A trio of 4L60E series input shafts. From left to right: heavy-duty late-model 4L60E input shaft (4L75E), hardened 4L60E input shaft from Performance Automatic, and the stock 4L60E input shaft.

PerformaBuilt overcomes shortcomings of the 4L60E with the right combination of aftermarket parts to hold over 1,000 hp. Building the ultimate 4L60E is possible with these steps.

While the 4L80E uses a 2.48 First and 1.48 Second gear just like the TH400, the 4L60E has a 3.06 First and 1.63 Second, which was a holdover from the 700-R4 and better suited to a dump truck or ...