Need Comments From 915 Transmission Experts

coollx · 11-08-2008, 12:44 PM

Yesterday I added the following picture, comments and questions to a thread I started on July 17th regarding why people thought my transmission was grinding going into 2nd gear thinking I could keep that thread alive. However, I'm hoping some transmission experts can take a look at this so I decided to start this new thread to get their attention. Of course, with the issues associated with the 915 this thread may have some educational value to non-experts like me.

In any case, I am now working on pulling my engine and transmission in hopes of eliminating my second gear grinding that I had written about previously. Here's a link if someone wants to read it. Why Do You Think My Transmission Is Grinding Going Into 2nd?

Today, I started unhooking things and draining the engine and transmission oil.

I screened the transmission oil and found two pieces of metal attached to the magnetic drain plug. A picture should be attached.

I wasn't sure what to expect when I drained the transmission but thought there would be more debris than these two pieces.

So I have two questions for the transmission experts on here:

1. Are these two broken pieces likely to be indicative of why I get grinding going
into second?

2. Once I disassemble my transmission, will I really be able to see where the
source of my problem is so I can fix it? I'm a bit concerned that my untrained
eye may have difficulty finding the problem. I'd like to be able to find and fix
the problem myself. It will save me some money and boost my confidence. I
just want to be realistic.

Comments and thoughts are appreciated.

Thank you.

john walker's workshop · 11-08-2008, 12:56 PM

a macro pic would be better for detail,. but they appear to be teeth from the syncro hub. that's what holds the syncro ring and what the shift sleeve engages with.

coollx · 11-08-2008, 02:33 PM

John, that is suppose to be a macro picture. I have an older digital camera so that may be the best I can do. If I find a way for a larger image I'll provide it. I may also have to consider buying a new camera so I can take better pictures if I do the transmission myself.

In the meantime, if those are teeth from the syncro hub would that explain why I'm experiencing grinding going into second?

Or would there have to be a lot more teeth missing or broken? For all I know the gear oil may have been changed before by the PO and more broken teeth could have drained out.

Porsche_monkey · 11-08-2008, 02:42 PM

Regardless of our diagnosis the state of your tranny will likely be rather clear when you pull it. You likely need dog teeth, synchro's, brake bands etc. And yes, you will need a better camera to get your tranny diagnosed here.

It will be a worthwhile investment, there are a lot of helpful people here. Pulling a tranny off a second time is no fun. Diagnose it here, get the right parts and do it right the first time.

john walker's workshop · 11-08-2008, 03:16 PM

macro just means you adjust the camera for the close up mode. the left bit looks like a syncro hub tooth, (a dog tooth). the other one looks larger, maybe a chunk off the slider hub, or a chip off a gear. whatever, tear it down and we'll see.

coollx · 11-09-2008, 09:27 AM

I know I need to get the transmission out of the car and start disassembly before any real conclusions about what's wrong can to reached.

But I think I have a couple of better pictures of the parts I retrieved from the drain plug. Hopefully they are attached.

By the way, it wasn't the camera's fault the original pictures weren't in macro mode, it was operator error. I guess I don't know much about the camera which hopefully will be ok as I proceed through the disassembly.

Oh Haha · 11-09-2008, 09:49 AM

Yep, dog teeth.

john walker's workshop · 11-09-2008, 10:13 AM

dog tooth on top, looks like fudge on the bottom.

Oh Haha · 11-09-2008, 10:39 AM

shiny, metal fudge.

mmmmmmmmmmmmmmmmmmmmm

Matt Monson · 11-09-2008, 07:01 PM

That second one looks like the inner teeth on the slider to me. Though the thought of fudge is appealing.

coollx · 12-02-2008, 07:04 PM

Over the last three weeks since my last message, I've managed to do my first engine/trans drop and just today disassembled the transmission with the exception of the input shaft. As soon as I figure out how I'm going to get the 41mm nut off the input shaft, I'll have that stripped of its components as well.

Hopefully, I'll have some pictures of the first and second gear components tomorrow after I've cleaned them up a bit so help diagnosing my shifting problem can occur.

This I can tell you from an initial examination of the parts, although I found two metal pieces when I drained the trans fluid and attached a copy of them previously, all the teeth on the gears and sliders seem to be present and accounted for. I'm not sure if I should be worried or pleased.

I also want to mention that the infamous thread entitled "Can't shift into first" by Randy (rcecale) started on 4/18/04 gave me the encouragement needed to buy this first 911, as well as the confidence to drop the engine/trans and to try to fix the transmission on my own. Of course that's because of the great support and guidance of the terrific members of this forum.

Stay tuned for the first pictures.

coollx · 12-03-2008, 09:27 AM

I think I have to get a new higher resolution camera but hopefully the following pictures can help the 915 experts give me some accurate feedback. As I stated last evening after I got the trans apart, there doesn't appear to be any missing or broken teeth or pieces.

Just to remind everyone....the reason for pulling and disassembling the transmission is because I was experiencing grinding when shifting from 1st to 2nd gear with greater frequency. Plus, it was hard to get the transmission into 1st gear at a stop without putting it in neutral first then into first.

The transmission shifted perfectly upshifting from 2nd-5th and downshifted perfectly from 5th-3rd. And reverse was fine.

As a starter, I've attached pictures of the 1st/2nd guide sleeve, 1st/2nd slider,
1st gear and 2nd gear. Since I have 14 pictures, I had to break them up into two
pieces.

While this is the first time I've had one of these 915's apart, I've read many of the threads involving 915 issues to become as familar with the way things look and work. The one thing that stands out in my mind, which may or may not be a issue, is the way the inside surface of 1st/2nd slider looks. It has significant grooves or a valley in the center, but for all I know that may be normal since I've never seen a new one in person. The only other observation I can make is that although none of the dog or slider teeth are missing, the points on some look pretty blunt.

Please give me your thoughts.

Thank you.

coollx · 12-03-2008, 09:30 AM

Here are the rest of the pictures which are 1st and 2nd gear.

coollx · 12-04-2008, 04:25 AM

I'm getting worried!

50 new views and 18 hours have elapsed since I added my pictures and no responses or comments?

Do I need to provide higher resolution pictures to show better detail? Or do I need to show pictures from different angles to help assess what might be going on? Would removing the
snap rings to show the condition of the parts under them be helpful?

Or is the reason I'm having shifting problems not obvious to even those of you with transmission experience?

Please provide feedback.

Thanks

Rot 911 · 12-04-2008, 05:04 AM

coolx, there are very few 915 tranny experts here so most of us are watching waiting for someone like John W to weigh in. You might want to send John a PM or email and ask him to take a look. He is a good guy.

john walker's workshop · 12-04-2008, 05:31 AM

nothing looks really horrible, but if you're after a good shifting 2nd gear, replace the shift sleeve, syncro, dog teeth and internal brake band. can't lose that way. probably should do 1st the same way. i'm not big on partial repair of syncro assemblies, and both 1st and 2nd constitute an assembly. we want 100% good, not 80%. are you leaving the rest of the trans alone?

porschenut · 12-04-2008, 05:59 AM

One post for every 100 views seems about average. When it comes to trannies, most of us "watch and learn" rather than contribute anything meaningful.

Porsche_monkey · 12-04-2008, 06:05 AM

If I had to choose between comments from three hundred self-proclaimed experts and one from John Walker I know which one I would prefer.

The answer to your question is in reply #16 above. Buy the parts and get it back on the road.

Not that it matters, but I had the same issue and did basically what John suggested above. Problem solved.

(And if the number of responses really matters to you post a thread about 'which oil should I use', or 'will this coll collar help?' or even better, 'Has Anyone Considered a V8 Conversion?'.)

coollx · 12-04-2008, 06:29 AM

John, thanks for responding.

I want a good shifting second gear and have no problem following your advice to
replace all of the 1st/2nd gear components.

But I do have a few questions for my own 915 knowledge and perhaps for other Pelicans as well.

1. Are the grooves or valley in the inside of the shift sleeve normal and part of the
design and construction of the part rather than wear as I initially suspected?

2. Since nothing looks horrible what do you think is causing the grinding?

As I stated, the frequency of the grinding has been increasing and if I attempt to shift from 1st into second at a higher rpm, (over 2500 rpm) although shifting slow and careful, it almost always grinds.

As far as the rest of the trans goes I am undecided. As stated, the rest of it shifts perfectly and predictably. Over the last few days I've been trying to think through the best way to engineer a method and tooling for removing then re-torquing the 41mm nut on the input shaft so if I wanted to replace the 3rd-5th gear syncros I could.

What do you suggest I do with the rest of the trans? Sorry for answering a question with a question.

john walker's workshop · 12-04-2008, 07:53 AM

well, being that you didn't find any broken dog teeth after finding some in the magnet, the trans was probably repaired previously and not totally cleaned out. you may not have noticed how your 1st/2nd shift sleeve was positioned upon disassembly, but i've found several of them installed backward, that is, with the assymetrical side toward 2nd gear instead of 1st. they do shift that way, but not so great. the inner design of the slider, if you could cut it in half and view it from the side is kind of a double hump. the outer tips of each spline are curved so they match the curved shape of the syncro's edge and the center dip is where the syncro lives so it can stay centered under the sleeve when the sleeve is fully engaged with the dog teeth on the adjacent gear, and with it's spring tension and help from a detent, keeps the sleeve from popping out of engagement. the curved leading edge of the slider teeth rubs on the rough surface of the syncro and friction slows or speeds up the free spinning syncronized gear to match the driven slider for a proper engagement. when the syncro surface gets worn off and polished, there is considerably less friction going on, engagement speeds don't match anymore and you get balky shifts and occasional grinding. the shift sleeve contact surface also wears away in turn. shift sleeves often look pretty good, but are usually worn to varying degrees. the 3rd/4th sleeve is way easier to see wear on than the 1st/2nd one. without holding each component in my hand, under a good light source, it's hard to see all the detail in a picture.