EVO8LTW

iTrader: (41)

Had a partially successful weekend at Summit Point main circuit this weekend at a 2-day HPDE. The successful part was that, before the event, I installed SSB offset top hats on my Ohlins Flags (thanks Derek!), Whiteline offset lower caster bushings (always happy to find a use for that huge HF press taking up room in my garage), realigned things (more negative camber/zero toe) and adjusted my rear shocks so I wasn't riding so close to the bump stops (BIG difference there in ride quality alone). I also tried lowering my tire pressures on my fairly new NT01s (which I put on at the track and never drive on the street) and found more grip than my first time out on them running much higher pressures. My laps dropped into the low 1:24s with traffic, which is good for me, especially since my ECU boost was producing 15 psi down the main straight in 5th gear (street tuning 5th gear boost is hard).

I say the weekend was partially successful because after coming back into the pits in my second session and deciding to do an extra cool down drive (since I didn't get a good cool down on track), I noticed a significant vibration starting at about 25-30 mph on the track service roads (like the kind you almost feel in your teeth) and a loud humming noise. I took it out on the street around the track after that to further diagnose and noticed that this noise started at about 25 mph and happened whether in neutral or in-gear, whether accelerating or decelerating, and was probably from the front (didn't sound like the rear gears). I sadly concluded that the greater grip toasted the transfer case. So, I packed up the car (I drive the car to events) and put my street tires back on for the 50 mile drive home. I wasn't sure if I could drive it all the way home or not, but I figured I'd see if it was better with the car cooler. Worth a try. Well, sure enough it was completely back to normal with the street tires and cool down.

After getting home after an uneventful 50 mile drive, I decided that maybe a fluid change of the transfer case would solve the problem (maybe I hadn't filled it enough last time or something). So, I drained and filled the transfer case at 6am this morning before heading back to the track to try again. The Diaqueen that I drained looked new and there were a few metal particles, but nothing significant. I refilled with Diaqueen and drove back to the track. I did about a half session and then came in to see how things were. I took the car on the service roads again and found the car humming and vibrating once again, but perhaps not quite as loud (I'm not sure). But I was running full speed for those 15 minutes and ran another low 24. Figuring that I wasn't going to test my luck and get stranded, I put my street tires back on and came home early and somewhat puzzled. On the drive home, I wondered if maybe I had exhaust/driveshaft interference with heat (maybe things shifted with heat I thought) , but once I got home and looked, it wasn't even close to touching. Then, I decided maybe it was the tires? I put the NT01s on at home with the car cool and drove around the block. Same hum and vibration as when I came off the track this morning! I couldn't believe that the tires made that much noise and vibration, even at 30 mph. Maybe I skipped 1/2 my track weekend for nothing! Grrr! My teenage son was in the car for both of these street rides and thinks maybe the noise was louder when I came off the track yesterday, so I'm not 100% sure I'm out of the woods with the drivetrain.

My transfer case and transmission is stock (2004 RS) and I'm generally running 23 psi tapering to 20 psi on a BBK Full, so I'm not making massive power. I run Diaqueen in the transfer case and Redline in the transmission. Assuming that I *am* getting some additional drivetrain-related noise after track sessions (not sure), is it normal for the transfer case to get louder when its hot? Might switching to 75-140 Redline or Motul make the transfer case quieter? Since my car is 100% normal when on regular street tires and cooled down, I'm thinking it's unlikely that my transfer case is going south, but maybe the symptoms I've heard when hot suggest that it is? I'm not sure. Has anyone else had their transfer case get louder with track use? Or lost a transfer case from tracking the car? Should I run thicker fluid in a completely stock transfer case? Am I on borrowed time with a stock transfer case at my power level when I never launch the car? I wouldn't have thought so, but who knows. It has held up well for dozens of track events, but always on street tires until now.

Any advice welcome. I tried to keep this short, but I think I failed!

LetsGetThisDone

iTrader: (1)

It's the NT01's man. They're noisy. Really noisy.

Blown transfercase turns the fluid a nasty black/gray and there would be a lot of metal in it. It would look like black/gray metallic paint lol