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Ford E4OD Overhaul for Heavy Duty Towing and Off-Road Use

Posted in How To: Transmission Drivetrain on February 22, 2017
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Refurbishing a worn 4x4 that’s been sitting outdoors neglected for years isn’t an easy process. In our first installment we noted our 25-year-old full-size Bronco, affectionately called Eddie, was starting to show the ominous signs of transmission failure along with a 5.0L EFI that’d seen its last days.

We pulled the old engine and replaced with with a reman upgraded with a few moderate performance upgrades. Now that the engine is back in its cradle, we turn our attention to the next component along the powertrain line: The E4OD.

Eddie’s E4OD’s shifts were getting lazier and lazier as the weeks went by prior to the engine taking a dump, and the transmission felt sluggish pulling away from a stop or climbing steep grades. The transmission fluid was also closer to brown than red, with the faint odor of burned clutch.


When the engine was out we figured it was the perfect time to pull the tranny so it could be put in the hands of a professional rebuilder to diagnose and remedy the somewhat obvious internal issues. We didn’t have to go far to get the help, either.

A few miles from our office is a little shop out in the country that has more than 80 years experience rebuilding automatics between the owner and his head bench wrench. Gary Haslip’s Geezer Garage in the northern outskirts of Eugene, Oregon, is the best kept transmission secret in the Pacific Northwest. He likes it that way.

Gary, and his ace rebuilder, Phil Mitchell, have been overhauling automatics for 40 years, most of that time working for AAMCO. The two techs estimate they have rebuilt more than 1,500 E4ODs, and even after “retirement” from the corporate transmission world several years ago, they continue to add to that number as Ford truck automatics continue to come in the Geezer Garage doors.

Phil estimates he alone has rebuilt more than a 1,000 of Ford’s truck automatics since they were introduced in F-150/250s and Broncos in 1989. So we knew we were in good hands when we unloaded our greasy transmission on his workbench.

It took Phil less than 15 minutes to have the case gutted, the array of gears, clutches, steels, cases, planetaries, snap rings, valve bodies and shafts laying in a heap on the metal workbench. His diagnosis: Death by neglect.

It appears whomever the previous owners were never bothered to have it serviced since the day it left the dealer. Now, after some 220,000 miles, it was one off-road foray away from self-destructing. Our timing for having it rebuilt was perfect.


Ford’s E4ODs saw a lot of changes over the years, especially after 1994 and all the way into mid-1997 when Ford replaced it with the 4R100. (The 4R100 shares a lot of internal componants with the ’97 E4OD.) So our early model could be easily updated – and it could also be upgraded with many of the heavier-duty internals used in the Super Duty Power Stroke E4ODs of the era.

Our Bronco’s E4OD Forward Clutch pack was near death with friction splines worn down to points and the clutches burned. The Direct and Intermediate clutch packs were in similar condition.

Gary contacted his two primary parts suppiers to get their take on the best route to take for a daily-driven street/off-road 4x4 E4OD rebuild. Jerry Clopton, the owner of Perfection Plus Transmissions in Portland, Oregon, suggested using a mix of like-new used ’97 Power Stroke E4OD and ’98 4R100 components to replace some of the weaker components in the ’89-‘95 F-150/Bronco transmissions.

In addition to stouter internal hard parts, Gary ordered up high-performance Alto PowerPacks from the Portland branch of Transtar Industries, a major suppier of transmission parts world-wide, so we could upgrade the clutches with Red Eagle frictions and Kolene steels, along with a TransGo “Tugger” reprogramming kit.

The end goal building our psuedo-hybrid E4OD was shaping up. The overhaul would accomplish the following: 1) maximize durability; 2) minimize internal heat build-up; and 3) increase the crispness of overall power delivery on road and off. What we ended up with is essentially a ’97 Super Duty E4OD in an F-150/Bronco case.

We ditched the E9 (1989-’94) pump in our ’91 E4OD and replaced it with this F5 (1995-’97) unit we sourced from Perfection Plus Transmission. The newer model pump uses a 9-lobe vane, which provides more fluid volume and better cooling than the 10-lobe used in the early models.

It took Phil about six hours to handle our E4OD heavy-duty overhaul. Gary says the cost of such a rebuild would typically run between $1,800-$2,800 depending on the performance level of the rebuild, the year, and condition of the original parts.

He also recommends using Mercon/Dextron III ATF and a torque converter matched to the engine and vehicle use. We slipped in a TCI Staurday Night Special Maximizer TC, setup with a 1,800-2,200rpm stall to match Eddie’s warmed up 5.0L EFI. A little muscle work under the truck and some 17 quarts of ATF later we headed out on our first test drive.

What a difference a performance transmission and properly matched torque converter makes! Our truck’s E4OD shifted faster, with a nice crispness. The big Bronco pulled hard off the line, snicked up through the gears and settled in with a little bump into overdrive when it hit highway speed.

Downshifts are also quick and firm, and in Low range the feel of power is even more impressive – even for a little 302. Eddie-The-Bronco has never felt better—and neither have we.

(Editor’s note: Next month we tackle the rust cancer around the rear fenders, and wrap our Bronco with new look. Stay tuned!)

We kept the OEM solenoid pack because the ’95-later versions use a different connector and we didn’t want to change the wiring harness just for the sake of using a newer solenoid.
Phil installed the TransGo 4R100 LU boost valve, spring and seat so our F5 pump would provide firmer lockup and have higher durability than it would stock. Mods give the E4OD higher flow and pressure, which is a great combination for street performance and off-road applications.
TransGo improves flow and quicken shifts by enlarging the hole in the cup plug of the ’95-older E4ODs pump cover from .086” to .093.”
One safety step Phil uses in E4OD overhauls is “staking” the new pump body bushing in place because they have been known to turn after assembly, blocking the critical oil passage. No oil, instant fry.
Another preventative measure that Gary Haslip, the owner of Geezer Garage, takes with the F5/F8 pump body is to use super glue on the seal and install two tiny metal screws, one on each side, to ensure the seal would never blow out.
One essential tool for proper pump assembly is a locking band that holds the cover and body in perfect alignment while the halves are bolted back together. Phil says a common mistake DIYers make is just eyeballing the alignment, and then finding out the pump doesn’t fit properly in the case.
Replacing the three-friction E4OD OE Direct Drum with a four-friction version from a V10 4R100 transmission improves shift performance and durability because of the added clutch. We used Alto Red Eagle frictions and Kolene steels in our rebuild.
Our E4OD had two frictions/steels in the Intermediate Clutch. Phil upgraded to three Red Eagle frictions and Kolene steels, and used the thinner pressure plate that came in the Alto PowerPack (#26756) kit. Upgrade reduces clutch slippage and fluid heat.
Some changes in the clutch packs don’t seem that big, but Phil said going from the two OE steels and frictions to four thinner high-performance steels and frictions (Alto #26758A) in the Overdrive Clutch will make the shift from 3rd to O.D. firmer during ¾- to full throttle acceleration. This also requires using a thinner pressure plate in the clutch pack.
E4OD rebuild gasket kits come with a lip-type seal (top) for the Direct Drum. The TransGo shift kit replaces that with a lathe-cut seal, which provides a much better seal and ensures maximum fluid pressure to the 3rd/Reverse clutch pack.
Even though Phil has built literally more than a 1,000 E4ODs over the past 40 years, he still makes sure the spraqs rotate in the proper direction before they are placed in the drums. The sprags in the Intermediate and Overdrive drums turn counter-clockwise. The E4OD Low-gear sprag turns clockwise.
One of the most critical upgrades on any pre-‘95 E4OD is replacing the Center Support and Center Shaft. The OE outer ring of the aluminum support used in Pre-‘95s will wear (left) where they make contact with the transmission case. The slight wear in those critical areas is the leading cause of burned clutches in the Forward Drum.
The late-model E4ODs (and all 4R100s) use a redesigned Center Support (modified to accept a snap ring) and Center Shaft (right) that rotate in a robust bearing assembly. The earlier style (left) used a tiny bronze bushing around the Center Shaft’s tip to keep these critical components in perfect alignment. Our parts came from a ‘98 4R100, sourced from Perfection Plus Transmission Parts.
Another critical upgrade is replacing the factory E4OD aluminum planetaries with steel versions found in 4R100s and Super Duty E4ODs. The reason for the switch is because the steel splines that mate with the Input Shaft will not strip out when used with diesels and high-torque V8s.
Phil upgraded our E4OD’s Forward Clutch from the three OE frictions to six Alto PowerPack high-performance Red Eagle frictions, Kolene steels, and a thinner pressure plate for greater holding power and heat dissipation. Perfection Plus Transmission raised the snap-ring groove in both the Forward and Direct drums to accommodate the additional clutches.
Maintaining proper clearances when the clutch packs are rebuilt is critical. The Alto PowerPack notes say the gap between the Forward Clutch pressure plate and the selective snap ring is between .040-.075-inch. Ours measured .053-inch.
We upgraded the Forward Planetary as well, going from the three-pinion aluminum version to a steel six-pinion (left) used in the ’97-2005 4R100s.
Perfection Plus Transmission modifies the inside of the six-pinion Forward Planetary to accept a thicker Torrington bearing (right), which means it’ll handle higher-than-stock torque loads.
Another modification that Phil did to our E4OD was replacing the brass bushing in the Output Shaft with a steel cup plug that comes with the Center Shaft hub assembly kit. The plug has an orifice that allows lubrication to the Rear Planetary and Park gear.
“Staking” the rear thrust washer is a trick Phil found quite helpful when re-assembling the E4OD. This keeps it in place when the transmission is inverted to stack the parts inside the case.
A junk transmission case makes a handy stand to support an E4OD as it’s reassembled.
Pay close attention the the Line Pressure Modulator Valve. The one in our transmission was worn and scuffed. Any wear in this critical area leads to loss of line pressure and burned clutches. We replaced the worn one with a larger (.427”) version to bump line pressure to that found in a stock Super Duty E4OD.
We used a TransGo reprogramming kit (#T36169E) for our ’91 Bronco E4OD rebuild. It contains all the springs, valves and other parts to beef up the ’89-’94 valve body, including detailed directions and diagrams.
When the drilling stopped, Phil had popped more than a half-dozen new holes in our ’91 Solenoid Pack per the detailed instructions that came with the TransGo reprogramming kit. The mods help increase fluid volume, cooling and line pressure, all which lead to better on- and off-road performance.
TransGo also includes a new Accumulator Valve Body plate in their reprogramming kit. We then enlarged three holes (per the diagram/instructions) to make the 2nd, 3rd, and OD shifts slightly firmer. Kit fits 6-cyl, V8/V10 and Diesel E4OD/4R100 applications.
After the E4OD has all of its guts back in the case, Phil bolted the modified valve body components back into place.
Don’t paint the edge of the E4OD bell housing. Leave it bare and make sure the engine block mating surface is also bare metal. This ensures a good ground between transmission and engine, preventing electrolysis from eating up the bronze bushing in the E4OD pump. Once electrolysis starts, pump failure soon follows.
We capped off our E4OD overhaul with a TCI Saturday Night Special Maximizer (#492210) torque converter, custom built to provide 1,800-2,200rpm stall. The bump in rpm will give our warmed up 5.0L FSB quicker acceleration and greatly Improve low-end power on and off road.
Gary (right) marks every automatic transmission that heads out the door of Geezer Garage with notes on when it was rebuilt, who did the work, and what upgrades were made. The mods made to our hybrid E4OD made it a cross between the transmission used in a ’96 Ford light-duty and ’98 Super Duty.
Mixing and matching th right parts will beef up any Ford E4OD to handle more power and the demands of hard off-road use.


Upgrades/updates to beef up your truck’s Ford E4OD automatic to handle the rigors of engine mods and off-road use. Tips courtesy of Gary Haslip, Geezer Garage:
Rear planetary. Keep the three-pinion OE aluminum one if it doesn’t show signs of wear. This planetary seldom causes issues. If in doubt, replace it with a six-pinion steel version used in the Power Strokes.
Low Reverse Clutch. When installing the Low reverse frictions make sure the clearance is between .020-.040” to shorten the delay going into reverse. You can use perfromnace frictions and steels to get the tighter tolerances.
Center support. If it has a little bronze bushing (Pre-‘95). Toss it. Upgrade to the bearing version (’95 E4OD and 4R100). While the center support is out, add a gasket available from Sonnax #36743G.
Front planetary. Change from OE three-pinion aluminum to a six-pinion steel used in the Power Strokes because the splines in the aluminum planet strips.
Intermediate Clutch: Replace the two OE frictions and steels with three Red Eagle frictions and Kolene steels.
Overdrive planetary. Change the overdrive planetary to steel. This is a must as the aluminum versions had a tendency to split the neck.
Center Support Hub: Install a ’96-4R100 version that uses the roller bearing assembly instead of a bronze bushing found in’95-older E4ODs. Requires newer Center Shaft, too.
Pump. Nix the E9 (’89-’94) for an F5 (’95) or F8 (’98 E4OD) to provide better cooling and higher line pressures.
Servo piston. Replace the OE servo piston if it has the snap-ring and plate for a ’96-’97 style that’s sans snap-ring/plate.
Bearings and bushings. Replace all bearings and replace brass bushings that show wear.
Note: If this is your first E4OD rebuild rodeo, get an Automatic Transmission Service Group (ATSG) Ford manual and the companion “Update Handbook,” which covers the numerous upgrades made between 1989-1997.


Geezer Garage

Perfection Plus Transmission

Transtar Industries


TCI Automotive
Ashland, MS 38603

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