north of $1,000 and that isn’t in our budget at all.

So with that in the back of my mind, life went on as usual until the fateful day of September 19th. This was the day of the Corvette Autocross at Grissom Air Force Base. As Professional Awesome has close ties to a Purdue Automotive club, which would be attending the event, it was decided that we should take the car. Well I should clarify this a bit, going to this autocross was up to Grant (head mechanic) and me (driver). Mike (crew chief) said specifically we should not bring the Evo as something would break, but the two-to-one majority ruled so we drove the Evo about an hour from our home base to Peru, IN. The one stipulation about running the car at the event was not to drive the car too aggressively off the line or in other words, launch it.

My definition of not launching is to slip the clutch from the line, rather than dumping the clutch quickly. Mike and Grant’s definition is to daintily move the car off the line and then to drive at or below the posted speed limits. Everything was going quite well until the second-to-last run of the day when after a MILDLY aggressive accelerative moment, the rear ring and pinion decided to redesign themselves with slightly fewer teeth. While this did make the car a little bit lighter in weight, it just didn’t seem to work well… or at all.

After my fine uncles helped trailer the car back to the PA garage Grant tore down the differential to diagnose the situation. After the negative prognosis, I started scouring the Internet to find a replacement differential. As some of you may know, as our car is an Evo VII and was never officially imported to this fine country, it’s not exactly easy to find a replacement differential. So it was quite fortunate that I read that Ebay listing about an Evo X differential fitting without issue. The one problem with the Evo X is that even though it was officially imported here, there aren’t many on the roads yet. Luckily they are mostly driven by hooligans, so a few crashed cars existed and our new differential was sourced in Nashville. Rather than wait a few days for shipping, the PA crew headed straight down and a lovely Evo X differential was in our possession. We proceeded to make a beeline straight back to the garage and rejoice in our luck (and substantially lighter wallets).

Soon Grant had the differential in place and I returned with the celebratory pizza and sequins only to discover that the driver’s side axle did not fit properly. That night there was no joy and the pizza was thrown away. Next, a plan was in place to take an Evo X axle and fashion a combination of both the X and VII axle and everything would be peachy… in theory.

As we should have learned earlier, nothing goes as planned. The two axles couldn’t easily be combined, no custom machining could be easily done or afforded and things actually looked pretty bleak. I may have lost a few nights’ sleep thinking about what Mike would do to me if a solution wasn’t found. I even went as far as going to that original Ebay posting, finding the name of the shop in the UK, then calling them only to find out they never actually installed an Evo X differential into an older Evo. Apparently they ran into the same problem we did and rather than find the solution, they just installed an older differential because they are lucky enough to be able to get them from Mitsubishi easily. In my search for other options, a random phone call to a bearing company yielded a potential idea: dowel pins.

One thought Grant had earlier was that we might be able to get the two axles to play nicely using oversized needle bearings in our inner joint of our Evo VII axle, but needle bearings are incredibly hard to find individually. Hardened dowel pins, on the other hand, are very common, relatively cheap and sure enough, a common size was extremely close to what we needed. One call to Fastenal, a trip to Indianapolis and a few hours later, Grant had the two axles combined. Shortly there after, everything was in place and finally, after a little help, we had the Evo on the road and everything is working quite well.

Time will tell if everything holds up on the track, but we are cautiously optimistic. And unless it can be proven otherwise, I am proud to say that when it comes to swapping an Evo X differential into an Evo VII, Professional Awesome is the first in the world.

 

Got a picture of how you fitted the axle together?

 

Nice I would like to see pictures of the work done if you have.

 

What pictures would you like? To get everything to work within the axle we needed the Evo X stub along with Evo X tripod bearings attached to the Evo VII tripod without it's bearings and the hardened dowel pins.
Dan

 

I´m very interested since I own an Evo VII.

 

Okay, I know this assembly had to be something very clever and I admit I am still trying to figure it out. You used the X stub with cup that goes in the X differential and an Evo VII tripod. You put Evo X rollers on the Evo VII tripod and for bearings you used hardened dowl pins? If this is correct no picture is needed.

If this works, I know, down the road (no pun intended), there will be others doing this modification. Let us know how it holds up.

Again, I say, very clever.

 

You are correct sir. I won't release the measurements of the dowel pins until after we race on the axle to ensure it works. It is a common size, but they are undersized by a few thousandths. Now this isn't a high RPM part, so it shouldn't be a huge issue (and judging from the OEM machining on these parts, they don't seem to care too much about perfection either). Also, there was a little bit of ingenuity involved in keeping the bearings in place, but I would rather have Grant (the scientist/mechanic) explain the specifics on that after we have tested everything.

Dan

Dan

 

Looking forward to your comments on its performance.

 

Fingers crossed a few parts will arrive in the mail over the next day or two and we will be able to head to the track!

Dan

 

Headed to Gingerman Raceway in South Haven, MI to test the car tomorrow. If you live close you should stop by and check it out.

Dan

 

Any news?

 

A little update about the weekend and a little background information. Grant is our head mechanic, Lewin is our crew chief and Mike Fleege is media. For more info on the team head to our website.

There are two types of Professional Awesome mornings. The mornings I enjoy are the ones that consist of 11 am wakeup calls, good breakfast and a comfy couch for the remainder of the day. The other type of morning is a different animal all together. Generally the air is chilly, the Sun has yet to rise and a long day awaits. Our Gingerman test day was absolutely the latter type of morning.



Arising at 4:45 AM our weary-eyed crew started the day with the constellation of Orion prominently in the sky. After the usual predictions of how many bathroom breaks I will need on the drive up and a competitive curse word contest, we headed off. Being reasonably well prepared, Grant and Lewin took the lead in our lovely tow van (free candy to all kids!) with Mike Fleege and me following closely in his Civic SI. On the way up Grant would say everything was going too smoothly and something bad was bound to happen. Damn him, damn him all to hell. I have personally witnessed Grant predict the future of Iowa football games and he was exactly right with the latest prophecy. Ms. Cleo, be afraid, your job is not safe.


After a ritualistic Burger King breakfast, we arrived at the track right on time. As I had the driver’s meeting the crew rolled the Evo off of the trailer. It was great to hear the old war bird start its engine with the smell of E85 permeating through the air. Grant’s 'something bad' started out strong with problem numero one; the straps that hold the Evo to the trailer were mysteriously loosened. The Evo went the 3 hour trip secured only by hopes, dreams and luckily a safety chain. Grant suspects that drunkards in the middle of the night may have played with the car on the trailer as it sat in the driveway. I think that we just need to check the straps more often, no harm no foul, lesson learned.



The primary goals of testing the car this weekend were to learn how the car handled with our brand new Kogition rear wing, ensure the Evo X differential worked well in our application and also try out new CL RC6 brake pads. With the first few warm up laps underway, everything was working as planned. The track was cool at about 45 degrees and the car felt very strong. At our initial wing settings, the grip was astounding, I mean genuinely crazy. How does steady state above 1.40g sound? How about a peak at 1.48g measured via GPS (I think our g-meter measured at peaks near 1.60g)? The added confidence of having the wing was fantastic too. The Evo has always been a little tail happy, even at very high speeds. Because of this, one would have to pucker thy butt at higher speed turns. With the new wing holding the rear of the car in place it is much easier to stay in the throttle. Did I mention the wing is AWESOME?!

Testing goal number 2 was going well too. The rear differential helps mostly in lower speed turns and boy does it help. The car would go into what I would describe as a set vector that was a few degrees off of what I would hold the steering wheel and just continue around the corner with tenacious grip until I was straight again. It is tough to describe, but it felt like a 3 wheel drift with the last wheel keeping everything from getting too crazy. My best morning lap times started around the 1 minute and 44 seconds mark.

Testing goal number 3 was for later in the day. First to get some feel with our usual Raybestos ST43 pads and then second, switch to the new CL RC6 pads for a direct comparison. Well this is about the time Grant’s prediction started to grow wings. After completing my second or third somewhat aggressive lap, downshifting from 4th to 3rd gear after turn 1, the clutch pedal hit the floor and decided to stay there. I managed to get the car back into 4th gear and limp it around and back into the pits. I explained the bad news to Lewin and Grant, they looked the car over and came to the conclusion that a snap ring that holds the clutch’s pressure plate to the throw-out bearing had released and couldn’t be fixed unless the transmission were pulled out. Grant, in his usual straightforwardness said “Well, we have two choices, either pull the transmission or put the car on the trailer.” I, in my usual laziness, didn’t feel like pushing the car up the trailer. So I said “We (by we I mean Grant and Lewin) better pull it.”



1 hour and 12 minutes. This is all the time it took to pull the transmission out. Being prepared is a good thing, a very good thing. We had all the tools organized, had practiced this before, had modified the exhaust to be quick release, had foreseen this being a potential issue. The snap ring that failed was still useable, but had to be bent and contorted to work. I heard “Piece of crap bad design” murmured numerous times throughout the process. I believe it took 3 or 4 test fittings of the transmission to make it work, but work it did and the crew had the car running with about 2.5 hours of track time left.



While the crew worked on the big problem, I took the time to swap out the Raybestos pads for the new CL-6 pads. A few minor suspension settings were changed and the wing was set to a more aggressive angle. Back on the track the car didn’t grip as well as it had in the morning. We are blaming it on two things, the rear differential stopped working, we believe due to the active differentials not being bled fully before going back on track. Also with the more aggressive wing settings, the front of the car felt lighter and it cornered with more understeer. This isn’t to say the car was slower, quite the opposite actually. As I got more comfortable with the added performance and new track layout, lap times kept coming down. I started to focus on releasing the brakes at higher speeds when entering turns which I believe is one of the next lessons I have to learn to improve my driving.



After an extended first stint, brake fluid boiling reared its ugly head. What happens is as the brakes generate massive amounts of heat it is transferred into the brake fluid and it boils. The now gaseous fluid doesn’t stop the car well, or at all, and the fluid has to be replaced. This wasn’t a scary situation as I have grown accustom to the symptoms and coasted around the track slowly and brought the car into the pits. This is when Grant discovered boiled over coolant coming out of the reservoir. This is a symptom of a blown head gasket, another problem that is familiar, but we had hoped solved. A quick check of the head studs was made to ensure they hadn’t loosened and the car was buttoned back together. There was one 20 minute lapping session left and no time to make any additional changes or bleed out the bad brake fluid. The good news was we had the lap times down to 1 minute 40 seconds.



Lewin sent me back out with strict orders to take it easy on the car, but we all know I don’t listen to orders. As I drove around slowly I kept a close eye on the coolant temperatures and felt the brake pedal to ensure it was nice and firm. Everything checked out and I slowly built up speed. The track was nice and clear as most other cars stayed in the pits and I started to click off faster times. 1:43, 1:42, 1:40 and then on the last lap 1:39.8! The car felt strong, still it had understeer, still the rear differential didn’t work magically like earlier in the day, but the brake pedal felt great, the clutch was perfect and my driving was getting better, OHH the potential! I cruised the car around for 3-4 cool down laps, keeping and eye on all the gauges and everything checked out, back to the pits to load up and go home.



So how was the weekend? I’d say pretty successful. We learned the wing is killer, we learned the rear differential is killer and I learned I can drive faster than earlier this year. Up for debate are if the CL brake pads are better or worse than our existing Raybestos, but only because the Raybestos are so good. Back to the garage to pull the cylinder head, tweak the aero and get the car ready for California. Confidence is high and the car is a grip monster, all we need is for Grant to keep is mouth shut and we’ll be fine!

 

This is great, very interesting.

 

Nice info

 

For extra info, the tires we use are beat to crap Hankook RS-3 street tires... they are amazing! They have 3 Redline Time Attack weekends, a few autocrosses and 2 full track days on them.

Dan