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Ford E40D Transmission Upgrade - Dieseltech

Upgrading A Ford E40D Automatic Transmission

Photography by K.J. Jones

A quick fact check:
It makes no difference which Ford engine is under the hood of your truck. The bottom line is the truck's driveline is nothing without a dependable transmission. Our '95 F-350 dualie is powered by the venerable 7.3L Power Stroke diesel powerplant, and thanks to a great maintenance regimen that includes regular oil changes and other truck-care services every 5,000 miles, the engine is as strong as ever with 90,000 miles showing on the odometer. While 90K is considered low mileage by many diesel fans, the same cannot be said about other parts of the drivetrain, especially the E4OD four-speed automatic transmission.

Our second-generation (mid-1990s) version of the E40D really isn't the heavy-duty transmission you'd think a vehicle like a 1-ton needs. This four-speed, overdrive first came on the scene back in 1989 as the successor to the truck-minded C6 three-speed automatic. Despite having overdrive (an answer to the cry for better fuel economy), the E4OD left a lot on the table in terms of shift quality, overall performance, and durability, which are the three main criteria that have raised our concerns about the transmission.

Our truck's transmission is basically the same unit found in Ford's lighter-duty pickups and vans, and it does work well in those vehicles. However, in a workhorse like the F-350, which spends the majority of its road time hauling heavy payloads or towing a (usually) loaded, enclosed race car hauler, the factory E4OD doesn't have nearly the same performance lifespan as transmissions found in comparable vehicles from other manufacturers.

The last time we were at STC, the guys had concerns about the line pressure in the rig's original transmission. Prior to getting started with the swap, Dave Rangel connected a gauge to measure line pressure and took the truck for a road test to see exactly how the unit was doing. The results were not good:

First Gear, idle: 65 psi
Second Gear, 1,800 rpm: 70 psi
Third Gear, 1,800 rpm: 75 psi
Coasting/no brake: 65 psi

These pressures are well below the 100-plus-psi required minimum. We also noticed during the road test that the soft-throttle shift points were lower, but not too far from normal.

Some of the common problems for E4ODs are (forward-clutch) center-support failure, flat-spotted sprags, coast-clutch failure, slipping torque converters, and extremely sloppy First-to-Second and Second-to-Third gear shifts. While we're fairly certain that the first two internal maladies were among our tranny's issues, there's no doubt whatsoever that the other three (failing coast-clutch, roasted converter, and late gear shifts/slipping) were at the forefront for transmission concerns to be addressed.

While we were aware of the lack of snap, overall sogginess of our truck's transmission (up- and downshifts) and the total lack of any sort of engine-braking capability on deceleration, the trans was still somehow getting the job done whenever we climbed or descended big grades with a load in tow. That being the case, we admit that we put up blinders to any real problems. We were diligent about the service routine and assumed the low-miles gearbox was theoretically in the same good shape as the engine. It was wishful thinking on our part.

Bill Sanders of STC Performance Truck and RV gave us the reality check about our transmission when we visited his Norwalk, California, facility so that lead technician David Rangel could install BD's exhaust brake and TorqLoc torque converter lockup system.

Diesel engines are torque monsters and generate their power in the lower rpm range, usually between 1,500-2,500 rpm. Stock '94-'95 E4ODs like ours don't have the type of low-rev line pressure needed for performing well under severe-duty conditions. The transmissions end up failing because of this, in addition to weak sprags (an E4OD has three of these "one-way" clutches, which allow a part to rotate in one direction, while holding locked in the opposite direction), the bushing for the forward-clutch's center support, and other internal components' overall inability to live under the stresses imposed by the engine's torque output as it works hard against a payload.

Some sort of corrective measure was needed, and while rebuilding the trans was an option (there are several upgrades that should all be done on mid-'90s E4ODs when rebuilding), we opted to replace our worn-out OEM tranny with a TCI MaXimizer E40D (PN 491400: $2,822.65; specify 4x2, 4x4, gas, or diesel) and Truck Master high-torque, diesel converter (PN 492202: $1,144.79), also by TCI. In the long run, the new pieces cost only a couple hundred dollars more than a rebuild.

Known more for its strong lineup of high-performance street and racing transmissions, TCI of Ashland, Mississippi, also makes transmissions and torque converters for heavy-duty truck applications. The MaXimizer E4OD features several different components that help make it the true, heavy-duty gearbox for any truck that sees regular towing duty. Among the new parts are a replacement center-support that features a ball bearing instead of the factory-style bushing (which is prone to wearing and seizing); new intermediate, reverse and overdrive sprags; and TCI's Trans-Scat valvebody recalibration kit, which helps improve fluid flow, reduces heat buildup, and enhances shift quality to a level that's much firmer than the original transmission but not quite as "neck-snapping" as the gear changes of a full-competition unit.

It's important to note that a MaXimizer E4OD's shift points will not be any different from the factory-programmed intervals. E4OD transmissions are controlled by the PCM, so despite the improvement in valvebody operation, the transmission's shift points won't change unless modifications are made in the processor.

Our new Truck Master torque converter features a 6-lug, billet-steel cover as well as a triple-disc clutch pack and steel stator. With our truck's stock 7.3L turbodiesel, the converter's flash stall is around 1,300 rpm-a 30 percent reduction, as the stock converter stalls at 1,800-2,000 rpm. According to Lowell Poff of TCI, there's a major efficiency benefit in going with such a low-stall converter. "Our transmission and torque converter work well for this type of truck (used primarily for towing) because with the higher fluid pressure and low stall speed of the converter, and subsequent lower engine rpm, the converter has less potential to slip. This helps keep heat to a minimum and increases the longevity of the transmission unit. Heat is by far the number-one killer of a transmission," Lowell says.

The last order of business is a final road test and pressure check. The test shows that line pressure in our new MaXimizer E40D is well within TCI's accepted pressure ranges for this transmission, a major improvement over the numbers we logged in our initial road test.

First Gear, idle: 95 psi
Second Gear, 1,800 rpm: 120 psi
Third Gear, 1,800 rpm: 115 psi
Coasting/no brake: 125 psi

Cool Cool Stuff Stuff
Our tow vehicle is often subject to mega-mile trips through some seriously hot territory in the Western states (California, Nevada, and Arizona). As we mentioned earlier, heat is one of the biggest killers of any automatic transmission.

The truck's new TCI MaXimizer E40D transmission (along with its high-torque converter) performs flawlessly, with smooth and firm upshifts and distinct downshifting when coming to a stop. The truck handles the West Coast freeways and grades at 65-70 mph without any problems. We switch the Overdrive to "off" for the steeper grades, which is recommended for heavy towing. The new transmission allows our BD exhaust brake to work much better when compared to its performance with the original tranny. It is the MaXimizer E4OD's definitive downshifts on deceleration that make all the difference.

After driving and towing the truck for about two months (approximately 2,500 miles) with the new transmission, we decided to drop the trans fluid to get an idea of how things were going with the new tranny during its break-in period. Everything looked OK by us, and the transmission fluid was still blood red. At the time of inspection, we decided to add a bit of cooling insurance by installing TCI's High-Tech Racing Performance tranny cooler (PN 823800: $99.96) and a "Max-Cool" diesel aluminum fluid pan for the E4OD transmission (PN 498010: $453.70). The new pan was filled with TCI's "Max-Shift" transmission fluid (PN 950600: $71.40 for 3 gallons) when the installation was complete.

While these parts are not required, we strongly suggest you consider adding them during the tranny swap. They will definitely help keep the tranny cooler, which will enhance its performance and extend its life.

SOURCES
Advanced Technology Lubricants Inc.
www.atlinc.org
TCI Automotive LLC
151 Industrial Dr.
Ashland
MS  38603
www.tciauto.com
STC Performance Truck & RV Inc.
www.stcperformance.com
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