• 2020

Corroded Lines



One of the many jobs that Ram pickup trucks perform is snow plowing. This is usually the domain of the 2500/3500 models equipped with a snowplow package. In many areas of the country where snowplowing is done, salt and brine is often used on the roads to melt the snow and ice.

The downside of using these chemicals is the possibility of corrosion damage to the underside of the truck. On modern vehicles which utilize a significant amount of zinc-coated and corrosion-resistant steel, this damage is not necessarily seen on the sheet metal and frame; rather, the corrosion damage can be seen on the brake and transmission lines. While corrosion damage to sheet metal, at first appearance, is a cosmetic problem.

While you might think that this should be an issue with passenger vehicles, too, it is much more common on trucks because of the amount of time spent on salty roads and the concentration of salt encountered. In addition, the air flow around a plow can direct salt spray and salt water into locations not normally reached by routine driving. Finally, passenger vehicles are washed much more frequently than snowplow trucks. This results in the removal of much of the salt buildup.

More often than not, the corrosive damage from salt is seen more on transmission lines rather than brake lines. This is due to the fact that brake lines are located higher than the transmission lines and less prone to be splashed by the snow/ ice/water mixture. Also, brake lines are better protected from the elements by other components than the tranny lines which, in some locations, are exposed directly to debris from the road. For this reason, this article will concentrate on replacing the transmission fluid lines. Specifically, our subject vehicle will be a 2014 Ram 3500 (D2 body style).


On all truck models equipped with an automatic transmission (gas and diesel engine), an externally mounted, oil-to-air transmission oil cooler (TOC) is standard equipment (see Figure 1). It is mounted to the front of the radiator, above the power steering cooler. This cooler removes heat from the transmission oil before it returns to the transmission. The oil leaves the torque converter and flows through the TOC supply line ②, through the cooler ④ and then back to the transmission sump through the TOC return line ③. The arrows in Figure 1 show the direction of the flow of the transmission fluid.

The transmission oil cooling system contains a dual function bypass valve ① between the transmission and the oil cooler. The bypass valve closes, bypassing the TOC, when the transmission fluid temperature is below 158ºF in order to aid the fluid in reaching operating temperature. The bypass valve begins to open when the oil temperature reaches 158ºF and it is fully open when the oil temperature reaches 178ºF.

Figure 1


One of the first signs that there might be a problem with one of the transmission lines is a performance with the transmission. This would be the result of transmission fluid leaking from the bad line. This might also show itself as a leak under the truck. Either way, you have a problem.

Figure 2

The corrosion is usually found in one of three locations. The first is at one of the mounting clips that secure the lines in place. The metal clip is a spot where salt can build-up. Another location where corrosion leaks occur is at the crimps on the flexible hose (see Figure 2).

NOTE: Most of the lines are made of rigid steel, but there is a short section on each line that is a flexible hose, allowing for vibration between the transmission and cooler.

The steel crimps on each end of the flexible hose is another location at which road salt can easily accumulate. The last location is the flared end of the steel line which snaps into a quick connect fitting. Salt can also build-up in this location.


Our subject vehicle is the gasoline version (5.7L/6.4L HEMI® V8) of Ram 3500. Refer to the appropriate service manual if the truck being serviced is equipped with the 6.7L Cummins Diesel engine.

The transmission fluid lines are removed in the following manner: (1) recover the refrigerant from the A/C system; (2) remove the air cleaner body; (3) remove the right front tire and wheel assembly, then remove the RH side splash shield; (4) disconnect the transmission fluid lines from the transmission cooler.

NOTE: The transmission fluid lines are disconnected from the transmission cooler using a special disconnect tool 8875A, or equivalent (see Figure 3); remove the dust cap ② from the quick disconnect fitting ①; place the disconnect tool ④ over the transmission line ③ and slide it down and engage the fingers of the tool into the
retaining clip on the fitting; when properly engaged, the tool will be flush against the fitting; rotate the tool 60° clockwise to expand the retaining clip; while holding the tool against the fitting, pull back on the transmission line to remove it.

Next, (5) remove the fasteners that secure the transmission line clips (there should be three such clips); (6) disconnect the transmission fluid lines from the transmission in the same manner as used to disconnect the lines from the cooler (see Figure 3); (7) disconnect the A/C suction and discharge lines from the A/C compressor; (8) remove and discard the O-ring seals and gaskets; (9) remove the transmission lines from the vehicle.


Install the new transmission oil lines in the following manner: (1) properly position the lines in the vehicle; (2) lubricate the new O-rings with clean refrigerant oil and install the O-rings with new gaskets into the refrigerant line fittings; (3) connect the A/C suction and discharge lines to the A/C compressor; (4) install the nuts that secure the A/C lines to the compressor; (5) connect the transmission lines to the transmission.

NOTE: Align the transmission line with the quick connect fitting while pushing the line straight into fitting; push the line in until a click is heard or felt; slide the dust cap down the line and snap it over the fitting until it is fully seated and rotates freely; the dust cap will snap into place only if the line is correctly installed.

(6) install the fasteners that secure the transmission line clips (there should be three such clips); (7) connect the transmission fluid lines into the transmission cooler in the same manner as used to connect the lines to the transmission; (8) install the RH splash shield, then install the right front tire and wheel assembly; (9) install the air cleaner box; (10) charge the A/C system.

Figure 3