First I want to mention this is a long post, and a lot of detail. If there are any experienced performance trans builders in here who have worked/modified the 1964 ST-400 as it is a single year only trans I would be eternally grateful for any advice. Since the 64' case passages, and matching valve body are NOTHING like the 65+ units, it renders all of the normal 65+ "shift kits" and mods useless for this trans. This makes for a fun pile of challenges when attempting to modify the trans for faster,crisper shifts. One example: there is not a lower spring or even a place for a lower spring in the front servo/accumulator like there is on 65+ valve bodies. The shift quadrant is P R N D L (Single Range trans) when you pull into L the governor dictates whether or not it drops from 3-2 or from 3-1 / 2-1 depending on speed, typically below 25 MPH = 1st, much above that its always 2nd gear only. My particular trans is in my 64' Riviera with a built, injected, 425 Nailhead. Hughes 2500 stall 10" converter, 3.07 stock rear The trans has worked well for many years, I had enlarged a couple of feed holes in the plate about 4 years ago and its served me well until recently when it starting making a bearing noise at idle in gear, no up-shift to 3rd when hot and when I dropped the pan to investigate it was a glitter factory. Time for a rebuild. Yanked it out, tossed on the bench and tore it down. Nothing was glaringly wrong, clutches were good, could still read the print on the frictions, bushings were worn and appeared original as the previous re builder did not replace them, worn rings on the center support (iron). Appears the converter bearing might be the culprit, was a Hughes 2000 Stall 11" converter. New Parts and Build: The original pump had some minor scoring on the gears, and since it is a .625 gear set and no replacements were available I ordered a new .727 reman pump. Installed a new Sonnax LB1 boost valve kit into it. (original pump had 2 horseshoes and a washer with a stock spring for slightly bumped pressure) Green High energy 4 disc intermediate clutches - new steels Red Alto and Kolene Forward and Direct clutches- new steels I used the .010 per friction clearance for the packs. Is .045-.050 too much clearance? The 64 trans used wave plates for ALL THE PLATES, I went back in with no waves at all. The trans had been 1/2 way dual-fed by the previous builder, and what I mean is the second ring was omitted from the center support, the inner seal omitted from the drum, but the reverse hole was NOT blocked in the case or at the valve body plate. Valve body plate gaskets were not present- AKA none installed just metal to metal. I sourced original 64 VB gaskets from Fatsco along withe the new 8 bolt .727 gear pump. High energy rear metallic band was in perfect shape- reused it High energy red front band was in perfect shape re-used it In the 64 ST-400 the front band APPLIES during a 1-2 auto shift and a 1-2 manual shift from L range. 65+ do not apply the band on auto shifts from Drive, this one does. I swapped in a 34 element sprag New roller clutch- old one had some grinding marks on it where it appears it had been rubbing on the drum due to excessive center support bushing clearance. It was still good but replaced it anyhow. New modulator- Bench tested it, works great. Old one was functional but had some fluid inside the hose. Rebuild the valve body- exactly as I had it before for years. New cooler and lines New converter - Hughes 2500 Stall 10" 4L80E Teflon center support rings There was not much wear on the ring surfaces inside the drum so I don't think I have any issues there? Teflon front pump rings Drilled drum to eliminate centrifugal apply Sonnax no walk rear case bushing with roller bearing (fully rollerized trans) All new bearings All new seals All new bushings - yes every single one is new and pressed in perfectly square New umbrella seals on all the pistons Now for the challenge: Symptoms: 1-2 shifts only at 3200 RPM pedal position seems to have zero effect on shift points. 2-3 shifts at 4000 RPM again, pedal position seems to have no effect on the shift point, drives fine in high gear or 2nd gear It will remain in high gear until I slow down to about 65 then it auto downshifts to second regardless of pedal position. Shifts are solid but not as firm as expected, much like stock. First suspected the modulator or vac source to it was the culprit- Modulator works perfectly, used vac pump, tested it on bench, vac source to manifold is good, adjusting modulator had zero effect. Pulled the kick down solenoid and replaced with a new one just in case the detent solenoid was leaking - no change Pulled VB, rebuilt it all again, verified, no issues found. - no change 1-2 accumulator valve is the adjustable type, set it back to exact specs as it was before the rebuild - car shifted normally for 5 years prior to this. Pulled the governor, removed gear, valve is clean, moves freely, no issues, new gear etc. Manual shifting the governor is functional and will downshift to 2nd if above 30mph, and 1st below 30mph. A manual upshift will not occur until 3200 RPM 1-2 or around 4000 in 2-3. Linkage/manual valve are adjusted perfectly Line Pressure Checks: Conditions: Fixed vac pump on modulator with 20" vacuum. Engine idle around 1000-1100 (mild street cam etc) Reverse 100 psi Neutral 70 psi Drive 75 psi L 210-215 psi Conditions: No vacuum on modulator - Car off the ground, wheels free spinning, 1100 RPM Idle in Park150 psi Neutral 150 psi Reverse 185-190 25-30 mph Drive 70 psi idling about 20-30 mph Conditions: 30" vacuum on modulator - car off ground, wheels free spinning, took it up to 4000 RPM Speed up to 40-50 mph it shifts to 2nd but you cannot feel it happen, @55 mph 3000 RPM = 95 PSI and no observable pressure drop during the 1-2 gear change. Idle - Neutral/Park 70 psi Drive 70-75 psi L 210-215 fluttering needle, bump throttle/rpm to 1400 it comes down a bit to about 185-190 psi on or off the brake doesn't matter. Never shifts to 3rd gear even up to 70 mph with 30" on the modulator. Road testing it takes about 80 MPH to hit 3rd.
Sure wish I could help, seems you've been VERY thorough so far. Unfortunately my only ST400 rebuild/modification experience has been '65 and up.. Hoping you can get some good input, I'll be following hoping to learn something too. Devon
I too have not had experience with the '64 ST400, however, the following manual does include that particular transmission and references the '64 when required ... the diagnosis chart seems to point to the governor issues as some of the problems you are experiencing. https://www.tradecraftspecialties.com/RandomStuff/AutoLiterature/TH400-Service-Manual also, GM service manual for that year would be invaluable ... https://www.ebay.com/itm/3851569083...TlOytAk/TYnb1x2QSeujMcnw==|tkp:Bk9SR6i747WfYw
I realize this does not directly address what you are asking, (and actually just re-enforces what you know) but I think you would have better outcome if you can locate a 66 nailhead patterned ST400. It would make any "upgrade/performance enhancements" easier to accomplish. Swapping over as many performance and other good parts you already have, it may be less costly than continuing with the '65 unit.
Our NE Chapter resident Transmission expert is Mark DeConti. He is dcm422 here, and e mail is dcm422@aol.com. Try asking Mark. He doesn't come on here much, so I would try and e mail him. Put 64 ST400 Question? in the title so he doesn't delete it. https://v8buick.com/index.php?members/dcm422.716/
I have the ATSG manual, the early Th400 manual, the factory shop manual, and the 1964 Riviera Manual, along with the Ron Sessions TH400 Book aka the Bible of Th400's. Each of them mentions the 64 ST-400 but as you stated, only as necessary does it mention things such as "Except in 64" but never actually explains "The why". I think my issue is low governor pressure. Trick now is to sort out why.
One thing I thought of last night, which I do not recall seeing when I cleaned my case, apparently these buggers came with inline screen filters on governor case passages where the lines go into the case at the rear. So gov pressure off the valve body is filtered by a little screen (cone type filter that inserts into the case passage). I never recall seeing one there and if it is there, I sure as hell did not clean it other than blowing everything out with air and parts solvent. The new checklist: Check for governor screen and if present remove/clean ensure not collapsed or blocked Remove trans, tear it all down again, verify the .727 later model pump ports are matched (I am 99.999999% certain they are identical) Remove the inner spring I added to 1-2 Accumulator shift valve (not the accumulator itself) Replace my direct drum with a 4L80E drum to eliminate the small bit of ring wear I saw from the previous iron center support rings, couldn't feel anything with a fingernail but the spot where the rings rode against was "polished" from 60 years of use. Swap out the Teflon gap-less rings I used for the later "plastic" 4L80E rings on the center support. Its possible that I did not size the Teflon rings perfectly or that the wear in the drum is causing a leak. I do not see evidence of this on the pressure checks but if I have it out of the car I am swapping the drum and rings while I am there. Maybe tighten up my clutch clearances from .010 per disc to .005 per disc? I want quick firm solid shifts but also do not want to go too tight and cause the clutches to drag. Weld the two holes I enlarged in the separator plate back up, re-drill them to stock size. The holes I opened up should be the 3rd clutch feed, and intermediate feeds. However I had to take photos, superimpose them over one another in Photoshop, then trace the oil passages to determine which ones to open up, remember no shift kits for the 64, and the holes in the plates are NOT the same as 65+ so I cant just look at other kit instructions and "do the usual mods". At some point I plan to do an overdrive swap anyhow, I have the Bendstens adapter. The long range plan is a 4L80E core and build it for 1000 ft lb capability (not hard with an 400 or an 80) upgrade my injection to a Terminator X-Max or Dominator ECU to control it and enjoy overdrive... I wish someone made an SFI bolt on bellhousing for the nailhead to 4L80E. Martins have one for the 700/4L60E but I will never intentionally run that (@&#$ trans in anything I own. The 4L80E is just an electronic Th400 with overdrive, same shift feel etc. Might even be able to use a single piece driveshaft and get away from the 127,000 U joints in the Riv. OD would make this car so nice on the freeways here, posted limit is 80-85 in many places around me and I don't like cruising much over 70 which is 3000 RPM with 3.07 stock gears. 2500 lockup converter for a 4L80E is around $1600 bucks Controller is another $1700 Core trans about $600 Driveshaft - Tunnel mods? The 80 is a bit larger but I think it will fit without modifying the tunnel... not sure
