Adding programmers, exhausts, cold-air intakes, suspension lift kits, bigger tires, and larger diameter wheels looks killer on today's heavy-duty diesel pickups. A 3/4- or 1-ton truck just looks right with all the added burliness and muscle-not to mention the authoritative exhaust note from all those angry ponies. With today's technology, it is quite easy to add 100 hp, or even 200 hp, with over-the-counter bolt-on modifications. The transmission is where the problem arises. Factory diesel transmissions are far stouter than ever, right off the assembly line; but that's still not enough. With a computer tuner set on "kill," and a stock transmission trying to harness it all, slippage and parts breakage were sure to follow.
We visited with our friend, Nic Germano, and glanced over his wounded '01 Ford F-250's transmission. Plenty of power, coupled with a stock automatic transmission and 39-1/2-inch tires, and Nic's 4R100 said adieu. Luckily, a gracious Northern California dealer put the transmission on the warranty list and handed Nic a fresh in-the-crate replacement. After conversing with Matt Bozarth at ATS Diesel Performance, we had a pile of parts to install with the new slush box that was sure to help. We then added to that a full synthetic lubrication allotment from Amsoil. Check out how it all went together.
Hanging from a forklift at Irvington Wheel and Brake, we began by pulling the drain plug and draining the fresh fluid out of the new, Ford replacement transmission. | 
With the fluid removed, it allowed us to pull the miniscule stock transmission pan. Automatic transmissions hate heat and we need much more fluid to help counteract the forces that ate the first transmission. |
Side by side, the differences between the stock trans pan and the new, huge ATS piece is apparent. | 
Per ATS's instructions, we pulled free the front valve body and accumulator plate. The plate will be modified and the valve body will be swapped for the reworked ATS counterpart. |
A couple of the accumulator holes needed to be drilled out to modify the 1-2, 2-3, and 3-4 shift firmness. Our choices were between soft, firm, and hard; we picked firm, and then drilled out the accompanying holes to the corresponding sizes per the enclosed paperwork. | 
After aligning the accumulator plate and ATS valve body, the two were cinched to Ford factory specs. |