Automatic
Transmissions |
| Background and History |
My 4Runner came equipped with an automatic transmission since it started life in my family as a family truckster. My wife was the primary driver of this rig for several years. While she is certainly able to drive a 5-speed, I didn't want one. I had spent literally hours in stop and go traffic during commutes for past jobs. Not only that, but I'd rather concentrate on my offroad driving instead of worrying about shifting and clutch work.
| A340H |
My 4Runner came with the A340H model automatic transmission. This transmission is a three speed plus overdrive. It was found in all 4Runners and Pickups that came equipped with the 3.0 V6 (3VZE) engine and automatic. This unit is unique compared to most other 4WD autos manufactured by Toyota. It has the transfer case as an integral part of the transmission housing - it even shares the automatic transmission fluid with the transfer case. The transfer case is the chain-driven variety and cannot be fitted with different gearing like the venerable R1FA gear driven cases. In all, I found this transmission to be very reliable and only had one instance of it overheating - and this is with the stock transmission cooler.
For those who want to add lower gears to this transmission, there have been some recent developments. Two aftermarket companies have introduced ways to add crawler gears to the A340H transmisison. See the links below.
| A340F |
Toyota changed gears when they introduced the 3.4L V6 (5VZ-FE) in 1995 1/2. The automatic transmission used behind the 5VZ is the A340F. This transmission features a removable transfer case. While the transfer case can be removed, it is still of the chain driven variety and again cannot have changes made to the gearing. The other big change is that the front output was moved to the oppposite side, now residing on the driver side. Not to worry, those who wish to retain their driver side drop have an option with Marlin. Marlin's MC09 adapter and V6 adapter plate allows a R1FA gear driven case in between the transmission tailhousing and the existing transfer case.
| A341E |
The A341E is a 2WD transmission and is found behind the 4.0L V8 (1UZ-FE). This transmission is largely like the A340F internally, however it includes an additional "shift quality" solenoid. The relevance of this transmission's inclusion here relates to harvesting the parts that will enable connecting the A340F to the 1UZ. The parts that have been taken from the A341E that will be used include the bellhousing, torque converter, oil pump and input shaft/planetary assembly.
| Tundra Components |
I learned of the availablity of some used Tundra transmission parts and chose to get what I could until I could be certain that what I wanted to accomplish would work. I bought the Tundra bellhousing, torque converter, oil pump and tailhousing. Unfortunately, the input shaft had been destroyed.
I was pleasantly surprised when I received the parts. It appears that the bellhousing and oil pump are identical to the A341E. Also, the tailhousing is the same as the tailhousing off of the A340F. One difference I observed is that the Tundra torque converter is heavier. In a quest to keep from grenading transmissions, this is a good thing. I weighed both and it appears the Tundra torque converter is roughly 5 pounds heavier.
| UZ Hybrid A340F |
I call what I've come up with as the UZ hybrid A340F. My setup will start with the Tundra bellhousing, Tundra torque converter, A341E input/planetary, and the Tundra oil pump mated to the A340F (from 2000 4Runner) including the A340F tailhousing. I will need to work out the speed sensors as the A340F has one on the tailhousing, while the A341E has one up front near the bellhousing. I need to do whatever will be compatible with an LS400 ECU for my swap.