915 Rebuild (Part II) - Time for Assembly

[Porsche_monkey]

Yes. I'm not 'everyone'. But I concur.

[sc_rufctr]

Matt

Are you any further along with your assembly?

[arbita1]

I ordered my new shims and they'll take about a week to get. Plus I'm on vacation this week. Taking the little guy to Disney World. So I'll update on progress next week. Thanks for checking in.

[arbita1]

I'm back from vacation. My shims were at the door. Everyone went to bed early so I decided to do some work.

I installed the shims, put the 1st/2nd shift rod in the housing, and installed the gear stacks. I have a couple of questions before I get too far.

1. 1st/2nd Detents.

When I inserted the 1st/2nd shift rod into the differential housing, my detent (pill) was completely hidden in the space above the 1st/2nd rod and below the 3rd/4th rod. (I hope this makes sense.) I think it's in the right position based on the picture in the Bentley manual...but can someone confirm.

2. How do I know if my gear stacks are fully seated into the housing? I think they are but it's hard to tell with the shims there.

[sc_rufctr]

I took these two photos for reference when I dissembled my gear box.
Apologies for the quality... (Camera phone shots)

This is the "Diff" side... Just to confirm the pill goes between the shift rods. (1/2, 3/4)
Install 1/2 rod first, then with the pill in the detent install 3/4...

Once the rods are in place with the pill between them install the two pills and springs from outside the case...



This is the "Front" side. A bit more complicated but I tried to make a record of the position of each component with this photo.
They are shown in order in this photo. Note the two roll pins that hold the spring, spacer and double pill in place. They are sticking up out of their holes in this photo.



Please remember... All of the detent springs work together as a system to ensures you can not select two gears at once when the transmission is fully assembled.
Apologies for being obvious but if you keep this in mind it will help you get everything back together as it should be.

Note: With all of the detents in place you can select two gears at once with the from cover off because your doing this by hand and not by the shift rod.

Photo below for reference only (stolen from another thread)

[sc_rufctr]

Originally Posted by arbita1

2. How do I know if my gear stacks are fully seated into the housing? I think they are but it's hard to tell with the shims there.

If you have bolted down the retaining plates until they meet the face of your new shims the gear stacks should be fully seated into the housing.

Please use new spring washers on the retaining plate nuts. (M8)
If you reuse the old ones, 99% of the time they'll be fine but the workshop manual says to use new ones every time.

Just for information... WEVO recommends drilling and safety wiring these nuts in place.
I think this is over kill but I would at least use new springs washers.

Good luck with the build...

[Jesset100]

Pete,
Just ordered your book, thanks for helping us mere mortals.

[arbita1]

A step back...

So I dropped a nut into the damn differential housing and had to open up the side cover and remove everything to get it out.

Remember that problem with the ring gear not spinning when I put the side cover on? Well it's back.

Before we start going into troubleshooting again...let me ask two questions.

When you turn the flanges...is the ring gear supposed to spin? I can turn the ring gear by hand, but when I turn the flanges the ring gear doesn't spin. This is with the cover on.

I also tried taking the cover off and putting pressure by hand on the carrier bearing and when I do that I get resistance. Is this right?

[sc_rufctr]

Originally Posted by arbita1

When you turn the flanges...is the ring gear supposed to spin? I can turn the ring gear by hand, but when I turn the flanges the ring gear doesn't spin. This is with the cover on.

Set-up like this the ring gear wont spin when you turn the flanges from outside the gearbox...
The normal pre load of the diff carrier bearings is enough to stop the ring gear turning...
Instead the the planetary gears in the differential itself are are turning as these have no pre load like the differential carrier.

Originally Posted by arbita1

I also tried taking the cover off and putting pressure by hand on the carrier bearing and when I do that I get resistance. Is this right?

With the side cover off the differential may or may not be straight in the housing.
This could be causing the resistance your referring to.

The way to confirm everything is at it should be is to install the differential into the housing with the side cover on... (no O ring)
Then turn the differential as a whole using the procedure outlined by Peter Zimmerman earlier in your thread (this one) about checking pre load.
You need to make or source a washer to lock the flange to the differential so that the planetary gears wont turn when you turn the flange.

If you're having trouble finding a suitable washer you could make a circular ring from a piece of
welding rod that will do the dame thing. (2mm preferably but the more common 3.2mm will work as well)

Just bend it around the flange shaft so it's the right size and trim off the ends.
Make sure it's flat but brass welding rod is soft so it will flatten when you tighten up the flange bolt.

Hate to be obvious but make sure nothing drops inside the gearbox while doing this. Absolute cleanliness is essential at final assembly time.

I have included a picture posted by Grady Clay in my thread about measuring the differential back lash on a 915.
915 – P259 tool measurement request… (With pics)

Take some time to study this picture and try to understand each component and it's function as it may help you understand what's happening in your gearbox and how to lock the flange to the differential carrier.

P-357 is the washer which locks the flange to the differential carrier.
You won't need the M10x110mm bolt as you can use your OEM flange fixing elastic bolt.

[arbita1]

Never mind. I jumped the gun. All is well again.

Differential is back in and side cover torqued.
Flanges are installed and torqued.
Gear stacks are in with new shims and torqued to the case with new lock washers.

I'll take some pictures before I move on.

We had touched on sealing the case. So what should I use?

1. Gasket only (yeah right)!
2. Curil T. with gasket
3. Locktite 574 with gasket
4. Locktite 574 without gasket
5. Other?

[sc_rufctr]

2. Curil T. with gasket.... Peter Z
3. Locktite 574 with gasket.... Porsche monkey

I'm planning on using Curil T with gaskets. But then again I may go with the Locktite 574.

What did the factory use from new?

That may be the safest option.

[Peter Zimmermann]

Originally Posted by sc_rufctr

2. Curil T. with gasket.... Peter Z
3. Locktite 574 with gasket.... Porsche monkey

I'm planning on using Curil T with gaskets. But then again I may go with the Locktite 574.

What did the factory use from new?

That may be the safest option.

My mind might be a little fuzzy regarding this, but I think that the 915s were assembled with gaskets only - no sealant. This will not be successful during subsequent repairs. As stated above, I final clean all sealing surfaces with either MEK or lacquer thinner, and Q-Tips, followed by a thin, even coat of Curil T. There are probably a million ways to spread the Curil, I cut the tip off of a Q-Tip, and use the shaft, held perpendicular to the gasket, to "pull" the sealant across the gasket using very light pressure. The Q-Tip's white shaft will hold any excess sealant, so, for me, it's a very quick and easy method with zero risk of contamination.

[arbita1]

Originally Posted by Peter Zimmermann

My mind might be a little fuzzy regarding this, but I think that the 915s were assembled with gaskets only - no sealant. This will not be successful during subsequent repairs. As stated above, I final clean all sealing surfaces with either MEK or lacquer thinner, and Q-Tips, followed by a thin, even coat of Curil T. There are probably a million ways to spread the Curil, I cut the tip off of a Q-Tip, and use the shaft, held perpendicular to the gasket, to "pull" the sealant across the gasket using very light pressure. The Q-Tip's white shaft will hold any excess sealant, so, for me, it's a very quick and easy method with zero risk of contamination.

If that works for you I'll just follow your lead.

Will one tube be enough?

[Peter Zimmermann]

Originally Posted by arbita1

If that works for you I'll just follow your lead.

Will one tube be enough?

More than enough - you'll only use a small amount of what's in the tube.

[arbita1]

3rd/4th gear selector rod orientation -

Can someone show me how the detents are supposed to go for the 3rd/4th gear selector rod.

The Bentley manual is unclear.

[arbita1]

Originally Posted by arbita1

3rd/4th gear selector rod orientation -

Can someone show me how the detents are supposed to go for the 3rd/4th gear selector rod.

The Bentley manual is unclear.

Ok...maybe someone can just explain which way the rod is supposed to be oriented. I'm having trouble getting it into the case and I'm not sure which way I'm supposed to turn it.

[sc_rufctr]

Please see my earlier post for further details about the detent pill locations...

I would install the 3/4 shift rod before installing the 1/2. (3/4 just before 1/2 if you don't want to remove th shift forks)
You won't be able to get 1/2 in without the detent pill sitting in the 3/4 detent groove. (This is how the detent system stops two gears being engaged at once)

You need to get the 3/4 rod in place so that the detent pill sits in the detent groove of the rod then you should be able to slide 1/2 rod into place.

Once both 1/2 and 3/4 rods are in place and the detent grooves of 1/2 and 3/4 rods are in the same location in the case
with the detent pill is between them... Then install the two external detent pills, springs and bolts to hold the two shift rods in place.
Then re secure/glue the cap at the top that seals the hole going do to the detent pill between 1/2 and 2/3 shift rods.

I know this is a long winded explanation but I can post a picture of the two rods and pill showing their orientation to help.

Please let me know if you want this picture.

[arbita1]

Originally Posted by sc_rufctr

Please see my earlier post for further details about the detent pill locations...

I would install the 3/4 shift rod before installing the 1/2. (3/4 just before 1/2 if you don't want to remove th shift forks)
You won't be able to get 1/2 in without the detent pill sitting in the 3/4 detent groove. (This is how the detent system stops two gears being engaged at once)

You need to get the 3/4 rod in place so that the detent pill sits in the detent groove of the rod then you should be able to slide 1/2 rod into place.

Once both 1/2 and 3/4 rods are in place and the detent grooves of 1/2 and 3/4 rods are in the same location in the case
with the detent pill is between them... Then install the two external detent pills, springs and bolts to hold the two shift rods in place.
Then re secure/glue the cap at the top that seals the hole going do to the detent pill between 1/2 and 2/3 shift rods.

I know this is a long winded explanation but I can post a picture of the two rods and pill showing their orientation to help.

Please let me know if you want this picture.

Peter,

I'm pretty sure I have the pill locations straight. I'm looking for the orientation of the 3/4 shift rod. Which way are the recesses in the rod supposed to go.

The picture in the Bentley manual shows the smooth side of the rod only. So it's hard to tell exactly where those recesses go.

[Peter Zimmermann]

Originally Posted by arbita1

Peter,

I'm pretty sure I have the pill locations straight. I'm looking for the orientation of the 3/4 shift rod. Which way are the recesses in the rod supposed to go.

The picture in the Bentley manual shows the smooth side of the rod only. So it's hard to tell exactly where those recesses go.

Matt: pm me with a fax number and I'll send you a couple of pages from the factory manual...

[arbita1]

Originally Posted by Peter Zimmermann

Matt: pm me with a fax number and I'll send you a couple of pages from the factory manual...

Sent you a PM.