A Switch Pitch 400 feature in a 64 ST400

[Rivi-98]

I have both a 1964 St400 and a 1966 ST400 I want to put the 66 switch pitch pump and torque convertor on the 64 trans, is this OK to do or is the st400 missing ports for oil or something?

Edited May 20, 2023 by Rivi-98 (see edit history)

[RivNut]

The transmissions are different. The 64 has a single spline input shaft, the 66 has a dual input shaft. It's not just the converters that are different, plus other differences.

Edited May 20, 2023 by RivNut (see edit history)

[JZRIV]

Yea more involved. There is a solenoid that triggers oil flow to change the converter blade angle. Electrical connector is a 2 pin for the SP vs 1 pin (kickdown) for non SP and thats towards the rear of trans so either the whole housing or valve body is different at a  minimum.  

[telriv]

NOT POSSIBLE with a '64 trans.

 

Tom T.

[NTX5467]

Is this more of a model year issue, on the upgrade, rather than a SP issue per se?  Reason I inquire is that I remember reading (back in the later 1960s) where people with a normal THM400 added the SP THM400 converter and pump, then toggle-switched the converter angle mechanism (in the upgraded items).  On the production SP THM400s, that would have been handled by items relating to the throttle linkage, as I recall.

 

Just curious,

NTX5467

[RivNut]

Urban myth.  Those are two separate transmission. They don’t even share the same pan. Why Buick chose to call them both ST400s is a question.  Buick chose to call the GM Turbo-Hydramatic (TH400) a Super Turbine (ST400) to keep the turbine name in front of the public. For years their “Turbine Drive” transmission - the Dynaflow- was noted for smoothness.  They wanted to retain the name even though they applied it to two different transmissions.  Somewhere along the way the someone got the idea to call the ST400, with the variable pitch version, the SP400. SP being short for Switch Pitch. There’s absolutely nothing in any factory literature referring to the 65 - 67 transmission as the SP400. Another urban myth that has perpetuated its way into daily belief. 

Edited May 23, 2023 by RivNut (see edit history)

[californiamilleghia]

I love the idea of the "switch pitch" trans , 

 

When it was new was it worth having ?

 

is there something similar  from GM  in a newer full size car or van ?

 

Thanks for the info 

[RivNut]

Besides the performance issue, when the brake pedal was applied the torque converter also went into the high stall mode.  This kept the car from creeping at a stop light.  It made it easy for high torque engines and gray haired little old ladies’ with weak brake pedal toes to peacefully coexist.

[65VerdeGS]

10 hours ago, californiamilleghia said:

I love the idea of the "switch pitch" trans , 

 

When it was new was it worth having ?

 

is there something similar  from GM  in a newer full size car or van ?

 

Thanks for the info 

The switch-pitch feature was only offered by GM for three years, from 1965 to 1967, in TH-400 equipped cars offered by Buick (who developed it), Oldsmobile, and Cadillac.

 

Switch-pitch was effective in improving transmission performance by allowing the angle (pitch) of the torque converter (TC) blades to be varied between two positions, controlled by a micro-switch on the throttle linkage.  In normal driving and cruising the TC blades would be in the low position, to give higher efficiency and better fuel economy.  When the throttle was opened past a certain point the TC blades would go into high position, increasing torque multiplication.  This was like having an extra gear, without gearing down!  When the car was stopped at a light (for example) the TC angle would go to high to reduce 'creep' at idle.  As soon as the driver touched the throttle in moderate driving the TC angle would switch to low.  If he put his foot 'into it' more, this wold trigger high angle, improving acceleration.

 

The switch pitch feature really helped to 'wake up' a heavy car, giving better acceleration along with reasonable efficiency at cruising speeds.  Combined with Buick's legendary high-torque motors, it was a winning combination!

 

Switch-pitch was dropped in 1968.  Reasons quoted include cost, along with the increasing cubic inch displacement of engines in the late 1960's which made 'tricks' like SP less necessary to maintain acceptable performance.  Some said that SP was unreliable and may have caused warranty issues.  However, I suspect the average driver might not notice much difference if the SP system wasn't working, for its main advantage was in improving 'toe in' when accelerating briskly.

 

I think GM was the only car firm that used SP in their transmissions.  The ST400 was the most highly developed of the modern SP transmissions, and Buick led the way thanks to their experience with variable pitch torque converters in their earlier automatics.

 

Others please chime in with your Switch-Pitch lore.

 

 

 

 

 

 

 

 

 

 

 

 

[drhach]

Could you just swap the whole transmission if you have both? 

[RivNut]

1 hour ago, drhach said:

Could you just swap the whole transmission if you have both? 

Yes. But if you do that, get the carburetor and throttle linkage to go with it so it will function properly.

[RivNut]

7 hours ago, 65VerdeGS said:

The switch-pitch feature was only offered by GM for three years, from 1965 to 1967, in TH-400 equipped cars offered by Buick (who developed it), Oldsmobile, and Cadillac.

 

Switch-pitch was effective in improving transmission performance by allowing the angle (pitch) of the torque converter (TC) blades to be varied between two positions, controlled by a micro-switch on the throttle linkage.  In normal driving and cruising the TC blades would be in the low position, to give higher efficiency and better fuel economy.  When the throttle was opened past a certain point the TC blades would go into high position, increasing torque multiplication.  This was like having an extra gear, without gearing down!  When the car was stopped at a light (for example) the TC angle would go to high to reduce 'creep' at idle.  As soon as the driver touched the throttle in moderate driving the TC angle would switch to low.  If he put his foot 'into it' more, this wold trigger high angle, improving acceleration.

 

The switch pitch feature really helped to 'wake up' a heavy car, giving better acceleration along with reasonable efficiency at cruising speeds.  Combined with Buick's legendary high-torque motors, it was a winning combination!

 

Switch-pitch was dropped in 1968.  Reasons quoted include cost, along with the increasing cubic inch displacement of engines in the late 1960's which made 'tricks' like SP less necessary to maintain acceptable performance.  Some said that SP was unreliable and may have caused warranty issues.  However, I suspect the average driver might not notice much difference if the SP system wasn't working, for its main advantage was in improving 'toe in' when accelerating briskly.

 

I think GM was the only car firm that used SP in their transmissions.  The ST400 was the most highly developed of the modern SP transmissions, and Buick led the way thanks to their experience with variable pitch torque converters in their earlier automatics.

 

Others please chime in with your Switch-Pitch lore.

 

 

 

 

 

 

 

 

 

 

 

 

The Buick Dynaflow. Also used the variable pitch converters.

[XframeFX]

6 hours ago, drhach said:

Could you just swap the whole transmission if you have both?

Certainly. Three Bellhousing types were cast for the TH400. The Nailhead was first in the 1-year only/ Nailhead only 1964 transmissions. After that, the Nailhead bellhousing was used for 2 more model years shared with other GMs which by 1967, there were only two for GM. That would be Chevrolet and BOP/Cadillac.

 

So, a direct swap. If you have an AFB, swap out the primary shaft for one having the switch-pitch bellcrank. This will allow use of a 1965/66 Combo switch. You will also need a 1965/66 dashpot bracket.

I did this to my 1963 AFB and fab'd a lever to use the Dynaflow's variable pitch to function (image-1). If you have a Rochester 4G, best to swap it out, good luck finding a donor carb.

[XframeFX]

On 5/20/2023 at 4:04 AM, JZRIV said:

Yea more involved. There is a solenoid that triggers oil flow to change the converter blade angle. Electrical connector is a 2 pin for the SP vs 1 pin (kickdown) for non SP and thats towards the rear of trans so either the whole housing or valve body is different at a  minimum. 

BOP TH400s were available with switch-pitch for BB Buicks & Oldsmobile for the 3 years from 1965-67. Chev TH400s can be converted by swapping out the Torque Converter, Front Pump and rear poly bung for one with a 2-prong connector. The last item is to install an orifice in the image below. A cap broken off an AGC fuse with the glass cleaned out and drilling a hole works.

 

TH400 Variable Pitch 13" Torque Converter and Variable Pitch Front Pump showing 2-prong connector extracted from a BOP 1966 340 cu. in. LeSabre 400:

 

 

 

 

Edited May 25, 2023 by XframeFX (see edit history)

[drhach]

You probably also could just convert the 64 unit to a regular TH400. I think among what's been said, you would also have to swap out the valve body. I converted from a Dynaflow to an ST400, it wasn't too big of a deal. Is the 64 shift quadrant different as well? 

[XframeFX]

1 hour ago, drhach said:

I converted from a Dynaflow to an ST400

What did you do for a shifter and enabling the Start/Backup Switch to function? You have the switch pitch version of the ST400?

 

Since you have had both transmissions in the same car, can you please comment on before/after throttle response? I'm sure it was worth it. I need some positive motivation along with $2K or so to rebuild my core ST400.

Still curious if I can insert a 1964 front drive shaft into the yoke of the 1963 rear drive shaft at the center support. Possible?

 

1 hour ago, drhach said:

You probably also could just convert the 64 unit to a regular TH400.

If it's possible, not worth the trouble. Just look for a 1965-66 unit. That might be difficult as well because I've noticed some Nailhead ST400s on wrecking yard shelves that have been converted away from its original switch pitch during a rebuild. Warning signs of a rebuild are a painted case.

 

I have amassed various switch pitch torque converters and front pumps in recent years after being told I'm 15 years too late.

[RivNut]

IF, and it’s a big if, you’re looking for performance from your ST400 with the variable pitch converter, consider using the variable pitch converter from the same years ST300. Higher stall speed  = improved off the line performance.

[XframeFX]

3 hours ago, RivNut said:

performance from your ST400 with the variable pitch converter, consider using the variable pitch converter from the same years ST300

Ed, careful with your recommendation. Because you did it. I'm now following-up with my personal experience. It is based on "You're 15 years too late"

 

What you see below is a rebuilt 12" Variable Pitch Torque Converter meant for a ST300.

 

Story:

After many attempts to locate a unit, "NO" after acknowledging the 13" VP Torque Converter. However, some did say they can do it with a $100 core charge. "Fine" I said, keep the $100 because I don't have a core. "We have no core either. You bring us your core". Several places were this way. Even J. Weiss at V8Buick had zero cores of either size. Size? From him, I learned of two, the 2nd being a 12" VP Torque converter. "You'll want that one"

 

Fast forward 5 years. I have acquired several 13" units locally. The 1st required extracting the seized Buick 340 in under an hour to make an appointment. Others were there for the taking because engines were already gone, thank-you.

My 1st and only 12" required another seized Oldsmobile 330 extraction during a bitter December. It required 3 trips and sneaking a torch into the wrecking yard. That core was in my checked bag on a business trip to a Refinery in Vancouver area. After my meeting, I did a hectic triangle in my rental during a weatherly rush hour. I barely made the shop before closing then rushed off to YVR Airport because my wife announced she was joining me that day.

The following week while travelling on another trip, the shop called to say they had one rebuilt on the shelf after all. "Would I like that one?" Dumb-founded, "Sure", then out of cell-phone service. Not long after, I came to realize that $25 core saved me $75 of the $100 core charge after all that effort! Also, the off-the-shelf rebuild would not be according to J. Weiss's instructions! The next day back in cell-phone service I called the Shop and too late, that rebuilt unit was sent out on a Greyhound. I was mad enough to purchase two!

 

Go ahead, Laugh!😆

 

I have crawled under many wrecks with a 12V battery pack to listen for a solenoid click on that 2nd prong. It saved me a couple of engine pulls because there was no click. Many rebuilt transmissions had that VP function removed. I won't allow being Laughed at Twice!

 

13" VP Torque Converters are a rare find today because I have the remaining few! That baby 12", even worse!

 

12 Inch Variable Pitch Torque Converter - Mystery Build:

 

 

Edited May 25, 2023 by XframeFX (see edit history)

[drhach]

20 hours ago, XframeFX said:

What did you do for a shifter and enabling the Start/Backup Switch to function? You have the switch pitch version of the ST400?

I have to qualify this by saying that I didn't do this to a Riviera. Also, I had a column shift unit. I don't know the interchange of the various Riviera floor shifters. But I would think you could swap the 63/64 unit with a 65 unit. I'm sure someone will have an opinion about why that won't work. My car is a 62. I was planning to use a shifter from a 65 and make it work in the 62 Wildcat console. In the meantime, I used a shift quadrant from a 66 and used the same column shifter with a new linkage. It works quite well. 

 

I still have not sorted out the backup switch/starter issue. Again, I think if you were able to use a 65 Shifter, the problem, would sort itself out.

20 hours ago, XframeFX said:

 

Since you have had both transmissions in the same car, can you please comment on before/after throttle response? I'm sure it was worth it. I need some positive motivation along with $2K or so to rebuild my core ST400.

Still curious if I can insert a 1964 front drive shaft into the yoke of the 1963 rear drive shaft at the center support. Possible?

Honestly, I don't think I would do this again. At least not for a stock to mild performance application. The difference is not night and day. It was fun and I learned a lot. But really there wasn't a huge bang for my buck. One of the things I can say that I gained was that there's a ton more product support and knowledge around the 400 platform. I was able to put in some upgrades to the stock transmission and it should outlast the car; and probably me. I was concerned that if I ran in to a problem with the Dynaflow, it might be hard to source some obscure part or talk to someone who really knew what they were talking about. This concern was probably amplified because I decided to do the rebuild myself.

 

It didn't turn the car in to some kind of street terror though. I think I improved my fuel economy a little too. But I offset that by installing dual carbs  I wouldn't discourage anyone form doing this swap, but don't expect miracles. 

 

 

20 hours ago, XframeFX said:

 

If it's possible, not worth the trouble. Just look for a 1965-66 unit. That might be difficult as well because I've noticed some Nailhead ST400s on wrecking yard shelves that have been converted away from its original switch pitch during a rebuild. Warning signs of a rebuild are a painted case.

The issue with the ST400 versus the TH400 is specific to the pump and the Torque converter. You can buy a brand new pump and torque converter for a TH400. Unless you can find NOS, everything for the ST400 is used or used/rebuilt. I don't think it's a huge deal but again, as an inexperienced rebuilder, that might be a concern for me. I measured everything 2-3 times and felt confident that what I was reusing was good. But if I had a bad pump gear or housing, it would have meant trying to source a good used one. That would be the only real consideration for converting. I think the ST is almost a smooth as the Dynaflow (very close). To me that suits the Buick and justifies trying to keep it ST specific. I think that's a taste or preference thing though. 

 

20 hours ago, XframeFX said:

I have amassed various switch pitch torque converters and front pumps in recent years after being told I'm 15 years too late.

I actually had an ST300 torque converter rebuilt and installed in the car. The stall was too high for me. I didn't care for it. I ended up going back to the 400 converter. Again, it's a preference thing. I find as I get older, I like a little more civility in my cars. Nailheads make their torque down low. I built the engine for that. So, to have the stall converter come on late seemed contrary to the engine's purpose. 

Edited May 25, 2023 by drhach (see edit history)

[Rivi-98]

On 5/24/2023 at 3:04 PM, XframeFX said:

BOP TH400s were available with switch-pitch for BB Buicks & Oldsmobile for the 3 years from 1965-67. Chev TH400s can be converted by swapping out the Torque Converter, Front Pump and rear poly bung for one with a 2-prong connector. The last item is to install an orifice in the image below. A cap broken off an AGC fuse with the glass cleaned out and drilling a hole works.

 

TH400 Variable Pitch 13" Torque Converter and Variable Pitch Front Pump showing 2-prong connector extracted from a BOP 1966 340 cu. in. LeSabre 400:

 

 

 

 

So you don't have to change the input shaft? I thought the SP shafts had 2 sets of splines on them? Is that all you would need to change? Oil pump, 2 prong Plug, T.C. and the spline shaft?

[Rivi-98]

On 5/20/2023 at 4:55 AM, RivNut said:

The transmissions are different. The 64 has a single spline input shaft, the 66 has a dual input shaft. It's not just the converters that are different, plus other differences.

What if you had the 66 ST400 dual spline shaft put in the 64 ST400? Is that the only other holdup?

[XframeFX]

13 minutes ago, Rivi-98 said:

So you don't have to change the input shaft? I thought the SP shafts had 2 sets of splines on them? Is that all you would need to change? Oil pump, 2 prong Plug, T.C. and the spline shaft?

I'm not that intimate on TH400 details. I have collected parts I know are hard to find recently in wrecking yards for SP TH400s. Basically what I mentioned is what's needed to convert a TH400 to SP and only 1965 and later units.

None have dual shafts. The outer splines are narrower for SP front pumps and like the wider splines for non-SP, holds the stator inside the torque converter stationary.

 

25 minutes ago, Rivi-98 said:

What if you had the 66 ST400 dual spline shaft put in the 64 ST400? Is that the only other holdup?

1964 is one-off Buick production . Leave it alone or swap it out.

[RivNut]

2 hours ago, Rivi-98 said:

What if you had the 66 ST400 dual spline shaft put in the 64 ST400? Is that the only other holdup?

Oh no! Actually completely different transmissions

[RivNut]

On 5/24/2023 at 2:35 AM, 65VerdeGS said:

The switch-pitch feature was only offered by GM for three years, from 1965 to 1967, in TH-400 equipped cars offered by Buick (who developed it), Oldsmobile, and Cadillac.

 

Switch-pitch was effective in improving transmission performance by allowing the angle (pitch) of the torque converter (TC) blades to be varied between two positions, controlled by a micro-switch on the throttle linkage.  In normal driving and cruising the TC blades would be in the low position, to give higher efficiency and better fuel economy.  When the throttle was opened past a certain point the TC blades would go into high position, increasing torque multiplication.  This was like having an extra gear, without gearing down!  When the car was stopped at a light (for example) the TC angle would go to high to reduce 'creep' at idle.  As soon as the driver touched the throttle in moderate driving the TC angle would switch to low.  If he put his foot 'into it' more, this wold trigger high angle, improving acceleration.

 

The switch pitch feature really helped to 'wake up' a heavy car, giving better acceleration along with reasonable efficiency at cruising speeds.  Combined with Buick's legendary high-torque motors, it was a winning combination!

 

Switch-pitch was dropped in 1968.  Reasons quoted include cost, along with the increasing cubic inch displacement of engines in the late 1960's which made 'tricks' like SP less necessary to maintain acceptable performance.  Some said that SP was unreliable and may have caused warranty issues.  However, I suspect the average driver might not notice much difference if the SP system wasn't working, for its main advantage was in improving 'toe in' when accelerating briskly.

 

I think GM was the only car firm that used SP in their transmissions.  The ST400 was the most highly developed of the modern SP transmissions, and Buick led the way thanks to their experience with variable pitch torque converters in their earlier automatics.

 

Others please chime in with your Switch-Pitch lore.

 

 

 

 

 

 

 

 

 

 

 

 

Actually, Buick’s ST300 (an actual 2speed  transmission) had the switch pitch feature in its torque converter. Run the smaller 2 speed ST300 converter in the larger 3 speed ST400 transmission for additional torque multiplication (aka power) for quicker hole shots. But along with that performance increase you also get higher transmission temperatures.  It’s a trade off.  Flip a coin.

[XframeFX]

9 hours ago, RivNut said:

But along with that performance increase you also get higher transmission temperatures.  It’s a trade off.  Flip a coin.

In Canada, I never have to worry about overheating.

[61LeSabre]

On 6/28/2023 at 11:57 PM, XframeFX said:

In Canada, I never have to worry about overheating.

XframeFX, I was wondering if you could comment on my post.  I was going to send you a message but I can't yet because I don't have enough posts.  

 

[61LeSabre]

On 6/28/2023 at 2:16 PM, RivNut said:

Actually, Buick’s ST300 (an actual 2speed  transmission) had the switch pitch feature in its torque converter. Run the smaller 2 speed ST300 converter in the larger 3 speed ST400 transmission for additional torque multiplication (aka power) for quicker hole shots. But along with that performance increase you also get higher transmission temperatures.  It’s a trade off.  Flip a coin.

Rivnut, I was wondering if you could comment on my post.  I was going to send you a message but I can't because I don't have enough posts yet.  

 

 

[XframeFX]

16 minutes ago, 61LeSabre said:

XframeFX, I was wondering if you could comment on my post.  I was going to send you a message but I can't yet because I don't have enough posts.

Actually this post is on the 1-year only BUICK ST-400 that did not have the Variable Pitch Feature (yet). For 1965 production, this transmission was refined and offered in 2 additional integral Bellhousings, BOP & Chevrolet. Of these, only high end offerings (Cadillac, Buick & Oldsmobile) had variable pitch between 1965 -67 production years.

 

So, for 1961, original transmission? Dynaflow? Must be if you're dealing with a mechanical linkage. If so, I do not have an answer. Maybe someone here can chime in for the both of us.

 

I have never experienced variable pitch because I was unaware of this feature in my earlier rides. This includes my current 1963 Riviera that was sent into a 30-year sleep partially assembled. I farmed-out the rebuild before this and was unaware of variable pitch then.

So, I don't know how distinct high pitch mode is supposed to feel in the Driver's seat. Our cars are 30 - 40 years older so, I seldom do WOT to find out.

 

I tried WOT occaisionally the last couple of summers to test for secondaries and high pitch. Hmm, I hear the secondary cicuit but high pitch? The linkage travels only about a 1/4", normal? I've locked it high pitch mode, re-installed the air cleaner, dropped the hood and went for a test drive. No chage in creep at idle in Drive. No change accelerating to speed.

Could it be possible the shop goofed in my rebuild back in the early 90s? I wouldn't be surprised as they failed and had to to go back into the transmission a 2nd time.

 

Question: How noticeable is Dynaflow high pitch at idle and during acceleration?