Bits in transmission, the rebuild progress and questions
 

I tore into it, and there are more dog teeth to be found. It seems the 1-2 synchro are half gone, 2-3 synchro is also missing about 10 teeth, the other are all worn out but not broken. Gears seem to be alright.

Questions: 1) where to buy these? 2) should I change all synchros?

Picture 1: the starting point
http://forums.pelicanparts.com/uploa...1229287090.jpg

Picture 2: end cover off
http://forums.pelicanparts.com/uploa...1229287142.jpg

Picture 3: 5th gear selector ring off
http://forums.pelicanparts.com/uploa...1229287203.jpg

Picture 4:

Picture 4: Hub out
http://forums.pelicanparts.com/uploa...1229287285.jpg

Picture 5: upper gear out
http://forums.pelicanparts.com/uploa...1229287325.jpg

Picture 6: sequence of hub parts
http://forums.pelicanparts.com/uploa...1229287360.jpg

Picture 7: 5th gear out
http://forums.pelicanparts.com/uploa...1229287395.jpg

Picture 8: sequence of hub and gears
http://forums.pelicanparts.com/uploa...1229287436.jpg

Picture 9: shift cover plate off
http://forums.pelicanparts.com/uploa...1229287528.jpg

picture 10: worn 5th gear synchro
http://forums.pelicanparts.com/uploa...1229287560.jpg

picture 11: broken 1-2 synchro
http://forums.pelicanparts.com/uploa...1229287601.jpg

Picture 12: broken 2-3 synchro
http://forums.pelicanparts.com/uploa...1229287636.jpg

worn 3-4 synchro
http://forums.pelicanparts.com/uploa...1229287682.jpg

worn 3-4 synchro
http://forums.pelicanparts.com/uploa...1229287714.jpg

I would firmly recommend replacing all parts while you have it apart. You shouldn't have to touch it again for many, many years.

I wish I could go back in time to when I sent my trans out for a second gear synchro gone bad. I would save the cash and do it myself now that I have the knowledge an the Pelican forum.


Nice job on the documentation, BTW.

I've torn into many 901, 915, 914 and 714 transaxles - managed to put them back together too! There are many parts that makeup the Porsche synchro assembly. The simple answer (and less costly upfront) is to replace only the broken bits and those showing extreme wear. The best is to replace all wearable synchro items so you won't have to worry about it for years.

If you do it yourself, take lots of pics while you're dis-assembling for reference when you put it back together and have the workshop manual handy.

As daunting as the inside of the trans looks, it's not that hard to get it right. Pelican has all the replacement parts you'd need. Good luck.

input rolling bearing out. It was by accident that I bought this puller kit 3 months ago.
http://forums.pelicanparts.com/uploa...1229301710.jpg

output roller bearing out.
http://forums.pelicanparts.com/uploa...1229301730.jpg

Sequence of first gear synchro, note the missing teeth.
http://forums.pelicanparts.com/uploa...1229301777.jpg

Selector fork out, this time I measured the distance to the end.
http://forums.pelicanparts.com/uploa...1229301831.jpg

Sequence of 1-2 synchro gears

http://forums.pelicanparts.com/uploa...1229301888.jpg

wow, mitchell!!!

i was just about to post up and ask you if you needed help dropping your motor...hahah. looks like you got that part all worked out.

isnt there a hint to leave that gold forkie thing in place? buddy and i pulled one apart and i seem to remember reading something like that.

disclaimer: i dont know squat about transmissions..

measuring the fork position is a good idea, but you never know if the last guy did it right. the idea is to center the shift sleeve between the pairs of gears.

Thanks, I forgot to measure the position of the 5-reverse selector fork, so I was going to ask you what to do next. It also appears that the transmisison has been opened at least once before (the stake position of the big nut was different).

OK John Walker. Now that I have time to look at the damage, here is my plan, what do you think?

I am replacing the synchro rings on the 1st and 2nd gears
I am replacing the dog teeth on the 1st, 2nd, and 5th gears.

Everything else stays. Any big problem with that?

the shift sleeve and brake bands are a good idea to replace. may as well do a complete repair on that assembly. for sure, if you tear the rest down, you will find things that are worn somewhat and it'll cost you. i've done plenty of 1&2 only repairs.

first gear sequence
http://forums.pelicanparts.com/uploa...1229422129.jpg

Position of gap
http://forums.pelicanparts.com/uploa...1229422157.jpg

Second gear sequence
http://forums.pelicanparts.com/uploa...1229422198.jpg

Position of gap
http://forums.pelicanparts.com/uploa...1229422226.jpg

Does it matter where the gap is with respect to the gear?
I gotta take this to the shop to get the dog teeth out.

doesn't matter.

After taking the 2 synchro gears to 2 shops and they don't have the tool to remove the dog teeth gear, I tackled the job myself.

1) cut them off with dremmel tool, messy and took 90 minutes, with grinding bits flying all over the place. Not recommended. But, did get one off.

2) the second one, I followed the advise on this board and used the exhaust clamp trick, a gear puller, judicious use of a bench grinder, a large socket, and the thing came out in 30 minutes.

Now, I am ready for the gears to press back in (I have a bench vise for that.

Questions for the expert:

1) how do I line up all the selector shafts before I re-install the selector plate window (with the funny looking fork thingy)?
2) how do I ensure that the punch pin engages the reverse switch when I reinstall the end cover plate (the last step).

Thanks,

you may want to lightly dress the swaged tips of the splines that the dog teeth press onto with a fine file. the swage can distort the bore of the gear so the inner needle bearings bind a bit. don't take them completely off, just clean them up a bit. BE SURE that the detent in the end of the center housing is all the way down in it's bore before installing the housing. you can't change it later. the center housing and shift rod assemble over the gear sets, which need to both be in neutral with the notches in the two shift shafts lined up together. the end of the dongle sits in those notches. the guide fork must capture the dongle when the plate is installed. the 5th/reverse fork also needs to be in neutral before installing the end cover. the skinny end of the reverse light pin faces the switch.

Sorry for being dense. It is my first transmission.

Where is the detent in the end of the center housing? A picture would help if you have one, or can point to it on the diagram.

How can I tell if the all forks are in neutral. I mean, the 5-Reverse selector rod has 2 notches, I assume one for each gear, but where is neutral?

HI yelcab1
the photo of the center case detents for you ,

http://forums.pelicanparts.com/uploa...1229506680.jpg

the idea is NOT to loose No' 4 up the top, to/near No' 2.
and as for the selectors, as the box was shifting OK before it was stripped the set up should be good, even if some one has been there before you, as you now have puled the forks off the shafts thay will need setting back up (you did not need to remove any forks to dismantle the box).

http://forums.pelicanparts.com/uploa...1229507019.jpg


http://forums.pelicanparts.com/uploa...1229507042.jpg

as Mr john walker has pointed out, you need the sincro hubs in the neutral to set the distances on the sincro bands to slider .

the photos are for your education only.

regards mike

picture 11: broken 1-2 synchro
http://forums.pelicanparts.com/uploa...1229287601.jpg

I am buttoning things up but I run into a strange and baffling issue. Look at the picture above, this is how my tranny was before. The first gear to the left is bigger than the other gear, has the unsymetric dog teeth and is referred to as 1st gear in the Bentley manual. The same bentley also states that the synchro ring with a groove should go into the first gear, and yet my tranny has the grooved synchro ring in the smaller gear, which is referred to as the 2nd gear. To further throws things off, the picture in the Bentley shows the 2nd gear to be bigger than the 1st gear.

Before i button this up, can someone shed some light on this? What is right?

yelcab1, I'm going through a 915 tear down and rebuild right now as well.

Here's what I've learned.

-First gear is bigger than second gear even though it doesn't appear that way in
the bentley book.
-First gear has asymmetrical dog teeth on the syncro
-The first gear syncro ring has a groove but the second gear syncro ring is solid
with no groove.

Hope this helps.

subscribed

in post #13, i don't see a groove in 2nd syncro.

OK, I buttoned up the transmission,
http://forums.pelicanparts.com/uploa...1229731627.jpg

put it in the car, top off with fresh Redline MTL (note the newly finished gleaming fan on the newly rebuilt alternator)
http://forums.pelicanparts.com/uploa...1229731691.jpg

When you finish a job this big, there has got to be some left over bits, so here are the bits:
http://forums.pelicanparts.com/uploa...1229731751.jpg

So, I drove it for 5 miles, it shifts fine, drives good, but there seems to be more noise from either the gear box, or the CV joints (I can't tell). I went back and checked all my work visually and mentally, and I think I have done everything right. Except that there is one thing I am unsure of and that is the reverse idle shaft... I am not sure if the end of the shaft is engaged with the ball totally... Unless the experts have something obvious to suggest, I am just going to drive it for one season (I put just 3K miles on this a year) and see where it is next year.

Next time, if I ever do this again, I would make a check list and check it off once at the intermediate housing and once more at the end cover. Too many things for the first timer like myself. Take very good notes and lots of pictures on the disassebly so you have some reference on re-assembly.

Finally, thanks to JW, and all others who gave advise, and info. Oh, and that yellow thing is the new member of the family who just joined when the Porsche was in the operating room.
http://forums.pelicanparts.com/uploa...1229732204.jpg

Awesome:D:cool:

Viva Desmo!

HI yelcab1
is the noise still there in 5th?? or has it gone!!

regards mike

Hi Mike

The noise is not noticeable in 5th, but at high way speed where I use 5th gear, there are so many other noises from the road that it is hard to tell.

The noise is not a grinding noise, not a groaning noise, but more like a gear slapping noise. I did torqued the two big nuts tight with an impact wrench (1/2 inch Ingersol Rand) which easily hits 150 Nm.

HI yelcab1
when you set the 5th/Rev selector, did you set it up as the photo with APP' 1mm gap, the prob' could be the Rev' idler could not have been located/pushed fully home up against the thrust bearing and the support shaft, you did fit the thick flat washer on the end with the Rev idler??

regards mike

Mike

Yes to all the above. I did push the Rev Idler against the thrust bearing, and set the gap between 5th and Reverse to 1mm approximately. I also put the big flat washer on the end before the O ring gets installed.

There are very many 915 threads on here with tons of great repair info, so i'm surprised by some of the questions you posed:

>Redline MTL? Should be using a mineral oil, as the 915 doesn't like synthetic. Do your new synchro assemblies a favor and put some Swepco or Castrol 80W90 in there.

>With broken dog ring teeth everywhere, I hope you did decide to take JW's advice and replace the slider/shift sleeves. The sleeves directly act on the dog teeth, so these sleeves that have broken off the dog teeth is certainly going to be beat up as well

>A puller is not necessarily needed to disassemble the gear stacks- gravity works every time. Strike the shaft on a hard table top and off drops everything. It should be clarified that you did this because you didn't want to pull the shafts from the bellhousing (bearing retainer plates were left in place), correct? Hopefully your bearing separator assembly did not harm/distort the bearing cages- is it possible this could be causing your noise?

>Torque the collar nuts with a impact wrench? Hmmm..........

Hello Kevin

Thank you for jumping in to offer assistance and advise.

1. Redline, I am partial to that stuff which has been proven to work in my BMW's for 20 years. I did try the blue stuff before on a previous 84 Carrera, was not impressed and has avoided it since. I understand many people prefer Swepco, me not included.

2. I inspected the 1-2 slider and found that it was not damaged, or excessively worn out, so I elected to save the $200 and not replace it.

3. A puller was necessary in my case because I did not want to remove the gear stacks like you said. I did look at the bearing cages and found them to be undamaged. But, if they are making that noise, then I am comfortable leaving the noise as is until the next winter when I drop the engine again. Unless, of course, you can educate me as to why I should fix it now. It is for me all my labor (plus fluid) so that is sort of free.

4. The impact wrench method was deployed because the tranny was sitting up side down on the floor, I did not have the proper locking tool, and therefore it was impossible to use one of my 4 torque wrenches on the nuts. What I did was a rough torque angle method by using the impact wrench to move the nuts back to the same positions before they came out. The smaller nut has the cotter pin position marked, and the bigger nut has the stake position easily identifiable. This is roughly the torque angle method which is perfectly acceptable and in some circle preferred to be more accurate than the clicker wrenches. Porsche headnuts are torqued that way (used to be anyway).

Oh yes, I did a lot of searching and reading up on it, but ... nothing beats getting your hands dirty.

So, Kevin, should I drop it again or drive on it for a while?

Well if you like the Redline and have had good results, then for sure stick with what you know. BMW's are a different synchro design with the Getrag transmissions, so that's akin to driving a G50 in Porsche-speak, and hence Redline would certainly serve those transmissions well.

I don't blame you for saving $200 if the slider sleeve was still good. They are not easy to inspect because most don't really see how these wear and therefore think they're in good shape, when in fact it may not be. Only reason I suggested the slider replacement is because we viewers/armchair mechanics are looking at photos which show a slider that was operating on a dog ring with many teeth busted off, so it's a natural reaction to assume the slider is notsogood.

If the bearings look good, then great. My comment was based on:

1. the puller pulling on a bearing cage, which one typically doesn't want to do. Those pullers usually grip on a hardened race part of the bearing.
2. You said you now have noise, which is typically bearing-related or gear mesh related. The puller made me think the bearings might have been tweaked a bit during pulling.

I don't debate the impact method of reinstallation if the nuts return to the same position they came from- assuming they were torqued well by the last guy. But you don't need the special locking tool (the splined Y-shaped gig that bolts to the bell housing) if you lock the trans in two gears at once.

Good of you to clarify some things so somebody who comes across this thread in the future knows why you chose to do things a certain way. Agreed nothing beats getting your hands dirty. I've done three 915 repairs myself on three friends' cars. So I know there's more to wrenching on these things than just what you read, and you can't type every single thing you've done.

I don't know what to tell you about the whining, other than the obvious- it shouldn't whine. Before tearing into it again you should make sure you're not imagining things. If you can drive somebody else's 915, if you haven't already, that might give you some point of comparison???

Good luck. And good job knocking out a job most people spend weeks doing!

Kevin

One thing you can clarify for me is ... the position of the reverse idler gear shaft. It is the shaft with a big notch in it for the 5th gear to fit into. The end of that shaft is pushed into the case and supposed to be engaged with a ball, right? Does one push the rod in until it clicks? That part, and the 2 main bearings are the only iffy things in this job that is worth checking again.

An engine drop is 3 hours for me (and 3 more on the way back in) so if my company forces me to take another week of vacation shut down, I might drop it again.

A little hint for you. No noise at steady speed in 5th gear. If it happens, it is not a whine, but more of a rattle. Last, in a slow left hand turn, the noise is more noticeable (that leads me to think of CV joints)... But my mechanic side is telling me it is related to the last job.

One last question, my clutch pedal has about 1/2 inch droop. I can use my foot or my hand to pull up on the pedal, and when I let go, it drops back down about 1/2 inch or so. Is there an adjustment at the pedal box?

did you remove the fork from the 5th/reverse shaft or did you just pop it off with the slider as a unit? a rattle noise audible in gears 1 thru 4 but not in 5th or reverse would be indicative of the reverse idler teeth contacting the 5th /rev slider. if you didn't remove the fork, that probably isn't the issue.

JW,

I did remove the slider, did not measure the distance the the end, and used the Bentley manual method to reinstall the fork (with the 1mm clearance). So, if that was the issue, the fix is to drop it, open up the end cover, and ... ?

reposition the fork?
reinsert the idler shaft?

you would move the fork/slider a bit closer to 5th. you could jack the car up, put it on jackstands, fire it up, put it in 2nd and use a hose in your ear or a sterhoscope to locate the noise. should be obvious if it's in the end cover.

added some text in bold above

Kevin,

What should the two the nuts be torqued to???

John
my1badvw@msn.com

Mike,

The pictures you sent for our education! What manual or book is those out of?

John
my1badvw@msn.com

I've used redline MTL in older BMW 2002 and 320i Getrag gearboxes with the brass cone type borg warner synchros and it's almost magic how much better they shift with it in there.
But, it's a synthetic GL4 oil and is much thinner than the GL5 oil that belongs in a 915 or 930 gear box.
Redline Manual Transmission Lube or "MTL" is almost as thin as automatic transmission fluid and the overengineered porsche synchros wear faster in synthetic oil apparently because it's too slippery for them. That could be part of the problem before and again in the future.

I know some very experienced street and race mechanics that don't like swepco and won't use it. They like the plain old inexpensive valvoline nonsynthetic gearbox oil that was the best thing there was back in the 70's and 80's.
Valvoline gearbox oil is what went into all the 935 and 962 gearboxes back in the mid 80's when I worked at gunnar porsche.

They had a Porsche with swepco in it that would not shift out of 5th gear at Daytona. They brought it in and drained the swepco and put in valvoline and after that the transmission shifted correctly.

Those tranny shaft nuts with the neck on the end that gets bent over into the keyway on the shaft aren't too expensive and you should use new ones, especially the third time.
And an air impact gun should not be used to torque down those shaft nuts. you could damage something or over tighten it that way.
With the cover off the bottom you can gingerly use a big screwdriver or prybar to move the shift rods and forks to select 2 gears at once to keep the shafts and gears from turning while using a torque wrench to tighten the nuts.

Final chapter:

After 200 miles, the noise is gone, so whatever little interference was there is no longer interfering. Ground down, or ... I am going to let that sleeping dog lie undisturbed.
The pilot bearing and the throw out bearing are noisy and will get replaced the next year when I do my annual engine out regimen. I might open up the tranny again at the front to make sure nothing really bad happened.
I do need to adjust the shift coupling a little bit to engage reverse a little better.
I will leave the Redline stuff in there for the moment and may switch over to Valvoline in a few months. No hurry on this one.

Epilogue: I had 3 915 trannies in the last 15 years and they all broke. It is likely the way I drive. I am very used to BMW, Acura, and Toyota manual gear boxes and I shift the 915 the same way. It is very likely that the 915 and I are not best of friends and may never be. On the other hands, double clutching (in the last 15 years) showed that the synchro rings were barely worn at all, including the ones I took out of this 915 this time.