years ago, I made a spring compressor from two pieces of flat steel bar left over from other projects in about 5 minutes. It has served me well for decades and the total investment in the part was only a few dollars. Similar tools can be fabricated from steel flat plate and longer pieces of threaded rod. It mounts easily in a large shop vise for clutch drums with a protruding shaft. If necessary, a hole can be drilled through the workbench to accommodate these drums, which allows the tool to be used on a flat work surface if a large vise is not available. If you don’t want to build your own, spring compressors are also available through most commercial tool supply stores.
While certainly not required, a transmission holding fixture, if available, makes the build go much easier. However, being able to turn the transmission in any direction and lock it there really helps with the disassembly and assembly process. Several different types are available.
General Motors was kind enough to cast bosses into the case to accommodate a special holding fixture. Two round pins engage the case, one on each side, and then a long threaded bolt is tightened against the top of the case. Because no oil pan bolt holes are used, the entire transmission can be taken apart and reassembled while in the holding fixture.
Most universal holding fixtures use a couple of bolts that bolt into the pan rails. They still provide stability for the unit and the ability to lock it into any position, but the tool must be removed to install the oil pan and complete the rebuild.
A suitable working surface is a must for building transmissions. Use a heavy-duty table or workbench to effectively support the weight of the transmission if a holding fixture is used. The more surface area on the top of the bench the better, as it allows you to keep the parts separated and organized during the procedure.
A roll-around cart makes a great place to keep your rebuild kit and other parts clean and separated from the work area.
If a holding fixture of any type is to be used, it needs to be securely attached to a heavy-duty table or workbench. The workbench may need to be counterbalanced to offset the weight of the transmission. A simple heavy-duty workbench can be easily constructed from a couple of 4 × 8-foot sheets of plywood, 4 x 4s, several 2 x 6s and some good wood screws. The benches I use in the shop have storage space under them. The weight of the parts on the lower shelf provides enough stability so that the weight of the transmission doesn’t cause the table to fall over. The 4 x 8 work surface provides plenty of room to spread out all the parts removed from the transmission.
Several types of holding fixtures are available for transmissions. General Motors was kind enough to cast bosses on all TH350 and TH400 cases to accommodate the appropriate holding fixture.
Universal holding fixtures are available that utilize the pan’s bolt holes to attach it to the case. The downside of these fixtures is that they have to be removed to install the transmission’s oil pan.
Roll-around carts also make a great place to lay out rebuild kits, bushing sets, thrust washers, and other items used to rebuild transmissions. They can be pulled right up to the work area without mixing up the new parts with used ones, and then pushed away when cleaning off and blowing parts dry with compressed air.
A shop vise, especially a large one, can be a nice addition to your list of tools for your transmission rebuild. A set of soft jaws can be added to hold shafts without damaging them. You can also use it to hold the valve body when you need a third set of hands to keep it stationary for removing valves, springs, etc.
Although not part of the list of tools for most folks, having a small lathe or access to one helps if you are rebuilding a “max-effort” TH350 transmission. It is also especially useful if you want to increase friction capacity to one of the drums or custom set the endplay for a particular clutch pack by removing some material from the apply piston. Most TH350s show up with a four-clutch-pack direct drum. It is very easily increased to five frictions by removing some material from the apply piston. You can also use a lathe to remove material from the low/reverse apply piston, or forward drum apply piston. You can also use it if you are working with a light-duty TH350 and want to increase the clutch capacity in those drums.
A heavy-duty shop vise is like an extra set of hands and comes in handy for holding components that you are working on. You need a set of soft jaws or couple of wooden blocks when clamping down parts that you don’t want to damage.
Small shop lathes are becoming increasingly popular and part of many hobbyists’ home workshops. If you have a lathe, or have access to one, it can come in very handy for transmission rebuilding. A lathe can be used to spin and polish shafts with very fine auto body sandpaper to remove rust and light pitting or smooth up the surface where it rides in a bushing. A lathe can also be used as shown here, to remove the appropriate amount of material from an apply piston to add an extra steel and friction to a clutch pack. This saves the expense of buying a shorter apply piston when you are beefing up the TH350 for a high-performance application.
Large commercial-grade cookie sheets are great for laying out the internals of the transmission as they are removed from the case. The cookie sheets hold the oil draining from the parts, and keep any small parts, such as check balls, from rolling off onto the floor. Frictions and bands need to be soaked in clean automatic transmission fluid (ATF) for at least 15 minutes prior to assembly. A one-gallon ice cream pail with about a quart of ATF works well for this; they generally have a lid to keep out dirt and debris. ATF also works well for lubricating Torrington bearings, and dipping apply pistons prior to installation in the drums.
Large commercial baking pans keep parts on the bench from rolling off onto the floor. They also hold any fluids draining from removed parts.
You need a container to soak friction and band material prior to installation. One-gallon plastic ice cream buckets work well for this purpose, and their lids keep dirt and debris off the new parts.
