There is one alluring fact about running a hopped up vehicle with an automatic transmission: There is no driver out there who can shift his manual tranny faster. Add a basic tranny shift kit, and your truck is even more potent. Not only does the right tranny shift kit make your stock gearbox shift faster, the kit makes the tranny stronger and shift with more authority, and in some cases, increases the life of your gearbox. The improved shifting characteristics of the revised tranny will also transfer a little more power to the rear wheels, due to quicker, more positive shifts, from decreased friction and "shift delay", a neat thing to prove to the Mustang in the next lane. For the purpose of this article, a "shift kit" will be defined as any aftermarket transmission kit that does not require removal of the tranny to install the kit, nor require ripping apart the entire transmission to install parts. Kits such as those offered by B&M, Trans-Go and other manufacturers are good examples. Nor is this article to be substituted for your shift kit's instructions. Read everything first!
I decided to select a Trans-Go kit based on past experience. I have been nothing short of fully satisfied with the Trans-Go kits. There is a little more work and time involved with installation as opposed to most of B&M's and other, cheaper-easier kits, but Trans-Go kits seem to provide the most noticeable difference in shifting, and the company provides all necessary hardware as well as other parts to make your tranny more durable, and even includes a video for your aid. If you are pulling apart your tranny on your own (which I assume you will be if you are reading this), you might as well just get the best you can get. This is not something you want to do twice, economically or time-wise. You will need to be confident in your ability to machine parts with the Trans-Go kit, as there are holes to drill, holes to fill, and lots of oil to spill.
First get the truck up in the air on all 4 corners if you possibly can. Proceed to loosen all of the bolts on the tranny pan and remove all except one on the front and one on the rear of the pan. Now, with a LARGE catch tray in place, hold the pan up, and remove the front bolt, then slowly drop the pan to release all of that oil into the tray, over your arm and down your sleeve, into the driveway, and so on, trying to retain as much as possible in the catch pan.
On a side note, you will want to pick up a drain plug kit for your tranny pan. This quick retrofit is probably the best mod you can do as far as servicing your SS. Once you drop the tranny pan to drain all that oil, you will know why. Imagine having no oil plug in the engine oil pan, and having to drop it every time you wanted to change the oil. Fifteen minutes and either a weld-in or screw-in drain plug kit (if you can weld at all, get the weld-in type), and you will never have to clean up a 3 foot diameter puddle of tranny fluid again, which, by the way, should be changed every 15,000 to 20,000 miles or 2 years, or sooner of you tow or race. Member Lurker Mike recommends using a torch and flux brazing rod to seal the drain plug in, which is easier and faster, but steel rod and an arc welder works just as well if you are out of brazing equipment. The pan MUST be extremely clean to accomplish this, no trace of oil can remain around your work area for a good, strong bond. While you are at the auto parts store, you will also want to get a few cans of carb and choke cleaner, and if you do not have a compressor, some form of compressed air (like compressed air-in-a-can).
Now with that out of the way, you can go ahead with the shift kit installation. Your tranny is all metric measurement, even the threads on the bolts, if it is a 4L80E (I am not sure about the TH-400 at the time of writing), so you will need a set of deep 3/8 drive metric sockets (mainly 8 and 10 mm) and Torx bits, and a long flat blade screwdriver for removing the electrical connectors, if you have a 4L80E. If you have a 91-early 92 4L80E, you might also want to pick up a set of revised solenoids to replace the stockers with (sol A and B which control the 1-2 and 2-3 shift valves, force motor, the TCC in the torque converter which you can't get to without dropping the tranny to access the torque converter, and PSM), as these were suspect of failure. Replace whatever you can get to. The Trans-Go kit also increases the capacity of the direct clutch by 300%, as they claim, so a weak direct clutch is no longer a problem.
Begin valve body (VB) disassembly by removing the long "lube tube" which is secured by 2 bolts to the valve body. Careful not to mismatch the single short bolt that secures the front lube pipe to the VB with the other 10mm VB bolts, which are all the same size. Unclip all of the wires running to the solenoids and electrical connectors and remove all of the bolts securing the wiring to the VB if you have an electronic tranny, and tuck the harness out of the way. Don't worry about mixing them up, each wire has a different block connector on it that doesn't allow you to swap wires from one solenoid to another. Remove the 6 8mm bolts that secure the pressure switch to the valve body, and lay it aside along with its 6 o-rings. If the o-rings do not stay with the switch, use a little bit of Vaseline to hold them temporarily. You will not need it until re-assembly so put it and all other removed parts in the tranny oil pan, or another CLEAN parts tray to keep things organized. I can't stress organization enough here. Remove the bolt securing the tranny dipstick stop, forward pass. side of the VB. You will no longer need the dipstick stopper. Now remove the bolts securing the shift linkage tension spring, midway on VB on driver side. Now remove the rest of the VB bolts, except the rearmost one, which is just loosened so as to drain the VB; then remove it. Take care to lift it down slowly, as there is a plunger mechanism that might remain resting on the valve body instead of in the tranny case if it is lubed very well and little worn. Additionally there are 8 steel check balls just lying on top of the VB, which will roll off if the VB is tilted extremely. The VB will weigh about 5 pounds but it feels like 50, trust me. THIS AND ALL RELATED VALVE BODY PARTS ARE PRECISION PARTS. TAKE CARE NOT TO DAMAGE THEM.
Next to remove is the rev. servo, to the rear pass. side of the VB. Six bolts secure it, all 10 mm. You may change the spring that needs to be changed right now (it is the heavy orange spring in the Trans-Go kit) and replace the servo in the tranny and torque it to 18 ft-lb, to eliminate parts clutter as you work.
Now remove the pressure regulator valve in the tranny case, to the driver side front of the VB, for which you will need a set of snap-ring pliers. This assembly is also a no-brainer; just discard the stock, softer set of springs and plunger, and replace with the provided shift kit plunger and tougher springs. Reinstall this assembly. You may do this now too, as this will not interfere with the other VB mods or re-installation of the VB. Prepare to spend some good bonding time with your tranny if you don't have a good set of snap-ring pliers.
Remove the front-most black drilled-through bolt on the tranny case, above the VB, having a hex key insert. Trans-Go supplies another bolt with a smaller drill hole. DISCARD THE OLD BOLT. It is intended to stretch upon tightening and may break if re-used; this is a one-time-use-only item. Torque to 97in/lb.
Now take your pan and go to a GOOD CLEAN workbench. You will be here for a while, so pull up a seat if you like. Remove the accumulator housing from the VB; it helps to have someone else hold it down as there are 2 large springs (under pressure of course) under it. If your searches find no willing participant, just hang on to it well as you remove the bolts. I believe these are 8mm also. Discard the old gasket. Lay all the parts from it aside in an organized manner (see the pattern? Disorganization is how you get a tranny apart quickly, but organization is how get your tranny back together the first time instead of the 21st). Remove the old gasket and discard. You should have a set of new gaskets in that package somewhere. Lift the separator plate, now visible, off the valve body, and lay aside until later. As far as the B&M Shift Improver kit goes, you just need to replace your stock separator plate with their plate, and then reassemble the tranny. But if you have the Trans-Go kit, remove and discard the gasket underneath it. Now it is time to start cutting and hammering on that VB.
Using the provided drills, mark, center punch, and drill the holes the kit tells you to, of course, in the size needed, after removing all the valves, springs, and other parts as necessary. It is best to remove only one assembly at a time, ie open the 1-2 shift circuit, modify it, and replace it before moving onto the 2-3 shift circuit. Remember what I said about organization. It is critical that you keep these parts precision. Holes MUST be the EXACT size and in the EXACT places specified to work properly, which is why you mark twice, cut once.
I highly recommend installing the Gear Command feature. It allows you to manually upshift and downshift as you see fit. It's like having the ride characteristics and shift ease of an auto while adding the control you have with a manual. You have the tranny apart anyhow. Better to just install these Gear Command parts now while the tranny is apart, than it is to not install Gear Command, button up the tranny, decide you want the extra control, and then have to rip it apart again for more VB and separator plate mods.
Your included video goes into detail on how to go about modifying your VB and separator plate, so I will simply tell you that you must eventually remove almost all of the shift valves, both solenoids, and other moving parts in the VB. When you go about drilling the holes, try using a little thick grease, like wheel bearing grease, smeared on the drill bit to "stick" the metal shavings to the bit as you drill. This will aid in cleaning, as there can be NO metal particles that remain on/in the VB. Wrap a little electric tape around the drill bit starting about ¼" up from the tip of the bit, so as to eliminate scuffing of other parts of the VB while you are drilling the horizontal holes. When you are finished drilling holes, clean the VB out with carb and choke cleaner, then blow dry with compressed air. Do not use too high a pressure. If you do, you may lodge particles in fluid ducts and passages, and you may not be able to get them out without a large loss of time, if at all. Gentle 20 psi is fine. On the separator plate, you must drill out holes 1, 2 and 3 to set desired firmness. Drill to .076 for softer than stock, .086 for "stock", and .096 for firm or .120 for use with a high stall converter on a strip-only application. If you want to maximize your fun ratio, I highly recommend the "firm" setting for some real interesting shift action. Other holes need to be filled with the included plugs. These are soft aluminum, and will expand with relatively little force, so don't beat the hell out of them. Finally you file down any high points on the plate after you modify it, and clean it off with the carb cleaner and then compressed air.
Now it is time for assembly of the VB components. You do have tranny fluid on hand, right? No? Well this is not a good time to think of that. I hope you have shop monkeys, er, siblings on hand to go get some. Anyhow, squirt a little oil into the valves and check plunger movement. Then, smear oil on one side of the VB gasket, lay it on the VB, and smear oil on the other side. Lay on the separator plate. Oil both sides of the plate gasket and lay it on the plate. Lay the accumulator gasket on the VB too after fully oiling it. Slip 2 bolts at opposite parts of the VB through the mounting holes to line everything up. Then bolt down the accumulator after changing the stock springs with the Trans-Go springs, and torque to 97in/lb. Lay on the 7 (you will not install one) check balls, aided by the use of Vaseline to keep them in place.
You're in the home stretch! No celebration beers yet though. Take the pan and associated parts back to the truck and get them back in. With any moving parts, check for free movement before you install them or get the tranny back together. If anything is stuck, deal with it now. CAREFULLY lift the VB up to the tranny, and install one bolt on the front, one on the rear of the VB. Do not torque. This is to hold it for you. Install the pressure switch spacer, pressure switch (still has the o-rings on it, right?), and Gear Command plates. Don't torque these bolts either. Now start the remaining VB bolts. Torque in a clockwise, one-across-from-the-other pattern to 97 in/lb., NO MORE, NO LESS. Now install all your other peripheral parts, like the lube tube, wire looms, connectors, and so on. The pressure switch, with the 8mm bolts, will need to be torqued to 71 in/lb.
Review what you have done, and review your directions. Are you positive you did everything you should have? Do you have any leftover parts? Leftover parts are a bad sign. If you are satisfied, get the pan back on, and torque the pan bolts to 18 ft/lb. You may re-use the old pan gasket. Open the hood, and fill the tranny with 7 quarts of Dexron III ATF. Say a Hail Mary or two and start the truck, then add another 3 quarts or so. Allow warm-up (no beer yet---you still have to test drive it), and then play with it. With your foot on the brake to keep a little pressure on the wheels, select R, N, OD, D, 2 and 1. See if it shifts to all gears. It does? Great! Lay the truck down and road test it.
When you come back, which I assume will be about 2 hours later, your wife will think you have been cheating on her with some hot college chickie, what with the grin that will be on your face. But alas, you were not (I hope…), you were just shifting the performance of your tranny into the next higher gear.