Charlie,
Here are some tips on rebuilding your transmission. Forty five years ago I was really good at this, but then changed careers and got into the computer industry. I haven’t rebuilt one of these since the late 70’s. Anymore I have a hard time remembering what I ate for lunch yesterday. So take my advice for what it’s worth nothing. Honestly like anything else if you do you research and take your time you can do it.
In the early 70’s while in high school I went to work in a transmission shop part time in what was called a work study program. I got straight A’s in my shop courses and thought I knew something about cars. My first day on the job was a real eye opener as to how ignorant I really was. It probably took me three hours to remove a cast iron Powerglide from an early sixties Chevy. Like anything practice makes perfect. Years later one of my coworkers timed me pulling a transmission out of a Chevy Nova. With the car up on stands and all of my tools ready I had the transmission on the ground in 12 minutes.
Eventually one of the owners started teaching me how to rebuild automatics. It got to the point where lesser skilled guys would perform the removal and replacement I would do the bench work or actual rebuilding. On a good day I could rebuild several transmissions a day.
Most the time except in catastrophic cases the hard parts such as planetary gears sets, clutch drums and thrust washers do not fail. On an automatic all the gears are constantly in mesh. Different ratios are obtained by locking a ring gear or sun gear with clutches or bands. So rarely do you have damaged gears like you might in a manual transmission. With heat and age rubber lip seals on pistons fail applying less pressure to the clutch packs. The clutch disks (very similar to a motor cycle clutch) are made up of alternating friction and steel plates. If the clutches slip enough you will have steel on steel and eventual metal fragment contamination throughout the transmission. Assuming your transmission is just tired a rebuild is fairly straightforward. But you really won’t know until you tear it apart.
If you do your research, get good manuals and take your time you can do this. Disassembly is somewhat messy. I would suggest using a metal top work bench if possible. A window squeegee and roaster pan on the floor to swipe the oil into. You can use a small air ratchet or battery impact for disassembly but all reassembly should be done with a speed wrench by hand. Since the case is aluminum you have to be extra careful not to overtighten and strip the case. I recommend an inch pound torque wrench tightening to spec. As you disassemble you want to lay out all the parts in the sequence you remove them. Use small trays or pie tins for the little parts.
Start by laying the transmission on its side. Take as many pictures as you can on disassembly. Remove the oil pan, filter, vacuum modulator and valve. Remove the kick down cable if you haven’t already, especially paying attention to how it is connected to the valve body. Turn the transmission so it is laying pan up. There is a metal plate towards the front of the transmission that is held in place with approximately 6 bolts, do not remove them yet. Remove the valve body bolts, something like 16 – 18 bolts. Pay attention to how the spring and roller is installed for the manual valve (gear selector). Next you will remove the support plate near the front of the transmission. The plate should come right off after you remove the bolts. It holds a steel separator plate that will probably be stuck to the case. There are four metal check balls under the plate. You need to remember where the balls were installed, take pictures. If the Trans is not laying pan side facing up these balls may fall out and get lost. Towards the front of the case there will be a small kind of thimble shaped screen, take a picture and remove the screen. There is also a servo piston that drives the intermediate band that has to be removed. Take pictures of the components, piston, washer, pin, cup and spring so you reinstall in the correct order. You will likely spend a lot of time cleaning the gaskets from the separator plate, case and valve body. Be careful when cleaning the case as the aluminum is soft. Unless there are metal particles in the valve body you will not have to disassemble it. Clean with mineral spirits and use a small flat blade screwdriver to make sure all valves are free.
Next I would remove the speedometer drive and four bolts for the extension housing. Then remove the governor cover that is held on with a spring clip. You will need a large flat blade screwdriver and hammer working around the edge of the governor cover driving it out. The governor will pull right out. On the output shaft there will be a speedometer drive gear, I believe held in with a metal clip. The gear will have to be removed before you can remove the output shaft.
Now you can start removing the guts, starting with the front pump. Remove the pump retaining bolts, eight bolts if I remember right. You will need a slide hammer to remove the pump. While the pump is held in with 5/16” bolts, the housing has several holes threaded for a slide hammer. I think 3/8” X 16. You can make a slide hammer with threaded rod, heavy washers and a large deep well socket. You will probably have to give a couple pulls on one side of the pump and then switch to the other, working side to side it will come out pretty easily. Once you have the pump out you can split it in two. Look at both the driven and drive gears where they rub against the pump body. They should be smooth with no grooves. Look at the inside of the crescent of the front body. There should be little wear and you should be able to drag your finger nail against it without getting caught. You should replace the bushing where the torque converter rides on the front part of the pump body, right behind the front lip seal. If the bushing is worn and not replaced, the new front seal will not last.
Also you should replace the bushing in the extension housing at the back of the transmission. These always wear out. People replace the leaking rear seal and not the bushing; a new seal won’t last if the bushing is worn.
The back of the pump houses a piston for the intermediate clutches. You will have to remove five bolts that hold a retainer with spring pressure. Once the retainer is off you can remove the piston. All parts should be cleaned with “clean” mineral spirits and blown dry. Cleanliness is essential during assembly. Install new lip seals on to piston. Coat with lightly with lithium grease. When reassembling you may have to use a feeler gage to help slide in the piston. Be very careful not to pinch the seals.
You will have to go through a similar process with the forward clutch drum and the low reverse clutch pack housed in the rear of the case. For these two clutch packs you need a way to compress the retainer and a snap ring plier. A small arbor press works well for the direct clutch. For the low and reverse clutch you will have to fashion something using a threaded rod and collars allowing you to compress the springs. Several types of snap ring pliers, spring hooks or cottar pin pullers might help.
During disassembly, when you get to the center support. It is held in with a snap ring. But there is also a horse shoe shaped spring the holds it in. It’s very easy to overlook and you need to note where and how it is installed.
The case should be thoroughly cleaned inside and out before reassembly. A small amount of dirt can cause valves to hang. Parts should be lubed with transmission fluid. Friction clutch plates should be soaked in transmission fluid. Use a little lithium grease on thrust washers. To reassemble the case should be standing on the rear end with tail housing removed. You should have a hole cut in the bench large enough for the tail shaft to fit through. You drop the assemblies through the front using gravity to hold things together. Turn the shafts, drums, etc back and forth allowing the parts to seat. Once the front pump is bolted on you can install the valve body, pan, tail shaft, governor.
When installing the torque converter you should hear three clunks while turning it back and forth while applying slight pressure. If the torque converter is not completely installed it will put pressure on the pump drive gear and destroy the transmission. The converter can easily slide forward should the front of the transmission pitch down during installation. Once the transmission is bolted to the engine you will have to pull the torque converter forward slightly against the flex plate as you tighten the converter bolts. This tells you the converter was installed correctly. Make sure the converter bolts are tight, roughly 30 foot pounds. Put about four quarts of fluid in the transmission before starting the engine. Then add fluid but do not overfill. You can run through the gears while the car is in the air making sure it shifts, put a slight drag on the brakes while doing this. Once the car is on level ground and hot recheck the fluid level.
