text of this document (ocr, may contain errors)
Page 1
IMPORT.
SERnvice
Last month we took you through the disassembly
of the Saab 900 5-speed transaxle. With any luck, we
should be able to turn that pile of parts on the
workbench back into a working transaxle.
Since our last installment, we found some exam-
ples of the damage that’s done when the pinion hous-
ing breaks. I can’t overemphasize the importance of
carefully inspecting the pinion housing. Cracks that
are just getting started may be impossible to see
without magnafluxing the housing.
If you're working on a pre-1983 model 900, your
safest bet would be to replace the original pinion hous-
ing with the latest design. The cost of the housing is
small in comparison to the cost of the other parts that
could be damaged if the housing breaks later.
The bearing preload on the two pinion housing
bearings is adjusted similarly to the pinion bearings
in a conventional rear drive differential. Tightening
a large nut on the pinion shaft removes the bearing
end play and collapses a steel crush sleeve.
aab
nsax
Rep
xle
air
PART TWO
Tighten the nut slowly and stop to measure the
pinion bearing preload several times using a fish scale.
If you overtighten the nut, replace the crush sleeve and
start over. Never loosen the pinion nut to set bearing
preload.
Before you start putting everything back together,
take the time to give the rest of the transaxle parts a
thorough cleaning. Now's the time to find any other
worn or broken parts that might be lurking under a
layer of worn out gear lube. Getting this transaxle out
of the car is no picnic. I know I wouldn't enjoy doing
it a second time on the house.
Remove any leftover gasket material from the case
and cover parts. Don’t use anything sharp that might
damage the machined aluminum case surfaces. The
primary gear case mates to the transaxle case without
a gasket so both surfaces must be smooth, clean, and
dry. Any gouges on either surface are an open invita-
tion for a leak.
—By Karl Seyfert
Page 2
Necessity is the mother of invention, and I’m not talk-
ing about Frank Zappa. A scrap synchronizer hub
(arrow) does a good job of holding the pinion shaft
in the vice. The factory tool does exactly the same
thing. Use one or the other, but never clamp the pinion
shaft directly in the vice.
Use a 47 mm wrench or a really large crescent wrench
to loosen the pinion bearing retaining nut. The Saab
tool number for their wrench is 87 90 453. Notice the
added persuasion at the end of the wrench. The nut
was peened over and had threadlocker on it to boot.
Never reuse the nut.
This press plate (arrow) prevents damage to the pinion
gear when removing the pinion bearings and hous-
ing. Different plates are used for different final drive
ratios. Use 87 91 097 for 1982 and later 900s. The plate
removes both bearings and the housing from the
pinion shaft in one pressing.
Use an old outer bearing race as a drift to install both
new bearing races. The edge of the housing is
chamfered so the old race can’t get stuck in the hous-
ing. The races bottom against recessed shoulders.
Don’t apply 20 tons trying to close the shoulder gap.
It’s supposed to be there.
Press the new outer pinion bearing onto the shaft first.
Slide a new crush sleeve over the shaft. Then place
the new pinion housing over the outer bearing. Enlarge
the I.D. of an old inner bearing race and use it as a
press tool to install the new inner pinion bearing.
Lock the pinion shaft in the vice again. Apply
threadlocker to a new pinion nut, then tighten it until
bearing end play is removed. Wrap a rope around the
pinion housing and attach a fish scale to the free end.
Correctly adjusted new bearings require a 10-15 pound
pull to rotate the housing.
Page 3
After a few tries, you may be able to tell how 10-15
pounds feels by rotating the housing by hand. Don’t
take chances until you do. Never loosen the pinion nut
if it’s overtightened. Replace the crush sleeve and start
over. After properly torquing the nut, peen it with a
punch.
Here’s a side by side comparison of old (left) and new
(right) pinion bearing housings. They’re both alumi-
num, but the one from the ’82 doesn’t have the
strengthening ribs that the new design has. Also the
machined area (arrow) near the flange is wider. This
is the area where cracks occur.
If you're lucky, you won't be taking the transaxle apart
because this happened. This 1982 pinion housing
broke flush with the flange all the way around the
housing. Cracks in this area can be very difficult to
spot. The transmission can jam if the piece on the left
starts turning.
After the pinion housing breaks, fourth gear gets
pushed against the pinion shaft support bearing in the
primary gear case. Notice the wear on both the gear
and the bearing faces. The support bearing race on the
pinion shaft had to be split with a chisel before it
could be removed.
Fourth gear (right) should spin freely on the pinion
shaft. A broken pinion housing will push fourth gear
against the 3-4 synchronizer hub (left). The added fric-
tion and heat can weld the synchronizer hub and gear
together, leaving you stranded in fourth gear.
Clean the pinion housing bolt holes in the case. Install
the pinion depth shims, then reinstall the pinion hous-
ing and shaft assembly. Install the beveled corner of
the pinion housing facing the cluster shaft hole
(arrow). Apply threadlocker to the bolts, then torque
them evenly to 20-25 Nm.
Page 4
The correct pinion depth setting for each ring and
pinion set is scribed on the pinion. This pinion was
marked -5, meaning -.05 mm. There’s a pinion
depth tolerance of +.05 mm. The Saab dial indicator
must be used to measure the pinion depth when a new
housing is installed.
Hold the tool against the bearing housing openings
in the case. Rock the tip of the dial indicator up and
down over the face of the pinion and note the highest
reading. If the reading is higher than the correct value,
increase the shim thickness. If it’s lower, remove
shims. We're right at -.05 mm.
Place the pinion housing installed height measuring
tool as shown, then measure between the tip of the
tool and the pinion shaft nut. This tool tells you how
thick a spacer to use between the pinion nut and
reverse gear. The original spacer should work if pinion
depth has been reset correctly.
Disassemble the synchronizer assemblies. They're all
different, so take them one at a time. Hold the brass
synchronizer ring down, then remove the retaining
ring. The synchronizer rings for each gear are dif-
ferent. They can be identified by the number of marks
Note the proper position of the retaining spring
(arrow). The bent end of the spring must fit in this gap
in the teeth of the synchronizer ring. The bend at the
opposite end of the spring fits in a gap in the retain-
ing ring. The springs are color coded for
identification.
(pointer) on this inside edge.
The synchronizer spring retaining rings can get worn
by the gears they bottom against. This ring from the
damaged transaxle is an example of extreme wear.
Worn retaining ring ears (arrow) let the ring slip past
the gear. Then the retaining spring gets tangled in the
gear.
Page 5
Check the shift forks over carefully. If the owner is in
the habit of driving with his hand resting on the shift
lever, the fork may wear in this area (arrow) from rub-
bing against the shift collar. Match each fork to its shift
rod and check for excessive wear between the two.
Install the selective washer chosen in photo 15, then
start loading gears back onto the pinion shaft. Seat
each gear completely before installing the next. It’s
easier to reinstall the selector shafts and shift forks if
the reverse gear shift linkage is moved all the way back.
Make sure that this caged bearing in the end of the
cluster gear is in good shape before you reinstall the
cluster shaft. Pull the bearing out of the gear and check
the bearing bore inner surface. Also inspect the cluster
gear shaft for wear in the area where the caged and
needle bearings ride.
Hold the cluster gear in position in the case, then
guide the cluster gear shaft into position. The Saab
tool we used in part one (arrow) helps here. Have an
assistant hold the gear in position. Slide the shaft in
until it reaches the end of the cluster gear. We'll finish
You can see the end of the cluster shaft (arrow) in this
photo. The primary gear case mates to the main
transmission case without a gasket. Clean both mating
surfaces, then apply a thin coat of RTV. If the faces
are smooth and clean, you shouldn't need a lot of
sealer.
installing it later.
Reinstall the primary gear case. It may be kind of tricky
because you have to line up all three shafts at once.
Install a new pinion shaft lock nut with threadlocker.
Peen the nut in three places after torquing it to 50 Nm
+10 Nm.
Page 6
Reinstall fifth gear and its selector assembly. Slide the
shift fork over the selector shaft, then reinstall its
locating pin. Hold the selector collar and fork in this
position while guiding the transfer gear and bearing
into the front of the primary gear case.
Hold the input gear needle bearings and collar in
place while reinstalling the input gear. Slide the
cluster gear shaft into the case to support the input
gear. Slide the collar (arrow) back between the input
gear and the cluster gear, then reinstall the retaining
ring and side cover.
Here’s a tip that makes the transfer chains and gears
easier to reinstall. Wrap tiewraps around the tensioner
feet to hold them in against the spring tension. Apply
thread sealer to the tensioner bolts to prevent oil leaks
between the chain housing and the clutch housing.
Reinstall the chains and gears. Reinstall the retaining
ring to lock the upper gear in place. Install a new nut
on the lower gear, then torque it to 100 Nm +10 Nm.
Peen the nut. Reinstall the primary gear housing cover.
Reinstall all remaining primary gear housing bolts.
Install new seals on the side bearing housings. Remove
the snap rings that hold the stub axles into the hous-
ings. Then push the stub axles out of their housings.
Replace the seals and o-rings, then reassemble the
housings. The preload shims will only fit one way on
the housings.
Check the differential side bearings, then reinstall the
differential. If the pinion depth has been set up prop-
erly, backlash should be where it was before repairs
began. If pinion depth and backlash aren't reset close
to original, noise may result when reusing a ring and
pinion set.
Page 7
Reinstall the side bearing housings. They’re both
marked top (arrow). Apply sealer to the housing bolts
to prevent oil leaks. Tighten the bolts evenly to avoid
damaging the sealing o-rings on the outside of each
housing. Torque the bolts to 20-25 Nm. Reinstall the
speedometer driven gear.
If you don’t have a measuring instrument built into
your wrist, check backlash with a dial indicator. The
specification is 0.17 mm +.05 mm. Mount the indi-
cator button perpendicular to the ring gear tooth.
Reinstall the differential cover, then refill the
transmission.