Actually, you also have to drill one small passage in the Chevy 400 parts. I have a small fabricated electrical throttle activated switch on my SBC ... to make the switch pitch work.
depends on what year your Chevy case is, they did away with the drilled hole in the late 70s, then a few years later they got rid of the casting so it won't work at all. So if you have an earlier Chevy case, go for it. I have a few of them, they're fun
I know this is an old thread, i found it digging around for some SP400 parts. That statement is not true, i have an 80K all original except paint and wheels 2bbl 389 4 door 66 catalina, that has the switch pitch 400 trans. It has the heal detent pan, switch setup near the carb, 2 prongs side case, etc. Nothing has been cut, hacked, switched around or swapped on this car...i am the third owner and you can tell that the harness is part of the car. I can take pictures later of the linkage, pan, etc if someone thinks i am mistaken (which i mean i guess i could be.) Being as i have a 66 cat, i check them out on ebay/craigslist frequently and lots of people post pics of their undersides...i have clued in a couple 66 cat owners that they have a SP trans and asked them to send me pics of their throttle linkage, and it matches what i have and also appears factory. The reason i'm jumping in this old thread is that i've been googling around for that throttle switch setup...i'd like to yank the 389 complete down to every bracket and bolt and mothball it and save it. I have a 428 that i want to put trips on and drop in it's place, and i want to adapt another of those linkage/switch setups to the trips if i can find one, instead of taking the one of the 389. I want the 389 to just be on it's storage stands complete, carb, dist and all, linkage springs, etc, ready to go back in. Pontiac linkage looks different than the buick setups i've seen googling around today.
Had one behind a 455 Pontiac in a '72 Lemans. I wired it to activate with the brake pedal, and also had a toggle switch on the shifter (Hurst dual gate from a 1968 GTO) to operate it manually. It was a lot of fun!
Switch pitch converters have just about vanished, and the remainder of the support parts are getting very thin on the ground. I have a TH425 switch pitch, and a TH425 fixed pitch transmission sitting in the shop right now, and have the ability to build either one, but I'm having trouble finding any support parts for the switch pitch one. I will likely have to pass on it.
What parts are you referring to? I had a converter rebuilt by Hughes a few years ago, no problem. The solenoids have not been available forever new, but used ones work...the brittle wire insulation can be a problem. The sealing ring on the input shaft is hard to find, I bought a few NOS ones years ago, haven't had to use them yet, I don't think. With the non-SP converters available today, there really isn't much reason to use a switch pitch, except for special applications. Like building a sort of period car using a 55 year old 12" converter that you want to drive a lot, and run low 10s with.
Every single solenoid that I have been able to get my hands on is dead. Everyone that I buy online is dead. Everyone that I find in person that I check first, is dead. I have an SP TH425 that is now the mock-up transmission, because I can't find anybody who wants to rebuild the torque converter on it now, or a solenoid to put in it.
bummer. I guess I better not get rid of any solenoids, then.... (but I'll look and see how many I have, I know I have one complete transmission, and maybe another pump and some other stuff)
There is a guy who builds an electronic controller for the convertor. It controls the convertor based on manifold vacuum and brake input. It works quite well. All you need to add is a switch to give a full throttle downshift. I've got one of his controllers on my Model A (Buick nailhead). I'll look up his information tomorrow.
I know this thread is over 2 yrs old, but I'm compelled to add my .02. Ya, the guy with the Pontiac and a sp tranny really aroused my interest, as I've never seen one in a Pontiac, ever, and I'm now 66 yrs old having owned a Nailhead since 1976. Back then, even in the rustbelt, solid 60's sheetmetal was still easy to be had. You'd be surprised how many peeps at car shows and cruise nights look at me like I'm from Mars when I mention anything about the sp400. One guy enlightened me about the Olds tranny from around '62 that had 2 converters somehow, 1 is on the inside. (Perhaps one of the olds guys here can chime in). Ya, I got a '64 Nailhead 425 with a '66 st400 behind it, 3.42 posi, in a fully optioned Riv. (heavy car). The stall speed with energized convertor is around 2200 rpm by tach. The 4w drum brakes can hardly hold it back. Remove the juice it's around 1800 at low stall. I tried a hydraulic stoplight switch just for kicks, and didn't really notice a difference, although the setup seems more reliable like that. I prefer the stock setup though mostly for appearance. Some Buick people around here may know me...I'm the guy with the '67 Riv which I retro fitted with a 2x4 Nailhead. If I wanted speed or simplicity I would have just used a 455, but this was so much cooler. I've been around since the '90's. When I rebuilt the sp400, I used the later style pan and filter, along with a later valve body, w/ part throttle 3-2 downshift that will drop from 3 to 1 in drive at speeds below 35mph. (ooh 'ya!) A note on the th400....governor mods will alter full throttle shift points but be careful to only do it a little at a time. The low speed 1-2 short shifting really can't be fixed with gov mods in my own experience. I don't understand what all those colored springs do, so I just left them alone. lightening the secondary weights however will increase the wot 1-2 shift rpm points up to to a certain degree. I had a few spares to sacrifice until I got it just right. I wound up with about 5,000 rpm's. Stock was 4,400 if memory serves me well. If someone has advice on the pt short shift problem that some th400's have around 20-25 mph I'd love to hear solutions. I hope this info I have provided helps someone.
Not mentioned that I see, but GM and Chevrolet trucks also used them. I put one in my 409 powered, 61 Impala. Fun trans. to play with. Mike
I was helping to clean up a pile of '73 to '78 GMC Olds powered motorhome parts. The lad I was working with said some of those torque converters were switch pitch. He could tell just by looking down that tube.
I wonder if that was the NH powered GMC and Chevy trucks from long ago that I've read about? BTW, your 409 powered Impala is one of my favorite cars.
I've never seen a Chevy reference anywhere to switch pitch, I'd be really interested in any evidence for this, beyond rumor. I should see it in my 1969 Chevy parts book that covers all the Chevy trucks, eh?
Yep, that was the first place that I learned about them. A friends Dad had a Chevy truck (don't recall the year, but this was the late 60's). As I recall, it had a switch on the dash. I asked what that was for. It turned on the "activation" of the converter. You (that truck), could run with the converter working "normal", or as the..."switch pitch". He ran it both ways for us. So yes, I've seen it first hand in a Chevrolet truck. Mike
I was there...were you ? His dad was NOT the mechanical type. Automobiles were transportation...period. Mike
I read somewhere, and I can't recall where, that s/p trannies were used by GM to help get heavy cars moving. Caddy, Buick, Olds seem to fit that statement, as many .Chevy and Pontiac cars (except for Bonnevilles and such) were light by comparison to the big cars. This makes me question why they didn't find their way into motorhomes. Lots of torque is one thing, but using it efficiently is another. I recall getting spanked badly by a '67 olds 88 back when I still had my '66 Riv. It was embarassing! Maybe it was that cheap gas I was using.
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