4R100 Transmission Cooler 1996-97

A 1996 or 1997 Ford F-350 that tows or plows is hard on its transmission plumbing, and on a truck this age the steel lines between the automatic and the radiator are often the weakest point in the cooling circuit. This is a new cooler line set listed for 1996-97 with the F-350 as its reference vehicle. The photo shows two long formed steel tubes with their bends already made, not a cooler core, so this is the part you want when a line has rusted through, been crushed, or started weeping at a fitting.

One note on the name: the listing says 4R100, but Ford did not introduce the 4R100 until the 1998 model year. A 1996-97 F-350 automatic is an E4OD, the unit the 4R100 grew out of. Our 4R100 vs E4OD comparison covers how to tell the two apart if you are not sure which you have.

What the cooler lines do on a 1996-97 E4OD

Fluid heated in the torque converter leaves the case through the feed line, passes through the cooler in the radiator, and comes back through the return line to oil the geartrain. Behind a 7.3L Power Stroke or 460 V8 pulling a trailer, that loop is what keeps the fluid out of the range where clutches glaze and the converter clutch starts to slip. On the late E4OD and the 4R100, Ford also used an outboard cooler bypass at the case fitting; Sonnax lists its bypass valve kit for 1997-and-later units with either style of outboard fitting. On a 1997 truck, check whether your lines connect through one of these bypass fittings and move it over to the new lines.

Signs the lines are the problem

• A fresh drip at the front of the truck or a wet streak along the frame
• Fluid level falling between checks with the pan gasket and seals dry
• Heavy rust flaking off the tubes, especially under clips and near the radiator
• Bent or flattened sections from a jack, a rock or past repairs
• Temperature climbing on long pulls, or fluid that turns dark quickly after a change
• Soft engagement or slipping that started after a leak lowered the level

How to confirm before buying

Wash the lines down, fill to the full mark, and drive until warm. Then look along both tubes with a light from the case to the radiator. A leak is usually obvious once the area is clean. If nothing leaks but the truck still runs hot, measure flow before replacing hardware. Our E4OD cooler line replacement guide gives baseline flow numbers and explains why a kinked line, a plugged radiator cooler and a worn pump valve each show a different pressure and flow pattern.

Fitment

This set is listed for 1996-97 and referenced to the F-350. Routing on these trucks depends on engine (7.3L diesel, 7.5L or 5.8L gas), two- or four-wheel drive, cab style, and whether the truck had a factory auxiliary cooler, so a line made for one configuration can miss on another. Hold your old lines up to the photo and compare length, bends and end fittings, or send us the year and VIN so we can confirm before it ships. The full range of parts for this transmission is on our E4OD and 4R100 parts page.

Install notes

• Penetrating oil on every fitting the day before saves a rounded nut. Use a line wrench, never an open-end wrench.
• Photograph the clip locations first, and re-use or replace the clips so the new lines cannot vibrate against the frame.
• Flush the radiator cooler with compressed air or a cooler flush before connecting the new lines.
• Do not over-tighten the fittings; damaged sealing washers are a common cause of leaks after a line job.
• Fill with MERCON V, which Motorcraft lists as the service fluid for these units, and check the level warm in Park.

If the transmission ran low long enough to slip, pull the pan before you call the job done. A 4WD truck with a leaking or bent pan can take the E4OD/4R100 4WD oil pan with gasket, and a unit that is shifting soft may need the E4OD pump for 1995 and later or a shift kit during an overhaul.

My 1997 F-350 has an E4OD. Will this 4R100-labeled line set fit?

Yes, that is who it is for. Ford's 4R100 name started in 1998, so 1996-97 trucks have the E4OD. Compare the bends and fittings to your old lines or send your VIN to confirm your configuration.

Is this a cooler or just the lines?

Just the lines. The photo shows formed steel tubes that connect the transmission to the cooler in the radiator. The cooler itself is not included.

Do I need to replace both lines at once?

If one has rusted through, the other has seen the same salt and heat. Replacing both while the fittings are already apart avoids a second job and a second fluid loss.

What fluid should I refill with?

MERCON V. Add it slowly with the engine idling, cycle through the gears, and set the final level on the dipstick with the fluid at operating temperature.

Should I add an auxiliary cooler when I replace the lines?

For a truck that tows heavy, extra cooling is cheap insurance, but fix any leak or restriction first. An add-on cooler cannot make up for a crushed or plugged line.

• E4OD Cooler Line Replacement Guide
• 4R100 vs E4OD: Differences, Interchange & Which Is Stronger
• E4OD Common Problems and Fixes
• E4OD Pressure Control (EPC) Solenoid Symptoms