info on 2f engine swap? can't find what i am looking for

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Jan 26, 2009
hey, i am sure this has been discussed an infinite amount of times on here,,, but i can't seem to find the answers i am looking for.. if anyone can steer me in the right direction,,, i will greatly appreciate it.. all those who point and laugh at me,,,, i completely agree..... anyway..

i have a pretty clean and bone stock 71 fj40 with low miles 48k,, but the there is a seized piston issue,, anyway. i recently just bought a very complete but rotten 78 parts truck (which comes in handy for my other 78 dailydriver/wheeler. spare trail parts, YEH).. As i stated earlier the 78 parts truck is rotten,, but lucky for me, it has a running 2f with low miles 78k, 4 speed tranny, transfer case and discs.. all of which i plan on putting in the 71.. and here is where i seek some advice or information... what are the things that i need to address when swapping all the above into the 71? or can someone post some links with this info for me (not sure i have mastered searching this site,yet)... ... but i am trying to perhaps learn some things that others may have encountered when doing these swaps.. any help would be greatly appreciated,,, and if anyone needs any odd and end stuff off a 78 fj40 let me know... i will stock pile most for my arsenal,, but let me know. thanks again.

2f swap with four speed and transfer case into 71 fj40? will mounts line up? any other issues? driveshafts? etc?

disc brake conversion? is it best to use whole axle housing or can the 78 discs be mated to 71 axle from knuckle out? so i can keep birfs and thirds for other 78 trail rig?

thanks ahead of time... and i am sure this will anger some of ya,, i apologize for that,,, and i am sure that this info is on this site,,, i just can't find it... thanks again.
i did my 70 with 2 f and 4 speed and it all bolted up.i used the 70 manifold ,carb and dissy. good luck
I did that and it was not too difficult. The additional length of the drivetrain will interfere with the rear tube crossmember so it is best you service the parking brake and TC rear output seal then swing the whole thing in together...engine, transmission, TC as one unit. Mounts are the same. You'll need to use the shroud from the '78 as the fans are different diameter. Use the '78 driveshafts and just swap the F/R axles, too. They are most likely fine-splined pinions.
I also had to trim about an inch off the tub near the tranny hump to allow the slave cylinder adequate room.


thank you so much for the info... much appreciated. if anyone has anything else to add,,, please feel free. i need all the help i can get. you guys rock...
would it benefit me in anyway to run the 78 wiring harness, instrument cluster, and steering column? or will the 2f work fine with the 71 harness?
well i dont have any specific tips, but if you get into the swap and have questions just post, i might be able to help, if not im sure alot of the more knowledgable members will be able to help no doubt. check out the FAQ section there is alot of stuff there also.
No obvious benefit to swapping the harness, column, etc.

A friend did this swap and kept everything the same. Ignition on dash, floor dimmer switch, etc.

If you prefer those things on the column then go for it.

info for ya:D since mine is a 71 it should all apply

2f will work fine with the 1f harness---some other possible issues might be compatibility between senders for oil and water temp and gauges, I have a manual oil pressure gage and my wat temp does not work right so I am looking at that
You may need to run a switched hot wire to the carb solenoid---any source that is hot with ign will work so pretty easy
what is required for the alternator depends on which one you install

also picked up this undersized alum pulley for cheap

Part # Item Box Status Price Qty Price
PWM-111 2-3/8" VBELT PULLEY Shipped on 04/27/09 $7.95 1 $7.95

Topics in the post cover

ALTERNATOR & Alternator wiring
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Kevin, there are 2 approaches for mating the trucks.

One way would be to bolt on upgraded parts where it is easy (swapping the 2F longblock for the F, 4-speed & d-shafts for the 3-speed stuff), but keep as much of the 71 stuff as possible.

The other way to do it would be to gut the 71 to a bare tub and chassis, then swap in the 78 wire harness, steer column, electronic ignition, brake booster & master, all brake lines, newer clutch MC and all lines, complete 2F, 2F throttle linkage, 78 drivetrain from tranny to axles... Basically build a 1978 in a 71 shell.

Being more interested in wheeling than wrenching, I would lean toward the first method. Swap in the 2F, but keep all the F engine electrical & fuel stuff in place. Swap in the 4-speed, but leave the clutch linkage in place. Swap the front axle, but leave the rear axle in place. Leave the 71 booster in place, only swappin in a later MC if necessary.

Post here as you put it together. If there is a sticking point, someone has usually come up w/ a solution for mating different year parts together. Or maybe you've figgered a way to get it done. Either way, there will be a document to help the next person.
Jim, not that I have any right or creds to question you:doh:, but if he has fine-splied pinions, why not swap in the rear axle, too? I think if you have only one finespline, it should go in the rear. I do realize that you are saying swap in the front to get the disc brakes, but as long as you're swapping one axle and the garage already smells like burning rubber;), why not do both? He'd eliminate drive flange incompatibility, too!

Yes sure, it can be done, but is not a necessity, and unlike swapping the 2F or the 4-speed or the disc axle, will not net any instant improvement in driveability.

Drive flange incompatiblity is dealt with by slipping together a hybrid d-shaft w/ 75-84 u-jt on one end and early u-jt on the diff end.

You're right that's it's better to only inhale Eau du Latex Flambe once if possible, so there is that.

If I am not mistaken the 71 rear has the 4.11 gearing as opposed to the 3.70 on the later?

after the lift and 4 speed swap I had my driveshaft lengths modded locally for $140 each--one old end and one new and they fit

funny how so many 71s survive to take on transplants from the later models :)
Seriously gentlemen, thanks for the info.. After some more thought and the info you guys have provided. I plan on leaving the 71 it as stock as i can. The 71 40 has never been messed with, i consider it unmolested, and it is a very solid truck for the rust belt. It is the kind of vehicle that screams low miles,,, and no salt.. was stoked to find it in cincy. It was imported from puerto rico in 79 and parked in a garage til about march 09. It has no heater (but has stock heater delete panel bolted in, and no hub cap clips on the rims (only differences i have noticed in comparison with usa 40)

Regardless i plan on leaving it a very stock daily driver. But with the seized piston in the f,, and the extra 2f tran and tc, i figure they must be swapped in. I want that reliability of the 2f, not to mention the gearing of a 4 speed. I was hoping keep the extra 78 axle parts for the trail truck (since it too is a 78)

So as far as the axles on the 71... i am thinking they will stay as is. But as far as disc brakes on the 71, i guess i need to do some research on other disc brake conversions for the 71 axle (allowing me to keep the extra trail parts). It seems obvious "now" to leave the wiring harness in the 71.

I will keep ya posted on the progress. Right now, the t-case shifter linkage (on the donor 78) is seized on the arm it bolts to, thus rendering itself the last thing standing in the way of engine/trans/tc extraction.. a little pb blaster and some heat in the morning, hopfully will do the trick.. if not,, cut off wheel and welder,,.. Thanks again for the information you guys have provided... please feel free to keep it coming... i am going to go pick the rust out of my eyes...

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