anyone know of a company other than eelco making nailhead to chevy auto trans kits at a reasonable price?is there any way to adapt them myself with minor machining?any body make their own adaptor? thanks for the help.
I'll leave it to you to define "reasonable price", but here's a source: http://transmissionadapters.com/53-66_nailhead.htm Bob
you looking to put overdrive behind one? if not if you have a 364 401 or 425 get a 64-66 buick/cadi round bell type st400 trans, theyll bolt to the motor and take small mods on the flywheel and pilot bushing and starter. JEFF
I've never heard of that trans in a Caddy, but it did come in Jeep Wagoneers from 66-69. Possibly Jeepster also, behind a Buick V6 or V8 engine.
Im in the process of making one right now for a caddy not to bad so far some machine work on a sbc fly wheel make a ring out of 1/2 in flat plate to bolt to cad block then drill and tap in same flat plate for sbc standard trans bell housing not done but getting there
Jeep, in the last years before Kaiser sold to AMC, bought motors and transmissions from General Motors to allow them to offer some options like a V8 engine. The trans they got was the same TH400 used behind the Buick 400/425 - GM sold this as sort of a universal fits-all because the shorter bell on the case let you cast up an adapter to bolt it to most everything. In an irony, it got used behind Buick engines with the conventional BOP pattern via an adapter. You'll need to source a yoke and a short tail for 2WD elsewhere. I forget who else got this trans, Jaguar, Rolls Royce, possibly someone else. AMC would switch over to Chrysler transmissions when they purchased Jeep, though.
That's what i meant!!! The transmissions that "bolt up" are only going to fit the last of the nailheads, the 401. I believe that bellhousing pattern came about in 1963 or so. Anything prior to that needs an adapter as far as I know. I do know that Wilcap stuff is top notch, and they have quite a few applications.
57-66 bolt pattern is the same, the change in '64 has to do with the crankshaft and flexplate. I would imagine the specifics are as far away as using search to look for a post on nailhead tech -
yep, 64 cadi for sure (64-66 i think) cause i pulled one out of a buddies after he tosted the motor and bolted it to a 401 that i have. JEFF
I've posted this info 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"
What are you putting the nailhead /turbo in? If you say 57-60 Buicks then you won the torque tube prize. If not then the 64-66 (and the Jeep versions) SP/ST400 transmission should bolt right up. You will need to do crank mod and flexplate mod to fit the older crankshaft flange.
I understood the Caddy had the Dual-Coupling Hydramatic through the end of '64, but if some came with an ST400 or early TH400, it may be worth checking '64 Pontiac Bonneville or Olds 98's as well (I know the big Pontiacs had the dual coupling and not the roto-hydramatic "slim jim"). Perhaps they phased over to the new trans in stages? In any case the adapter piece that lets that trans bolt to an early Caddy block might be worth a buck, pending some research on what bolts where. I'm not that well versed on pre-65 Cadilliac engine/trans bolt patterns.
You should be good to go with SP/ST400 transmission from 64-66 Buick with Nailhead engine. The driveshaft can be changed over to yoke that matches the SP/ST400 transmission. Check the Buick websites for any available.
If you don't get the yoke for the SP/ST400 you're better off putting a short tailshaft from a regular TH400 on there. Then you can use standard yokes.
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