84 transaxle into an 86 - speed sensor issue!
 

have the tranny out of the 86 while doing a clutch job, and was going to swap it for the low mileage one from the parts car (84 model) because the synchro has gone out on 3rd gear - I notice the tranny's have the same cast numbers, and the 84 model tranny even has the threaded hole for the speed sensor - but it is plugged.

Can it still be used with the speed sensor - do you just knock the plug out of the bottom, or what????

Can the 84 tranny be made to use the speed sensor, or do i need to swap just the gear sections and the crown wheel out?

On the '84 tranny that you have, is there a plug threaded into the case? Or is there just a hole that has a bottom to it? On '87 and '88 924s trannys there is an actual plug threaded into the same place that the late 944 has the speed sensor. On these 924s trannys all you have to do is take that plug out and pop the seal out on the same side and drop in the plastic drive gear and replace the seal. Then just thread in the speed sensor and your off to the races. On the '84 you may have to actually finish drilling the hole out and tap it with the correct threads, and then put on plastic drive gear. From the early trannys that I have seen the hole appears to be in exactly the right place to put the threads and make this conversion. Hope that this will help you some.

Im pritty sure you can just swap the speed sensor right over to the other tranny

NO WAAAY ! !
I would say it would be easier swapping the case