Monday, November 28, 2005

How to make grinding sounds vanish: lubrication!

In an earlier post, "Running, but now a noise", I noted that on the last run of the spring PCA autocross at Marina airport, Seaside, CA, I was greeted by a loud whining sound emanating from the transmission area. A whining sound that went away when I depressed the clutch. Since then I had only taken Legs out for very short runs, hoping the sound would go away. No, I didn't actually think she would heal herself (though hope springs eternal for the busy and lazy). In the summer I took an afternoon to see how quickly I could replace a throw-out bearing. The thinking was that the pressure-plate and clutch, pressing against a worn-out bearing would silence it, under load, and aligning it under pressure to better than the noisy, sloppy state with the clutch out.
Alas, this was not the problem (more on that if you stick with me here), but I did learn some things. To wit: if you get past the idea that removing your engine is a daunting task, you can R&R a throwout bearing in two hours. I did, and I even had problems with one of the engine mounting bolts (small problem really, requiring more joints in my wrist and elbow and shoulder and wrenches on the starter-side nut than I had available--but I finally got it). I didn't drop the engine completely, but just back and low enough to swap out the bearing. I surprised myself, but still don't live up to those weekend racers that do complete engine swaps between classes and other feats of motoring heroism (let's not even start on what drag racers do!). So I pretended I was in the garage at LeMans, and could still save a first-in-class over those less reliable Matra-Simcas if I could jest get back on the track and log some more laps within the next three hours.
When I took Legs with her new T/O bearing down to the grocers, my heart sank as the sound was still there. No worse, but no better. I skipped the AutoX the next day, didn't make the required 4/6 events in order to score class points for a trophy, and never got to go heads-up against the only other Class Ap entrant of the year.

I was sure that the noise was then coming from the input shaft main bearing. The shop manual illustrations showed that this was a likely candidate for the noise. It fit the symptoms. I ordered a replacement bearing at modest cost. Then went to the shop manuals again and started reading the procedures. Perhaps I should stop trying to educate (and scare) myself before starting any project of this kind. Because it stopped me cold. I started investigating purchasing a new (used) transmission. Opportunity for upgrade, it would be a 741 trans, I would take it to Ron's Transaxles up in San Pablo and have them go through it, I would swap out the stock 716 nose cover (to match the mounting points and A-shifter) and I'd be better than new. But that was a serious $$ commitment, and the $$s didn't fall into my pocket over the summer.

Eager to make the Coastal Driving School's December event at Laguna Seca, I was ready to dive into the removal of the transmission during my T'Givings vacation. Luckily, the lightbulb went off in my head before I did that major surgery (done once before in 2000 to replace a broken hockey stick, but that's a different story). I thought, "check the fluid in the transaxle before you do the Full Monty".

I did, on Wed. Nov. 23, and was rewarded (kinda, but considering the alternative, you know) in only a pint or so of transaxle fluid falling out of the drain hole. The shop manual confirmed a 3.5Liter (3.17qt) normal operational volume, so I was sliiiightly low. Drips on the bottom of the trans case at the median line were observed, and one of the swing axle boots had a tear. Enough to lose 2.75 quarts? Over 4 years, and hard driving, yes. Nary a spot under the car (observed, anyway, there may have been some on the gravel drive) means that the loss was under pressure and probably mostly on the freeway at high gear speeds. The exit point was likely the boot and also at the nosecone-to-trans-case junction. Where, in 2000, I neglected to reinstall the new paper gasket. There's a metal-metal contact there, which shouldn't be, but which is almost good enough, but not quite. So I will be R&Ring the transaxle to fix (rather than patch with a transfusion) this problem, but not until 2006 and warmer/drier weather. And maybe I'll find a good deal on a 741 transaxle when I'm not shopping under a deadline.
The Porsche Gods smiled upon me, when after pumping (and pumping, and pumping--something like 150 strokes of the hand-pump per quart) in the requisite volume of Valvoline multigrade 85-140 gear oil (with the leaks I wouldn't trust a synthetic to stay in), and firing up Legs, the whining vanished like a toddler placed on Santa's lap.