I recently bought a ST400 Switch Pitch Transmission to go behind my 364 Nailhead but the seller did not have a torque converter. I have dug around on the internet quite a bit but I'm coming up short. Does anyone know where to get a converter for this transmission?
They're kind of scarce. Been several years since I had one worked on by Hughes in Phoenix, and even longer since I found a core...by talking to a guy at a swap meet, who happened to have one at home. Letting people know where you are will also help. There's a place in your forum profile, to put your location.
They are out there, but you need to dig. There are three candidates. The first is from the native ST400. The second is from the ST300, which would have higher stall speeds, as it has a smaller diameter. The third is from the TH475 FWD transaxle, found in the first few years of the Oldsmobile Toronado. Not sure, but that might be the same as the ST400 one.
French Lake Auto Parts regularly parts out Toronados. I have a SP TH475 from them. It came with the converter. It might be worth giving them a call. https://www.frenchlakeautoparts.com/ They ship.
also look on ebay. https://www.ebay.com/itm/225366369206? This is the ST300 he mentioned, it's smaller diameter, uses the same bolt pattern as the TH350 converters. And it's what I run in my switch pitch 400s. Illinois is only one state away from you
You will want to familiarize yourself with the identification of them, since not everyone knows. On the inner convex curve closest to the center, you will find rosette welds. These are not present on fixed-pitch converters.
It all depends on your performance level. @squirrel runs a blown big block that has admirable quarter mile times. If you are just making a weekend cruiser, you might not need the higher stall speeds that come from using a ST300 converter in a ST400.
The difference between a stock 300 and 400 converters is not very much. But having them modified can make quite a difference in stall speed. For example, the converter I have in my Chevy II gets about 1800 in low stall, and 3000 in high stall. Usually they have only about 500 rpm difference when switched.
Some of the modified ones out there have reaally high stall on the high side. I had Poston do one for me a long time ago, and it was supposed to be 1300/3000 with my combination, but its more like 1300/5500! Found out after I ran it for years that the guy was kinda a hack.
electric switch. Was originally to brake lights but I saw article that said wire it through digital timer to keep in high stall for first 60'
Thanks, and is there a solenoid maybe? that is also installed? If so where? I ask as Jim says he uses one in his Chevy with a 400, which I’m thinking is a “regular TH400”? Dang a lot of question marks in one reply
i have a bop switch pitch trans and convertor, don't know if the same as your's or not. it's in bama so it is a good piece from you.
after looking i don't believe they are the same, the bolt pattern is different, your's looks round and mine has a valley between the top two bolts. i know mine can be converted to use a reg convertor but i don't know if the convertor can interchange.
Buick used the switch pitch in 65 & 66 behind the Nail Head (rounded bell), and in 67 (BOP bell with valley between the bolts). Converter was the same in all 3 years. The ST400 was also used by Buick in 64 behind Nails, but was non-switch pitch and used the regular 400 converter. I have a couple of those. Cadillac also used the SP400 in some models along the same years, but not sure about the bell pattern (BOP?)
Russ Martin's NailheadBuick.com is a wealth of technical information on Buick nailheads. https://www.nailheadbuick.com/tech-info The nailhead transmission options explains different transmission options & how he wires the converter to switch it on and off. https://www.nailheadbuick.com/transmission-options-for-the-nailhe This is his wiring schematic. https://www.nailheadbuick.com/t300-st400-wiring-instructions
Have an st 400 out of 65 riv And a st 300 out of a 64 425 riv , but in Canada and no I don't want to sell the converters ,but would sell the complete transmissions
There is an electric switch on them. The wiring plugs into the side of the tranny and goes to a solenoid on the inside. After that I cannot tell you. It can be run to a switch on the dash or shifter and then it becomes dealers choice. Otherwise it works off the throttle.
Not all of them. The passage for fluid to shift the vanes in the torque converter was no longer finished in the mid 1970's. I don't have an exact date.
I had a 1977 case that had the casting, but no holes drilled in it. And a 1981 case that did not have the casting. 1972 still had the holes.
^^^^ One of my 64 cases has neither, a different valve body, and a sprague in lieu of a roller clutch on the output drum. Haven't torn the other one down yet, but suspect the same. A 71 case I have has the holes.
The set up in my '35 pick up came out of a '65 Wildcat......has the switch at the throttle linkage on the carb.
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