Converting 95-02 Auto Transmission to 03-04

Howdy everyone, I figured I'd make a sort of write-up on how I got a pre-2003 automatic transmission to work on my 2003 by swapping the valve bodies. Once the swap was done, the new transmission worked perfectly with no trouble codes, and I promised @BartMaster1234 that I'd make a write-up for his reference.

A bit of background on why I did this: I'm almost done with a PreRunner to 4wd conversion on my truck, and a major issue that I came across when looking for a transmission was that there's a lot of 95-02 transmissions and not a lot of 03-04. This makes sense, since you're looking at 7 years of one style and 2 years of another, so there would be a lot less 03-04 automatics out there.

A quick rundown of the differences between the two: the earlier automatics have a mechanically-controlled throttle valve with a physical cable running into the transmission from the throttle body. The later transmission, however, is controlled off of the ECU. This means that having the wrong year would result in improper transmission control as well as ECU and hardware issues.

The usual remedy -- at least if your goal is to convert your PreRunner to a 4x4 -- is to tear apart the whole transmission: valve body, clutch packs, planetary gears, etc; just to reach the output shaft so that you can swap those with the tail housings and put it back together. I thought this was a bit ridiculous, and after doing some quick research on the differences between the two transmissions, I found that the only differences were the ways in which the throttle valve was controlled, which would mean the only difference is in the valve bodies, since they control the transmission.

Next post will show the process as well as my personal tips for swapping the valve bodies between the two types of transmissions.

 

So first things first, you have to pull the transmission. This should go without saying since most of the time this swap is applicable is for 4wd conversions, but it makes the whole job a lot less messy and a whole lot easier to manage.

Once you have both transmissions drained and on a stable place to work (for me it was my work table and a forklift). Remove the oil pans and have some rags on standby because you'll have a lot of ATF dripping out, even if you have the pans drained.



Pictured above is the 03-04 innards. Notice the solenoid circled in red - that's the part of interest, and is the only difference between the two valve bodies.



Compare the first image to this one, where the throttle valve is controlled by a cable on a rotor.

Unfortunately I do not have any pictures of my swap since it was at 10PM and I wasn't thinking that I'd be making a write-up for it. However, removing the filters is easy enough, you can clearly see the 4 bolts holding it on. Remove this to access all of the valve body bolts.



As a tip: be sure to put the bolts into 3 separate bins to keep them organized. Also I recommend writing which lengths go into which spots as you remove them, since some diagrams are incorrect (if you have the Hayne's Manual, it has the wrong lengths for some locations. BE CAREFUL AND KEEP YOURSELF ORGANIZED)

After removing the valve bodies, swap them onto the opposite transmissions along with their respective wiring harness. There is also a cap for the electronically-controlled trans that needs to be swapped over to plug the hole left behind from the cable once it has been swapped over.

With the valve bodies and wiring harnesses swapped, you can then re-install all of the bolts as your diagram indicates. I do not have the torque specs on hand, but most manuals will have that available for you (online I am seeing 7ft*lbs, but take my word with a grain of salt for torque specs).

With the valve bodies and filters reinstalled, you'll want to remove the gasket material from the rim of the main body housing in order to re-seal the oil pan. Just remove the old stuff with a razor blade and re-seal with oil and heat-resistant sealant.

With the oil pans back on, the sealant cured, and the pans torqued properly, you now have the correct throttle valve control for your 03-04 Tacoma. Keep in mind, this swap also works just as well if you are trying to install a transmission for a 95-02 but have miraculously found yourself with an electronically-controlled model.

Final notes and a word of warning in the next post.

 

So with the correct valve body in your transmission, you must make note of one thing: you must also swap your torque converter, as it can only operate correctly with its respective valve body!!

When I did my swap, I neglected to consider the torque converters, and had to go to the trouble of re-dropping the transmission and swapping the original torque converter back in. Don't make my mistake and be diligent about it the first time around. Failure to swap the correct torque converter will result in a truck that runs decently, but you will have major issues on the freeway, as the torque converter will not know when to lock-up, causing efficiency issues and possible transmission overheating under otherwise normal operating conditions.

If you make sure to swap your valve body and torque converters correctly as mentioned, you should have zero issues with your new transmission. I did this exact procedure on my transmission and do not have any trouble codes or even minor issues. This swap is not only less invasive than a full automatic transmission rebuild, it is also perfectly doable by yourself using simple hand tools. Depending on your own comfort level with rebuilding an automatic, it can even save you a significant bit of money since you do not have to pay a shop to do the work for you. I would highly recommend this method of converting to electronic throttle valve control, my only word of warning is to be very anal about the whole thing, taking your time and making sure everything goes back together as it should.

Now of course, because this is still fairly technical work, I'll tell you to do this at your own risk. Also consider that I am 22 years old as of this post, and that I had attempted this swap without any prior write-up or suggestion. Use that disclaimer and supplemental information as you see fit.

I hope this write-up was thorough enough and helpful for any of you who may be stuck in a 4wd conversion with the wrong year transmission and are looking for options.

Happy wrenching!

- Lfaub03

 

Great writeup! Love the last picture haha.

Can’t believe people go through the trouble of doing an output shaft swap if it’s this easy.

@tymeson do this instead.

 

This is what I was asking about @gearcruncher @mechanicjon

 

Given how much less invasive and intensive the VB swap is, I’m surprised it’s not really been covered yet. Happy I could give some insight on the swap!

 

Great write-up! It covers everything in detail.
Only thing I would add is do it in a clean area. With clean rags. It only takes a small amount of dirt to cause problems. Was there a steel plate between the VB and case? Do you swap it? No check balls to worry about?

 

Nice write up. If i did not fall into a good deal on a 04 trans i would have tried this. The amount of research on the 4x4 trans swap, especially for those of us in the 03/04 game is such a mountain to climb and this makes it so much easier. You will save someone alot of grief.

 

Yea definitely make sure your workspace is clean, no doing this in a sawmill or anything lol.

Behind the VB was just the fluid channels to control the clutch packs, but there wasn’t a plate or shim or anything in between the body and its mounts. As far as check balls, I don’t remember having to worry about any, but it was also half a year ago and I could be mistaken. Either way it’s not a big deal so long as you remember to keep everything in place when re-installing the VB

Also I’d recommend having a buddy hold the VB in place while you get the bolts started. It’s just nice to have

 

I didn't have many options with a 300,000 mile transmission. Figured I'd spend the same buying a cleaner history transmission or swapping output shafts. If I lived somewhere with more of a Toyota parts market I probably would have gone this route.

 

It’s all about weighing your options. Sometimes it’s more worth it to go one route, sometimes the other. I was fortunate enough to find a donor with even less miles than my factory trans, so the VB swap made more sense for my individual case

 

True that.

 

This is Not something I would normally do , however , it worked and in the end that is all that matters . With this being said , awesome job and thanks so much for the write up
Up until a few months ago , I didnt know a valve body swap from Throttle Valve to Throttle Position Sensor could be done . This is only do -able with Toyotas !
I am not saying a vb swap cant be done . Its fairly obvious that it can be done and will save you from taking the transmission all apart to grab the 4x4 output shaft .
You get 2 thumbs up from me !!
Guys have asked me in the past and I always steered them away from a vb swap but I am a transmission tech . I always fixed the original transmission .
If I had to install another transmission , I made sure to calibrate the valve body according to the rear differential ratio as well as the size of the engine .
I think you were lucky enough that the donor transmission was very close to the same year of your truck ., same engine size , same cooling system computer controls .
Torque converters in most cases are married to the transmission they are bolted up to . Converter stall stage , converter lock up control , converter clutch lining and the type of transmission fluid you use do come into play here .
I have a booklet here with all the information you need to know about the A340 series transmission .
Send me a PM with your e mail addy , and I will pass it along .

 

I wanted to ask you. When I did my 4x4 swap I was forced to use my old A340E torque converter with my A340F since the original A340F TC was warped. Shop said something about different stall speeds between the two. Is running the A340E one going to be okay? I’ve been running it for more than a year at this point.

 

Yeah I definitely made sure that the 4wd transmission was calibrated for a V6 vehicle with 4.10 final gears (That it was off of a TRD truck)

I had considered the possibility that it wouldn’t work and weighed my options. Luckily my hunch was correct and my new transmission works perfectly like my old one

 

After driving with both torque converters, I did notice a difference between the stall speeds, the 4wd TC has a higher stall speed. I suspect this is so you can have more torque from a stop because the engine is at a slightly higher RPM.

Tbh i doubt it makes much of a difference so long as your ECU is happy and your torque converter clutch doesn’t slip on the highway. I’ve wheeled in my PreRunner enough that having the lower stall speed just feels natural anyways

 

How do you calibrate the transmission for a certain gear ratio?

 

can't say I know, tbh. I'm not a transmission expert. I believe it has to do with tuning the valves and such so that it shifts at certain points given the fluid pressure created inside. The "calibration" that I have is just whatever the V6 TRD had, so I haven't touched or tuned anything aside from the VB swap itself

 

What was the condition of your 2 wheel drive transmission ? Did it function ok ?
Torque converters are married to the transmission they came from .
If there was a bunch of contamination in the bottom pan of your 2 wheel drive transmission , and you installed it to get your 4x4 transmission working again , the 2 wheel drive converter will contaminate the 4x4 transmission .
Chances are if you have been running it for over a year now , any contamination from the 2 wheel drive torque converter will now be sitting on your magnets .
Are you planning to change your oil anytime soon ?
I think you had enough bad luck last year . Lets keep our fingers crossed that everything runs good in 2019