-- The Vintage SAAB Information Source!
How To Evaluate a Used
a Used Transmission
Here are a few things you can check to determine
if a used tranny might be a good candidate for your car. Of course, none
of these indicators on its own indicate a bad tranny. We're also assuming
here that certain parts haven't
been switched during its life.
see how worn the top hole for the bearing is. A new one is round.
The more elongated it is, the more use that the tranny has seen.
- Examine the throw-out (or release) bearing
Look at the connection between the slave
cylinder rod and the throw-out bearing fork. The hole in the shaft was
once round, with a little play. If it's really sloppy, there are lots
of miles on it.
Check out the inner drivers. Feel the
faces of the flats inside. If there's a pronounced groove or dent in
the face, where it "pushes" the half-shaft bearings, this
indicates either a lot of miles or severe lack of lubrication. By the
way, these drivers can may be swapped side-to-side to present a smooth
driving face to the bearings, reducing some "judder" on
Put the tranny in fourth gear and turn the
input shaft back and forth. If the freewheel is good, you should be
able to drive the gears turning it clockwise, but not anti-clockwise.
Lock out the freewheel and grab both
drivers. Turning them back and forth, there should not be a lot of
play in the differential or ring and pinion gears. There should also
not be clunking or rattling from inside the case. The speedometer
drive should also turn smoothly without play between directions.
Take off the top cover. Look for wear on
the shifter rod arm in the cover, as well as the faces in the grooves of the
gear selector forks in the case.
Examine the bronze synchros. Check to see
how much wear is on the teeth. If the teeth are worn down to sharp
little points, it's a good sign of a lot of miles.
Examine the faces of the shifter forks where
they contact the synchro slider rings. Shiny, worn grooves indicate
many miles as well.
Look at the teeth on the gear sets for wear
pitting or rust and watch for play as you turn the drivers.
Unscrew the drain plug and look for metal
filings on the magnet. There always seems to be a small amount of very fine
stuff, but large pieces would be bad.
Separate the two halves of the case and look at
the teeth on the ring and pinion gears. If there are no deep grooves
worn in them and not a lot of play, this is good. If the pinion shaft
bounces around, that's bad.
Look at the teeth on both the lockout slider and
the freewheel hub. You will be able to tell if these have a lot of
wear. If they are very small and worn or even broken off, that shows
high mileage or abuse. If the freewheel works, it doesn't really matter,
as long as the broken teeth aren't floating around somewhere. If you
want to drive with the freewheel locked out and they're not too bad, you can
elongate the hole in the nylon slide on top of the tranny to allow the slider
to engage further into the freewheel hub.
Check the number of teeth on the ring and pinion
gears to see if you might have a Sonett tranny. 8/32 is the standard
trans. I think the Sonett is 9/43 (?). This is also etched into
the edge of the ring gear.
If you want to be really adventurous, pull off
the rear cover. Check your shop manual for how to deal with the poppet
balls on the gear selector shafts.
Once off, look for play in the rear
bearings. The nuts on the shafts have a bad habit of backing off.
Sometimes they can be removed and the locking tabs straightened out and re-tourqued,
but if they're really sloppy then the bearings and the gear teeth are probably
If you have more than one tranny you can compare
these wear points to tell if one is better than the other. And some
components can be swapped without tearing the tranny down too far. Of
course, all of this may not seem too
and you might still have a nice whine while driving. (Not that I am advocating drinking and driving.
That's up to you.) Sometimes you can still find
a really low mileage tranny that was taken out of car that rusted out prematurely or was wrecked.
Other than rustout, this was truly the weak link in
the car, and a lot of owners never figured out the proper way to use the
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July 01, 2021