I have a brand new rebuilt 67 variable pitch 400 trans, all the good stuff inside and never even had fluid in it yet. I also have a 65-66 nailhead ST400 case and i'm wondering if I can have the guts of the new rebuilt trans installed in the older 400 case.
It was 1984 when I built my '66 ST400, so I'm a 'little' hazy on the details... There were some changes around 66-67. The early trans used an intermediate sprag, the later ones went to a roller clutch. The sprag is the preferred design, you can get a performance one with double the amount of elements (34 vs 16?) for more holding power. You also need to use the drum that was made for the sprag style. The center support in the 66 lacked the snap ring that helps keep the support from moving around and damaging the case. The 66 case can be machined for the snap ring. Filter style changed. You can use the later filter, but need to drill/tap the valve body for the filter support bolt, or maybe use a later valve body. Again, I'm unsure if these changes were made for 67, but you can look into it. And you know about the different size yoke and tailhousings used on the early ones.
The 67 guts will interchange with 65-66. The cases don't change for a long time, the center support backing ring is machined into the center section. The old type center section might be machined, or use a newer one. I believe this change was some time in 69. The newer style filter/pan only came in late in 67, case not affected but require a 5/16 threaded hole in the valve body, have added it myself to an earlier trans. The output shaft doesn't change although there is the O ring or non style. The outer tail housing can be swapped without taking the trans apart, for different yoke dia. And I think there was an early style governor with different support shaft arrangement, never ran into it here. I have encountered cases with only 6 front pump bolts. But the casting had the metal, so I ran a tap in and converted to 8 bolts. Of course a lot of different bell housings were used for different engines, Buick went BOP by 67, Cad by 68. SWP big Olds had no speedo output. Bruce Roe
I checked my source, the 'Turbo Hydramatic 400 Transmission' book by Ron Sessions. The 16 element sprag was used 64-70, the less desirable roller clutch started in '71. Center support... Bruce got it, 1969-earlier should either use the later center support or machine the existing one for a 0.040" spacer ring. his prevents wear/damage to the case.
One other thing that should be talked about is the valve body.. The 67 Valve body has a tiny 2-3 shift valve as detailed in Mark DeConti's article (http://www.buickperformanceclub.com/SPTrans.htm) I too have a 66 ST400 I'm looking to eventually build, and in the parts I've been saving I have a valve body from one of my favorite transmissions, a 71-72 big Olds OR TH400.. I've actually has a couple of these transmissions, you can modify shift points and firmness but the 2-3 kickdowns are like the car is telepathic... So they question is: are there any specific modifications to installing a later valve body, other than using a later filter, bolt and support? Mark's article doesnt mention any. Has anybody tried a big car valve body swap? what was the result?
You can put any valve body + valve plate combination on any 65 up TH400. I generally use an early 70s transmission (of course from a big block ap) and convert it to a switch pitch plus a few other upgrades. The switch pitch valve bodies are not considered best. The later valve body set will work in the early trans without modifications. Bruce Roe
So to just confirm one more time. I should be able to install all these components in the 65 transmission case and the only thing I'm going to have to worry about is checking for proper clearances?
As I recall about the only thing to redo is the input and output end play. Check that the governor shaft is the same. There are few tricks putting these together. good luck, Bruce Roe
