A little after the sloshing wet rain event I managed to find a diff for sale online. My plan was to just call up Planet Miata and buy a Viscous Limited Slip Differential from them. I did call them and they first told me the diffs did not come with a rear housing. That is the part I really need! They are an additional $150. Second they told me they didn’t have any viscous diffs. They are too hard to come by. So it would have cost me $350 for a complete open diff. Screw that. I decided to see what I could find for sale elsewhere. I had tried Miata.net’s classified section before and I did not get any email response from any of the diffs for sale. But I tried again and I saw 5 different 1.6L diffs for sale. Some open and some viscous. I actually got a response this time from someone selling a viscous. It cost me less than $200 shipped! Great deal. And it was from the south so it wasn’t all rusty!
The diff showed up within a week but right before an event on 9/2 at Boeing. Again not a lot to say about this event. The course was basically an oval loop with a slalom and some offsets in the middle. During the 180 turns I felt the car understeered a bit. But they were fairly tight as Boeing is a small lot. 4th out of 7 in class (.095 out of 3rd) and 26th out of 93 in PAX. I could have been distracted as this was the day I proposed to Irene! What a sweet day. I got to go autocrossing in the morning and proposed and had a great evening.
The next weekend I was up at Irene’s Dad’s to put the diff in. All went well except one of the bolts holding the cat to the exhaust didn’t want to come free and we broke the stud. So that had to be drilled out. We had some trouble drilling it out. It ate a few drill bits before we could put a 3/8″ slot in the cat flange. The drills were walking to the side. I went to Autozone and got some 5/16″ fasteners to stick in there. Well when trying to put the other bolt on that stud broke. The 5/16″ hardware on the other side wasn’t really working out anyway. So I ended up buying a cat from my Dad for $110. Sigh.
The new cat went in pretty easy. I had to grind two spots because the pipes stuck out past the flanges because of the angle the flanges were welded on. I used this opportunity to try and make the exhaust fit better. the center pipe hangs a little low and misses the hanger past the cat because of the snafu with the downpipe bracket when we first put the exhaust in.
I got to try out the diff the next weekend at South Jersey SCCA event. This event went very well on a couple of fronts. The lot SJR uses is at Camden County College in Blackwood, NJ. The lot is small. Not as small as Boeing, but small enough where you end up with a lot of tight elements. They usually set up the course so you run along the outside of the lot and get some higher speed elements and then the course kind of loops inside itself where you get the slow speed stuff. Unbeknown to me b/c I hadn’t run there all year they are doing construction right next to the lot and there was tons of sand that blew onto the course. And b/c the lot is old the asphalt binder has worn down allowing the sand to get caught in the valleys formed by the aggregate (those small rocks in the asphalt). If you got off line you just slid in the sand.
I didn’t really notice the diff working. The car felt pretty much like it did before. But the general consensus is that viscous diffs do not do much locking and when the get to high mileage they pretty much function like open diffs. But these are the same people who say it’s a must have item to be competitive. Who knows. Anyway I noticed that on a medium-to-slow increasing radius 180 turn the car would understeer on corner exit and I started noticing a clunk going into and out of the turn. I checked underneath the car between runs by turning the wheels to lock and saw that the sway bar was hitting the upper control arms! I thought there was enough clearance when I put it on but that was with the ar in the air. That would certainly cause understeer. I also suspected that the swaybar was binding in bushings as it is a common problem with the Racing Beat bar and I didn’t have a chance to remedy it when installing it a month or so ago.
Despite this the handling wasn’t bad and I got a win in STS2! Granted there was only one other competitor in class, Barry. We often talk and his car is less prepared than mine so I should beat him. But it is still nice to know that I didn’t allow him to out drive me. The bigger surprise was that I ended up 5th in PAX! I really wasn’t expecting that. The prevailing theory is that the lot is so sandy that street tires are a help and not a hindrance compared to R-comps. There were 2 very fast drivers on R-comps ahead of me so it wasn’t just the tires. I got a nice little “PAX” magnet and a boost of confidence. And now I knew I that little bit of understeer I felt sometimes was really something and shouldn’t be there. I had some more work to do on the car. But it is just the “working the bugs” out type stuff that I knew I would have to do some of no matter how much I tired to plan ahead. In my next installment we fix the swaybar issue and go autocrossing all weekend!