Outline of Procedure
We will not discuss the removal and installation of the transmission in the car. Once removed, the process of rebuilding an overdrive and transmission is as follows:
remove overdrive from transmission
disassemble transmission and overdrive
inspect and evaluate, then order parts
reassemble the overdrive first, then the transmission
mate overdrive to transmission
Of course, if you don’t have an overdrive, you will skip those steps. The manuals call for a “dummy mainshaft” when rebuilding the overdrive. Since you’re not likely to have a dummy shaft, you will use the actual mainshaft. Thus, the overdrive must be reassembled first.
When the transmission in my TR250 went out in 1970, I pulled out my workshop manual (reference 3). It states “Out of 14 special tools, the manufacturers consider 5 to be essential for working on the gearbox. If the owner has any doubt on his ability to strip and reassemble the gearbox he is advised to take it to a suitably equipped agent.” On that advice, I had the transmission rebuilt by the dealer for $300, which was a lot of money in 1970. Actually, this advice is quite wrong. If you’ve got some experience working on cars and have a reasonably well equipped garage, you can rebuild your transmission and overdrive without special tools.
These are the tools you need in addition to basic hand tools: large bearing separator type puller snap ring (circlip) pliers some angle iron for pullers (1¼ inch) some 1 ¼ inch pipe for driving on bearings some ¾ inch rod (for TR3 loose needle bearings)
These additional tools will make the job easier or more thorough: hydraulic press compressed air 50 lb scale (detent release force) Churchill tool for 3rd gear circlip bushing driver set (for shell needle bearings) pilot bearing puller (for shell needle bearings) dial indicator and base (overdrive) pressure gauge with overdrive fitting overdrive test stand
You will tend to adapt your methods to use the tools that you have. I was surprised to learn from Bob Kramer that he does not use a press when rebuilding a transmission; instead he drives all the bearing with a piece of pipe. When I asked him why he didn’t use his press, he said that when he first rebuilt transmissions he did not have a press, and he never changed his methods.