Project Paw-Paw: Part 8

January 6, 2020
Story By
Mike McGlothlin

Stage 4 hybrid fuel injectors, a larger displacement high-pressure oil pump, a T4 turbo mounting system and an S400 series turbo should be more than enough to push our ’97 F-350 into 600hp territory. And thanks to adding head studs, stiffer valve springs and stronger pushrods, the 7.3L should have zero issues handling elevated boost and rpm. However, as far as the factory E4OD automatic is concerned, it won’t last a day behind that kind of horsepower—and especially the 1,100 lb-ft of torque that comes with it. It goes without saying that we’re pulling the trigger on a performance transmission build this time. It’s a pricey proposition, but we didn’t come this far only to be denied the ability to enjoy 600hp!

To get one of the best E4OD transmissions money can buy, we took a trip to the southern California desert and spent a day with John Wood Automotive. Thanks to our visit with this E4OD/4R100 mastermind, we were walked through everything that fails in Ford’s four-speed automatic, as well as what Wood does to ensure it never happens to his customers. Then, we went over all the hard part upgrades that go into one of his Street Performance E4OD transmissions. From the Maraging 300 steel input shaft, to the increased count BorgWarner and Alto clutches, to the billet stator torque converter, we have zero doubts about our fortified E4OD’s ability to harness Paw-Paw’s newfound power.

John Wood’s Street Performance E4OD

Budgeting for a transmission that needs to be able to handle big power isn’t for the feint of heart. If you want an E4OD or 4R100 that will last behind a 600hp 7.3L, you have to make every upgrade you can afford once you’re inside the transmission case. The recipe John Wood Automotive settled on for its Street Performance unit has proven reliable in applications making north of 1,000 hp at the wheels. To be sure, this slushbox is absolute overkill for our needs, but the upside is that we’ll never have to pull it again. Our advice: pay the experts to do their thing. Do it once and never worry about it again.

Street Performance E4OD/4R100 Price: $6,595

Billet Triple-Disc Converter

Transferring power from the engine to the input shaft will happen very efficiently thanks to this triple disc torque converter. Manufactured by Sun Coast to Wood’s precise specifications, the converter features a billet front cover, a billet stator with heat-treated splines and furnace-brazed internals. To help drive the sizeable turbo we installed last time (a billet S468), Wood spec’d our converter a tad looser than stock. Our stall speed will check in around 2,100 rpm, which is roughly 200-rpm higher than factory.

2,500 LB-FT Rated Input Shaft

Arguably, the input shaft is forced to absorb the most abuse in a transmission. For this reason, not even a 300M billet-steel input shaft is good enough for John Wood. Instead, an input shaft made from Maraging 300 alloy steel is employed for its higher torsional strength. Precision ground and heat-treated, the Maraging 300 steel input shaft is rated for 2,500 lb-ft of torque.

300M Intermediate Shaft

While you can get by with a cryogenically-treated factory intermediate shaft in milder horsepower setups, John Wood includes a 300M billet-steel unit in every Street Performance E4OD he builds. As for the output shaft in our transmission, it will remain stock but will be cryo-treated for added strength and improved wear resistance.

Billet Forward Drum

In high horsepower and drag racing applications, spline failure in the forward clutch drum is extremely common. To eliminate this, Wood scraps the factory piece in favor of this heat-treated, stress-relieved, billet-steel replacement.

CNC-Machined Pump

Beginning with a reusable core, Wood removes roughly 0.040-inches worth of material from each side of the transmission pump in his CNC lathe. This is crucial because, like the transmission case itself, the pump becomes warped and untrue over time. Also notice the pump gears shown above, which have been cryogenically-treated and micro-polished.

Indestructible Low/Reverse Hub

A major weak link in the E4OD/4R100 design lies in the Low/Reverse hub. Under periods of high torque loads and stress it can flex and even blow apart (this is especially common on high-powered trucks with big tires). To keep this catastrophe from ever occurring, Wood TIG-welds an Inconel reinforcement ring to both the top and bottom of the L/R assembly.

Re-engineered Coast Clutch Drum

Due to only being secured in place by a small metal dimple, the factory retaining snap ring within the coast clutch drum assembly is prone to working itself loose over time. John Wood’s end-all, be-all fix for this frequent problem is to cut a groove around the entire coast clutch drum. Now, the drum itself is what holds the snap-ring in place.

The Right Mix of Clutches

For optimum holding power, Wood increases the clutch count within the transmission. However, it’s the trade-secret mix of BorgWarner and Alto clutches that make the Street Performance E4OD so special. Over the years, his vetting of various clutch materials has landing him a combination that can stand up to big torque input while also lasting indefinitely.

Improved Center Support

Eliminating the sloppiness found in every E4OD/4R100, Wood machines both sides of the center support, removing nearly 0.070-inches worth of play (as well as machining grooves to accept snap rings). Tightening up these tolerances allows the center support bearing to lead a long, healthy life by keeping everything inside the transmission operating in a straight and centered line.

Custom-Tailored Valve Body

John Wood’s built transmissions have long been known for their quick, yet smooth, shifting characteristics. Based on input from the customer and a list of all of the truck’s engine mods, Wood adds the final touch to his transmissions via a custom-tailored valve body. In our case, we expect firm, crisp upshifts with very little rpm drop—but not shifts so hard that you feel them in the dash.

Extra ATF = Added Insurance

Seeking a transmission pan that offers increased fluid capacity, a port to install our temperature gauge and that doesn’t break the bank, we’ve settled on the E4OD/4R100 pan from Goerend Transmission. Its CNC-machined pan is made from lightweight cast-aluminum, it accommodates a 1/8-inch NPT temperature sensor, comes with a high-quality Duraprene gasket and adds an extra 4.5-quarts of ATF to the equation. Goerend’s pan was also designed with a sloped floor, so you get 100-percent drainage during service intervals—something we’ll be doing annually to keep our Street Performance E4OD in tip-top shape.

Transmission Pan Price: $235

Billet Flex Plate

Big torque is known to tear the center section out of factory flex plates in diesel applications, so we’re taking no chances once Paw-Paw is up and running. Much stronger than the factory piece, this flex plate from Elite Diesel Engineering is made from 4340 billet-steel. And because the 7.3L Power Stroke is externally balanced, the counterbalance that’s built into Elite’s flex plate makes it a direct bolt-on.