Let’s investigate each of these things separately. Second, we need to know what normally fails when a stock torque converter is subjected to heavy loads and/or high power output from the engine.

A 100% coupling is achieved only after the lockup clutch, if the torque converter is so equipped, is engaged. First, a 100% lockup is never achieved by the fluid coupling in a torque converter. That’s a gross oversimplification for a complex device, but there are only a couple of things we need to know. For this discussion, we can define a torque converter as an RPM-controlled fluid coupling that replaces a conventional clutch to allow the engine to continue running when the vehicle is stopped in gear. If you want to know more about how a torque converters work, see “Understanding Torque Converters” and “Understanding Stall Speed”. To most folks, the internal workings of a torque converter are largely a mystery, and we’re not going to try to explain how a torque converter works here, except in the most rudimentary way. However, for those owners who will subject their diesel trucks to frequent or sustained high loads, the torque converter is another potentially weak part of both Dodge and Ford diesel automatics, and that is what this article is all about. Similarly, it would add extra cost to provide torque converter capability beyond the minimum needed to meet most anticipated vehicle usage. We’ve already talked about the compromise between automatic transmission shift quality and reliability of Ford E4OD and 4R100 transmissions in “Why Add a TransCommand” elsewhere on this site. Things like vehicle weight, towing capacity, engine speed and torque output, shift quality, and cost are all considered by the vehicle manufacturer, and this is where compromises are made. Of course, the automatic transmission used in such vehicles must be up to the job, while still providing acceptable drivability, smoothness, and reliability. In fact, many such vehicles aren’t even offered with a manual transmission. Nowadays, most people prefer an automatic transmission mated to the diesel engine in a pickup or SUV.

Dodge 48re torque converter drain plug