Two problems related to automatic transmission cooler have been reported for the 1998 Dodge Ram 2500. The most recently reported issues are listed below.
I noticed automatic transmission fluid leaking under the truck when returning from a trip. Close inspection revealed that two of the transmission lines had been rubbing together which resulted in a break in one of the lines. Fortunately, I noticed it before the transmission had lost enough fluid to fail. Had I been on a long trip towing a trailer the results of a highway speed transmission failure might have been far more serious, especially on a mountain road. The line should be replaced. This appears to be a design/manufacturing/assembly defect.
While driving, the transmission started slipping. Vehicle was taken to dealer. The transmission cooling lines had been rubbing together, which caused them to leak. The transmission had to be replaced.