Testing PPE’s deep transmission pan on a ’15 GMC Denali

Diesel transmissions have quite a tough job. As horsepower levels rose on 3/4 and 1-ton pickups, the manufacturers have done a good job at upgrading the factory slushboxes–but there’s still more that can be done. When it comes to transmission temperatures, as long as the fluid is warm enough to flow through the lines correctly there really isn’t too low of an operating temperature. Modern transmissions can run well below 150 degrees without damage, in fact, lower transmission temperatures dramatically extend transmission fluid life.

However, since diesel transmissions are some of the hardest working automatics in the business, they very rarely operate at optimal temperature levels–especially when towing. To save on production costs, most transmission pans are also usually shallow and flat, which doesn’t do much to dissipate excess heat. Fortunately, there are upgrades available!

Xtreme Diesel owner Jason Carrier started out by draining all the fluid out of the stock Allison 1000 in preparation for the new PPE pan install.
After all of the fluid ran out, Carrier then loosened all of the pan bolts, and dropped the factory stamped pan. Notice that it’s kept level to avoid spillage, as a bit of residual fluid will still be in the bottom of the pan.
When compared side-by-side, the difference between the stock pan and the deep PPE version is dramatic. Not only is the PPE pan reinforced and more rigid, it also is deeper, to the tune of 4 extra quarts of capacity.

While it might seem odd to take a factory part off of a brand-new truck, the transmission pan we acquired from Pacific Performance Engineering (PPE) is better than the OEM version in every way. The transmission pan from PPE starts off with a solid 4 quart capacity increase, which means fluid will take longer to heat up. When it does, heavy-duty 3/4-inch cooling fins help dissipate the heat. Also included is a magnetic drain plug, that’s designed to trap any particles that might end up causing trouble down the line.

After the pan is dropped, Carrier removes the factory filter, as it will not be able to be reused with the PPE pan.
PPE includes a deep filter that perfectly matches up to its transmission pan. When tightened down, internal ribs inside the PPE pan keep the filter locked firmly in place.
With the new filter in place, it was now time to install the PPE pan with the provided hardware. The factory gasket was reused.
Carrier snugged up the PPE pan hardware to the recommend specs, where it will provide added transmission and fluid life for years to come.
The final step before the test drive was to top the transmission off with fluid. Since some fluid is still left in the transmission and converter when drained, Carrier was careful to check as he went so as not to under or overfill the unit.
With PPE’s trans pan upgrade complete on the ’15 Denali, it was time to exit the lift and hit the road. Carrier reported about a 20 degree drop all around, which he said helped especially when climbing grades

Since talk is cheap, we decided to put PPE’s new pan for the 2015-’16 GM trucks to the test, by installing one on Xtreme Diesel’s shop truck, a ’15 GMC Denali. The truck had been upgraded with a 50 horsepower tune as well as larger wheels and tires (both hard on transmissions) and the owner promised to tow his 42-foot toy hauler up a grade and report back to us. He did, and an all-around drop of about 20 degrees was the result. When it comes to budget transmission upgrades that can last the life of your vehicle, there’s not much that can match the benefits of PPE’s Deep Heavy Duty transmission pan.

Pacific Performance Engineering

Xtreme Diesel

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