Build 1UZ Swap into LJ78 Prado

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Postoy

Postoy

10 Year
Joined
Sep 25, 2012
Threads
29
Messages
345
Location
Chilliwack BC Canada
Figured since my other thread is more of an overall build of my truck I would start a thread dedicated to my 1uz swap. I am hoping to get a bit more traffic from the NZ guys or SA guys since as far as I know there is only one other guy in my area that has successfully completed this swap.

So lets get on with this...

I hate to jump ship on my beloved little 2lte but this showed up today...



This will not be a quick project but I will be chipping away at swapping my 2lte for a 1uzfe.

Started pulling things apart.



Been talking with pradocruiser and he has run into some issues with the spitronic for the auto Trans. Going to be looking into some options to run the Prado Trans off the 1uz ECU.

Pulling all the dirty crap coming out.





Engine, trans and transfer case are out!












Couple pictures showing some of the differences between the 1uz trans and the lj78 trans.



Prado trans showing shift linkage (don't mind the bent shifter arm..)



1uz trans showing the shift linkage (opposite side of prado) and no space to mount the T Case linkage pivot arm



1uz tag on top of the trans



Prado tag on trans

 
Pulled the Lexus trans off the 1uz and pulled both bell housings



The housing match up perfectly. You can see the main difference is the bump for the starter. The 1uz is that the top since the 1uz starter is under the intake manifold. The 2lte is on the side.



1uz is top






Next up is to stick these things together...(Edit, this was a bit premature - See comments below)



So I pulled the Transfer case off of the A343F and compared the rear output shaft with the 1uz trans. The 1UZ trans is approx .20mm smaller than that of the A343F so options to cut down the rear shaft on the UZ and bolt the transfer case to it are in my opinion not an option. The collar seems to fit perfect but the splines are not biting deep enough and I think in the future could cause problems.

Originally thought I would be able to just swap the bell housing over from one trans to the other and run the stock Prado trans with help from a aftermarket TCU. I have found quite a few results where guys have burnt out their clutches from doing this. It would seem the A343F is not built to handle the added power of the 1uz. Its weird that it would not since this is the same series trans that is in the v8 powered LC's. Maybe the age and mileage has something to do with it.

Working towards swapping bits from the A343f trans into the 1uz trans (retaining the 1uz pump and clutches) In the efforts to retain the 1uz ECU to run both the engine and the trans.
 
Will be a nice build. Haven't had much to do with the engine but have friends who have done the swap....
As for the auto's.... Mr Toyota used the A340 series autos in all sorts of vehicles... But while they share the same basic construction the innards are different. The ones from the 2LTE trucks have less clutch plates than those from the 1KZTE. The soarer V8 autos have more clutch packs again....
Then they also changed the way the line pressure is controlled... Early autos use a cable which is pulled up when the throttle is moved. Some people think this is a kick down cable.... IT IS NOT.... all it does is open a valve and allow more pressure into the auto when you give it more gas.... Having this incorrectly adjusted will burn clutches.
Then they did a series which removes the cable and has a 4th solenoid... this is controlled by the TCU/ ECU ....
I am still learning about the auto and no longer run a factory TCU... I looked at Spitronics but found a man in Aussie who made a unit for me which we are playing with....
To get the factory TCU/ECU working you will need to make sure all the sensors are installed and working... As it looks for engine temps, speed. TPS settings, gearlever position.... etc etc....
If you are using the same motor/trans/ecu with its wiring loom you should be ok.....
Oh and I suggest you keep the factory hydraulic radiator fan it works better than any electric and is simple........

NOTE: If you weren't aware, When assembling the auto to the engine... Remove the torque converter from the flexiplate/engine... Slide it into the auto first.... Mate engine and trans together and bolt. Then thru the lower cover align the Torque converter to the flex plate and boltup.... If you try and do it with the TC still on the engine there is a very high chance it won't align the pump drive correctly and destroy the pump innards.
 
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Kbushnz - Thank you for the great information. I probably would have tried to slam the trans and engine together so thank you for saving me that headache.

I don't have the factory fan for the engine and I am not certain that mine was ever fitted with the hydraulic version so I may have to look at a flex style fan or another factory toyota fan.

Clintnz - What fan have you fit in your truck?
 
Tapage - I'm open to 5spd but I figured I would need to source more parts if I went that direction. (Pedals, ECU, Transmission, Bell housing adapter)

I already have the A343F, A341E, 1uzfe auto ecu and my truck is a factory auto. 5spd prado's in my area are a bit rare although I could probably make a set of mini truck pedals work if I had too.
 
As a side note I have found a 77 front clip. From my understanding these were 5 & 6 cylinder trucks. This clip looks like a direct swap onto my truck and looks like it might offer more under hood space.
 
Most who run autos behind their 1uz swaps say that running the factory matched a340e with the 1uz wiring is the way to go. Those who did not go this route and used an AW4, or their existing a343f, etc, are stuck finding a stand alone controller or using a radesigns manual shift kit. You would lose full auto control if you went that route. As @kbushnz mentioned, your a340e does not have manual line pressure via gas pedal, instead it has a 4th solenoid. I do not remember off the top of my head which type the a343f has. If I were you, I would tear down the a343f and utilize the output shaft and housing from it on the a340e. It should be a direct swap. Either transmission would handle the power of a stock 1uz. The a340e behind the 1uz is second in strength only to the a340e in the later model supras as far as strength goes in the a34xx family.

edit: i see you have an a341e, is this from the ls400 then? the sc400 had the a340e. the sc400 first gear is 2.804 vs the 2.531 in the ls400 transmission.
 
Yes my engine and trans combo is from a 92 ls400. The trans I have does have a cable coming off of it that is for the line pressure I assume as Kbushnz mentioned. Ill have to sort out how to adjust that in the future once the engine is in and running.
 
Some transmission information (Credit to @GTSSportCoupe)

Prado A343F ratios are:
1 - 2.804
2 - 1.531
3 - 1.000
4 - 0.753
R - 2.393

LS400 A341E ratios are:
1 - 2.531
2 - 1.531
3 - 1.000
4 - 0.705
R - 1.881

Interestingly, the SC400 A340E ratios are closer to the Prado; more sporty than the LS400 I guess:
1 - 2.804
2 - 1.531
3 - 1.000
4 - 0.705
R - 2.393
 
Postoy said:
As a side note I have found a 77 front clip. From my understanding these were 5 & 6 cylinder trucks. This clip looks like a direct swap onto my truck and looks like it might offer more under hood space.
Click to expand...

Having looked at both, I'd say the Prado front clip is better suited to a 'V' engine. Prado engine bay is shorter but wider, giving more room on each side to work on a V motor. Heavy duty 70 series engine bay is longer but narrower, more suited to the inline engines. That said, the heavy duty 70 series front clip does look cooler IMHO; I've thought about swapping a few times.
 
Yeah I wondered if there would be narrower inside. I know they look like they are from the outside but I figured maybe there would be less space between the inner skin and outer skin of the fenders (if that makes sense)

Maybe Ill wait till the engine is in and mounted then measure everything up as see whats left.
 
Postoy said:
Clintnz - What fan have you fit in your truck?
Click to expand...

I think it was just the factory viscous clutch fan on the engine. Not sure what 1UZ cars had that fan though. I'd imagine you could pull a suitably sized fan & viscous clutch setup off quite a few different Toyotas & make it work.

Postoy said:
As a side note I have found a 77 front clip. From my understanding these were 5 & 6 cylinder trucks. This clip looks like a direct swap onto my truck and looks like it might offer more under hood space.
Click to expand...

You'll probably find the inner guards will interfere with the front coil mounts? Front body mounts are likely different too. The LJ/KZJ front end does work really well with a V8, plus the position of the front chassis crossmember lets you tuck a winch right in without compromising approach angle. The 'proper' 70 series front end does look good though.

Cheers
Clint
 
I have decided to go the route of running the stock A341E trans with my 1UZ.

I enlisted the help from Jeff (Pradocruiser) as I know very little about the internal workings of a auto box and he has had success with his truck going this route. (took Jarrat and myself for a little test drive... was not disappointed)

To properly mate the A341E to the Prado T-Case the 2 the rear output shaft have to be swapped. Since the Prado only has a 2 prong pick up for the speed sensor that had to be removed from the prado output shaft and the 4 prong from the 1UZ had to be modified and fitted in its place.

The shifter shaft on the 1uz comes out on the opposite side from prado so that was swapped to the other side to match.

While he was in the Jeff replaced the Pump, shifter shaft and Torque converter seals.

Here is the 2 output shafts side by side. Top - Prado (with the 4 prong pickup already installed) / Bottom - 1UZ



Prado case and output shaft with the 2 prong pick up



Left is the 1UZ trans fitted with the prado rear shaft and the shifter shaft swapped
Right the the sad remains of a prado trans



There is a few details that I am leaving out for now but I will touch on those when it comes time to mate the Trans and Tcase together.


Thank you again Pradocruiser for all the help and the rip in your truck, It was very generous of you to invite us into your shop not only to pick your brain for over 2 hours but putting your truck up on the lift so I could thoroughly inspect was very informative. Jarrat took 136 pictures of your truck that I am sure I will be referencing in the near future while I tackle this swap.
 
Glad you finally met Jeff and saw his truck! Must have been a motivating experience to get a ride in it! And that is awesome he was able to help you out too. That is a big questionable part of the project out of the way now.
 
Ok, made it back out into the shop today...

One of the major differences between the Prado trans and the 1uz trans is the rear section of the trans.

This is the prado trans...



You can see the channels are open on the left and right compared to the 1uz trans seen here...



Since the mounting surface of the 1uz trans tail section is quite a bit smaller the side sections have been open to the elements their whole life and need to be cleaned thoroughly before assembly (which I have already done in this picture)

I guess if one got really adventurous you could take the entire trans apart and mill out these sections to match the prado trans but theory has it that there is enough pressure pushing fluid back and forth it shouldn't be a problem. As a side note, I did not opt to drill and tap out the bottom bolt like I've seen on other swaps. I think with the right sealer there should be enough bolts holding everything together.

Another hurdle to over come when converting the 1uz trans to 4wd is the 4wd shifter pivot point.

Prado shifter pivot mount


The 1uz trans lacking of a shifter pivot point


So after a few measurements I came up with a fairly easy solution for this pivot point.



After sorting out the shifter pivot point it was finally time to assemble this whole thing once and for all (knock on wood)



Now I just have a bit of wiring to sort out then its time to mock this thing up in the truck and fab some mounts. This wont be for a few weeks as I am packing up and moving one town over next weekend but I am super motivated to get back on this thing! I cannot wait to drive it again and start going on some adventures.
 
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