Thought I should update this thread since going back into the unit last weekend. I found a good rebuilt pump. Basically, a good used 732 case with new rotor, slide and vanes. I swapped in the heavy(Sonnax) slide spring, after inspecting and re-cleaning the pump. I also swapped in the big boost valves from the previous pump. The pump came with the TH350(wider than the 700R4 bushing) front support bushing, a new teflon pump bushing, and I installed the wide teflon rear bushing.
I kept the pump that came out. No scoring damage from running it after the sanding job. The body is still in great shape. In fact, the pump only has about 6Kmi on it since a fresh rebuild. The only issue was a small scored area on the cover, probably from digesting friction material. I'll have it trued up in a lathe and save it as a spare.
Otherwise, I found where I'd left out the forward piston inner lip seal, just like Crosley said. Air testing the housing is really a good idea to save yourself this kind of headache. I seriously dropped the ball two weeks ago on this thing. This time around everything went great. I tore it all down to the bare case, washed all the parts, they were well coated in friction material from the wasted OR clutches. The other clutches all still looked just as good as they did two weeks ago. Even the forwards, which live right next door to the ORs, were in great shape.
I reassembled the unit using all the same clutches, aside from the OR and forward which I replaced with new. I washed the 3-4 frictions, brand new two weeks ago, in clean ATF and washed the 3-4 steels with the rest of the parts. After assembly, this time including the forward piston inner lip seal, I air tested the housing and it tested fine. I reused the teflon turbine shaft sealing rings since they're still brand new from two weeks ago.
As I think I said in an earlier post, the $32 turbine shaft sealing ring resizer from BET performance worked great. I used a funnel to spread the rings for installation.
One change I made in the reassembly was swapping in the Sonnax 2nd servo in place of the Superior. I feel like the change really did clean up the 2-3 shift. The 1-2 shift is still nice and firm under any throttle and mild at low speed light throttle. The change from the more firm Superior will take some getting used to but since the whole servo assembly seems to work better now, I'll keep things as they are. I installed the high rat cushion springs from the Ratio Tech kit along with the factory cushion spring and drilled vents in the steel cover. I used the stiffer TH400 intermediate servo spring in place of the factory spring. Using the Sonnx 2nd servo, I was able to install a 4th servo return spring. I already had the Sonnax 4th servo installed. Now I have the whole set.
One issue I found during the teardown is damage to the lugs of the Sonnax Smart Tech apply plate and to the tips of the apply ring legs. The damage appears to be from the apply plate coming off the ring and floating loose in the housing. I'm afraid the legs of the ring might even be spreading from g-force at high revs and passing by the lugs. Talk about centrifugal apply of the 3-4 clutch. I'm betting this has alot to do with the failure after just 6Kmi of what should be a very tough clutch stack.
The apply plate and backing plate have been hot spotted since the first 3-4 clutch failure but I've let that go. One thing I noticed after the first failure was that the apply plate had come off the legs of the apply ring and floated loose in the housing. No damage to anything else, just a rub mark on the inside of the plate from the input ring gear. No visible scoring to the gear. No damage noted to the lugs or the apply ring legs. I put things back together that time(3 years ago) and continued to run the housing without the boost springs in the 3-4 clutch. I was told to do this when using the CS-7 transgo springs.
I've talked to the trans expert who told me to leave the springs out, a good friend of mine for whom I have great respect, about the damage to the apply plate and ring. He was surprised by the news. I promised him photos once I have the parts out.
I believe the difference here is the Sonnax design of the plate. I remember noticing how much shallower the lugs of the Sonnax plate are than those of the factory style plate. I'm referring of course to the late style apply plate that goes directly onto the legs of the apply ring with no retainer between. The factory plate has deep enough lugs that the apply ring legs probably couldn't get past them, even in the event of a 3-4 meltdown. The Sonnax apply plate lugs are only maybe 1/8"-3/16" deep. Not much material there to keep the legs back without the boost springs keeping things firmly in place.
At the time last weekend I decided to reassemble with the boost springs and let the damage go. Since then, I've had second thoughts. The replacement parts are on the way. Sonnax sells a service kit for the Smart Tech, great price at just $100 and change, considering they could charge whatever they want for it. I got a fresh "7" apply ring from my friends at Perfection Plus hard parts(short legs for thicker steels on the factory heavy duty unit makes more space for the 3-4 clutch stack). Dana at Pro Built is sending me another 8 friction 3-4 clutch stack. The Smart Tech housing with the "7" apply ring has 1.25" inch 3-4 clutch capacity. That's with a no flex bolt on backing plate and a super rigid apply plate. Very cool.
I forgot to ask Sonnax tech, when I called about the repair kit, why they don't make those lugs deeper. There's plenty of room on the outside of the apply ring legs. You could make those lugs as deep as you want. Maybe they are thinking of rotating mass. Either way, they really really mean for you to use their long boost springs in the 3-4 stack, and I guess now I know why. For anyone planning to use this bad*ss input housing, learn from my mistake and DO NOT leave those springs out.
On this last weekend's build up, I went with the factory 3-4 and forward spring packs, making sure all the springs were in tact(none broken), and installed the boost springs. Those Sonnax springs are pretty stiff. I'm thinking they go a long way towards bridging the difference between the factory spring packs and the TG CS-7 springs. Crosley says he mixes the stock springs and TG CS-7 springs and uses the boost springs. I still have the TG springs incase I decide I want to do that down the road. I may also step up to a 9 stack next time, just for the heck of it.
I also yanked the TG orifice and installed a brand new AC Delco check ball. Two weeks ago, I replaced the 3rd accumulator check ball capsule. When I have a phone again, I'll post a photo of the cool tool I made from a 5/16" grade 8 bolt for removing the capsule. The tool with a slide hammer pulled the capsule right out nice and clean. The new capsule went in clean and easy too with a 3/8" roll pin punch.
For now, the unit is shifting great. I'll have all the parts to repair the 3-4 assembly in a week or so. I'll go in and do the repair right away. It'll only take a day, since I don't need to tear the unit clear down.