Automatics ?4R70?

TGJ said:

I know that the output shaft on the 4R75W has to be changed to work in a 4R70W car. I believe a lot of the internal parts are the same except for the VB, but I honestly don't recall. I say the 75 is little more stout because the numbers behind the R are a torque rating. 75 is greater than 70.

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I thought the 70 was for the O/D gear ratio .70

Nope, it's a torque rating. I'm not sure how they arrive at the number they use, but the way I understood it is if the number is 70, you're looking at a 350 tq rating, or 5 times the number (or 10X 1/2 the number). 75 would be 375 tq rating.

.70 is also the OD gear

Mine holding up, running 12.5's with 1.7 60ft and no trans issues.

Mines holding up well with over 380rwtq at the wheels. I did the J-Mod 2 years ago and combined with a good tune it shifts much better. It's also known to be quite stronger than the 5 speed Mustang trannys.

ProCharger GT said:

.70 is also the OD gear

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While this is true, it doesn't explain the "75" in "4R75W". I can guarantee you that the final drive ratio in this trans is not 0.75.

Discuss.

Matched to the new 5.4-liter V-8 is a new 4R75E automatic transmission, an evolution of the 4R70E used on the current F-150. Upgraded to handle the torque of the 5.4-liter engine, this transmission shares patented upgrades with the 4R70E, which backs the 4.6-liter V-8:

* A redesigned torque converter improves launch performance and increases efficiency.
* A turbine speed sensor improves transmission control, providing the basis for fully electronic shift scheduling to limit "hunting" and to fine-tune shift speed and feel.
* Increased microprocessor speed improves responsiveness and precision of the control system.
* "Smart" fully electronic shift scheduling knows what the torque will be in the next gear so it chooses the shift points based on the vehicle's projected performance in the next gear.
* Coupled with the electronic throttle strategy, the transmission computes the output torque required to maintain the vehicle speed, and chooses the correct gear and converter state accordingly.
* A sealed case and lifetime transmission fluid make the transmission maintenance free, while adaptive pressure control maintains consistent shift feel over time.

By predicting the performance of the truck in the next gear, the computer-controlled transmissions provide a more sophisticated solution to heavy demands than a simple shift delay switch, such as the one-size-fits-all "towing mode" some competitors use.