Every hour spend researching and reading the following articles was multiple hours saved in the rebuild process. The articles also cover bench testing, which might help you figure out if you need to go through the whole process.
https://www.vtr.org/maintain/TransRebuild/OverDriveA01.pdf
https://www.vtr.org/maintain/TransRebuild/OverDriveA02.pdf
and the 5! pdf's at the bottom of following page:
https://www.healey6.com/technical.htm
I printed out the articles and put them in a binder so I could use them in the garage.
I made a tool to pull the accumulator housing using a treaded rod, nut, big washers, a wing nut and a big rubber ring from the plumbing dept in my local hardware store. You might find an expansion plug that works in a plumbing store. Having a spare mainshaft helps for alignment and testing. Lastly I bought the OD oil pressure gauge from
https://www.geocities.com/jholekamp/index.html
I am finishing up the OD now, I have one more adjustment washer to order based on last measurement. Then over to the bench testing. Rebuilding the OD was a first for me, so I read all the above and worked slowly but accurately.
I replaced nearly all bushings, bearings, o-rings, oil-seal, Uni-directional clutch (was shattered) Annulus steel insert ring (shattered too), most springs, balls, washers, gaskets and the pump cam.
BTW I needed to replace the whole front housing, it was hit on the bottom and JB weld applied over the lower parts that were smacked off. This probably closed off the channel that allowed the pressure to bleed off when the OD is not engaged, breaking the OD next time reverse was engaged. Hence the gearbox ended up underneath a work bench gathering dust waiting for somebody to adopt and repair it.
Bert
56 BN2 WIP