5 speed transmission changes

Manual Transmission changes

THANKS TO Stephen and Zeke and David Prantl for this information. Don't take it as gospel, though, as some discrepancies have been noted

Major points:

The inner end of the axel has a three-roller "fist" (tripod joint) that goes into the driver cup on the transmission. These tripod joints/driver cups come in two sizes. The axel end tripod joint size must match the driver cup size. See the "Inner Driver" column of the chart

A major design change took place in '94:

Synchronizer added to reverse gear

First/second gear synchronizer totally redesigned

Three-ring sandwich for each gear instead of a single synchro ring

Larger diameter input shaft

94 and later transmissions will NOT mate to '93 and earlier engines

	Different mounting bolt pattern
	Larger diameter input shaft and clutch splines

94 and later transmissions are the best design

Much smoother, more positive action

Much tougher synchros on 1 - 2 gears

Note, however, that Eriksson says that the 3rd gear snap ring on the input shaft is a failure item on these transmissions. Saab did a mod to include a thrust washer, but no one knows when. Eriksson can do the mod for around $50 labor plus $50 parts

	Michael Smith reports that this snap ring failed in his 97 Aero at 74000 miles
	My 94 Aero had this failure at 97000 miles
	Symptoms are loud noises in reverse and/or a "clunk" of varying intensity in neutral - when it gets bad enough, it should scare you sufficiently to admit that yes, you really do have a serious problem and it's time to fix it. The symptoms are caused by the gear cluster moving axially (back or forward), causing the meshed gears to bind and then violently release, and it is perceived as a binding-up of machinery. The hell of it was that it only happened very occasionally at first and, fortunately, only in reverse and neutral. The most reasonable fix is a rebuilt transmission from Erikssen. Apparently this is not a widespread problem, as it is not reported as a common failure item.

Final drive ratios

Higher numerical ratio is a lower effective gear ratio

	Higher number/lower ratio = quicker, more revs per mile
	Lower number/higher ratio = less quick, better gas mileage, quieter highway cruise

Non-turbo transmissions have a very low final drive ratio

Necessary for non-turbo acceleration

86 - 92 turbo transmissions have a pretty low final drive ratio

Very quick off the line

93 and later turbo transmissions have a higher final drive ratio

Very "long-legged" on the highway. Less blitz, but better mileage, quieter highway cruising

88 - 93 trans have a dip stick to check fluid level

(although the fluid is so clear that it makes the usefulness debatable)

94 and later have no dip stick; they have fill, level-check and drain plugs

Interpreting the Type number (next to transmission serial number)

Earlier models ('85 - '87, from Saab service manual 333674)

ID number format: GMT5x0y

	GM appears to stand for "gearbox, manual"
	T stands for transverse-mounted
	5 is for 5 forward gears
	x is the final drive ratio
	y is the variant number

Later models ('94 -, from Saab service manual 355875)

ID number format: FMT5x yz SN

F stands for "front wheel drive"

M stands for "manual"

5 is for 5 forward gears

x is the final drive ratio

y is the engine/car adaptation

z is the variant number

SN is the 6 digit serial number

The first digit is a letter designating the production line

FM51 001 Final drive ratio: 3.13:1

FM54 001 Final drive ratio: 2.85:1

FM57 101 Final drive ratio: 2.54:1

The following chart is based in part on hear-say, particularly the years and numbers that are in yellow. Model year '93, indicated by peach colored text, is a crossover year that I think has the '94 style transmission, although I think some '93 models may have the earlier transmissions. Final drive ratios are stated as the overall ratio, not the 5th gear ratio; the final drive ratio is lower because 5th gear is an overdrive gear.

Model Year	Trans Model #	Final Drive Ratio	Spider Bearings	Inner Driver	Fill hole location	Dip stick w/Fill hole	Level plug and Fill plug?	Drain plug?	Reverse Syncro?	Improved Syncros?
86 - 87, Turbo	GMT5301 GMT5204	2.88:1 2.83:1	Bushings	Small	Rear	No	No	No	No
87, Non-turbo	GMT5202 GMT5203	3.04:1 2.99:1	Bushings	Small	Front	Yes	No	No	No
88 - 90, Turbo	GM57401 GM57301 GM57402	2.88:1	Bushings	Small	Front	Yes	No	No	No
88 - 90 Non-turbo	?	?	Bushings	Small	Front	Yes	No	No	No
91 - 92, Turbo	GM57403	3.04:1	Bushings	Large	Front	Yes	No	No	No
90 - 92 Non-turbo	?	?	Bushings	Small	Front	Yes	No	No	No
93 CST, CSET, Aero	GM57101	3.61:1	Needle Bearings*	Large	Front	Yes	No	No	No
Design changes in '94 make the transmission to-engine mating incompatible with pre-94 models
'94 CST, CSET, Aero	FM57101	2.54:1	Needle Bearings	Large	Front	No	Yes	Yes	Yes	Yes
94 Non-turbo	FM51001	3.04:1	Bushings	Small	Front	No	Yes	Yes	Yes	Yes
'95 - 98 CSET, Aero	FM571xx	2.54:1	Bushings	Large	Front	No	Yes	Yes	Yes	Yes
'95 - 97 CS LPT	FM510xx	3.04 : 1	Bushings	Small	Front	No	Yes	Yes	Yes	Yes

* The Saab repair manual says "In certain gearboxes the differential is fitted with needle bearings instead of wear discs." (Wear discs are cupped discs that fit on the back side of the spider gears). My 94 Aero does have needle bearings (incorporated into the discs).

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