4R70W vs. 4R75W

[BlueThunderPerf]

I finally had a chance to do some research on and take apart a 4R75W to see the actual differences between it and the 4R70W. They are minor, but are as follows.

The planitary ring gear was revised. It doesn't look much different, but the OSS sensor will send incorrect data to the PCM if used in an older vehicle. Basically a 4R70W has to be used with a 4R70W PCM, and a 4R75W has to be used with a 4R75W PCM.

The front pump assembly was revised to a much more efficient design. This part is compatible with a 4R70W, and would be a good upgrade if you have to replace a pump.

A wave plate is now used in the intermediate clutch. This part could also be used with the 4R70W.

Some of the accumulator springs may be also different, but these are the only major difference between the two. And despite some of the rumors going around the internet that the 4R75W can handle a WOT shift into overdrive, I wouldn't try it too many times. Especially if you have any mods. You don't want to have to take the whole damn thing apart to replace that overdrive band. The 4R75W is also used in the 04+ F-Series, E-Series, and Crown Victoria Police Interceptors.

[Petrograde]

Thanks for that info... :up:

[SergntMac]

The planitary ring gear was revised. It doesn't look much different, but the OSS sensor will send incorrect data to the PCM if used in an older vehicle. Basically a 4R70W has to be used with a 4R70W PCM, and a 4R75W has to be used with a 4R75W PCM. Hey, thanks for the defined 411, we have been beating each othr up trying to find exactly what's different. Would it be worth it to buy a complete 4R75W new or from salvage to install in place of the 4R70W. I have often said "not", but that was without knowing the full list of changes. Now, it all looks different.

BTW, I have the 4R70W in my early '03, and an '04 EEC with MAV2 software, are you sure they are not compatable?

Thanks in advance!

[David Morton]

I wouldn't just go using the wave plate in a 70 because the 75 has one. Chances are very good they added either a lot more fluid pressure or enlarged or deleted an orifice in order to use it. A wave plate basically cushions the application of a clutch pack, and unless something else is adding speed to compensate for it, it can cause the clutches to burn.

When I worked at Chevrolet the "125" 3-speed FWD tranny sometimes burned out the low-reverse clutches, causing the car to lose reverse and engine braking when in manual low. The stack-up for that clutch pack had two wave plates, one on each end, and the fix was to toss out one of them and use a flat steel instead. It made a firmer reverse engagement, but they never burned again.