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Project 4Reigner

Here is the in-depth write-up that I hope can serve as a how-to for OM617-swapping 96-04 Tacomas/4Runners (and T100's).

I picked up this $600 1997 4Runner 5VZ/A340 4x4 (rear e-locker) with roughly 250k miles and it was SHOT! Completely rusted out even though the body doesn't show it. Destroyed interior. Radiator blew up and mixed trans fluid with coolant to make a milkshake in the trans. Now I haven't read a single report of anyone flushing their trans and successfully driving it after that. Even the ones done under warranty at the dealership with the power flush had trans failure shortly after. Keep an eye on your radiator if you've got an automatic! The PO claims he noticed it right away and had it towed home where I picked it up. I flush the trans, added a new radiator, and put another 30k on the 5VZ! I daily drove it to work, used it to tow the mower trailer around, and even drove it 3 hours into Iowa with the trailer to get a band saw. Did a fair amount of wheeling with it, too, enjoying the rear locker. Eventually, it started losing coolant, so the 5VZ got yanked and sold.

The plan for this has always been for R&D. The only money I have into this rig is the new radiator and mounting the free tires someone was throwing away. Sold the 5VZ to cover the purchase. Can't beat that! I'm currently swapping in an OM617. I'll be using the 4Reigner to test trails I'm cutting in our pasture, as well as haul the tree cutting equipment around. Since the frame is already falling apart, I don't expect to keep this around much longer. I had originally planned to do a TDI swap after the 617, but have since decided not to worry about making TDI adapters for the Toyota Automatics, as the torque converter pilot stub would require turning down, and that is probably too much effort for most people. Once the frame folds in half, I'll pull the 617 back out to go into something long-term, and I'll save the rear axle and trans.

50 comments

50 Comments

Desmond Mcgrath

Apr 17, 2023

I like your attention to detail. I have over the years owned 5 Toyotas and Three MB diesels. I also currently have a MB 560SEL with the European Engine.. My daily driver is a 1998 Tacoma Extracab SR5 with the 2.4 engine RWD. I have been planning a contingency of putting in a 1985 300SD OM617 motor for sometime. My Tacoma has the A43D transmission which is a 4 speed Automatic non-lockup converter. 1st 2 3 4 Rev

2.452 1.452 1.000 0.688 2.212

Its the same transmission used in the Toyota Motor homes.

The 300SD was designed such that peak engine torque was around 60 MPH

mating the OM617 to the A43D with the stock rear axle on my truck would put peak engine torque at 75 MPH.

Desmond Mcgrath

Apr 21, 2023

Replying to

Your comments are interesting re the A340 Lockup in non-lockup mode.

Here is my Heat Stress experience with the 2.4 1998 Tacoma with the A43D. I acquired it in 2009 with 84,000 miles from a WWII tank veteran from the Battle of the Bulge, he was no longer allowed to drive. I completely serviced it in including flushing the transmission and putting in synthetic ATF (I also installed an auxiliary 4 pass Hayden transmission cooler downstream of the in-radiator unit). I drained the rear differential again adding synthetic Gear Oil. I also flushed the engine and installed a Frantz bypass filter. The engine has run on 0-40 European Mobil One for the last 14 years and 190k miles with a TP roll change every 2k miles or every two months and full flow (Wix) filter change every 12k miles or once a year.

Shortly after servicing the Tacoma I bought a 1995 Jaguar XJS convertible from an insurance auction and drove 500 miles to pick it up using a 2,200 lb U-Haul Car Hauler and returned 500 miles towing nearly 6,000 lbs. Before taking the trip, I installed a precision temperature Data Logger Amatek NVision. In the trip there the Trans Oil Temp maxed out at 175 and on the way back in stop and go New Orleans 4pm Traffic it maxxed out at 210 when the outside temp was 103 on I10. It was 190 for most of the 500 miles at 60-65 Mph on I59 I am not a transmission expert and only ever rebuilt one automatic myself, a 1962 Ford FMX in a 62 T-Bird. I am however a Petroleum Engineer and Hydraulics/Instrumentation expert, Heat in hydraulic fluid is in reality hydraulic Horsepower that was lost in the form of heat be it from friction or pressure drops. So, I can understand the dramatic difference between lock and unlocked. That being said you were operating the A340 in an off normal mode and at offroad speeds. The higher the stall speed the TC the more heat it will generate and I believe the high stall speed of the A340L convertor on non-lockup mode was the culprit.

Simply put the horsepower being transmitted though the transmission of a 1998 Toyota Tacoma towing 6000 lbs at 65 MPH is the same regardless if the engine is the original 2.4 Gas or a 3.0 Turbo Diesel. So the heat generated by the transmission would be the same IMHO.