Hello All! Been a lurker for a while, finally posting. Trying to keep it brief, but still cover the topic.

Several months ago I converted my Gen I 2.6L 5speed manual to automatic due to my situation and advice that the auto was generally tougher than the manual (for the record, I prefer a MT). Project was a little more involved than I anticipated but we got it done. Just want to share the experience in case someone else is faced with the same decision.

The auto was also from a 2.6L and bolted up with no problem (as you would expect). As has been mentioned here before, finding a flex plate was a real challenge (donor tranny had a bad FP - some chain parts stores THINK they have one, but it will NOT work!). There were a few little details that had to be covered though.

Rear drive shaft for auto is a little shorter than the manual DS. My 1987 Monty also lacked a bracket on the cross member hear the tailshaft, so this had to be welded in place. Also had to arrange a hook-up for the kickdown on my carb throttle arm (this will be the case with stock manual tranny carb or weber as neither has the connection for the KD).

Got it all done and it worked fine - as a THREE speed automatic. Not as peppy as the MT was, but OK. Still trying to get the wiring issues straightened out for the OD relay. Knowing the problems we all sometimes have with electrical issues I am trying to be ABSOLUTELY CERTAIN before I dive into the wiring harness to make the connections.

General notes and things to get from the donor vehicle.
Get the tranny, rear drive shaft (or be prepared to have a machine shop shorten your MT rear drive shaft), shifter and all interior components, transmission cooler, AT radiator (you need both per the factory manual), indicator light cluster is a good idea for the OD indicator, GET AS MUCH OF THE WIRING AROUND THE RADIO AND OVER TO THE FUSE PANEL AS YOU CAN (this will help you install the OD relay), get the OD relay, get the brake pedal (it fits on the MT brake pedal/clutch pedal bracket under the dash), get ALL THE WIRING GOING TO THE AUTO TRANNY you can get (this will also help with the wiring connections). Be sure to also get the kick-down cable. In short - GET EVERYTHING YOU CAN THAT MIGHT BE RELATED! Unfortunately, as I was finishing my conversion I dropped by the junk yard for a few parts only to find that they CRUSHED my donor car the day before (literally).

HOPEFULLY you will have a more skilled "auto salvage" mechanic to do the AT removal (instead of the junk-yard wrench that tried to lift my AT with a fork lift on the oil pan - BTW, anybody know where I can get a good DENT-FREE AT oil pan?).

I'm still hoping the swap ultimately turns out well. Right now (with a weber carb) I went from low to mid 20's MPG with the MT to mid teens with the AT. (Good thing gas is so cheap...) Hoping the OD will at least get me up in the high teens, maybe 20 MPG.

Hope this helps someone!

Oh, in case you wonder why the change. After a new head and the weber carb the thing was running GREAT, and it was apparently so strong that I managed to break a couple of teeth out of the Manual tranny. Tried to find parts or another manual tranny for overhaul, but no luck. Old MT had around 200K on it.

SO... IF you have an old MT and there are ANY PROBLEMS with gear mesh ("grinding" into gear) you may want to SERIOUSLY consider an overhaul with all new bearings and synchros. You can find new bearings, but not new gear clusters (and synchros are apparently a little tricky too).

You might want to also be VERY GENTLE with the older MT's. I think I broke mine with a harsh downshift driving uphill and into a strong AZ headwind.