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Thumbnail Filmstrip of 7.3 Powerstroke 4R100 Transmission Cooler Bypass Delete Kit DieselSite 4RCDK Images
From 1999-2003 the Ford 7.3L Automatic Transmission (4R100) 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 temps. Unfortunately, these bypass tubes commonly fail preventing transmission fluid flow to the cooler. Another design flaw is even when operating perfectly, the bypass never fully closes, meaning not all fluid is ever sent to the cooler, ever.
The result: transmission overheat.
Many delete kits are available on the market that eliminates 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 was 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.
The Dieselsite cooler bypass delete for the 4R100 comes with new banjo bolts with no spring and check ball to allow 100% fluid flow to the cooler. You must still delete the bypass tube itself!
From 1999-2003 the Ford 7.3L Automatic Transmission (4R100) 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 temps. Unfortunately, these bypass tubes commonly fail preventing transmission fluid flow to the cooler. Another design flaw is even when operating perfectly, the bypass never fully closes, meaning not all fluid is ever sent to the cooler, ever.
The result: transmission overheat.
Many delete kits are available on the market that eliminates 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 was 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.
The Dieselsite cooler bypass delete for the 4R100 comes[...]
From 1999-2003 the Ford 7.3L Automatic Transmission (4R100) 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 temps. Unfortunately, these bypass tubes commonly fail preventing transmission fluid flow to the cooler. Another design flaw is even when operating perfectly, the bypass never fully closes, meaning not all fluid is ever sent to the cooler, ever.
The result: transmission overheat.
Many delete kits are available on the market that eliminates 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 was 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.
The Dieselsite cooler bypass delete for the 4R100 comes with new banjo bolts with no spring and check ball to allow 100% fluid flow to the cooler. You must still delete the bypass tube itself!
5/5 Stars out of 4 Reviews
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Orry (Louisiana) | May 29th, 2025
I replaced my 4r100 in my 2000 f250 7.3 and realized the new trans didnt have the cooler bypass lines. I didnt need the bypass and needed these adapters asap to put the trans in the next day. The parts shipped instantly for the next day and was a quality machined part. It matched the threads in the transmission and the cooler line flare fit perfectly. No bending or modifications. Very pleased. will bring more commercial work here!
Shyanne Williams (Monroeville, IN) | May 8th, 2025
My husband wanted a 2002 Ford F250 7.3 Diesel Powerstroke, so now we are the proud owners of just that. Where I live, parts stores are few and far between, but diesel part stores? Basically nonexistent and usually they don’t carry parts for anything older than a 2010. I am on EST time zone, and their next day delivery is from their time zone. I paid for next day, and was not disappointed. I got it extremely early in the morning too so we were able to get it installed, the threading inside the tubing on our truck was damaged, but the threading on the part is well enough made that it did not get damaged and still threaded properly with the damaged set. 5 stars and no complaints.
Mike (usa) | October 12th, 2023
Work great on our 1999 F450 . excellent Product.
Captain Greg (Axson, GA) | September 21st, 2023
Worked perfect. Pretty sure my old bypass tube was failing and making tranny run warmer than usual. Installed, threw bypass tube in trash and all is well!??
Proposition 65 Warning Information -
P65Warnings.ca.gov
Fits: 7.3 Powerstroke 1999-2003 4R100
Fits: 7.3|6.0 Powerstroke 1999-2007
Fits: Universal - 80 Watts, 10 in, 800CFM
Fits: Universal