Many years ago I had a 66 Buick GS-401,PG that had it. So I'm familiar with the consept. I'm thinking about a 400 version to go behind my 56 hemi w 671 blower. same bolt pattern as any other BOP Turbo 400? Chevy pattern? Will it handle a blown hemi? What model and year range had them, what's a good donor? How are they identified Reliability? Performance build-ability? Parts availability OEM or after market? Converter stall options? Lock up available? alternatives to achieve the same concept? If they were so good, why GM stop producing them? Links? Anything else you think I'd want to know.
Used in the mid 60s in Buick/Olds/Cad, iirc. Not in chevys. You can swap the guts into a chevy case, as long as it's an older case, like mid 70s or older. Newer cases don't have the p***ages cast in them. The pump and input shaft are different, also there's an orifice in the case (small cup plug with a .030" hole in it). Pump has a spool valve and a solenoid that make the converter switch stall. So you need to give it 12v when you want high stall. I dont know if anyone's making converters for them now, the two places that I got them from in the past seem to be out of the business. I still have the first chevy trans I converted 30 years ago...although it hasn't been run for several years. It's a good setup. Kind of expensive to produce, and no one noticed how neat it was at the time, so they quit making it. I've run about 700 hp in front of them for years...although after a while the case will get eaten up if the center support bolt gets loose, but that happens with any th400 I'd talk to a good torque converter guy first, he can probably make a "normal" converter that will do what you want for whatever trans is easiest to adapt to your engine.
I used to race with the years ago, only blew up one converter. We were bracket racing and found the switching to be erratic and the car wouldn't repeat like we wanted so I went with a "normal race" converter. The car was faster but not as quick with the switch pitch. It was a 3300 lb Tempest with 455, ran 11.70 @ 121 mph every weekend for years. There were two different converters, one was a little looser then the other, sorry I don't remember which cars they came from. We used to get parts from A & Reds out of Wichita KS. It was a cool setup, the big cars they came in used them to get rolling with a higher stall speed then switch once rolling along. I could 500 to 600 rpm difference from low to high stall depending on how hard I power braked and how good the track was biting. Joe
As Squirrel said, with the addition of: Get a BIG cooler!!! The high stall pumps a LOT of heat into the fluid, necessitating a very large cooler. Or you'll have very short trans life. Don't ask how I know...but I know. Cosmo
They are not being reproduced, and are getting difficult to find. Jim Wiese, owner of Tri-Shield perfromance in Min/St.P is about as good an authority on these things as you will find. He also owns the V8Buick website. There's another guy in Texas who claims to be the premier SP guy, but you shouldn't believe him. Check out the V8 site for the inside scoop... That's all I'll say on that. The powerglide SP has the smaller [higher stall] converter as it was used in smaller lighter cars. The T400-SP is the lower stall unit. Also, the powerglide switch-pitch [actually the ST-300] isn't really a powerglide at all. It's an animal unto itself... Basically a "modernized" PG [shares no internal parts with a PG] that has a T-400 converter and pump. If you can find a ST-300, you can use the parts inside it to convert a T-400 into a SP. Squirrel has some good info there. The SP converters and pumps are built really well. That was actually the reason they dis-continued producing them. They were "overbuilt" and expensive to manufacture. They can handle quite a bit of power. I had one installed behind a built stroked [550cid] Cadillac V8 installed in a '70 Skylark that ran 10.27 @ 123, and it tipped the scales at close to 4000# with my big **** behind the wheel. A modern alternative is to use a 200-700 R4 with a very loose converter, and toggle the lockup function.
I know you can use a 300 converter in a 400, but the pump isn't the same, you'll need to find a SP 400 donor for that. It's close, but not quite.
Thanks for clearing that up Jim. I have long been under the impression that you could use the pump from a 300 in a 400... Now that I think about it, maybe what I heard was that you could use the input shaft from the 300 in a 400 pump At any rate, I wouldn't want anyone to get bad info, so I do appreciate you chiming in.
Thanks guys, How about where to find them, Identification, That 66 GS I had was a pleasure to drive. The car rusted away but the drive train lives on basically untouched.
They had two contacts on the electric connector, but so did a lot of early 70s cars with TCS (smog equipment). The stator support (hollow shaft around the input shaft, that supports the stator in the torque converter) is different, so when you pull the torque converter out, you can see right away if it's a SP trans. Normal TH400s have long splines on the stator support, and no machined surface. The SP has the smooth surface and short splines shown in the picture
If it does not have the two prong electric connector, it's not switch pitch. Look at the tag riveted on the side of the trans, look for a year code 65 66 or 67, and a Bx or Ox or Ax code. basically any non-chevy and non-pontiac 400 from 65-67 is likely to be one.
For others looking http://www.buickperformance.com/switchpitch.html http://www.jalopyjournal.com/forum/showthread.php?t=581304
something I've posted in numerous threads on here... "A source for TH400 ******s: wanted to give everyone a heads up on a good place to look for TH400 transmissions. keep an eye out for jeep pick-ups and wagoneers 1965 to 1972. they have the same bell housing as a 401 nailhead and are th400's. you can unbolt the transfer case adapter and bolt on a 4" tailhousing and your ready to go! the holander number is # 1331, so start looking. i had never seen one till today and stumbled across one. Also Rolls and Bentley you are correct about this trans bolting up to a nailhead, but the output shaft should be a course spline on the jeep & about 3.75" longer than a 2x2. Dave the one i found was out of a 1970 jeep p/u but the output shaft is the same length and spline as my 65 buick trans st400 i have! what do you think the deal is with that! maybe it was changed or something. Yea, sounds like someone changed the shaft to be able to use a later GM transfer case. Good deal for you tho. Just checked on the jeep cores I have & they both have the long course spline output shafts. But you will want to overhaul it anyway, so thats the time to switch shafts.I got tons of the 2x2 shafts if you need some. Dave Most of the nailhead cases in Jeeps have the fine spline short shaft used with the 4" extension housing for Buicks. the exception being the Quadratrac transfer cases. You can also find them in CJ7's until 1980. Even stranger, the Jeeps with a 350 Buick in them used the Nailhead case, with an adapter to bolt to the 350. this is the adapter that might be reversed and used to fit a BOP stick housing to a nailhead. Don't know that it would work, never tried it, May be impossible, I really don't know. The guts will interchange from any T400 to any other T400 case. there are differences. The Buick valve body will hold the trans in the gear selected, and not "blow" shift like a chevy T400.The ST400 parts will fit too, with qualifications. you have to use the ST pump with the ST convertor, and the is an orfice plug that has to go in an oil p***age behind the pump at the top of the case. Also, you can use a ST 300 convertor in a ST 400 to get more stall out of the trans. The ST 400 convertor is 13", the ST 300 convertor is 11" " But like Squirrel said in another thread you need the earlier case with the p***ages to swaop the stuff. And yes converters are getting harder to find, though they can be rebuilt. I got the last two one of the major parts houses had.
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