Choosing Transmission Cooler Lines for a 47RH
The cooler lines on a 47RH carry hot fluid from the transmission to the cooler in the radiator, through any auxiliary cooler, and back to the case. Replacing them looks simple, but the right choice depends on how the truck is built and how it is used. This guide helps 47RH owners compare replacement lines, check fitment before ordering, and understand what new lines can and cannot fix.
Define the job the product must do
The 47RH is a four-speed automatic with hydraulic governor control. It was used in mid-1990s heavy-duty Dodge Ram trucks, most often behind the 5.9L Cummins diesel. Many of these trucks tow or haul, so fluid temperature and line reliability matter. Start by deciding why you are shopping. You may have a line that is leaking, rusted through or kinked. You may have a damaged fitting, a rebuilt transmission going in, or an auxiliary cooler you want to add or reroute. Each of these leads to a different purchase. A single rusted section may only need a matched replacement piece. A rebuild or cooler upgrade usually calls for a complete set and a cleaning plan.
Confirm the problem before buying parts. Fluid near the radiator or along the frame rail suggests a cooler line leak, but the fluid can also come from the pan gasket, the front pump area, the output seal, or another system dripping onto the transmission. Low fluid can cause delayed engagement, slipping or erratic shift behavior. Those symptoms also have internal causes, such as wear, band adjustment or governor problems, so they do not prove a line has failed. Diagnostic codes are of limited help here, because a leaking line will not set a code. Clean the area, run the truck, and trace fresh fluid to its highest wet point.
Check compatibility
First confirm the transmission type. Related units in the same family, such as the 46RH and the later electronically governed 47RE, look similar but may differ in routing or hardware by year. Check the identification on the transmission case and the truck's build information instead of relying on memory or a previous owner's notes. Then record what affects fitment: model year, engine, two- or four-wheel drive, cab and chassis configuration, radiator type, and whether a factory or aftermarket auxiliary cooler is installed. A listing that simply says it fits a given Ram model may still assume a different cooler setup or routing than yours.
Next, look at the interfaces. Note the fitting style at the transmission case and at the radiator: threaded fitting, quick-connect, or hose with clamps. Note the tube diameter, the end form or flare type, the overall length and bends, and the mounting clips. The most reliable comparison is your old line laid next to the replacement or its drawing. Also confirm the fluid specification for your truck. Chrysler originally specified ATF+3 for this era, and ATF+4 is widely used as its replacement. Check your service information, and make sure any hose you choose is rated for automatic transmission fluid at operating temperature.
Features that affect the choice
Replacement lines generally come in three forms. Preformed steel lines in the original style have the factory bends and end fittings, so they install with the fewest modifications. Their drawbacks are limited availability for older trucks and the risk of being bent in shipping. A universal kit built from coiled steel tubing costs less, but it requires a tube bender, a flaring tool for the correct end form, and patience. Rubber hose sections are the easiest to route. They must be transmission oil cooler hose, typically identified as meeting SAE J1532, and they need clamps sized for the hose and fitting.
Braided stainless or PTFE-lined lines with AN fittings resist abrasion and look tidy. However, they need adapters at the case and radiator, and every extra joint is another possible leak point. The braid can also hide deterioration of the inner hose. Treat labels such as heavy duty or towing grade as marketing unless the listing backs them with specifics. Useful evidence includes the tube or hose material, wall construction, pressure and temperature ratings, end fitting type, and the exact fitment notes. Corrosion resistance matters in salted-road regions. Coated or stainless steel holds up better than bare steel, which can rust under clips and where it touches the frame.
Limitations and ownership costs
New cooler lines do not repair internal wear, correct shift problems caused by valve body or governor faults, or add cooling capacity. They also do nothing about debris already trapped in the radiator cooler or auxiliary cooler. After a transmission failure or rebuild, flush or replace the coolers so contamination does not return to fresh parts. Some rebuilders make this a warranty condition, so check their terms. An inline filter can catch residual debris, but it adds another service item and more connections to inspect.
Budget beyond the lines themselves. Plan for fittings, clamps, mounting clips, and enough fluid to replace what is lost. You may also need flare-nut wrenches to avoid rounding old fittings, penetrating oil, and tube tools if you build lines yourself. Seized fittings at the radiator can damage the cooler connection, which can turn a line job into a radiator replacement. After installation, check the fluid level using the procedure for your truck. Inspect the connections after the first few heat cycles, and make sure no line rubs against the frame, exhaust or steering components. Record the work in the truck's service history.
Build a practical shortlist
Use a short checklist for each candidate. Is the transmission confirmed as a 47RH, and are the year, engine, drivetrain and cab configuration known? Has the leak source been verified, rather than inferred from symptoms? Does the product match both end fittings, including any auxiliary cooler connections? Is the format right for your tools and skills: preformed steel, a tubing kit, approved hose, or braided lines with adapters? Are the material, coating and temperature rating stated? Does the kit include clips, clamps and fittings, or must they be bought separately? Have you planned for cooler flushing, fluid and possible radiator fitting damage?
Set aside listings that give no fitment details or that rely only on generic claims. Compare the remaining options on stated specifications, completeness of the kit and your installation conditions, not on price alone. Your repair options also include replacing only a damaged section with properly rated hose and correct fittings, or having a transmission or line shop fabricate a matched set from your originals. Avoid makeshift repairs on a pressurized, hot fluid line. If routing, fittings or the leak source remain uncertain, a professional inspection is usually cheaper than ordering the wrong set twice.