I have a 1992 Toyota Previa LE 2WD non-SC Automatic. It has over 400,000 miles on the original transmission. Engine swapped out for a JDM at around 389,xxx miles when the original was overheating.

So my concern is that the transmission, the A46DE, tends to overheat. Or so I assume. I am experiencing the transmission, when hot or overheating, slamming/jerking into drive or reverse from neutral. This only happens after a lot of driving. Never when just starting my drive.

I figured that it was overheating, so I put a transmission cooler on it after the ATF went through the original radiator cooler. That did not help much in stop and go traffic. So I added an electric fan. This seemed to solve the overheating problem in most scenarios. Even in hot (90+ degree) weather in stop and go traffic the transmission never got hot enough to exhibit the slamming into drive/reverse from neutral.

I wanted to stress test the cooling capacity, so when it was 95 degrees out I went for a 80 mph cruise for approximately 25 minutes. When I pulled off the freeway to a gas station, the transmission would slam into drive/reverse from neutral. So under these severe conditions it did increase the temperatures significantly. This was with no cargo, just me the driver.

My thinking now is that the fluid capacity in the A46DE is insufficient for any severe duty. I get the fact that driving 80 mph in a minivan is highly inadvisable, especially with any passengers or cargo, but I feel that the transmission should be able to withstand this sort of abuse without overheating. At only 6 quarts total capacity, it seems that the Previa was designed for the 55 mph federally mandated speed limit in America when it was sold. Although, if I'm not mistaken, this transmission is sold elsewhere with the same fluid capacity?

Either way, I am under the impression that the Previa A46DE/A340E (in Supercharged Previas) are bulletproof. I just want to get some feedback on what other Previa owners' experiences are concerning transmission temperatures.

From my understanding, only the 4WD Previas came with a transmission temperature sensor. Although, I might be wrong.