4R100 Transmission Cooler 1998, new and ready to install. Fits the 4R100. Ships fast from the USA.
If your 4R100-equipped Ford is dripping red fluid at the front of the frame, or a steel line between the transmission and the radiator has rusted thin or been kinked, this is the piece that gets the truck back on the road without buying a whole plumbing kit. Despite the generic name, this listing is not a cooler core. The listing photo shows a pair of formed steel cooler lines and marks only one of them, the lower tube labeled 2C3Z-7H322-BA, as the part included. The photo is captioned for the E4OD/4R100 family across 1998-2005, and the listing year is 1998.
The 4R100 is the 1998-and-later evolution of the E4OD, built for heavy trucks with the 7.3L Power Stroke, 5.4L and 6.8L V10. Hot fluid leaves the converter circuit, goes out of the case through one steel line to the cooler in the radiator tank, and returns through the other line to lubricate the planetary sets and bushings. Because the return flow is the geartrain's lube supply, a leaking or restricted line costs you twice: the fluid level drops, and whatever is left runs hotter. On these units Ford also used a cooler bypass arrangement at the case fitting on 1997-later trucks, which Sonnax supplies a replacement valve kit for, so the fittings on your case may not be simple straight connectors.
Each of the two lines has its own bends and end fittings, which is why Ford gave them separate part numbers. Replacing only the failed tube is a common, sensible repair when the other one is still solid.
Degrease the area, top the fluid up, and run the truck to full operating temperature. A pressurized line leak usually shows within one drive. Trace both tubes from the case to the radiator with a light and note which one is wet. If neither leaks but the unit still runs hot, the problem may be flow rather than the tube: a plugged radiator cooler or a pump issue can produce the same heat. Sonnax's 4R100 Flow Issues article explains how low pump volume at low engine speed starves the converter and cooler circuit. Our E4OD cooler line replacement guide walks through the flow check, and the E4OD and 4R100 common problems guide covers the heat-related failures that follow a long period of low fluid.
This listing is for 1998 and the photo identifies the included tube as 2C3Z-7H322-BA, captioned for the 4R100 across 1998-2005. Line routing on these trucks changes with engine, two- or four-wheel drive, wheelbase and whether an auxiliary cooler was fitted from the factory, so one part number does not cover every truck in that span. Before ordering, read the number off your old line if the tag is still legible, or hold it against the photo and compare the bends and fittings. If you are unsure, send us your year and VIN and we will confirm. If you are not certain whether your truck has a 4R100 or the earlier E4OD, our 4R100 vs E4OD comparison shows how to tell them apart. Everything else for this unit is on the E4OD and 4R100 parts page.
If the truck tows heavy, pairing this line with the 4R100 auxiliary cooler kit adds margin. If the unit slipped while it was low and now shows burnt friction material in the pan, plan for an E4OD/4R100 overhaul kit for 1996-2005 rather than just a line and fluid.
| Fits | 4R100 1998 |
| Part type | Transmission Cooler |
| Condition | New |
| Brand | OEM |
| Ships | From the USA |
| Warranty | 1-year |
Doing this repair right usually means replacing these at the same time. Same transmission, ships together.
A cooler line. The listing photo shows two steel tubes and marks the lower one, 2C3Z-7H322-BA, as the part included. The radiator cooler and the second line are not part of this listing.
The photo is captioned for 1998-2005, but routing varies with engine, drivetrain and wheelbase. Match the part number tag or the bends and fittings on your old line, or send us your year and VIN to confirm.
Only one line is included. If the other tube is rusted or pitted, it is worth replacing at the same time since the fluid is already drained and the fittings are already apart.
MERCON V. Top up with the engine running, move the selector through each range, and check the level on the dipstick at operating temperature in Park.
Only if the old line is kinked or restricted. Check flow at the return side first; a plugged radiator cooler or low pump output can cause the same heat and will not be fixed by a new tube.
