What most people are looking for in transmission strategy is a quicker, firmer shift, or more technically a shorter shift duration. Shift duration is how long it takes for a shift to occur, or the amount of time that the clutches are slipping. A shorter shift duration has a performance feel, and generally is better for the clutches, because the wear on the plates happens during this "slip". Shortening duration also will reduce heat, which is responsible for most automatic transmission failures. The way to reduce shift duration is to increase the engagement pressure of fluid to the clutch during the shift.
One way to raise Line Pressure is to use a mechanical shift kit, or more simply, a set of valves and springs in the accumulator valve body. Since the accumulator is hydraulically "downstream" of the EPC, a mechanical shift kit does not interrupt any lubrication failsafes and since it is using a mechanical pressure boost (through the Line Pressure Boost Valve) it does not place any additional load on the pump. I have seen 3 basic variations of mechanical shift kits, a "Line Pressure Mod Valve" ($89-$99), a "3 springs and a valve (about $150, basically a Line Mod Valve and 3 additional springs) and a full accumulator ($200, a Line mod valve, springs, lower control springs and lower control valves installed into a new or rebuilt accumulator valve body). I'm not going to be coy about it, I designed, build and indirectly sell the Factory Tech/PSP Accumulator Shift Kit, so instead of trying to act neutral (I'm not) I'll tell you why I think the kit I build is a better kit, a better value and better for your transmission.
First, an accumulator is a fairly straightforward assembly. In the 4R100, there are 3 shift bores, and 1 line pressure/throttle bore. The 3 shift bores are identical, and different springs are set in them to control the reaction of the accumulator piston to hydraulic pressure, this reaction translates into shift duration on the shift controlled by that bore. All of the bores are fed pressure by the Line Modulator Boost Valve, which reacts to the Throttle Valve, controlling this circuit boosts line pressure into all of the shift bores. If you change the Line Modulator Boost Valve and raise line pressure throughout the body, the individual shift bores are no longer "tuned" properly and the reaction in the shift bores will be out of calibration for the elevated line pressure. For this reason, you need to recalibrate the shift bores, both in the top circuit (above the accumulator piston) and below (the 321-310 circuit). Also, in the 2001 model Lightings, I have found that increased pressure in the lower circuits caused the 321 valves to "side load" or bind up due to asymmetric application of hydraulic pressure during the shift, resulting in a "bang shift". A Line Mod valve fails to address these conditions. My last (but not least) concern with a Line Mod valve is cost, I don't think you get much bang for the buck if you pay $89 for a Line Modulator Boost Valve. I've been very upfront about this, I use a part very similar to this as part of the Factory Tech/PSP Accumulator Shift Kit. In may ways, I think the part I use is higher quality, my valve and sleeve are made from stainless steel and most of the other ones I see have aluminum sleeves. This can cause problems in the long run too, as the steel valve cycles though an aluminum sleeve, the sleeve wears faster than the valve and after a time this results in pressure loss and sloppy shifts, the condition the part is designed to correct. Also, of all the parts I have personally seen, only the one I use has an O-Ring seal to prevent pressure leaking out of the circuit. For all this, my cost for the valve is about $20, if you just want a boost valve, email me, I'll sell you one for $30, shipping included, and in a year I'll still be here if you need a new transmission, my Monster Box goes for $1500.
The second popular option is the 3 springs and a valve shift kits. Using this type of kit recalibrates the upper circuits to the elevated line pressure, but still ignores the side loading of the lower control valves. The kit of this type that I have seen also uses an aluminum sleeve/steel valve, and again, the cost is high, for the extra $50 give or take, you get 3 springs and more detailed instructions.
For the Factory Tech Accumulator Shift Kit, I start with a new Accumulator Valve body, Genuine Ford Part (F81Z-7G422-AA, List Price at your dealer is $150 +/-), I add a Line Modulator Boost Valve (about $20), recalibrate the upper circuit with different springs ($12) and upgrade the lower circuit springs and use a valve designed to cycle more freely in the bore to prevent both side loading and binding. (I won't tell you the price, a guy has to have a few secrets). Well, to tell the truth, I don't pay list on the other parts either, but between the kits and my custom transmission work I buy a lot of parts and I get some good discounts (buy 50 accumulators at a time and you can get the same discount, prolly). My point is, I've heard from quite few people who bought the other kits and asked themselves (and me) "Is this it?, I paid $XXXX for this?" I honestly hope that no-one ever got one of my kits and asked that question. The fact is, the final retail price of the Factory Tech/PSP Shift Kit is less than the list price of the components that go into it, and my distributor makes a profit, too.
And finally, I have my reputation. Read the "mods" on bulletin boards to see who my customers are, do a search for Factory Tech, and after you see who they are, E-Mail them and ask how they like the kit. As of this writing, I've sold or given away (for the first year I made them for people I work and didn't even charge them above what I paid for parts) about 500 accumulators and exactly one customer has let me know he wasn't satisfied, and in the end I even satisfied him. (he had installation issues, after the part was in right, he loved it). When the '01 Lightings first came out, the side loading issues on the lower circuit became evident, and I replaced 2 units after I redesigned the accumulator. Other than these cases, I know of NO customers who have had complaints about my parts. Just consider this, if you buy XXX parts, and have a problem, what's the chance of you getting the home number of the guy who designed it? If you bought it used off of E-Bay? If you have one of my parts and you have a problem, I'll fix it. That means if it needs to be replaced, you get a new one, no matter where you got it, it means that if you have a question about installation or performance that you can't get a good answer to, you can get in touch with me and if I need to talk to you to make it clear, I'll send you my home number, or call you. There is no-one selling parts for Lightnings that has built more 4R100s than me, I know this box and I stand behind what I build, because I want to sell you that Monster Box when you want it, when you're ready for it, not when you grenade the tranny and need it.
Thanks,
Gregg Evans