This goes out to the auto. trans. gurus out there. The th400 used behind 64 to 67 buick nailheads had a shorter bellhousing because of the engine block. My ? is, did the olds, cadillac, pontiacs of the same years use the same trans. with an adapter ring like the AMC's or did they have their own bellhousing. Thanks for the help.
Nailhead bellhousing pattern is unique to nailheads and that T-400 trans is unique because of it. The internal parts are essentially similar. The Buick-Olds-Pontiac-Cadillac pattern is the same, and Chevy is unique. So to answer your question, there are really three bellhousing patterns used on Turbo-400 trans: nailhead, B-O-P-Cad, and Chevy. BTW, nailheads stopped in 66, so a 67 Buick is not nailhead but the new style engine.
the early Cad th400 looked like a nailhead th400, I think they interchange but I'm not sure. Also there were the Rolls Royce and Jeep th400s.
Thanks, I had a feeling it was like that. So the quest begins for a t-400 nailhead style. W/the switch pitch of course.
Actually, I have heard the Jeep T-400's are actually nailhead pattern! My guess is that GM had a bunch of leftover cases, and since Jeep (American Motors) had business with GM, they bought them up and used them with adapters on the Buick engines (later model, not nailhead). This works because the nailhead has extended bellhousing, so the shorter bellhousing of the later engine can use the adapter to take up the space difference. Forgot about the Cad 64-65?? versions, i have no idea if they are same as nailhead or another unique bellhousing pattern. Also forgot about the Rolls-Royce and other foreign makes (Jaguar??) that GM sold the T-400 to. Doubt you will find many R-R in the junkyard though.....
you are correct about the jeep trannys being nailhead pattern, BUT as i recall the output shaft is a 4x4 spec shaft, so to make the tranny work you'd have to disassemble it to swap the output shaft. maybe there's a kit to do it easier? the Rolls th400 is worth mentioning though because they too used the switch pitch setup, along with some caddys, and some oldsmobiles. really the parts are interchangeable, you can make a switch pitch out of a non switch pitch and vise versa, and without much disassembly, basically swap the front pump and converter.
Most Jeep applications use a standard short tail 400 shaft, just remove the transfer adapter, and install a short tail housing. The exception is the Quadratrac. Hollander says the 64 to 66 Buick, and Caddy trans will interchange. On the switch pitch, there is an oil restrictor in the case behind the pump, that has to be switched over too, or a new one made. A Welch plug with a .060 hole drilled in it works.
a .060 hole seems to be too big, the original is more like .030. Some time in the mid 70s they quit drilling the passage for the switch pitch circuit, then they quit casting the passage in the late 70s. so get an early case if you want to do the conversion. The only Jeep th400 that I've worked on fit the AMC motor, it was not a nailhead case. This was a mid 70s Wagoneer.
The engine is a AMC 327 out of a 67 jeep. I thought a 30 ford sedan would look cool with this for a power plant.
As I've posted before... A source for TH400 trannys: 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 passage 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"
The Jalopy Journal
