The Preliminaries
A word of caution: I’ve only rebuilt three or four automatic transmissions in my lifetime so I am by no means an expert. All I’m trying to do here is to document my experiences to hopefully make it easier for others. The process that I’m going to describe isn’t that difficult. It is time consuming and requires attention to details and good organization. Don’t even consider doing it without a Factory Service Manual! Also, I’m writing this as I’m doing the work. I believe my chances of success are good but the outcome is certainly not guaranteed!
Warning! The following is full of endless detail, guaranteed to put you to sleep!
To switch the output shafts, almost all of the subassemblies of the AW450 must be removed. If you are going to overhaul the transmission, each subassembly is further torn down, inspected, and the wear items replaced. I’m going to stick to documenting the procedure for removing and reinstalling the necessary subassemblies only. For those interested in doing a complete overhaul, I would refer you to the FSM. If you are planning a complete overhaul, there are also certain measurements that should be taken as you remove the major subassemblies. Again, see the FSM.
There are several SST’s that the FSM says are required for this job. You don’t need them if you are willing to improvise. The IED (Improvised Extraction Device) that you will need is called an Oil Pump Remover by the FSM. This is used to remove, not only the oil pump but several of the major subassemblies from within the transmission case. I substituted a 1 meter length of M8 x 1.25 threaded rod, cut in half, some matching nuts, a 6” chunk of steel drilled appropriately and a standard gear puller that I already had. The first photo is of this puller.
To completely gut the case for a thorough cleaning, you need to remove the first and reverse brake piston (the next to the last item to be removed from the case). To accomplish this, you need to compress the piston return spring assembly so that the snap ring can be removed. The FSM calls for a J-44162, No. 1 Piston Spring Compressor. I made my own using a ½” length of PVC pipe, a bolt and some misc. aluminum. Photo 2 is of this tool. You don’t have to remove this piston to swap output shafts but doing so, allows you clean the case without fear of getting contaminants into the passages that feed pressure behind the piston.
These are the only two special tools that I had to make to completely pull all the subassemblies out of the case.
Some precautions:
¨ These automatics seem to hold an endless supply of ATF. Once you think it all has drained out, more will mysteriously appear so be prepared otherwise you’ll have a mess. I had some old commercial steel baking trays that worked well to contain the endless drips.
¨ Automatics are very sensitive to contamination so work in an area that is clean and dust-free. When not working on the transmission, cover the transmission and components to keep dust out. I like to use the 55 gallon clear garbage can liners as covers.
¨ The transmission is heavy and clumsy. You will need to maneuver it into different positions during various stages of the process. Although you could probably do it on a work bench, I would recommend some sort of stand. I modified a cheap HF engine stand to allow me to rotate the transmission to different positions. If you do try it on a workbench, be careful not to damage the various mating surfaces.
¨ Assuming that you are starting with a used AW450, clean the exterior BEFORE opening it up. Leave the torque converter in place, plug any external holes with rubber stoppers or duct tape and take the whole thing to your DIY car wash and wash it with hot, high pressure water. This will help minimize the possibility of internal contamination latter. When moving the transmission around with the torque converter in place, I bolt a small piece to steel to one of the outer holes of the bell housing to keep the torque converter in place.
¨ The FSM recommends that, during the disassembly process, you do not completely invert the transmission so that any junk that may have accumulated in the pan won’t get dumped back into the transmission. This does make it a bit difficult to thoroughly power wash the exterior. Here, I was lucky to have basically a new transmission so I didn’t have to worry about any contamination as a result of inverting the transmission. Sure made removing the pan a lot simpler.
¨ The FSM recommends using ATF or kerosene for washing the transmission parts so I have a 5 gal bucket of kerosene always available for rinsing the parts. The FSM specifically prohibits the use of gasoline and naphtha (white gas) or similar solvents on the o-rings, seals, and friction plates.
¨ You will be removing a lot of small parts, some of which are quite similar in appearance. To keep everything straight, I store all these pieces in labeled zip-lock bags. ! qt. Freezer bags work for me.
The third photo is of the AW450 bolted to the modified engine stand ready to be torn down.
