Before installing a shift kit, be sure the transmission is in good operating order. If your transmission is making noises, slipping, shifting bad or the fluid looks brown or smells burnt, take the transmission in for repairs. Now, if you have a good transmission, read on. This shift kit went into an FMX transmission, but the C-4 and C-6 are very similar. This job was more detailed than I thought. It took approx. 4 hours to do. (Note: Click on any picture to see it full size) Tools needed: Basic hand wrenches, sockets, torx drivers, 1/4 in. ratchet set with socketed screwdriver bits, a inch pound torque wrench, drill, rags, pans and buckets, 8-9 quarts of Type F Transmission fluid, shift kit, and filter and pan gasket kit. Total cost is approx 75 bucks. If at all possible, try to do this on a lift. Its not required, it can be done in the driveway, but much easier on a lift. Also, have a friend to help you. Here we go! Here is a pic of the shift kit I used. It is a Transgo brand and as you can see, it just a bag full of springs and one valve. Here is a pic with the kit out of the bag: The springs will make more pressure in the valve body and help the transmission shift better. First thing is to drop the pan and drain the transmission. Let it drain for a while. Better yet, let it drain overnight if possible. It just makes the job not as messy.
When the pan comes off you will see the filter. The filter is held it with a simple clip. Remove and discard the filter. The next pic shows the pressure regulator (the two big springs) and the valve body behind it. The two big springs are held in with a simple clip. The springs are under quite a bit of pressure, so be careful here.
After removing the springs, unbolt the regulator and remove it. This will exposed the valve body. Be sure and lay the parts you remove on a workbench in order so you know where all the bolts and screws go. Take pics. Next, you will need to separate the servo from the valve body. The servo is connected to the valve body with pipes. Loosen, but do not remove the servo. Leave the bolts loose. Now remove the bolts from the valve body. Carefully separate the servo from the VB by pulling on the VB and disconnect the pipes than run to it. Here is what it will look like with the valve body removed:
Next, take the valve body and set it on a workbench. Now you will need to disassemble the valve body. Watch closely how it comes apart and be careful with it because there are "check balls "inside so don t loose them. Have a friend to take pics if you need to. Use a 1/4-inch ratchet with socketed screwdriver bits to loosen the VB screws. They are on very tight (40 inch pounds) and a regular screwdriver may strip them. Take an awl, and make a strike near where you find the check balls. This way you know were they go when its time to re-assemble the VB.
Take the upper VB and remove the old Compensator spring and valve, the throttle boost spring and valve, the manual valve, and compensator cut back valve. Sounds bad but simple, the only valve you replace is the big compensator valve that comes with the kit. All you really doing is changing the springs. The instructions will help you. Do one at a time. Use a small pair a needle nose pliers to remove them. The springs are color coded so you will know where they go. Next, take the lower valve body and remove and replace the springs for the inhibitor valve, shift valve. Do not remove the rear pump check valve assembly. Then remove and replace the accumulator valve and spring in the upper VB cover. If you have a late 1972 model cat with a FMX, do not install the check ball in the upper VB cover. If you re not sure, leave it in there. If the transmission acts funny after re-assembly, you can just drop the pan and remove the upper VB with out taking it all apart again. If your car is older than a 1972, leave all check balls in the VB.
Next, you need to drill a hole in the separator plate. The kit comes supplied with the drill bit. The instructions will show you where to drill. This will induce more fluid flow thru the VB. Here is a pic of the different springs you are replacing. The new springs are on the right. Next, re-assemble the VB and tighten the screws to 40 inch pounds. That s a lot off torque on screws. They need to be that tight so use a torque wench.
Before installing the valve body, it s a good idea to replace the shifter linkage seal in the casing of the transmission. If it s not leaking now, it will later. It s a 40-cent part. (Note that these parts are not in the shift kit) To do this, unbolt the retaining nut, and then remove the big nut behind it. This assembly is spring-loaded and the nuts are very tight so be ready. Pull the shifter linkage out of the transmission. The lever inside will have an O-ring on it that will need to be replaced.
Take a large screwdriver and pop out the old seal in the casing. Install the new seal with a drift or a socket and make sure it is seated. Replace the small O-ring also. It was a little tricky getting the shifter linkage bolted back together. The inside fits on a shoulder of the outside linkage also its spring-loaded and is a PITA to get in, so be sure they are installed correctly. It took my friend and me 15 minutes to get it right and he is a Certified Transmission Tech. Once installed, connect the linkage to the cars shifter and make sure the car will shift in all gears (P, R, D, 2, 1) If not, recheck your work. Before reinstalling the VB, remove the modulator pin. It s the pin that connects to the modulator valve located outside of the transmission. Next, install the VB to the servo by connecting the pipes together. It s a little tricky so have your friend help you. Don t bend the pipes! Tighten all bolts and screws.
Now it s time to reinstall the pressure regulator. You will be replacing one spring in the regulator - the big yellow one. It s stout, so eat your Wheaties that morning. Have your friend help you compress it and get er clipped. Here are some pics of the spring, where it goes and the clip ready to be clipped into place:
Now we re getting there. Next the kit instructions will tell you to adjust the "bands". The internal adjustment is easy. You loosen the locknut, pull the servo arm by hand, turn the adjusting screw until clearance has been removed, then back OFF 7 turns and tighten locknut. (It took us a total of 10 turns) On the external adjustment: on the right side of the transmission you will see a locknut. Simply tighten to 10-12 inch pounds and back off 1 and 1/2 turns. Next, remove the modulator valve from the transmission, re-install the pin and re-install the modulator valve. Next, re-install the filter and pan gasket and pan. Get the rear wheels off the ground. (Use jack stands if you re not working on a lift) Add 5-6 quarts of Type F fluid, start the car, put it in reverse and make sure the wheels move. Slowly apply the brake and when the wheels stop turning shift to N, D, 2, 1, then back up 1, 2, D, N, R, P carefully applying the brakes as needed between gears. Do this several times then let the wheels turn. Put the car in Drive and let the wheels turn for 5 minutes or so. Keep checking the fluid level. It took 8 quarts to fill mine back up. Be sure to run the car long enough for the trans to get hot. You need to check the fluid when it s hot. Every so often go thru the gears and make sure the all work. Put the car in drive, give it throttle and listen for the gear changes... or watch your tach. If you experience any problems with gear changes or the trans won t go into particular gears, recheck the VB and make sure the check balls are there and in the right place. After the install, may trans shifted more smoothly. If you get on it, then you KNOW you have a shift kit. The gears will grab right in. The kit will help the trans run cooler and prolong the clutch packs. Last step: Enjoy!!