Here are a few thoughts I jotted down the last time I did it.
1.1 Lever Removal
(After shift knob removal) There is a flat for a wrench to keep the inner
rod from turning as you remove the top nut. Push the upper section down and
look on the inner rod just under the nut. On my car these is a wrench flat
there, fairly small for a wrench but needle-nose vice grips worked
1.2 Remove Separate from Engine
Undo the cover on the bottom of the bell housing and remove the clutch
pressure plate bolts, it is a lot easier to get the transmission out. Remove
the bolts by loosening each one a little and working your way around. You
need a way to rotate the motor to do this, but it's worth it. Basically,
once this is done, you only have to pull the transmission back enough to
clear the pilot bushing before it will start to drop. It works installing
too. A small jack with a board under the front of the sump will help tilt
the motor. With the pressure plate trick, you don't need to tilt the motor
as much.
I tend to leave the transmission in 3rd gear while removing it. You have to
take the shift lever off, but you can keep the dished washers in place with
a small tie-wrap around the stub where the shift lever goes. The groove for
the shifter pinch bolt will keep the tie-wrap in place. You can also leave
the short part of the drive shaft on. It makes a convenient handle.
I break the exhaust between the header and the pipe, then I put a block
under the front of the pan, After taking everything else loose, I jack the
front of the motor up a bit to get clearance.
1.3 Disassembly
1. Punch alignment marks on drive shaft yoke before removal.
2. Engage 3rd gear before attempting to remove recover. But it is
probably easiest, and safer for the rear seal, to remove tower vents
(careful not to lose or interchange shims) to install rear cover.
3. Removing shift rods:
a. First remove the detent covers, springs, and balls.
b. Detent balls are 7.930mm, but 5/16" is close enough.
c. Tall cap and spring go with 5th-reverse rod.
d. Remove bolt holding 5th-reverse fork
e. Note that there are 3 pawns (oblong balls) holding the shift rods
inside the rear wall of the half shells.
f. Position the box so that the shift rods are at the top and level
with the earth. Remove the center rod first, being sure to catch the pawn
that is inside the hole drilled through this rod.
g. Use magnet to extract the other two pawns, One is located toward
each remaining shift rod.
h. Pull out 5th-reverse rod.
i. Remove 5th-reverse fork
1.4 Reassembly
4. Installing shift rods
a. Install 5th-reverse fork onto 5th-reverse rod
b. Insert 5th-reverse rod in case and then through 1st-2nd shift fork
(if using 105 or 115 style forks)
c. Insert 1st-2nd rod through case and through 1st-2nd shift fork.
d. Position the box so that the shift rods are at the top and level
with the earth.
e. Use magnet to install two pawns. One toward 5th-reverse rod and
one toward 1st-2nd rod.
f. Install third pawn into hole in 3rd-4th shift rod.
g. Insert 3rd-4th rod in case, through 1st-2nd fork, and then through
3rd-4th fork.
h. Install detent balls, springs, and covers.
i. Center 1st-2nd and 3rd-4th shift forks so that the syncro ring is
equal distance from the gear on either side.
j. Bend over safety straps on 1st-2nd and 3rd-4th shift forks!
5. Reassembling 5th-reverse section.
a. So you can assemble 5th-reverse section:
i. Position the box so that the shift rods are at the top and level
with the earth.
ii. Remove 5th-reverse ball, spring, and cup.
iii.
Pull out 5th-reverse rod along with its pawn.
iv.
Remove 5th-reverse fork.
v.
Don't lose other two pawns
b. Install reverse-idler gear on stub shaft.
c. Install 5th-reverse shift fork.
d. Insert 5th-reveres shift rod, with its pawn
e. Install 5th-reverse detent ball, spring, and cover.
f. Alignment of 5th-reverse fork was made easier in late workshop
manuals by providing a 12.9mm (.508") measurement from synchromesh
engagement teeth (5th gear side) to the synchromesh ring.
g. Tighten bolt and bend over safety tab.
6. At the head of the "main shaft" ("output shaft") is a snap ring and
then a shim. Do not mix this shim up with other shims you will encounter
later. While the manual states that all three synchronizing hubs (3 legged
piece) are the same, you should keep track of this one, since it matches the
shim. This shim will only change if you have to replace a damaged 3rd gear.
7. Use something like Permatex aviation gasket cement on case joints
and the two long bolts holding the case together. Just apply to the outside
1/3 if the joining width, so it does not squish inside the gear box as you
torque down the bolts.
8. Torque specifications
a. From 101-1600 shop manual:
i. Nut on gearbox
main shaft yoke: 12 Kgm or 86.8 ft-lb (dry)
ii. Nut on gearbox layshaft: 8 Kgm or 57.8 ft-lb (dry)
iii.
Nuts on gearbox half shells: 1.8 Kgm or 13 ft-lb (dry)
b. From 115-2000
i. Nut on gearbox mainshaft yoke: 9.5-10.5 Kgm or 68.6-75 ft-lb (dry)
ii. Nut on gearbox layshsaft: 9.5-10.5 or 68.6-75 ft-lb (dry)
iii.
Nuts on gearbox half shells: 1.7-1.9 Kgm or 12.5-14 ft-lb (dry)
c. Form 115-2000 shop manual for 1991 model year
i. Nut securing rear cover to half shells: 1.7-1.9 Kgm or 12.5-14 ft-lb
ii. Nuts securing clutch housing to half shells: 1.7-1.9 Kgm or 12.4-14
ft-lb
iii.
Direct drive shaft bearing nut: 9.5-10.5 or 68.6-75 ft-lb
iv.
Nut for gear control trunion (forked gizmo in tower part of rear case)
3.3-3.6 Kgm or 23.6-25.8 ft-lb
Carl R. Davis
2823 S. Rocky Hill Road, Galena, Illinois, USA 61036
750E, 750F, 10121, 105.62, 115.01, 115.41S4
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