I have a 67, 442 with a post 67 Switch Pitch TH400. The transmission is clearly post 67 as it has a vin derivation code stamped by the kickdown/switch pitch connector. It also has a normal TH400 filter and pan so I assume someone converted it to switch pitch.
I was searching the webs for switch pitch parts and stumbled on a complete TH400 switch pitch with converter, never mentioning year or application. What I received was a complete TH400 Switch Pitch with converter, correct original shallow pan and filter, NO vin derivation stamp and original tag of "OG-67-4626".

I am trying to confirm this transmission would be correct for my 67 442. Best I can tell from the 67 CSM is the 67-OG was for V-8, 4Bbl with L-77-78 package. L-77 & L-78 = 400 cu in engine, L-77 being High Compression V-8 performance engine which the 67 442, 400 cu in engine had. Additionally, all I can find for the last 4 digits of the tag is that it identifies the production date? No idea what 4626 decodes to so if you know please share. I am fairly confident I got lucky and found the correct transmission for my car without intending to do so but would appreciate confirmation. Having it rebuilt now and planning to install soon. Would love to be able to confidently say it has the CORRECT transmission. Any input would be appreciated.

 

I looked through your photo album and your car is gorgeous, but it appears it has several deviations from original equipment so I'm not really sure where you're getting this need for "correctness" which is something of an arbitrary term anyway. Your car is likely not going to be judged at Pebble Beach anytime soon.

To my mind, a functional TH-400 in good operating order is plenty correct for your application.

 

I appreciate the compliment. You are correct in that I have most certainly deviated from original equipment to this car, most notably the W-30 package on a Freemont car. However, I do try to stay year/make/model correct as much as possible and thought it was pretty cool to get what I believe to be the correct transmission for this car without seeking it out specifically or paying crazy prices. The trans in it now runs great but has some chatter in park on decel at low rpm and leaks more than usual from the front shaft seal. I think the chatter may be the old switch pitch pump or maybe the converter which led me to seeking out switch pitch parts. Hoping this new to me trans will take care of all that and be correct for the car to boot.

 

Fair enough. I guess if you're going to go ahead and replace it anyway, you MAW get something as close to original as possible.

Unless ... ever think of converting it to a 4-gear?

 

4626 is a transmission serial. OG 67 is all you need to be "a correct transmission." If you were trying to be 100% original (and you are not), you would seek out one close to the correct number on the protectoplate, which you probably don't have. The idea is to have one made shortly before the car was made, that's how you play the dated parts game. However, for functional correctness, 67 OG is it. You have it.

You may need a throttle switch.

 

Thanks for the confirmation, sir! Also good to know what the last 4 digits mean. You are right in that I don't have the POP but I am happy with having the "correct" transmission. Fortunately, I have the switch pitch throttle switch as well, and it works perfectly so it should be an easy swap. Really appreciate the feedback!

 

You are slowing down or stopped with transmission in Park ?

 

It is most noticeable when stopped, in Park, revving up to 1200 rpm or so and letting off. On deceleration is when I hear the chatter, towards the low end of the rev. I ruled out lifter tick or engine related as it is focused underneath car at transmission around the converter/pump area. I do have a pretty quiet exhaust system making it easier to hear. That being said it runs and drives great with no shifting issues.

 

Do you have a heat riser ? They could "rattle" if the shaft is worn or spring is weak.

 

No heat riser sir.

 

Take it for a drive and have someone else drive while you direct them and move your head around to listen.

 

I had my friend work the throttle on the carb while I poked around and the best I can tell is it is loudest under the car right at the front of the transmission. Had him listen as well and we both agree that is where it is coming from. Scoured the engine with a stethoscope and am confident it is in the trans. I checked the converter to flywheel bolts and anything else in the vicinity and everything is tight. My best guess is the transmission pump is worn, or the converter is noisy. The converter was supposedly rebuilt but the pump was not changed as they are unobtanium. I am using a different builder this go round that does have switch pitch parts from back in the day, but he still has to farm out the converter rebuild. He came highly recommended and was very knowledgeable about the switch pitch, so fingers crossed.

 

If the transmission has the later filter and tube setup, then either someone swapped to a later valve body, or they drilled and tapped the early filter to accept the later filter and retaining hardware.

There are some calibration changes HydraMatic made to compliment the switch pitch setup.

 

http://www.buickperformanceclub.com/SPTrans.htm

 

Quick update to the Switch Pitch transmission issue and upcoming swap. I had the OG-67 trans rebuilt, adding a stage 2 Transgo shift kit and recalibrating the speedo drive gear and driven gear to match my tire diameter and gear ratio for correct speedometer reading. I also had the "original to the OG-67 trans", 13-inch switch pitch converter rebuilt.
I dropped the old transmission and noticed a few things of interest. First, there was noticeable chatter marks on the old converter which looks to be a result of the converter to flex plate spacing being too much. It was definitely more than the recommended 3/16 in max. So, I feel this would explain the noise i was hearing on deceleration before. Once everything was out and in open view i noticed the old converter did not have blank lug indentions on the bottom. From my research i have learned the 13-inch converter had these flat spots where no bolt lugs were mounted, in addition to the 3 mounting lugs. A 12-inch converter from an ST300 only had the 3 bolt lugs and no flat spots. Upon further inspection i was able to determine i have been running a ST300, 12-inch switch pitch converter instead of the stock 13-inch. Much like a TH350 converter in a TH400 the smaller TC gives higher stall. I looked for a 12-inch at the beginning of all this and found nothing rebuildable or offered rebuilt at any price. Seems to be a purple unicorn.
This may explain the performance of my bone stock 67, 442 with 3:90 gears. The thing is much quicker than one would expect for what it is. And here i thought i was just an awesome tuner, lol. Anyway, I'm getting the 12-inch rebuilt and will be putting it in with the OG-67. See pic of chatter on converter and back side of 12-inch.

 

Quick pic of the back of 13-inch Switch pitch converter.

 

Quick update on the 12" switch pitch converter spacing. After having the 12inch converter rebuilt and installing there was appx 5/16 gap between the converter and flywheel when converter was fully seated in trans. I ended up adding .135 shims between converter and flywheel and ended up with 1/8 inch gap. Once it was running the previous chatter on deceleration was gone. Just a note to check the spacing on your converter to flywheel gap on old rebuilds.

 

I’m no expert on TH-400 transmissions, but I can relate that in those years, Olds made no less than 3 switch-pitch/kickdown switches.

In my year ‘66, the switches sat at the center of a set of solid rods from the gas pedal to the carb. Later Olds went to throttle cables since (per Joe P’s excellent history) the unbending throttle rods could pin the throttle open and kill people.

Lemme keep it short. In 1966 (and probably 1967) Olds made 3 switch pitch/kickdown switches:
1) Cutlass/442 type - round in shape & not adjustable. Adjustments for switch-pitching or kick down would have to be done with rods.

2) 88/98/Starfire type 1 - round shape, with an adjustable with a spring steel-retained tab on top, The neat thing about this switch is you can rotate and secure the kick-in points of the switch pitch function & kickdown function. It’s a lot of trial & error to get it working right, but it’s fantastic if you get there. If you want to acquire this switch for a Cutlass/442 to upgrade to adjustability, it’s doable, but perhaps not factory correct. But it may buy you the freedom you want to get your “intermediate” working as you like.

3) 88/98/Starfire type 2 - square shape, not adjustable, referred to as “Littlefuse” switch in Oldsmobile documentation of the day. These can be used in the Cutlass/442, but again you’re back to using rods to get the switch pitch and kickdown function to work right. I believe these were the default switches for the Toronados too.

The switches are a little different, but all connect to the gas pedal housing with 2 3/8” hex heads. They all have the same bottom shape which means you can mix & match as you see fit. Or well, based on what you find.

What wears out in these switches are the brass contacts. Over say, 50-60 years, constant throttle movement mechanically wears down the switch contacts which can be repaired with a drop of solder and a bit of file shaping to recreate the original shape of the contact. Or you can swap in less worn contacts if you have ‘em.

I have a post here on CO on fixing these switches. If you get curious dig it up under my username.

Meanwhile, best of luck finding the transmission and switch-pitch/kickdown switch that works best for you and/or maybe gets to factory-correct.

Cheers
Chris

 

I can confirm I have switch type 1. The "tampered" with tabs on the switch indicate it has been serviced at some point, before I got it, but works as it should. The switch pitch operation is much more noticeable on this build then what i had before, so I am still playing with it to figure out exactly how it performs in different scenarios. The 12 inch converter definitely has noticeable stall increase over stock. And best of all is no more converter chatter.

 

Just to fill in, the tampering you’re seeing is probably because the switch brass contacts wore down. So they opened the pot metal tabs to try & fix the switch.

If you carefully bend the tabs on the pot metal which retains the bakelite retention parts, you can get at the interior brass/springs of the switch. Simply put, there are 3 triangular shaped brass contacts which are spring loaded to hold fast against their opposite members. Over time, the springs wear the brass contact points down from being forced together, or sometimes they arc from voltage. This is normal, especially over 50+ years.

So the previous owner had some switch pitch/kickdown malfunction, probably from worn contacts, then they opened the switch to repair it. That process leaves witness marks.

The bad part is no one makes replacement switch contacts.

But all 3 triangular brass contacts are the same. And it happens that one of the contacts gets very little wear. If you can acquire 3-5 of these switches together, you can cobble up an almost-new switch by reusing the least-worn contacts from your group. Having identified the 3 types of switches above, I should say that despite the exterior shape differences/designs, I believe all 3 used the same interior brass contacts. So, get a bunch of 66-67 switches & make 1 or 2 good switches from the best parts you can find.

If you fail to find spares, your move is to solder a drop of solder onto worn brass contacts to recreate the shape the contacts once were from the factory. The process is to melt a solder drop on the worn brass contact. Then use another correctly shaped contact to be a guide as to how “tall” & “round” to file your soldered drop to emulate the original contact shape.

Then sand & grease the h*ll out of the rotating parts so they work smoothly. I like the Amsoil pink synthetic grease for this. Factory recommends lithium grease but it dries out and latter day greases are much better and long lasting.

After the contacts are right, and the switch is rotating smoothly, the last task is making it clean. I use a dremel & flap wheel to get 50-60 years of grease, dirt & crap off the pot metal. You can dunk it in strong chemicals, but anything strong enough to get the crap off might corrode, solve, or otherwise destroy irreplaceable Bakelite parts. So I just polish the exterior parts to make ‘em presentable. I aim for nice, but not super-shiny: a clean consistent exterior finish, not show-chrome.

This combo-switch has a strong influence on your driving experience. If it works right & rotates smoothly, you’ll love the car’s throttle response for its precision & smoothness. Almost like modern fuel injection. So, when you come across rotating parts, take a second or 60 to polish them smooth with a #0000 steel wool. Future you will thank yourself. Springs & rods matter too - for the rods, run ‘em through a tap & die to get the threads clean so you can adjust the easily to your preference.

For all the throttle springs, dunk ‘em in Evaporust (great stuff) for a few days, or if you can find good replacements in your local hardware store’s Hillman section, replace them. The critical part with throttle springs is being 100% sure that the throttle spring is tight enough to positively close the carb primary throttle plates _completely_ when you let your foot off the gas.

What little I’ve learned about these thing over the past 40 years or so. Hope that helps you all.

Chris

 

The car was originally a 4 speed and was converted to auto at some point. When i replaced the trans in this last gig i noticed the crank does not have the pilot bearing hole so going back to 4 speed with this engine wont be happening. And, as much as i love a 4 speed my beat-up old foot doesn't much care for them anymore.

 

Very good info sir. Not much out there so this is good stuff.