04Green

iTrader: (1)

Title say sit all, this is long, sorry, is the engineer in me. Also, I usually figure out the easy ones and save the hard ones for this august group.

The particulars...

2004 6 speed. MT-90 transmission fluid, fairly new, track day, daughter, looking for 5th, found several things, possibly 3rd gear on straight, possibly touched reverse on straight, finally went in gear half a mile later. Worked fine after that. Did another session where I used the car hard. All was fine. Went to take someone out, would not go in reverse, then would not come out of reverse, then would not go anywhere (stuck in the center of the pattern not moving).

We pulled the shifter and the collar is sit in, but a socket in the hole in the shift rod, and wiggled it until everything started working again. 1&2 came back first, then 3&4, then 5&6. Reverse was the hold out.

I took a very slow lap around the infield, all 6 worked. Reverse would not engage. I held the shifter against where reverse was, and slowly let out the clutch. I could feel it rubbing, car moved back slightly, then it engaged. Reverse was pissed the rest of the day, and the car hung in reverse until you backed up a bit, but it slowly cleared too.

I arranged for a trailer, installed tow hooks, and used the next day as a "test to failure" event. We both drove hard all day. No issues (daughter did not go looking for 5th again), I used it every lap, no issues.

Towed my trailer 300 miles home, no issues, all gears work fine, reverse is now great.

Drained fluid today, was a bit dirty. But, the dirty part is strange, it was clear, but black. Kind of tinted instead of dirty. Another word would be cooked. No apparent shavings, at most a 1/10th of a cc, if that, small enough that I doubted I cleaned the magnet well last time. Fluid has a slight metallic sheen, if I put a magnet in, it makes a pretty magnetic field pattern. I strained it through a couple paper towels, not debris in towels, still has sheen. Straining through coffee filters at this time (slow process). And, as the fluid settled out parts are a bit pasty or greasy. Again, like it burned.

Question 1: Any thoughts on what would jam things up? And, why it would heal?

Question 2: Now that it is better, any thoughts?


A thought from this end. The stirring process looking for a gear probably pushed parts together (snychro disks) at speed well in excess of what they and the oil was intended to handle. This would generate a ton of local heat and could have stuck a lot of crap together. The subsequent runs slowly broke it all up. That is why it "healed" and that explains the black nature of the oil and the greasy paste. There was no gear grinding. They did not get past any snychros on the track.

dannobre

iTrader: (3)

You might be surprised how hot it got if you were running 2 run groups back to back

It takes it a long time to cool off from heat soaked...and the tolerances and the syncros weren't designed to run that hot

I have had mine not like the 4-5 shift at higher RPM's when it gets really hot...and when it cools of it is OK again

The final solution was a diff and tranny cooler for the track...way less issues since I went that direction

04Green

iTrader: (1)

Thanks,

So, for my mind. Car runs a session (20 minutes), sits for 15, with the trans right next to the cat, the whole thing is now really hot.. I did notice the heat in the car, and stuff binds.... Cooling down helps as much as anything to make it better..

How does trans cooler work? Lines, pump and a small radiator?

dannobre

iTrader: (3)

Basically you have to set up a pump, lines and an oil cooler....

You might want to wire in a temp sensor to the tranny and diff...you might be surprised how hot they get. If you think your tranny is hot...the diff will be worse

It's a slippery slope though. Where do you stop in the conversion to a track car

Next problem is getting the tranny to hold up to 500 HP ...not likely going to be able to do that with the stock 6 speed

04Green

iTrader: (1)

Not going to run into the 500 hp problem. But, we looked back. They went from 5 to 4 run groups, car was 20 minutes on, 20 minutes off. And, I was giving an occasional guest ride. Daughter is also progressing from coasting around the track to really running hard. She owned the blue group, from 4th gear.

I am thinking an exhaust without a cat might help, also a fan that blows under the car between runs. Good news is that if it is heat related, then I do not need a trans. And, heat, coupled with the stirring activity, and the interesting color of the oil, all kind of point that direction. And, I can figure out how to cool it.

That a lot

Edit:
I just realized that, because it was so cold on Saturday morning, I never switched the fans to run on low the whole time. That would kill airflow from running under the car while idling until the fans came on, and it was cold enough that they reall never did, no matter how hot the trans got.

04Green

iTrader: (1)

Closeout..

Seems it was temp related. New MT 90, shifts like a dream. New diff fluid as well to be safe. Still not happy about trans oil color, but if it really got hot, I guess that is what it would look like. It was black, but very translucent. I poured it out of the jar I was using, and it looked like the sides were tinted, but you could see through it fine.

Thanks Danno, Team and Swoop for talking me off the ledge. From now on, at track fans on low, and cool downs between sessions.