Beef Up Your Ford 4R100 Automatic Transmission And Extend It’s Life Span

Posted by on Friday, March 1st, 2013

The Ford 4R100 is a heavy duty automatic transmission that came behind the 1999 – 2003 Super Duty trucks. It is designed to handle up to 1000 ft lbs. of torque in a stock configuration. You would think that is enough holding power to live behind just about any motor. Sadly, it is not.

Guys and gals really abuse these trucks. They add power boosters that permit the big 7.3 diesels to make way more than 1000 ft. lbs of torque. Things like bigger turbo chargers, modified waste gates and nitrous all add serious power to these motors.

internal view of the 4R100


Not to mention that they abuse the transmission in other ways. They tow over the factory maximum recommend limit. The carry payloads that are heavier than the trucks were designed to carry. They keep their foot on the gas pedal going up step hills that leads to overheating. Some even use them in tractor type pulling events and extreme off-road contests.

Here are a few things that you can do to help your Ford 4R100 live a longer, happier life:

  • Install an aftermarket transmission cooler. The bigger the better. Better yet, get one that comes with its own electric fans. Be sure to mount the cooler in an area that will get good airflow while the vehicle is moving down the road. Here is a little tip: mount the cooler in between the cooler line coming out of the factory cooler and the return line going back into the transmission. This will provide extra insurance in the event that the motor overheats. The factory cooler sits inside the factory engine radiator and the engine coolant is used to help cool the transmission fluid.  If the motor overheats, it actually starts heating the transmission fluid which could lead to a quick transmission death. Ideally you want the transmission temperature to not go above 200 degrees. For every 20 degrees you go above 200 degrees you cut the life of the transmission by a factor of two. At 220 you can expect the transmission to only last half as long as it was designed to. At 240 the life expectancy is reduced to ¼.  At 260 it will be reduced to 1/8th. You get the picture.
transmission cooler with dual fans


  •  Use a synthetic transmission fluid that meets OEM specs. Synthetic fluids have much better properties under high stress and high heat conditions than do their organic counterparts.
  • Invest in a shift kit. Shift kits can be used to reduce the amount of time it takes for bands and clutched to apply. This in turn reduces wear and excessive heat buildup. A shift kit can also be used to increase the line pressure in the transmission which helps prevent the bands and clutches from slipping under server conditions.
4R100 shift improver kit


Don’t wait until your 4R100 dies. Go out and invest in the items mentioned above and keep your truck on the road with trouble free performance!

A transmission will not last forever, regardless of how well you take care of it. If a decision has to be made to replace the transmission, I highly recommend you consider a re-manufactured transmission as your first choice. They differ from a rebuilt transmission in the fact that they are as good as a new transmission at a greatly reduced price and often include modifications and upgrades that make them much more durable. A re-manufactured transmission also comes with a much better warranty: three years compared to 90 days for a rebuilt transmission.

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