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Re: 5spd Posted by Saana88 [Email]  (#207)  [Profile/Gallery]
(more from Saana88) on Fri, 29 Feb 2008 13:30:49
In Reply to: 5spd, tom, Fri, 29 Feb 2008 13:10:46 Members do not see ads below this line. - Help Keep This Site Online - Signup |
The final drive ratio is different from 1979-1990 inclusive. After that, I don't think the nonturbos were any different. Non-turbo 900s were geared a little lower/shorter during that period to help speed them up a bit.
As for internal differences, 1989 and later nonturbo transmissions had beefier pinion bearings (the Achilles' heel, typically) than '88 and earlier.
All 1991-1993 (and '94 cabrios) had different guts inside with revised shift forks. These internals are not interchangeable with older boxes.
Sometime around mid-1986 the inner driver cup size or axle length changed, I forgot which. Everything '87 and newer has the same size inner driver bearings. The driveshafts that connect to them changed lengths sometime 1989-1990 for ABS compatability.
Also in mid-'86 was a change in centering. Up to that point, the gearshift centering in the neutral plane had been on the shifter. After that point, it was done inside the gearbox.
The gearbox oil drain plugs disappeared sometime around 1990. People got sick of quick oil change places draining out their gearboxes and putting eight quarts of oil into their four-quart engines.
Gearbox dipsticks were shortened for 1990 nonturbos and I believe eliminated altogether for the turbos from then on. My '92 requires a bolt-capped short dipstick and side cover because the old dipstick will not clear the exhaust header. This operation is as easy as interchanging the side covers.
In general, be very suspicious of junkyard 900 gearboxes from cars which do not have serious frame rust or collision damage. It is definitely worth it to pull the lower cover and search for metal shavings, chunks, and rotten gearbox lube. Pull all the covers and inspect the reverse gear teeth as these tend to be punched off when the driver puts the car in reverse while still moving forward- reverse is not synchronized. Be sure the donor box will shift into all six gears; watch through the inspection covers if you can. Also, be sure that both inner drivers spin freely in both directions in neutral. A pinion-failed gearbox will usually see the final drive locked up and unable to move.
And finally, check the gearbox designation (located below the serial number barcode on the top of the primary chain housing) to see what that box started life as. It should be GM 557 14 or something like that. That number will tell you, short of any rebuilds that have been done during the life of the box, a whole bunch of information about it- how many gears, final drive ratio, which iteration of inner drivers and internals are in it, et cetera.
That's about all I can think of on that one. The link explains how to decipher those codes.
Jeff (not me, another one) and Royce's transmission ID page
, Fri, 29 Feb 2008 13:30:49 <-- Viewing This Message
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