915 Rebuild - By Marc Astore

[Tech Articles Editor]

This Tech Arcticle is a DIY giude to rebuild the Porsche 915 Transaxle. Photos and text by Marc Astore.
(Post 1 of 4)

8009
You know something needs to be replaced when your drain plug looks like this!!

After draining the oil and cleaning the case, remove the mounting bracket (4 nuts and washers).
Put the tranny in 5th gear if you can figure out which is 5th gear. (I did it after the next step since
I could see it) With Tranny horizontal, remove the end cap and the backup switch plunger that
actuates the switch.


8010

This is the 3rd/4th-5th/rev detent in the end of the gear housing. I'm putting this picture here so
that you start thinking about this detente set up NOW and keep thinking about it until you get to
the re-assembly part of this page. You will understand later.


8011
Picture and tip from Chris Bennet
TIP: To hold the shafts so you can remove the nuts on the ends of the input and pinion shafts, lock
the transmission in two gears at once. To put the transmission in 2 gears at once:
a. Start with the selector shafts for 1/2 and 3/4 in neutral. The ends of the shafts will stick out of
the intermediate case a little when both are in neutral. "A" is end of the 3/4th gear selector shaft.
It's in neutral.
b. Put the transmission in 2nd gear by gently tapping the end of the 1/2 selector shaft ("B") with a
plastic hammer. In the picture, it has been tapped into gear.
c. Then push on the 5th/reverse slider to engage 5th gear. 5th is the helical gear on the end of the
transmission, the other gear is reverse - a straight cut gear.

8008

Here is the 5th/Reverse gear set located in the end of the tranny. If you remove the end cover with
the tranny in this position (vertical) the back up switch plunger will fall into the gearbox. You can
retrieve it through the fork plate on the bottom of the case If you are lucky. Next time I'll pull the
reverse switch before removing the end cap.

Green Arrow - 5th/Rev Slider
Red Arrow - 5th free
Blue Arrow 5th/Rev Idler


8012

Interesting note - slider for 5th/Reverse (Red Arrow) has rounded teeth on the top and flat teeth on
bottom.

Green Arrow - Gear numbers facing up
Blue Arrow is O-ring - replace and lube.


8013

Green Arrow - polished area with gear numbers
Green Arrow - 5th gear fixed
Red Arrow - Reverse gear fixed


8014

There is a cross pin in the Main Shaft Nut, and a punch set in the Pinion Shaft Nut. Pin pops out,
punch set is a PITA. I used an Impact Wrench to remove Pinion Shaft Nut. I had to re-attach the
tranny to the engine to break the Main Shaft Nut. Pinion shaft nut must be replaced (per factory
manual anyway). I butchered mine.

Green Arrow - Main Shaft Nut 118 ft/lbs, P/N 900.079.009.00 (Pin P/N 900.309.005.00)
Red Arrow - Pinion Shaft Nut 180 ft/lbs, P/N 915.302.282.00


8015

Note the pin sticking out of the fork shaft. This is normal. It pushes the reverse plunger in and out.


8016

Good picture of the Syncro Ring - Green Arrow & Dog Teeth - Red Arrow.


8017

Pinion Shaft nut off, Output shaft nut loose. 5th/Rev slider removed with shift fork. Pull straight
up gently on slider making sure that the tang on the shift selector is clear.

[Tech Articles Editor]

(Post 2 of 4)

8027

Picture of 5th fork out


8018

A good "memory" picture. Pull Spyder off, then Idler gears noting the washer is on top. Next is
5th free gear, Reverse fixed, 5th fixed.


8019

Measure gap between fork and slider for wear. From factory .1 - .3 mm. Replace when greater
than .5 mm. Mine was .2 mm


8020

Here the gear housing has been removed. You have to play with the gear selector to clear the
housing.

• Light blue arrow is 1st free.
• Red arrow is 1-2 gear selector fork
• Blue arrow is 3rd free
• Green arrow is 3-4 gear selector fork
• White is 4th free.

Move 1-2 gear selector to neutral (half way between 1st & 2nd)
Move 3-4 gear selector up so that the slider engages third.
Remove 10 nuts and lock washers from the retaining plates.

Place the bell housing face down on a bench, pop it into 3rd gear, remove the 2 détentes that go
into the side of the diff housing, wrap your hands around both shafts and shift rods at the same
time, and wiggle out the whole works. The trick is to engage 3rd gear. Same for reassemble. - John Walker

DO NOT loosen the shift forks on their shafts during disassembly. This is not necessary. If you
loosen the forks you lose the selector fork alignment. You can remove both shafts at once along
with the shift forks. I tie a shop rag around all the gears (both shafts) and the shift forks. The rag
holds everything together so I can wiggle the shafts out of the case. When you assemble it you
should still check the alignment and adjust if necessary. - Chris Bennet


8021

Another memory picture from the back side.


8022

Top View.


8023

Thanks to Chris and John the stack came out without event.
Remember not to lose the thin metal shim that is under the retaining plates.


8026

This is how the roller bearing was pressed off. An old wheel bearing race placed on the bearing
and a piece of pipe "pressed" it back on. Make sure that your press tool sits on the case of the
bearing (part that touches the shaft), NOT THE Cage (part that holds the bearing).


8024

Order off of shaft.


8025

1st gear with dog teeth. The teeth were about 1/2 the size of the new ones.
Remove large C-clip. STOP !!!! Look at the brake band orientation. The long leg is on the left.
With the thrust block at high noon, the Anchor block is at 5:00.

Blue arrow is the Thrust Block.
White is the Anchor Block
Green is the brake band.

Used a cold chisel between gear and dog teeth to work teeth ring off the gear. Heated the new dog
teeth ring in front of a propane heater and it dropped on the gear with very little persuasion. There
is a difference between the 1st & 2nd gear syncro ring. First has a grove that runs on the flat
surface from end to end.

[Tech Articles Editor]

(Post 3 of 4)

8028

Bad Dog!! Bad, bad dog. No wonder I couldn't down shift into second without a huge crunching
noise. The brake band legs for second gear are equal in length so the above doesn't apply.

"Make sure the bearing cage and inner race turn freely in any gear you pressed new teeth on. The
bore can be distorted by the press work, causing future bearing failure." – John Walker


8029

Output shaft with HUGE nut in the vise. This is a punch set nut like the one on the end of the
pinion shaft. If you take a dremel and cut across the bottom of the metal that has been punched in,
the piece falls right out.


8030

To remove the 46mm nut, Eugene @ PP pegged the old clutch to a wall instead of making a tool
out of it.


8031

Sorry about the picture quality. This was DougE's clutch plate. Dremel off the 4 shaft ends that
hold the plate together, pull the springs out and install a nut and bolt as seen here. I used a rather
large crow bar and the nut gave way without any problem.


8032

Input Shaft Disassembly:
"The best way to disassemble the shafts is to use inertia. Grab it with both hands and knock it on a
steel plate repeatedly. The mainshaft takes a bit more effort than the pinion shaft. Put the plate on
the ground so it's solid. Don't worry about damaging anything but the plate. The shafts are
hardened, the plate is soft. The stack of gears comes right off. No press needed." – John Walker

Looks like that block has been used a few times.


8033

Holy Cow . . . . JW's method was a piece of cake. 4 wacks on a scrap of granite and everything
came loose. I wrapped a wash cloth around the shaft and Zip tied it to catch the bearing, etc. when
it did come loose.


8034

This is third gear. Syncro was worn badly. Teeth were ok, but will be replaced since I have them.
The 3/4 slider had some overall wear on the teeth and the grove in the center was more
pronounced than the new one.

Green arrow is the Thrust Block
Blue arrow is the Anchor Block
White arrows are the Brake Bands. (3rd & 4th have 2 bands rather than 1).

For this one I put the dog teeth/gear into a vice with protected jaws and closed the vice just enough
to support the dog teeth. With an old wheel bearing race I knocked the gear down enough to pry
off the dog teeth with 2 screwdrivers.


8035

Here is my tool in reverse. Main shaft is locked in vice so large flange nut (between retaining plate
and tool) can be tightened. Torque spec is 115 to 130 ft/lbs.

DO NOT FORGET TO PUNCH SET THE NUT BEFORE GOING TO NEXT STEP.


8036

There are 3 detantes, 2 horizontal (green arrow shows lower of 2) & 1 vertical (Blue arrow). Make
sure the vertical one is in between the 2 shift rod holes and that the 2 horizontal ones are pushed
back into their bores.


8037

FIRST THING . . . INSTALL STEEL SHIMS NOW!!
Pop the main shaft into 3rd gear (move slider by hand onto 3rd gear's syncro, line up the gear
stacks and install the shift forks. Zip tie around the two stack and one shift shaft. If you tighten
the tie too much the bearings will not line up. At that point the tie can be cut any way.

- Jiggle everything (helps to have someone turn the differential) and it will drop in.
- Install lock washers and nuts to hold retaining plates down.
- Install upper and lower detante springs and nuts.

[Tech Articles Editor]

(Post 4 of 4)

8038
Tip from JW: Permatex copper head gasket spray
Tip from local wrench: Use Mercedes Benz gray sealant with no gasket. I used this method after
having to re-open the case (you will see later, hint: it has something to do with that detent). So far
no leaks.


8039
Here is the stack showing good (blue arrow) and bad (green arrow) shift fork alignment for 1/2
(green) and 3/4 (blue). The slider should be half way between the dog teeth of the each gear. Since
I did not have the OE alignment tool, I put the case on, installed 5th and reverse as well as the free
5th gear and torqued the nuts at the end of the pinion and main shafts. I could see through the hole
in the bottom of the tranny case that 3/4 was right on the money. Couldn't see 1/2 with the case on,
but could tell it was off.


8040
Here you can see what 1/2 looks like after adjusting. I used the spider to align the fork.
Note the alignment of the shift rods at the top of the picture. The look like they are one piece of
metal.


8041

MAJOR SCREW UP. WHEN I PULLED THE CASE THE PIN (GREEN ARROW) PUSHED THE UPPER DETENTE
UP INTO THE BORE ABOVE THE 3RD/4TH SHIFT SHAFT (BLUE PILL). THIS IS BAD. ESPECIALLY WHEN YOU
FIND OUT ABOUT IT AFTER THE ENGINE AND TRANNY ARE BACK IN THE CAR.

THE PILL MUST BE PUSHED DOWN TO WHERE THE RED PILL IS BEFORE INSTALLING THE CASE. JUST
POP THE CAP (TO LEFT OF BLUE PILL) OFF AND USE A SMALL ALLEN WRENCH TO PUSH THE PILL DOWN WHILE
INSTALLING THE CASE.

The roll pin (light blue arrow) holds a collar that the pin slides in to push between the bottom and
top detentes. Put on the gasket and slide the shift rod into the case, and then feed the case and rod
onto the case studs at the same time.

5th/Rev fixed go on at the same time as the idler gears set, then 5th free, the spider and then the
shift fork and slider for 5th/Rev. Torque up the nuts again, insert the roll pin in the castellated nut,
and notch the flange nut on the mainshaft. You are ready for the end cap.

Replace the O-ring on the idler shaft and lube with a small amount of grease. Replace the seal that
the shift rod goes through. A 19mm socket will help set the seal in the case. Grease the lips of the
seal. Slide the cover on and bolt it up.


8042

Don't forget that the ground strap. Gasket for the shift fork plate gets the copper stuff too. Make
sure that the nuts holding the shift fork on the plate are tight.


8043

The torque spec that is chopped off is 118 ft/lbs. This was changed in 1984.



Great threads on 915 rebuilding include:

http://forums.pelicanparts.com/showthread.php?threadid=55921&referrerid=6302

http://forums.pelicanparts.com/showthread.php?threadid=64307&referrerid=6302

http://forums.pelicanparts.com/showthread.php?threadid=138132&referrerid=6302

http://forums.pelicanparts.com/showthread.php?threadid=57371&referrerid=6302 (Excellent thread by Jim Sims)

http://forums.pelicanparts.com/showthread.php?threadid=91901&referrerid=6302

http://forums.pelicanparts.com/showthread.php?s=&postid=1180869#post1180869