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4R100 Transmission Cooler Bypass Delete Kit

4R100 Cooler Bypass Delete Kit
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From $79.00 to $129.00
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Product Description

Allow 100% fluid flow to the cooler when deleting your cooler bypass tube!


From 1999-2003 the Ford 4R100 automatic transmission had an external cooler bypass tube that redirected transmission fluid from the pump output back to the return line of the transmission.  The bypassing of the cooler was supposed to happen until the fluid reached operating temperatures.  

Unfortunately, these bypass tubes commonly fail which prevents transmission fluid flow to the cooler.  Another design flaw is, even when operating perfectly, the bypass never fully closes.  This means not all fluid is ever sent to the cooler... ever.

The result?  Your transmission will overheat.


Many delete kits are available on the market that eliminate the bypass tube and the common failure.  However, these kits do not address the restriction in the banjo bolt.  If you look at the cut away photo of the banjo bolt, you can see the spring and check ball which restricts about 75% of the fluid flow to the cooler.  The spring and check ball were designed to allow the proper function of the cooler bypass tube.  

Once the bypass tube is deleted, this check ball and spring are no longer needed.


Works for any 4R100 model Ford automatic transmission, gas or diesel.

A kit for E-Series (Vans) is available to clear the exhaust on the front most return port.  Please choose the appropriate vehicle type when purchasing as they are not cross-compatible.

Simply remove the original banjo bolts from your transmission case, remove and discard the bypass tube, discard your original bolts, install your new DIESELSITE deletion bolts with provided crush washers, and reconnect your return lines.  Make sure the o-ring provided is seated in the head appropriately before reconnecting your return line.