hello, my name is chase and i was gonna throw together what i found helpful when i did my 3.4 swap on my 1991 toyota pickup sr5 manual to a 1996 toyota t100 manual i found it really hard to find a lot of the information i needed quickly and resources needed to get the swap done effectively.


im going to break this swap into a few different parts and explain what i had to do to get it done.


motor install.

this was actually the easiest part of the swap. when you take the 3.0 if you have a manual transmission you can bolt up the 3.4 engine with the 3.0 mounts but if you do your going to need to get a hood scoop or a 2 inch body lift. this is the one i used .

when getting the motor ready to install this is what i found to be the correct order of stuff to use. on my 1991 it had a ac pump that uses r22. so i had to use that compressor on my 3.4 mount. the problem i had was that my 1991 ac pump had a v belt instead of a serpentine belt. in order to get the ac to work properly and also line up with the rest of the belts i had to install a ac clutch pulley for a 1995 jeep cherokee. they have them pretty common at a wrecking yard and quite easy to get to seeing how its on top of the engine rather than the bottom of it.. the 3.4 ac pulley will likely not line up properly. i bought one and it was about a half an inch off. if yours uses r134a you can avoid a lot of this complexity. heres a resource for that https://www.yotatech.com/forums/f160...4-swap-251179/

i would not use the stock air filter box if you dont have to. it doesn't fit correctly in the compartment. i got an aftermarket one on amazon.

the crossover pipe is the hardest part on this swap.. all you have to do is follow this guide
https://www.yotatech.com/forums/f160...r-pipe-138902/

use the 3.0 power steering pump and mount it to the 3.4 so you can use all your fittings etc from you 1991
i used the alternator from my 3.0 and it mounted onto the 3.4 very nicely.
i used a flywheel and clutch for the 3.0, and the starter from 3.0.
one thing you will want to do before installing the motor is you should install the oil pan cover from your 1991 to the 3.4 because it will likely not fit properly if you do not. in addition you should move your oil sensor form the 3.0 to the 3.4 because if you use the one currently on the 3.4 it will fry your gauge. when you have the oil pan off you might as well drill the whole on the driver side for the dipstick seeing as the front facing one will no longer be viable due to fitting problems. make sure to plug the old dipstick plug as well.

after you get the engine installed here comes the difficult part which i had to redo multiable times. people on this website are not electricians so the guides they have are really confusing to someone like me with a electrical background.

i suggest the first thing you do is buy the 2 day version of TIS (toyota information system) and download all the prints for your 3.4 and 3.0

on mine i did it a bit differently. i made a adapter harness and it saved me a lot of confusion. i got the plug set from my 3.0 harness and cut the ends off and cut the body harness plugs off the 3.4 donor. so it was just a matter of using the guide and matching the colors and would allow me to return to the 3.0 if i ever deemed it necessary. i would definitely label each connector so you dont get confused when wiring them up and definitely double/triple check your work. frying a computer is definitely a possibility if its done hastily.

when installing the fan you may have to cut it down to get it to fit correctly into the shroud. i had that issue on mine but then i ended up scraping the fan and installing a ford taurus fan with a volvo relay. im really happy with it keeps the truck cooler than i expected with little/no hiccups.

electrical

here are the big things that i've noticed people on here get hung up on
-the starter
the starter is a little different when it comes to wiring then the 3.0. you need to run a wire from the starter to the ecm starter wire (typically b/w)
-fuel relay.
if you use the existing relay in your 3.0 it will save you a lot of time. its just a matter of hooking the cor relay (typically green/yellow) to the 3.4 fpr (typically green/yellow as well)
- the 4wd relay. tbh on this i experimented with a few different techniques and it didn't perform the way i wanted so i just used this tutorial and put manual hubs on my truck http://www.4x4wire.com/toyota/tech/autohub/. i plan to use the 4wd switch later to do my rear locker.
-hooking the the odb port
sense the odb is hooked up in the body harness you are gonna need to trace out the 2 wires and a ground to hook this up. it comes really in handy if you make any mistakes along the way.
the resources i used where


easy to understand diagram of wire matching for t100 1996
https://www.yotatech.com/forums/f160...emonch-223093/


wiring ac
https://www.yotatech.com/forums/f160...4-swap-251179/

body harness color codes for a 1991 (ignore the lexus half of it just handy to have a color guide to look at)
https://www.yotatech.com/forums/atta...psfa8e29b1.jpg
on the 1991 as well i had a hard time locating the reverse lights which was quite a challenge tbh. ill post a guide to that soon.



ill likely add to this thread more later just started a draft today. if anybody wants to add anything feel free