4R70W Transmission Rebuild - Ford Overdrive Transmission

We were unable to find a usable replacement case for less than $100 by the day we had scheduled for the build, so Glassbrenner decided to resleeve our damaged one. His employee Randy Scott used a special cutting tool to bore out the opening. He then cleaned up the surface with a ball hone on a twist drill.

Glassbrenner prepped the new sleeve with green Loctite 609 retaining compound and tapped it into place with a 3-pound sledge.

Scott then drilled the new sleeve to match the fluid supply and return lines from the valvebody.

Glassbrenner told us that during reassembly, you have to pay the most attention to the valvebody components, checking everything for wear. "You must verify the hydraulic integrity in the valvebody. The valvebody is regular aluminum, but the valves are hard anodized [aluminum] or sometimes steel. These electronic transmissions oscillate the valves much more than older transmissions, so there is a lot more potential for wear. All specs need to be spot on." Additionally, we should mention that Glassbrenner, seen here drilling an additional fluid pressure exhaust port in our valvebody, rebuilt our transmission with a Trans-Go shift kit and new parts and a rebuilt torque converter supplied by Tav-O-Matic Transmission parts in El Monte, California.

There are a few valves Glassbrenner told us he pays especially close attention to. The first is this solenoid regulator valve that oscillates rapidly in its bore. He replaced it with the new valve in the foreground. Its improved shape fits into and seals the bore better than the stock one. If this valve fails, it can cause a sudden Neutral (i.e., no forward gears).

The second is this overdrive servo boost valve, which Glassbrenner replaces in all '01-and-newer 4R70Ws. The original valve is steel (left, upper) and wears out the bore it fits in (left lower), while the new valve (the black one) is anodized and fits into a hardened sleeve. This valve helps control pressure to the overdrive band. When it goes bad, the band will wear excessively, ultimately resulting in the complete loss of overdrive.

The last valve to watch out for is this torque converter clutch lockup bushing. If it goes south, it causes low converter clutch apply pressures and TCC slippage codes. Glassbrenner always replaces this valve. In addition, he replaces all the shift solenoids as good insurance.

The rest of the build is straightforward clutches and seals stuff. Glassbrenner soaks the clutch friction discs in transmission fluid for about 20 minutes before rebuilding, and he lubricates the seals and their mating surfaces with a mixture of automatic transmission fluid and STP engine treatment (in the little coffee can in the photo).

He also verifies that all the seals are holding pressure by blowing compressed air into the fluid passages. You'll be able to hear the pistons apply. If there is no air leaking around the seals, you're good to go. Glassbrenner says, "If it works with air, it will work with fluid."

Be aware that transmission work will require special tools, spring compressors, access to a press, and a good set of snap-ring pliers. Here, Glassbrenner installs the retaining ring to the forward clutch drum.

Also, be sure to lubricate the oil pump rotor and housing. "Don't let it start dry," Glassbrenner warns. That's a good way to burn up all the money it cost to rebuild the trans in the first place.

Finally, Glassbrenner installed the valvebody, torquing the bolts to 95 in-lb, slapped on the pan, and sent us on our way.

He gave us a can of cleaning solution to flush out the cooler and lines. You don't want to contaminate your new transmission with trash left behind from your old one.