I had my trans rebuilt a year ago and i was told that back then you had to start off in "low" as if it was 1st gear and then shift it into drive. this is an automatic dynoflow and im not sure if the guy is telling me the truth or just making up an excuse for what he couldnt fix. It does take off better in low, being that the car is so heavy, but it just doesn't seem normal to me being an automatic. let me know what you think. Thanks

I'm no Dynaflow expert, but that sounds like a load to me...you should be able to put it in gear and go, unless you are driving in conditions where you want the low range.

It should start off in Drive like any other automatic.

stevo

Put it in drive and go. Use low and shift to drive all of the time and you will be rebuilding again. Dynaflows are very durable when left in drive but a heavy foot and low to drive shifts will make you an expert at remove and replace (as I well know from past experience...).

Is it possible for someone to put in "simple terms" just what does happen when a Dynaflow is put in low.

What is altered in the trans when in low to make it have more pep?

Use Drive most of the time.
page 7 of owners manual: "Maximum acceleration from a standing start is obtained by starting in 'L' and shifting to 'D' at 35 mph.
The shift fron 'L' to 'D' or vice versa may be made while th car is in forward motion by merely flipping the lever. thes shifts should not be made at speeds over 40 mph."

You will learn when extra accelertion is needed and use low accordingly. If desired get a service manual and the function of the dynaflow is described.

Willie

Hello buick840:

I'm not a Dynaflow expert (Hydramatic man) but here goes:

In Drive range, all transfer of engine torque is done hydraulically via fluid in the converter. Those '1000' gear shifts don't involve any actual gears. When Low range is selected, a single planetary gear set is added to the power flow increasing the gear ratio between the engine & the Dynaflow output shaft. It's kinda like increasing the rear axle ratio from inside the transmission. I think a band actually 'brings' the planetary gear set into the mix. Constantly shifting between Low & Drive ranges (while in motion) will eventually wear out the band.

It's really hard to describe how these engineering marvels work. I've been studying them for several decades and I'm finally getting a good feel for them...

Hope this helped.

Paul

Thanks Paul,
You'll have to forgive my severe lack of knowledge when it comes to these tranmissions.

I was aware that there is a gear involved in increasing power some how but it's still not clear to me if that gear then becomes a direct drive.

In other words, after bringing the gear into play are the motor and driveshaft actually connected by the gear?

Or is the gear used to amplify the volume/flow of the fluid and the driveshaft is still fluid driven?

Like I said.......I'm a novice when it comes to these transmissions...........
But what I have found is, that if you don't ask questions you won't get any answers

Selecting LOW range doesn't create 'direct drive'. The gear reduction (torque increasing) effect of the planetary gear set is added to the torque multiplying effect of the converter. In other works, the gear set & converter are 'in series'.

FYI: Henry Ford's Model 'T' used a planetary gear set transmission to provide two forward speeds & reverse. However, the 'gears' were manually selected by pressing the pedals in the correct combination.

Even if you never use LOW range with your Dynaflow, REVERSE motion is actually created by one or two (?) plantary gear sets. Planetary gear sets were invented by geniuses. By controlling which gear set member (sun gear, planet gears or ring gear) is held or allowed to rotate and by selecting which member is used as input & output, torque can be in either increased (gear ratio increased), reduced (gear ratio decreased) or reverse motion created...!

Sorry for the run-on but automatic transmissions are way cool!

Paul

PS: When I was in middle school, a teacher once told me: "He who asks no questions, learns nothing". Thank you Mr. Emil Sibi

Paul,
Thanks for a very informative explanation, certainly helps me to better understand how a Dynaflow operates.

Just to add a note to what Paul says there are two gear sets - one for low the other for reverse. The both are mounted on either the input or output shaft that connects the engine to the rear end (engine to torque converter) by either oil pressure and fluid only (that is drive [which is direct drive - no gears]) or a combination of oil pressure and fluid along with gears (low or reverse). In both low and reverse the maximum torque multiplication of 2.10 to 1 is multiplied to 4.55 to 1 so pick-up is much faster (note: the variable pitch stators in the transmission will be in the "performance" position when you floor it in both drive and low [reverse too if you are crazy enough to floor it when backing up] and pump pressures are doubled when compared to drive). In addition to wearing the band out shifting from low to drive when one does not shift as early as 40 mph (one can reach 60-65 if memory serves me correctly and when one is racing a Ford, Chevy, etc... one does NOT want to shift to drive at only 40 ) really bad things happen (like the band crushing the drum housing the gear set for low). Talk about bad rattling noises when that happens (and about five more miles before the stator blades break out, the entire drum disentegrates and the input/output shaft are no longer connected so the car will NOT move. Bad memories... but sure was fun! Of course $25 would get you a replacement at the local junkyard so...

Low gear in a Dynaflow consists of a band applied to the clutch drum stopping it's rotation.
When direct or high gear is selected the band is released and the clutches applied.

When reverse is selected a different band is applied to the ring gear.
One weak area in reverse is the anchor.
It is made from cast steel which gets very brittle and is subject to breaking.
This requires almost complete disassembly to replace but there is / was an aftermarket fix that was done in the vehicle.

Ah the good old days.

My parents always drove Oldsmobiles, but when I was growing up we had several friends and relatives who drove Buicks. I remember reverse engaging in a Dynaflow with both a "ka-lunk" sound and a moderate lurch/jerk. Is my memory correct?

Planetary gearsets can perform 6 functions:

Increase in speed
Reduction in speed (more torque)
Direct Drive Sun gear hold
Direct drive Ring gear hold
Increase in speed reverse
Reduction in speed (more reverse torque)


So in the case of dynaflows, drive range starts in a reduction (planetary gearset in torque converter) and gradually fades into a direct drive.

In Low it starts in both planetaries (Converter and low planetaries). As with drive the converter planetary reduction fades out leaving only the low planetary for reduction.

Lastly I find it hard to believe that the Low band would be subject to abuse if when you shift to DR the band is RELEASED, and NOT APPLIED! (this of course is a moot point if the low band release is slow and not actively released via servo release mechanism).

Hope this helps, oh and BTW you should look into the FLIGHTPITCH DYNAFLOW if you want to be schooled on converter based transmissions. Turboglides too.

Mine hits reverse with a vengeance if the engine is still on fast idle. Luckily, my garage floor is slippery and the tires spin a bit. Normally, I just wait for it to step down a notch on the cam.

"So in the case of dynaflows, drive range starts in a reduction (planetary gearset in torque converter) and gradually fades into a direct drive."


The torque convertor does not have a planetary system.

Older Hydramatics did but not a Dynaflow.

You need to study the 55 service manual where it tell you all about the torque converter planetary system

When I had my torque converter apart to replace the front pump seal there sure was a planetary gearset in there.

This info was recently posted by MartyWorld in response to my 'Dynaflow Evolution Question'...

Hope this clarifies the changes made to the torque converter over the years.
My understanding is that the original converter ('48 - '52) had only 3 elements: pump, stator and a single turbine.

Paul

**************************************************

Evolution of the Dynaflow:
1948-1952
Introduced in 1948, remained virtually the same through
1952. Transmission planetary gearset not used in normal
driving. All of the work is done by the torque convertor.

1953-1954
Torque convertor redesigned to incorporate twin turbines.
First turbine is geared to the second turbine using a
planetary gearset, ratio 1.6. Quicker takeoff.

1955
Addition of a variable pitch stator replacing the fixed
stator. Result, better overall couple when in low angle
but when in high angle, gives the effect of a "passing
gear" without any gear change to accomplish Buicks design
parameters of smoothness and continuous powerflow.

1956-1960
Incorporated an additional stator, named the first stator.
This is a fixed stator. Improved takeoff acceleration and
efficiency.

1961-1963
Same as the 1956-1960 with the exception that the tailshaft
housing is designed for an open driveline.

Marty

I stand corrected.

After doing some in depth research I discovered pre 55's did use a planetary in the convertor.