New C900T owner-need advise on trans install

[Foreign Object]

Hello,
I am the pround recipient of a 91 C900 Turbo SE convertible. I acquired the car with the 5 spd trans removed and in boxes and the engine is simply laying in the bay. I have also acquired a 5 speed trans from an 86 C900 from a Great Lakes Saab Club member who I shall name after I get the ok.
What I am looking for is advice on the best way to get this transmission in and driving with the benefit of Saabphile experience.
For example, the p.o. included 2 blocks designed to hold the suspension in place during the job, I also have just learned there is a gasket needed between the engine and trans case. Can I power wash the trans when it is out or should I wait until it is installed?
It is these little pointers I am hoping to glean from any who want to help.
I have not had a chance to snap pics yet but plan to introduce myself, the car and any ensuing Saab related items as I go.
Thank you, Michael

[jskrebs]

I recently installed a 86 trans in my 87 C900 8V.

Things to consider

Front motor mount may be different Hydraulic vs Rigid
You may need to swap the drivers - different tripode bearing size
The shifting mechanism is different - Internal vs external center detent
Change all the seals on the motor and transmission
You need the metal gasket and some silicone
I would get a new clutch slave while it is all apart and use regular bolts instead of torx

[Foreign Object]

Thanks! This is the type of info that can really save some learn-as-you-go headaches.
On the shifting mechanism, if my car is external and the new trans is internal, what is the procedure? Do I need more shifter parts from an 86 or do I swap something from my old trans?

[jskrebs]

The 86 trans is external. The centering mechanism is part of the gear shifter assembly in the cabin.

The 91 is internal to the transmission

I had the shifter mechanism from the 86 so I removed the centering spring assembly and shift rod and swapped it out on my 87. Took a hour or so. You have to remove a seat and peel the carpet back to remove the shifter. There are 3 screwy nuts that you will have to craft a tool to remove. I used an old cheap socket and ground it to fit. You can clean and lube the assembly while it is out of the car.

[AdyT16s]

You won't need the metal sump/gbox gasket,just use loctice 518.

Saab did do a special tool for the shifter housing but i find them easy to undo with long nose pliers

[nuclear944]

You won't need the metal sump/gbox gasket,just use loctice 518.

Are you sure about that? I have plenty of 518. The gasket is unreasonably expensive anyway. Have you done it that way or are you just speculating?

[s900t8v]

on the top of the primary drive housing of your transmissions will be a riveted on plate. The numbers will probably read GM45 or GM55xxx (let me know if they don't)

if the last 2 numbers are anything lower than 10 then you have external gear centering, if they are after 10 (including 10) you have internal gear centering. and by gear centering I mean selector centering (I'm tired)

to make the switch external to internal all you need to do is pull up the carpet and remove the little centering mechanism, everything else can stay. Going backwards is a bit more involved and requires donor external centering parts to do the job.

You want an internal centering box, the revisions mean the boxes are better quality and the shift characteristics are much nicer

[euromobile900]

Yeah--the switch to internal centering was mid-1986, and so was the switch to bigger inner-drivers on the non-turbo cars, so it's iffy whether you'll have either of these problems, but easy to tell.

If the inner drivers have three ridges on them, they are the smaller, less durable old-style, and need to be changed.

[AdyT16s]

Are you sure about that? I have plenty of 518. The gasket is unreasonably expensive anyway. Have you done it that way or are you just speculating?

Yep done it on 3 diffrent engine/box swaps,still no leaks even after a track days.

[Foreign Object]

on the top of the primary drive housing of your transmissions will be a riveted on plate. The numbers will probably read GM45 or GM55xxx (let me know if they don't)

Thanks, the donor trans is number GM45606 and the original trans is GM55706. Does this mean both are external ? Also, it was raining terribly today and I failed to check the drivers-more tomorrow on that.