new place to look for nailhead th400 transmissions

[FLAT-TOP BOB]

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.

[nailheadmerc]

what's the difference between a st400 and th400?

[Bruce Lancaster]

Also Rolls and Bentley...if you need to shake up the counter people at the local parts shp, just ask for a trans filter for your Bentley...

[shifts]

st400"super turbine" had a variable pitch torque convertor vs.conventional convertor.Valve body, pump, input shaft & convertor are NOT interchangeable w/ th400.

[shifts]

FLAT-TOP, 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

[FLAT-TOP BOB]

shifts'
never asked anyone, but can the st and th stuff be changed out with the same case.

[FLAT-TOP BOB]

shift's
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.

[shifts]

Yea, sounds like someone changed the shaft to be able to use a later GM transfer case. Good deal for you tho. Dave

[shifts]

FLAT-Top, I should have said earlier that the cases are the same (st-th). What I meant to say is those parts arent interchangable w/ th400. As long as you switch everything from one case to another you wont have any problems. Dave

[repoguy]

From what I understand, Jeep made a deal with Buick to use the ST400 trannies, as Buick had already switched over to the 430-455 motors from the nailhead, and the 430's & 455's used the standard BOP TH400.

[silent rick]

what about a manual trans? i'm sure those jeeps could be had with a 4 speed. then what would you need? a correctly balanced buick flywheel? just doin some thinking.

[FLAT-TOP BOB]

i was thinking the same thing. i bet the bell housing would work but the fork might be wrong . anyway the fork could be modified to work.

[shifts]

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

[Kustm52]

The way i understand...there was an adapter plate between the AMC block and the TH-400 trans. Thus the Jeep Manual bellhousing wouldn't bolt the the nailhead. But, if you took the adapter plate and turned it around....just thinking out loud here. Might be worth checking on. Enjenjo can tell you all the details of this swap....

Brian

[Fraz]

On a similar subject, can you take guts out of a BOP or Chevy TH400 and put them in a nailhead case? I ask because I have said case, but no goodies inside it.

[shifts]

yes Fraz

[shifts]

Just thought I'd trow this at you guys. I have an excellent video of how to rebuild a th400 step by step. If anyone wants to borrow it & copy it I could send it to you on a honor basis.Dave

[enjenjo]

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.

[enjenjo]

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"

[ray]

this is definately ToM material, after a while...not yet ryan.

few people think of the fun you can have with a switch pitch tranny behind your motor, kinda like a poor mans overdrive. almost.

[Southfork]

Ray, would you care to elaborate? How can you have fun with the ST-400 switch pitch tranny? How like an overdrive?I just got mine pulled and set on the work bench, and it's still a mystery to me.

[ray]

well i don't know much on the subject, but the switch pitch changes the stall speed of the converter, i dunno by a few hundred rpm's. i'm having a brain fart but there is something else in them that changes also(line pressure?), they can be actuated together or independantly. stock, of course is less detectable, when you stomp the throttle, it automatically "kicks down" to the higher stall speed, getting you a little deeper into the torque . they can also be setup with a toggle switch(s), where you could leave it in whichever position you desired, for racing, highway whatever.

so you get a little more torque, yet can help improve mileage and tranny heat.

i had a toggle switch setup on my 63 riv(65 tranny) i suppose switch pitch was worth a tenth in the 1/4 according to the seat of my pants dyno( maybe more?), but its been a few years so i can hardly remember how it drove. you could definately tell when you flipped the switch at a cruise.

anything is better than a dynaflow!

anyway, i've seen a few over the years, behind things like buick 350's and 455's. probably was quite a few in the late 60's and 70's. now for the bother of sourcing two 400 trannys to combine into one, an overdrive would probably be better spent money.