915 rebuild questions (several)

[Porsche_monkey]

Originally posted by rcecale
Dan,

One thing to ask about, do you have the copper gasket spray and Loctite 574 for when you put the case back together. The spray you can pick up at any auto parts store. The Loctite, if you don't have it, is difficult to find. You may have to check your local Porsche wrench, or order some from our host. Don't forget the Swepco! Consummables always seem to be the overlooked items we end up needing the most.

Randy

Sine I have a big leak on my 915 that I will be fixing next week:

Why do you need 574 and copper spray? Are there mating surfaces without gaskets?

[djmcmath]

Got it, thanks Chris. Your picture is perfectly adequate for mechanically inclined people. Until about a week ago, transmissions were just expensive black boxes to me, and I honestly couldn't tell a swage if I met one comin' through the rye. Your pictures help a lot; the captions really bring it together. I gotta be honest, I'm up to my ears in alligators on this project. In all reality, I'm not really rebuilding a transmission -- you all are rebuilding a transmission, and I'm just a set of hands on the wrong end of a long copper wire.

(sigh)

PBH, my thought with the gasket is to do what Chris Bennet suggested above, about halfway down page 3. I'm thinking that the copper spray and the 574 are probably redundant, so I'll rub the 574 into the paper gasket (CB), but not too heavy. If you go too heavy, it may squeeze out and tear the gasket (JWW). Then, apply a thin coat of WD-40 to the studded side of the gasket surface to make it easier to clean next time you go in. (CB) Most of that comes from pg 2 of this thread, though I think JWW's note about excessive sealant I think comes from another thread.

Dan

[Porsche_monkey]

The wrong end? I don't think so.

Let me know how the 574 impregnated gasket works out please. I'll be doing mine next week.

[djmcmath]

Ok, problem. I went to put 1st gear together, and discovered that the brake-block wouldn't go onto the brake band. The reason is that the brake-band notch is cut in different places on each side. Some pictures:

Randy's 1st gear brake band, complete with notches and anchor block, for reference purposes (thanks for the excellent pic, Randy!):



Quickly Drawn closeup of the notches in mine:




The question -- is that offset normal? My anchor block is shaped just the same as the old one, with no offset between the two sides. Is this a manufacturing problem, some new change that requires a different part, something I'm imagining? Help?


((BTW, I carefully dressed the swage on 4th gear with a tiny grinding wheel, hit it with WD-40, and tapped it "gently" into place with a rubber-faced mallet. Who knew? Thanks a gazillion for the help!))


Dan

[djmcmath]

Anybody? Is this normal? Help?

[john walker's workshop]

that offset notch doesn't look normal to me.

[djmcmath]

Your word is good enough for me. I'll call Pelican in the morning and arrange for a replacement. Thanks, John.

[john walker's workshop]

you might order a new stop also. sometimes the groove is too narrow for the new band. cheap, just in case.

[djmcmath]

Yup, got the new stop already. As per your earlier recommendation, all of the stops, bands, blocks, and rings were part of the original order.

Thanks,
Dan

[djmcmath]

Alright, Pelican happily agreed to send me a new 1st gear brake band, free shipping and all. That's good.

Next question -- when 4th gear went on, it went pretty stiff. 1, 2, and 3 slid right into place with no hassle. The tolerances seem clean, but the gears turn freely. Not so much with 4th -- while I can spin the others with a finger, 4th requires that I grasp it and turn to make it rotate on the shaft. Also, it spins counter-clockwise more easily than it spins clockwise (or maybe I've got that backwards). My gut instinct says that this is a serious problem -- I may need to replace the bearings, the race, or something, but I'm not sure what. Maybe it's something simple, like me being stupid in the assembly process? Randy, did you see anything like this when you were putting yours back together? Anybody else familiar with tight gears like this?

Thanks again, guys,

Dan

[john walker's workshop]

it needs to spin freely on the inner bearing. what happens occasionally, is the inner bearing surface distorts from the effort required to press on the syncro teeth. i've seen the bearing seize and the trans freeze up on a 914 1st gear after a new set of teeth. take it to an automotive machine shop and have them resize the bore on their sunnen hone. supply one of the other good gears so they can match it.

[djmcmath]

I was afraid of that. Instinct said that the extra force required to turn that one would produce excess heat, which would eventually cause real problems. (insert cursing here).

Thanks for the prompt and informative reply. I'll see if I can get it down to the local machine shop today.

Dan

[rcecale]

Originally posted by djmcmath
((BTW, I carefully dressed the swage on 4th gear with a tiny grinding wheel, hit it with WD-40, and tapped it "gently" into place with a rubber-faced mallet. Who knew? Thanks a gazillion for the help!))

Originally posted by john walker's workshop
what happens occasionally, is the inner bearing surface distorts from the effort required to press on the syncro teeth.

Geeze, Dan. Just how "gently" did you tap it?

Actually, no, I didn't have any problems like you mention. Did you take a look at the bearing at all? There is that needle bearing, that, if I remember correctly fits between the gear and the shaft. Could that be damaged?

Randy

[djmcmath]

You know, I thought I was being pretty gentle, really -- I even used the rubber mallet, instead of the plain old hammer! My bad, I should have just hunted down another bench-vice.

The bearing doesn't look bad, but then, neither does the race, so I must admit that my eyeballs aren't nearly precise enough to pick out the problem. My thought is that the bearing and inner race are the same parts that came off, they worked fine before, and haven't seen any abuse. The gear/outer race were involved in that nastiness with the mounting of the synchro hub, so they're more likely to have been egg-shaped-out.

My plan is to take it down to the local Napa or Westbay this afternoon. Some of those places have machine shops in the back where they rebuild trannies and engines and what-not. With some luck, they'll be able to mic the race and confirm that it's out of round before I spend a billion dollars having it honed.

(sigh) I'll post again when I know more. Thanks again for all the help, gentlemen.

Dan

[Porsche_monkey]

There is something to be said for persistence.

[john walker's workshop]

it takes about 2 minutes to choose a mandrel and pass the gear over it a few times, so it should be cheap. the distortion will be on the end with the syncro teeth. doesn't take much for the bearing to bind. been a while since i had to do one since i deburr now and use a press.

[djmcmath]

Well, it's down at the local shop. If they decide to work tomorrow (I love small towns), then they might be able to finish it by late Thursday, if they decide to work Thursday. Did I mention I live in the middle of nowhere? (sigh) That's another couple days lost.

On the bright side, Pelican gave me no hassle about swapping the bad brake band, which helps. Then I'll at least have all the parts I need (hopefully). With some luck, I could be driving by Sunday afternoon! (fingers crossed)

Dan

[rcecale]

Dan,

I'm flying out there on the 19th and am hoping for a PNW Pelican thing around the 25th. Hopefully you have plenty of mileage racked up by then!!!! Good luck, and stay with it!!!

Randy

[Porsche_monkey]

There is something to be said for unrelenting persistence.

[rcecale]

Soooooo, have you been out running around with your freshly built tranny, or what????

Randy