My thoughts on the Transgo shift kit
This is the second 545rfe I put the shift kit into. A tuner will move the shift points around in the RPM band, this shift kit will not do that. What it does do is shorten the time between gear shifts, that part is mechanically controlled. The OEM designed it to be nice, soft, and smooth for driver comfort. This is accomplished with a quite lengthy pause between one gear disengaging and the other engaging. The Transgo kit shortens this time to the point where it is not neck snapping but quicker and crisper which is especially more noticeable when towing. For example, the one in our Jeep the Mrs' hasn't even realized it's there. Another side benefit is it raises line pressures which has multiple benefits in an automatic transmission. There are also some other little things that are known problems in the transmissions, such as front pump relief valve sticking in early years and a slide valve in the valve body that sticks as well that this kit covers. The HD kit has a few more fixes, one for a retainer ring in one of the planetary drums but most of us won't be getting that deep. This kit is a lot easier to install than ones I have put in Chevy 350 and 700R transmissions. You are simply swapping some springs and replacing seals for the most part. The hardest thing I ran into is trying not to get covered in fluid when dropping the pan and then the valve body. My opinion is that it is a worthwhile upgrade if you have the pan off for a fluid change but I wouldn't necessarily install it just for the sake of installing it.