Should 2003 Dodge Ram 3500 Transmission Cooler be Bypassed for Derale Cooler Kit?
Updated 11/13/2025 | Published 10/26/2025
Question:
I have a 2003 Dodge Ram 3500 5.9l diesel. Your catalog lists your D13960 but can you tell me what size the existing cooler lines are, 3/8”or 1/2”. Also do you get better cooling bypassing the existing cooler? Thanks
asked by: Pete T
Expert Reply:
Hey Pete, thanks for reaching out!
I'm not entirely sure what the size is of your existing hoses, but Derale has the Hyper-Cool Remote Transmission Cooler Kit # D13960 as coming with hoses that are the same size as your OEM hoses so you won't have to worry about compatibility.
All of our coolers are aftermarket and should only be used in conjunction with an OEM cooler. These won't be sufficient enough on their own so you definitely don't want to bypass your existing cooler.
Did your old transmission cooler go out, or are you just wanting to add some extra help to it?
Product Page this Question was Asked From
Derale Hyper-Cool Remote Transmission Cooler Kit w/ Fan, -6 AN Inlets - Class V
- Transmission Coolers
- Remote Cooler
- Heavy-Duty Truck
- Remote Mount
- 13W x 10T x 5-5/8D Inch
- With - 6 AN Inlets
- Derale
more information >
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Jon G.
11/13/2025
Hey Pete, what did you end up doing with the Derale Hyper-Cool kit on your Ram? Did you decide to add it alongside the factory cooler or keep the stock setup as is? Your results could help others thinking about the same upgrade.