I am doing some tranny modifications to the 4R70W Transmission that is going into the T-Bird. I took it out of the lincoln Mark VIII that I had for a parts car, along with the aluminum driveshaft and DOHC 4.6 motor. I am starting with the transmission right now, But I thought I could show my progress with it, and also show any Mustang owners how to modify the valve body in the 4R70W AODE tranny. I just started this project, so more pictures are going to follow, and some thing will not apply to the Mustangs from 99 and up, due to alot of the internal components are already upgraded. If anyone wants to read an awesome article on this transmission, written by the guy who was on the design team for it go to. http://www.tccoa.com/articles/tranny/index.html#
Fortunately for me, the tranny was out of the car already, so it makes this process alot easier, but even if it is still in the car, it only takes 4-5 hours and your 1-2 and 2-3 shifts will be firmer, and the car will easily chirp the tires between these gears at WOT. The reason for this modification, isn’t just to improve performance, but to prolong the life of the tranny while adding a shift kit of sorts, except without having to compromise the life of the tranny. All parts used are Ford parts.
I started by draining all fluid out of the transmission and removing the oil pan. Then I removed the (25) 8mm bolts that hold the valve body in. I purchased an upgraded 1-2 shift accumulator and seal, a 2-3 shift accumulator and a new 1-2 accumulator spring. There are 2 springs in the 1-2 accumulator, if you leave the return spring out, it will firm up the 1-2 shift alot. When you remove and replace the 2-3 accumulator and spring, it is recommended to leave the spring out, firming up the 2-3 shifts for applications pushing over 300hp. (I will post pictures of this process later) I have included a diagram of the shift accumulators below
The second half of this modification involves removing the seperator plate from the valve body and drill out 9 holes on the seperator plate, allowing the fluid to fill the clutches faster and improving the firmness and quickness of the shifts. Drilling out the #7 hole eliminates the pause that occurs when you move the shift lever to low, because it takes a while for the reverse servo to fill with fluid due to its size. Again, this is just the beginning of the project and I will follow up more as I proceed with it and will include several pictures. I will include the drilling specs for all holes on the seperator plate, and what size bits to use. Most use numbered Wire Drill Bits (I have these if anyone is interested in doing this, and can help you out as well)
Accumulators and Servos (states 95 Thunderbird, but applies to most 4R70W transmissions)
Seperator Plate drill holes
These are pictures taken from Jerrys Thesis, you can find the whole thesis and walkthrough as well by following the link I posted above.