Bits in transmission, the rebuild progress and questions

[yelcab1]

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


Picture 2: end cover off


Picture 3: 5th gear selector ring off


Picture 4:

[yelcab1]

Picture 4: Hub out


Picture 5: upper gear out


Picture 6: sequence of hub parts


Picture 7: 5th gear out


Picture 8: sequence of hub and gears

[yelcab1]

Picture 9: shift cover plate off


picture 10: worn 5th gear synchro


picture 11: broken 1-2 synchro


Picture 12: broken 2-3 synchro


worn 3-4 synchro


worn 3-4 synchro

[Oh Haha]

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.

[mike55]

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.

[yelcab1]

input rolling bearing out. It was by accident that I bought this puller kit 3 months ago.


output roller bearing out.


Sequence of first gear synchro, note the missing teeth.


Selector fork out, this time I measured the distance to the end.


Sequence of 1-2 synchro gears

[vash]

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.

[vash]

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..

[john walker's workshop]

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.

[yelcab1]

Originally Posted by john walker's workshop

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).

[yelcab1]

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?

[john walker's workshop]

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.

[yelcab1]

first gear sequence


Position of gap


Second gear sequence


Position of gap


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.

[john walker's workshop]

doesn't matter.

[yelcab1]

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,

[john walker's workshop]

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.

[yelcab1]

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?

[MBEngineering]

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



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).






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

[yelcab1]

picture 11: broken 1-2 synchro


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?

[coollx]

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.