Alan 91 C2

Pulled the AO4 trans apart to find the fourth gear synchro worn out.

Spec for the synchro to gear is 0.5mm. As you can see in the photo clearance is zero. I was surprised the 4th gear shows little issues, and is serviceable. My old GM Muncies would have been toast.

Oddjob

Wow, how do you wear out a 4th gear synchro?

Alan 91 C2

Bought the car in that condition, last year. Still sorting out the other issues.

1988 Turbo S

Oddjob

What's the contact/inner friction surface look like?

Alan 91 C2

Very worn friction surface and the gear as shown. With a new synchro, I measure 1mm, with in spec for reassembly. I do not beat my transmissions, so should be good to go.

I have some wear on the first gear main shaft. May substitute 924s main shaft and first gear set.

DFASTEST951

I recently sent Lart a bunch of parts and one of them was the fourth gear synchros. Get in touch with him.

Oddjob

Most 924S/944 NA transmission parts are not interchangeable w/ a Turbo trans. Fairly certain the input shaft will need to be replaced w/ a 944S/S2/Turbo/TurboS part. Double check the bearing sizes.