2G 2nd gear grinding ~750 miles after rebuild

[drmuelr]

Let me preface this by saying I'm relatively new to the world of DSM's. I've done all my own maintenance for about 3 years now, to include 3 clutch & flywheel replacements... 1 on a 1G Eclipse 1.8L, and 2 on my current Talon. I've gotten disgustingly good at dropping transmissions. Feel free to replace "I know" in here with "I think."

Okay, I know DSM's are notorious for 2nd gear grinding. As far as I know, my Eclipse always did, but the only driving I did with it was after replacing the worn out clutch that I bought it with. (clutch change #1) After doing this job, I filled the transmission up with Royal Purple's "Max-Gear" 75W-90 gear oil. It would almost always grind into 2nd when cold, and about half the time when warm. Double-clutching helped.

My current problem is my 97 TSi FWD. I bought it a couple years ago with a completely blown clutch. I replaced it, along with a lot of other parts immediately after buying it (clutch change #2). Again, I filled the transmission with the exact same oil. (2nd gear grinded afterward) Unbeknown to me, one of the bearings for the input shaft was eating itself, and within a year of driving, there was so much slop in that bearing that the tranny continually popped out of 2nd. So I dropped and rebuilt the transmission.

I put in new syncro's and bearings, gapped out spacers, and checked for general wear on everything. There was a LOT of aluminum shavings... pretty much everywhere in the transmission from where one of the gears was grinding against the housing. The dogs on every gear looked fine. I cleaned the bejesus out of everything, but I think I overlooked the keys for the 1st/2nd shift collar. The rest of the keys did have quite a bit of shavings gummed into them.

The only that seemed strange was whereas 2nd's old syncro had dog teeth around the full circumference of the outer ring, the new one didn't have half of the teeth. It looked as though it was divided up into 6 equal sections, and every other section just didn't have teeth. Both old and new syncro's are the 3 piece design.

I assumed (always a good choice, right?) this was an attempt to remedy the notorious grinding problem this gear had, so I tossed it in.

I put everything back together, with a new clutch and flywheel (clutch change #3), but this time I put an ACT lightweight flywheel in. I did notice that the clutch wouldn't completely disengage when I pressed the pedal, and after dropping the tranny (again), determined that it was due to the slightly greater gap from the flywheel friction surface to the surface the pressure plate bolts to. The T/O bearing would need to travel slightly further than mechanically possible to completely disengage. Starting the engine with the car in gear and driving a block wore down the clutch enough to completely disengage it.

I did a creep test in every gear... passed every time.

I drove it nice and gently for about 500 miles. Everything was a gravy train with biscuit wheels. If I remember right, I did NOT change the oil after breaking in the tranny. Dumb/lazy/cheap, I know...

About 250 miles after that, 2nd starts grinding again... not too bad at first, but today it does it hot or cold, less frequently the warmer it is. WTF?! Everything else shifts flawlessly. That was about a year and a half ago, but 8 months of that I've been deployed, so she still doesn't have too many miles on the rebuild. 5,000 maybe.

The only time 2nd doesn't grind is when I shift VERY deliberately. As in gently pushing the shifter until I can feel the shift collar touch the syncro, and let it pop in.

Everything in the car is stock, minus the flywheel and an air filter... Even the shift knob is stock.

Too much info? I don't know, but I've given every shred of info I can think of that could potentially point to the problem.

I'm thinking of switching to the OEM recommended oil or AMSOIL to see if it helps, since I need to change the oil anyway. If any of y'all have fluid recommendations, I do not EVER plan on racing this car. I baby this thing, and the occasional "spirited" takeoff and hard cornering are all I ever do, so the super-ultra-mega-turbo-bad-arse oil isn't needed.

Thanks in advance, guys.

 

[bastarddsm]

Did you replace the 1-2 hub and slider? Were the teeth on the gear good and sharp?

To me it sounds like your synchro is gone again. I could straight power shift second in my car after i rebuilt it with a new double synchro second. 5000mi later, and I have to be a bit more careful to jam second good, but it still never grinds. So, there was something wrong upon assembly for it to be junk that quick with normal driving.

 

[bastarddsm]

Did you replace the 1-2 hub and slider? Were the teeth on the gear good and sharp?

To me it sounds like your synchro is gone again. I could straight power shift second in my car after i rebuilt it with a new double synchro second. 5000mi later, and I have to be a bit more careful to jam second good, but it still never grinds. So, there was something wrong upon assembly for it to be junk that quick with normal driving.

 

[luv2rallye]

... gapped out spacers

Did you do the shimming measurement properly with the crushed solder technique described here (also on p. 22B-33,34 of the DSM Backup manual): Dre

...determined that it was due to the slightly greater gap from the flywheel friction surface to the surface the pressure plate bolts to.

This is the flywheel Step Height and it must be exactly correct which is sometimes a problem on aftermarket flywheels if you don't also use their matching disc and PP. May need to have it machined correct. RRE's Clutch And Flywheel Tech Info

As far as tranny oil I use Redline MTL which is made for FWD. It sounds like your grinding is more than oil choice however.