915 rebuild questions (several)

[djmcmath]

I'm most of the way through taking my 915 apart, thanks largely to Randy (rcecale -- excellent documentary!), Ingo Schmidt, John Walker (many many thanks to you!), Marqesc, Chris Bennet, and dozens of others who have posted useful tips and pictures and hints and all sorts of neat stuff. Without knowing where to deviate from the Bentleys and without the confidence of seeing real people go through this mess before me, I never would have done this.

The car in question, BTW, is an '86 3.2L, mostly stock. I do not track it yet, though I'd like to eventually. The clutch and flywheel were replace about a year ago by the PO. Mode of failure was gradual, and I should have seen it coming -- 1st gear synchro has completely lost it's frictional surface, so I couldn't shift into 1st when the car wasn't moving. Last oil change, I spotted dog teeth in the magnetic drain plug, and first gear felt a little uneven through the shifter after that. Then last friday I was pulling away from a stop sign in 1st and it dropped out. I limped home (against what was really better judgement; the 10 minute flatbed would have been reasonably affordable, I'm sure) and decided to do the rebuild.

So here I sit, with a pile of 915 parts littering my garage floor, largely in Ziplocs with cute little labels on them, looking at a list of replacement parts that comes to about $1700 -- all of the rings, synchros, and sliders. Boy, that's a bunch of cash!

So question 1 -- how unrealistic is it to think that the 5/R slider ($431) is probably not going to get a whole lot worse than it is (it doesn't look bad at all, really), and will probably not fail before the 1st gear synchro fails again, and just skip replacing that one? How unrealistic is it to assume that the 3/4 slider will continue to work correctly for another couple of years? How bad (read:lazy, cheap) is it to just flip the synchro rings? Is it safe to flip them if they're visibly out of round? I guess what I'm really looking for is the experienced "signs of wear" determination -- I'm not at all sure what the parts would look like new, so maybe the teeth are more rounded than they really ought to be. Help?

Question 2 -- If I'm going to spend $2000, is there another good alternatives stepping up marginally in cost? I know the G50 upgrade is of marginal benefit and runs about $5000, which doesn't seem at all worth it to me. What about the Wevo 915 rebuild -- what does it cost, and is it worthwhile?

Question 3 -- If I'm going to spend all this money anyway, is there anything else internal to the tranny that really makes sense? Obviously the Wevo single-piece bearing plate makes sense at a practically trivial $250 -- what else? Does anybody make better synchros that can be installed? Are there aftermarket bearings or forks that are worth looking at?

Question 4 -- mode of failure was dog teeth from 1st gear synchro getting torn off the ring and going flying around the inside of the tranny and diff. I've taken apart the diff to look for little bits of metal (dog teeth), and have found a couple. How far apart do I need to take that thing? I mean, after you pull the access cover, there's only that one large piece in there -- do I need to take that apart to look for metal bits? How is this accomplished? Would it be wiser to just replace it with a newer/better/lighter/faster/spiffier piece?


Ok, that's all the 915 questions I can think of right now. Thanks again to all the folks who got me to this point -- I never would have had the confidence without reading Randy's thread, mostly supported by John and Ingo. You guys are amazing!


Dan

[ChrisBennet]

Q1: I would stone off the burrs on the edges of the "grooves" on the 5th/Reverse slider. The stones I'm talking about are called (machinist's) oil stones, "tool room finishing sticks", "abrasive files" or stuch. I use a 1/4 or 1/2" triangular one.
-Chris

[john walker's workshop]

i rarely replace the 5/rev slider. the hub it slides on gets large notches worn into it though. flipping syncros doesn't sit right with me. replace them all. the 3/4 slider is generally worn out. compare the little contact pads on each side (the surfaces that first contact the syncro). one side is usually worn wider than the other. the diff unit comes right out after taking off the drive flanges. just search around in the spider gear area for little bits. no need to disassemble.

[djmcmath]

Wow, 15 minutes posted and my humble post attracts both JWW and Chris Bennet! Thanks for the help, gentlemen!

Ok, I'll replace the synchros. Checked the contact areas, as you suggested, and sure enough, they're pretty well worn on 1/2 and 3/4. Hadn't even occurred to me to look at those. How do you tell if the brake bands, stopping blocks, etc are in need of replacing? Mine don't have any notches are unevenly worn places, though they look perhaps more round than they did when they were new.

The diff is dismantled, inspected, cleaned, and re-assembling. Thanks a bunch for the confidence that I don't need to take apart the diff itself.

Chris -- thanks for the advice -- I'll hunt down a "stone" tonight. What a way to spend a Friday night, eh?

One other question -- having pulled the circlip off the gear, how do you get the dogteeth off? I've tried the chisel technique, and it worked great on #1 ('coz there weren't any dogteeth left, maybe?) but it isn't working at all on #2 -- any hints for removing those?


Thanks a heap, guys -- you have no idea how much I appreciate your help.

Dan

[ChrisBennet]

Originally posted by djmcmath
I'll hunt down a "stone" tonight. What a way to spend a Friday night, eh?

Dan

Just say no to drugs.
-Chris

[rcecale]

Dan,

Looks like The Masters have found your thread. You are surely in good hands!

WOW! I'm glad I helped influence you to do it yourself. Once you complete the job and are back on the road, you'll see how easy it really is/was.

As far as separating the dogteeth from the gears, I used a chisel on both of them. My first, as you may have seen, was pretty much shot, so yeah, the chisel went right under the dogs. Second, well, just hold the gear steady, perhaps in a vice and keep working it til you can get the tip of the chisel underneath the dogs. My chisels were brand new, so the tip was nice and sharp. Just keep at it, you'll get it!

Cheers!

Randy

[djmcmath]

Randy -- tnx fer the encouragement. Always good to know I've got a DevilDog in my corner. What kind of chisels did you use? My little Sears chisel seems to be blunting on the dogteeth. I could take it back down and say "replace this 'coz it says Crafstman" but that'd get real old after about the first 3 trips this weekend.

Tnx again for the help, all.

Dan

(Friends don't let friends work on their cars while stoned...)

[john walker's workshop]

if you chisel the teeth off, use jaw pads on the vise. just raise it enough to get a couple of prybars under each side to finish working it off. there is a tool that does that. not too expensive and you can resell it later. wear eye protection. i always replace all the brake bands. you can't tell if they're good or bad unless they're mashed on the ends. they're a very important part of the syncro function.

[john walker's workshop]

if you chisel the teeth off, use jaw pads on the vise. just raise it enough to get a couple of prybars under each side to finish working it off. there is a tool that does that. not too expensive and you can resell it later. wear eye protection. i always replace all the brake bands. you can't tell if they're good or bad unless they're mashed on the ends. they're a very important part of the syncro function.

[rcecale]

Dan,

Believe it or not, my chisel was a 1/2 inch Buck Bros WOOD Chisel. It worked like a champ!

I don't mean to insult your intelligence, but I figured I'd post a pic of how I positioned the chisel.


edit: Oh, one more thing. Try working the chisel around the diameter of the dogteeth. It will give, just have patience and stay on it.

Semper Fi!

Randy

[djmcmath]

John -- thanks for the wisdom. I'll replace the brake bands, then. What about washers and bearings -- those look mostly good, but again, I'm not sure what I'm looking for. Obviously the bearings have all their rollers, they don't make funny noises when you move them or shake them vigorously. There doesn't seem to be much play, but then, I don't know how much is normal.

Any idea what that tool is named, the one for prying these doodads off? I've got a great little small-town tool shop here, with an old guy who can get all kinds of random stuff.

Randy -- that's exactly what I'm doing, except it's a 1/4" Craftsman, instead. I've been tapping at one spot, then rotating 120', then tapping again, then rotating ... 1st came real easy, 2nd isn't budging, so I was worried I had dorked something up. I'll just keep at it.

Oh, and Randy -- don't worry about insulting my intelligence. It helps to know that I'm doing The Right Thing.

Thanks again, guys. I'll post again when I make progress.

Dan

[ChrisBennet]

Originally posted by djmcmath
John -- thanks for the wisdom. I'll replace the brake bands, then. What about washers and bearings -- those look mostly good, but again, I'm not sure what I'm looking for. Obviously the bearings have all their rollers, they don't make funny noises when you move them or shake them vigorously. There doesn't seem to be much play, but then, I don't know how much is normal.

Any idea what that tool is named, the one for prying these doodads off? I've got a great little small-town tool shop here, with an old guy who can get all kinds of random stuff.

Randy -- that's exactly what I'm doing, except it's a 1/4" Craftsman, instead. I've been tapping at one spot, then rotating 120', then tapping again, then rotating ... 1st came real easy, 2nd isn't budging, so I was worried I had dorked something up. I'll just keep at it.

Oh, and Randy -- don't worry about insulting my intelligence. It helps to know that I'm doing The Right Thing.

Thanks again, guys. I'll post again when I make progress.

Dan

This what the tool looks like:


There are a couple, one for 1st/2nd and another that fits 3rd/4th/5th. I have drawings of them if someone has a machine shop and wants to make their own. They run about $100 each so I doubt it would be cost effective to have them made.
-Chris

[djmcmath]

Oh, those are the "sychro hub removal tools" that our host sells. For $200 for the pair, I'll spend another hour or so carefully beating my transmission to smitherines with a chisel. If I still can't get it, then I may end up adding 2 of those babies to my order. Thanks, Chris.

Dan

[rcecale]

Keep at it Dan, it'll come!

One question, have you got access to a press to put the new ones back on? You'll need it.

Randy

[djmcmath]

A press? Um ... I can find one, I'm sure. (fingers crossed) I'm assuming it would be a crime punishable by death to gently tap the thing into place with the rubber mallet, right? Just checking.

Thanks again -- and Randy, I read your whole thread, I can't believe how far you've come! I'm having a hard time reconciling the Randy of 4 months ago asking "Is this a good spot to set the jackstands" with the Randy of today.

Dan

[rcecale]

Dan, if you're able to "gently tap the thing into place with a rubber mallet", I'll buy you a bottle of your favorite adult beverage.

You're gonna need a lot more pressure than you can generate with a rubber mallet, or even a steel hammer. AND....you'll want to make sure the gears aren't crooked when they go together...you'd just be creating more problems for yourself. Matt (UT_KharmannGhia) pressed his together with his vice, but I wasn't having any luck using mine.

If you need to, find a local machine shop or something, and have them do it. I used a local Porsche Shop that I had done business with in the past. $20.00 bucks for the peace of mind that they're going together properly is certainly worth it. As expensive as the parts are, you only want to buy ONE set of replacements.

Randy

[ewave]

When I was replacing the dog teeth, I froze the gear in the freezer, and heated the dog teeth in oil. Then I tapped them together with a brass hammer. I figured I had about 5 seconds to do this once the two pieces came in contact. It worked great!

[djmcmath]

I just resharpened my chisels, and the 2nd gear is now in the freezer. I'll try your little trick in the morning. My arms are tired from tapping on this thing all day long. I think I'm just beginning to get a little gap on one side, but I could be imagining it.

Randy, given your words of wisdom, I'll just take it to the local machine shop. (sigh) I hate paying someone else to do my work, though....

BTW, thanks again for all the support, gentlemen. I would have long since given up and paid a mechanic to rebuild this thing if it weren't for you.


Dan

[ewave]

The freezing/heating was for putting the parts back together... Not taking them apart!

[djmcmath]

Oh.

/disappointed.

/feeling sheepish.

Well, thanks for the idea. I'm going to go back to hitting my dogteeth with a chisel. (sigh).

Dan