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Oldsmobile AST


Guest r40blanken

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Guest r40blanken

There is currently a clip on YouTube of a ride in a '38 Buick equipped with Buick's optional Self Shifting Transmission, identical to the one optionally used in 1937-'39 Olds, called the Automatic Safety Transmission (AST). It reminds me of the day 60 years ago when I explored a wrecked '39 Olds which had a clutch pedal, but also a shift quadrant on the steering column that seemed to be for an automatic. I was familiar with Hydramatic and Dynaflow, so puzzled over the presence of that clutch pedal. Today I know the AST didn't have a fluid coupling, so needed the clutch pedal to shift into R, L, or H range at a standstill and get the car moving in the conventional way, but gears automatically shifted after the car got moving.

In more recent years I've come to realize that what I saw was a '39 Olds equipped with AST. I wonder if anyone in an Olds collectors club happens to own a '39 so equipped? I am curious as to what the shift quadrant looks like. The one Buick used was mounted in line with the shift lever to the right, as in the engineering sketch I've seen of the one in '37 Olds. The sequence of ranges was R N L H on both.

I realize this will be seen as total needless trivia to most people, but I'd love to get another look at the AST shift quadrant on the '39 Olds. I wonder if it resembled the Hydramatic one that was introduced in the 1940 Olds.

rblanken@yahoo.com

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Guest r40blanken

Here's a link to the best documentation I've found on AST and Hydramatic history.

http://ateupwithmotor.com/technology/246-hydramatic-history-part-1.html?start=1

The next link is the YouTube link to the '38 Buick. About 40 seconds into the video the driver pulls up to an intersection, stops, then cross the street and continues accelerating promptly through the gears. About 2 minutes 10 seconds into the ride he stops at another intersection, crosses, and accelerates a little faster, and probably a little down hill. The old Buick goes through the 4 gears pretty quickly.

I'll attempt to attach a small snapshot of the Buick shift quadrant. Looks like the attempt failed, but I could e-mail it to you if you wish.

R. Blankenship

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Guest De Soto Frank

I really couldn't hear the engine / tranny sounds in the you-tube clip... does the AST up -hift under load/acceleration, or does the driver have to let-up on the accelerator for the shift to occur ?

At Hershey 2009, on Saturday there was a '33 or '34 REO with the Self-Shifter transmission in the HPOF class... it was sort of an ivory-beige color.

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Guest r40blanken

That Buick video is a cell phone recording with wind noise, but with the volume turned way up, its engine sound is very clear. The clearest shifts located at 40 seconds into the recording, then again at 2 minutes 10 seconds, are very distinct. To answer the question as to whether it shifts under power, yes, definitely.

In this particular sample, there may have been a slight band misadjustment that produced momentary engine loading on the 2-3 shift, or it may have been the driver easing up on the throttle a bit to smooth out the shift. The 2-3 shift was very complicated because it involved the bands and clutches changing simultaneously in two clutch packs, and adjusting them to get smooth shifting was a task to be done deftly. That was also true of the original Hydramatics before the dual coupling versions that had no bands.

All other semiautomatics I know of other than preselectors, shifted once, and only after the accelerator was let up for a few moments. I've felt somewhat irked by some automotive writers who were clueless as to the AST's operation, but tried to sound authoritative in describing it as similar to Chrysler Corp. M6. The only similarity between them is that they had 4 distinct gear ratios.

r40blanken

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Guest De Soto Frank

" I've felt somewhat irked by some automotive writers who were clueless as to the AST's operation, but tried to sound authoritative in describing it as similar to Chrysler Corp. M6. The only similarity between them is that they had 4 distinct gear ratios. "

I, for one, appreciate your sharing some information on the AST... my MoToR's manuals of that period say precious little about them.

Being a flathead-Chrysler Corp enthusiast, I am more than a little familiar with their version of a semi-automatic, and am a stickler for folks describing that animal correctly!

It's greatest shortcoming ( in my experience) was it's inability to up-shift under-load; but then it was essentially a four-speed sliding-gear transmission which had been modified with an "automatic" gear-change device... not "bands & clutches", which are the hallmarks of a "true", "modern", automatic transmission (in my opinion).

Would love to see some engineering drawings / cut-aways of the AST some time...

Will also play around with my computer and see if I can hear those shifts !

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Guest r40blanken

Yes, Frank. Do get some help with your computer sound if you can't lick the problem yourself. Once that Buick recording is removed from YouTube, you may never get another opportunity to see almost first hand, what the AST could do. They are rare these days, especially in Buicks.

I've read that AST shifts were predetermined to occur at specific vehicle speed, no matter the throttle opening, except if the accelerator was floored. That proves to be true in the recording if you study what's going on in the start from the second intersection in the video. The car is accelerated harder, but the shifts aren't timed any later. If the accelerator had been floored, though, each shift would have occurred at its maximum limit. AST also had a full throttle kickdown to a lower gear for safer passing. That was done exactly as it is done in our contemporary transmissions, under power with no momentary engine interruption.

I like your DeSoto! I have something of an affinity for the old workhorse Chrysler Corp. flatheads too. My first car was a '50 Plymouth Special Deluxe.

R.Blankenship

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