Convert manual to auto

I have an ‘81 f150 2wd long bed with 300 and a T18 transmission that I’m looking to convert to automatic. (I know, just sell it and buy an auto, due to sentimental reasons I’d rather go through with the conversion)

There is a local ‘81 f150 2wd long bed auto with a 5.0 302 that is for sale near me. Would the transmission be “swappable” on these?

300 and 302 share bellhousing bolt patterns, so an auto from behind a 302 will work behind the 300.  Make sure you get the block plate, as the standard and auto are (I'm 99% sure) slightly different.  Grab the auto steering column, too.

You've got the mechanical clutch linkage too.  I'd like to have a set of that hanging around.

Perhaps you didn't get the email I sent when I confirmed your membership.
I'm going to ask that you make an introductory post in the New Members Start Here section so we can know a bit about you and that you've seen the members guidelines.

With a C5/6 transmission you're going to need a source of vacuum for the modulator and if the transmission is AOD you definitely need an aftermarket (likely Lokar) kickdown cable, since the 300's carb is set way off on the right a kickdown linkage from the donor won't fit.
And though the C-series transmissions can work with only vacuum and without the rod, an AOD will eat itself without a TV rod or cable.
Look for the T code on the door sticker or -P R N OD D 1- on the selector.

You might also want the carpet without a hole on the hump but I have no idea what the interior of the donor looks like.

85pig wrote

300 and 302 share bellhousing bolt patterns, so an auto from behind a 302 will work behind the 300.  Make sure you get the block plate, as the standard and auto are (I'm 99% sure) slightly different.  Grab the auto steering column, too.

You've got the mechanical clutch linkage too.  I'd like to have a set of that hanging around.

Note the flex plate from the 302 WILL NOT work as the balance is different between the 2 motors.

You could swap parts between the 2 trucks, just need the right flywheel for the 302 and a motor side linkage  pivot as the 300 six one will not work with the 302 also.
Then you could sell the donor truck.

BTW if you want to sell the 300 motor side pivot I would like to buy it.
I would like a spare for when mine breaks again
Dave ----

there are a couple more details than that but yes, it is a perfect swap to do. everything should be able to be found. especially if you were to get a donor truck as a whole. there are fine details and idiosyncrasies though. the flex plate (flywheel for an auto) is a key piece as it must be made for the engine and type of trans. not all autos are the same. the length of the trans as a whole is often a different length so a different drive shaft will need to be used. autos need a linkage between the carb/throttle body to modulate internal fluid pressure and a manual will not have this linkage. there is a little wiring involved as you change over clutch lockout for neutral safety switch and backup light switch. Swapping the dash brace/ pedal assembly is  a bit involved but I have seen it done without changing it (I guess it depends on the ocd of the person doing it) there is the steering column which is also the auto shifter and don't forget the brackets and linkage for that. there is bit more too but I'm sure I will think of them. maybe I will get reminded.

Good catch on the flywheel/flex plate; forgot about the balance difference.

mat in tn wrote

there are a couple more details than that but yes, it is a perfect swap to do. everything should be able to be found. especially if you were to get a donor truck as a whole. there are fine details and idiosyncrasies though. the flex plate (flywheel for an auto) is a key piece as it must be made for the engine and type of trans. not all autos are the same. the length of the trans as a whole is often a different length so a different drive shaft will need to be used. autos need a linkage between the carb/throttle body to modulate internal fluid pressure and a manual will not have this linkage. there is a little wiring involved as you change over clutch lockout for neutral safety switch and backup light switch. Swapping the dash brace/ pedal assembly is  a bit involved but I have seen it done without changing it (I guess it depends on the ocd of the person doing it) there is the steering column which is also the auto shifter and don't forget the brackets and linkage for that. there is bit more too but I'm sure I will think of them. maybe I will get reminded.

Mat also good catch on the carb linkage thing is he wants to put the auto from a 302 into a 300 truck and it uses a different linkage set up that could be hard to come by but ..........
I wounder if he could find a cable from Lokar that would work?

The auto NSS is another thing needed to work out, back up light connection should not be hard.
Dave ----

I didn't think the '80-'81 trucks had starter interlock.  
At least the '81 EVTM doesn't seem to show it.

Edit:
I'd be sure to check the transmission cross member.
I know these early trucks can have some pretty weird mounts and automatics are usually longer than manuals.
That can be challenging to remove with the upper rail bolts trapped under the bed.

not certain about the ones that do or dont have the interlock but covering the bases. on the cross member, it sometimes can be turned around 180 degrees and change the offset and sometimes moved to a different set of bolt holes.

I did that swap on an 89 F250, but my engine and trans came over together. Rather than swap columns, I used a Hurst Pro-Matic 2 floor shifter. Didn't even hook up the kick-down rod due to using Edelbrock carburetor. If I need to down-shift I just slap the ratchet shifter down a gear and back up when the need is past.

Thanks for the replies

I’ll get a New Member post this weekend Jim.

Any thoughts on how much you’d expect to pay a shop to do the swap. Sounds like it might be over my head. Unlikely but If anyone is near northern Indiana with time for a side project I’d prefer to pay someone from the forum.

It sounds harder than I think it is.
With both trucks side by side makes it easy.
If they both had the same motors would make it even easier with the carb / trany linkage for the auto.
The rest of what was posted were things you  need to look out for is all.

As for a shop to do the work might be hard to find as most shops will not touch older cars & trucks and it is all labor and they would not know how much to quote as they dont know what they may run into.
Then again you may get lucky and find one but what would it cost????
Dave ----

Thanks, I found an 83 auto with a 300 (and 4wd). The body is in rough shape but it runs and drives. It’s Cheap so I may buy that one so that I can get both trucks next to each other and as similar as possible. Not sure if the 4wd would cause any issues

if you are not using the transfer case then there may be an issue. often the internal output shaft will have a specific length for 4wd and a different one for 2wd so just swapping the tailshaft housing with the adapter does not work. the transfer case is not added to the transmission so much as it is mated with it by replacing the tailshaft housing with a shorter adapter housing making the two work as one unit with more gears. also the 4wd will not have the tailshaft housing that a 2wd needs so you are still looking for more parts. unless of course if you were wanting to have 4wd then of course you project can and will grow. but maybe in the direction you like?

Slight change of plans. I picked up an 83 with a c6 and 300. So now I have an engine that matches mine to make things easier. Only problem is the 83 has 4WD so I’m left looking for a driveshaft or swapping the tcase as well (probably wouldn’t bother doing the full 4WD swap buy may want to in the future)

If both trucks are the same length then it is easy to swap.  Might as well go ahead and make yours 4wd while you have the parts.

Yes, forgot to mention they are both regular cabs with 8 ft beds.  Easy for you and easy for me may be worlds apart.  I do oil changes, have changed an alternator and a driveshaft once.

F150 2wd to 4wd swaps are bolt-on.  Not so with F250's and 350's as the frames are different.

another layer of the onion would be the rear axle gear ratio. the one used with the t18 should be close to the one used with the 4wd but may actually be different. enough so that you would want to verify if not use the one from the 4wd, front and rear must be the same the matched set from the 83.
yes, you must know your own skill set (tools) and know your own limits. but .....if you want to learn then how better than to jump in? especially when there is so much info and coaching available to draw from. just do things with a little safety in mind. these are heavy and never heavier than when laying on you! as far as converting to auto only its far more simple than doing the whole 4wd conversion