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Discussion Starter #1
There was a little bit of interest on here when I posted last month about rebuilding my T56 so I thought I'd share some thoughts about it now that I've just about got it all back together.
First off, here are a couple of resources that I found really helped in the rebuilding:

After that I'd say that having gone through the process, there are probably a good few more people who've taken apart T56s than those who've put them back together. There are a couple little trickeries like getting the 5-6 shift rail in position right that isn't really covered in most written tutorials I went through. Making sure that you heavily document/mark the synchro removal is very helpful in making sure it all goes back together as well being that the inner synchro hubs are directional and won't sit right if it's upside down when pressed back onto the mainshaft. Also If you're looking to do the job in a home garage, a shop press if not an absolute necessity is still super helpful in making the job easier. I picked up a 12 ton press from HF for around $150 that has been very useful for the rebuild.

You will 100% need to make the gear puller like shown in one of the above links. I used a HF gear puller and some steel straps from Home Depot that I cut into 12" bars to extend it enough for 5-6 driven gear. With this in mind there is a distinct possibility that if your T56 has some miles on it that the mainshaft splines that hold the 5-6 driven gear in place will be worn, causing a slightly loose fit and allowing the gear to come off by hand. If this happens you have a couple of options. Many shops just send it and leave it as is if the splines aren't too damaged. In doing so though you essentially allow a ticking time bomb to stay in your freshly rebuilt trans as once they wear enough they WILL shear, more than likely taking out the driven gear and the accompanying 5&6 mainshaft gears. The other 2 options are replacing the mainshaft with a new unit or having your existing mainshaft worked on to fix the issue. The fit on mine was loose but the splines were still in good shape so I ended up sending my mainshaft to Jason at TDP to weld and remachine it. Total cost was around $125 with shipping both ways from FL which was a good bit cheaper than buying a new mainshaft.

Next be aware to compare the replacement synchro springs against the ones that came out of it when replacing the synchro keys. The replacement springs for the 3-4 synchro had alignment tangs on both ends whereas the ones that came out only had a tang on one end. Using the springs as is was causing an issue with the synchro keys not being supported correctly, which was keeping it from actuating as intended. After confirming with TDP who sold me the rebuild kit on this, I needed to slightly grind down one of the tangs for the synchro to engage as it was intended to. Apparently that's how Tremec is selling them now but I suppose depending on the supplier of the rebuild kit your mileage may vary.

When taking everything apart, make sure to inspect not just the main teeth of the gears but also the synchro engagement teeth on both the gears and the synchro sleeve. Chances are if you're rebuilding a T56 you had an issue with either synchro engagement or the slightly bigger problem of having more than one neutral. In either case, it doesn't do any good to reassemble the trans with damaged or more notably heavily worn engagement teeth. This is actually a problem that delayed my build as I found that my 5-6 synchro teeth were very worn on reassembly being that I didn't thoroughly inspect it enough on disassembly.

My last point might not apply to everyone but is worth noting anyways when getting replacement parts. Borg Warner / Tremec used the T56 in a ton of applications and almost all of them came with slightly different gearing configurations. The T56 I've been rebuilding is actually a '93 "M29" T56 that's going back into my '82 El Camino which has been my Guinea pig for deciding if it's worth rebuilding the T56 in my GTO. The reason I bring this up is being that they all had different gear ratios, that can limit your options as far as cross compatibility goes. My specific problem is that being a '93 model, it has gear ratios in it that aren't shared with any other T56. This caused a problem for me being that my 5th and 6th gear synchro engagement teeth were damaged from a failed synchro key and the gears can't be purchased anymore. The solution for this is to use 5th, 6th, and the 5-6 driven gears from a later model which have taller gear ratios.

If wanted I can go through my file dump for pictures on the whole process. Hopefully this can help someone. If I had to do it again I probably would though it certainly is a pain to go through everything right.
 

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"there are probably a good few more people who've taken apart T56s than those who've put them back together. "

I've not been into the guts of a T-56, but based on my experience repairing and rebuilding a number of other manual transmissions (T-5, Mustang 4 speed OD, Toyota five speed), that's an insightful observation. Photographing every step during disassembly is great advice, and applies to every transmission out there. Back in the seventies my life would have been much easier if I had a smart phone handy to document each project step.
 

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This really sounds like one big headache you are working through.
But in the end, it will all be worth it. Rowing the gears beats plopping it in drive every time...... :);)
 

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Discussion Starter #4
Yup! I don't regret doing the project but it's certainly an undertaking to do it correctly. Lot's of researching online and a fair good amount of phone calls and messages to the company that sold me the parts to get it all back together right.
 
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