direct drive th350

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pdq67
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Re: direct drive th350

Postby pdq67 » Tue Apr 25, 2017 2:44 pm

pdq67 wrote:I have a stupid question and I think that the Pontiac guys did it at one time say like in the '63 or '64 Tempest rear tranny cars??

Can we hook two PG's together to make a 4-speed automatic?

I mean, heck, the PG is one stout tranny.. IMHO, it just doesn't have enough gears is all........

pdq67


Anybody by chance knows who did this?

AND

How was it done?

Looks like a real winner for a bullet-proof 4-speed PG tranny!

Guys, we really need to get info like this out there because us old-heads are fast dying off!

The pup's won't know anything about stuff like this that has been done way back then is all.

pdq67

Brian P
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Re: direct drive th350

Postby Brian P » Tue Apr 25, 2017 3:21 pm

Counterpoint, perhaps I'm one of those "young pups" (50 years old??) but why would you do it that way in this day and age?

If a Mopar/ZF 8-speed will handle the Dodge Challenger Demon, and the Ford 10R80 and GM equivalent (I don't recall their nomenclature but it's the same transmission) will handle the Ford Raptor and Camaro ZL1, that's plenty good enough for most people, AND those have overdrive (several choices, in fact) AND those have lock-up torque converters (that are capable of handling full engine output torque and staying locked through gear changes!) AND those don't have an awkward 2-3 shift where you have to shift one two-speed gearset from low to high while simultaneously shifting the other one from high to low, AND it's lighter AND it's more efficient AND it's capable of shifting quicker than anything with old school hydraulic controls ever could.

I get that the Powerglide has its place in historic vehicles and specialized drag-race applications, but there's no purpose to doing further development with it ... the automotive industry has moved on.

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Re: direct drive th350

Postby pdq67 » Tue May 09, 2017 2:18 am

Brian,

I just wanted to know how they did it is all. That is, hook 2 PG's together.

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Re: direct drive th350

Postby Brian P » Tue May 09, 2017 7:41 am

The original Hydra-Matic transmission (1940 - mid-fifties) was basically two simple two-speed planetary gearsets one after another (and another set for reverse). There are some interesting videos on Youtube showing how this transmission works and how it was built - it is a very interesting design. Obviously this was before they figured out how to couple planetary gearsets together in ways that gave multiple ratios from the same unit.

Two two-speed transmissions coupled together requires an awkward shift. At some point you have to simultaneously shift the range box from low to high range while shifting the splitter box (to borrow tractor-trailer terminology) from high to low. With the Hydra-Matic this was the 2-3 and 3-2 shift. The Chrysler 62TE in my van has a similar situation (because it is basically a 4-speed gearset followed by a secondary splitter) - it has an awkward 2-3 shift and this is an electronically controlled transmission. I can imagine how much of a nightmare it was to fiddle with band adjustments and the like to get pure hydraulic controls to do that.

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Re: direct drive th350

Postby pdq67 » Tue May 09, 2017 7:38 pm

FWIW, I have two Motor manuals that date from something like 1932 up to before 1955.

One, an engine spec. book and the other, a flat rate one.

The engine spec book is fascinating to say the least to be able to look at ALL the engine spec's from the V-8 Flathead.

One of the books has a section dealing with overhauling the old Olds 4-speed Hydro.

I don't know how many of them that I cracked open like an egg to separate the steel from the cast-iron scrap metal the summer that I worked for the salvage yard in Moberly, MO back then. Its still there too..

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Re: direct drive th350

Postby F-BIRD'88 » Sat Jun 24, 2017 6:33 pm

If you were to couple 2 power glides together and they had the same 1.76:1 ratio
then the result is a 3 speed transmission. You'd have 3 forward speeds.
3.097, 1.76 and 1.00 :1

But if you were to couple 2 powerglides together that had different low gear gear ratios
you would then have 4 forward speeds. Althou if using the stock available ratios
will result in a odd ratio spead. EG: couple togeht4er a 1.76:1 ratio PG with a 1.82:1 ratio PG
The resulting 4 forward speeds ratios are 3.20, 1.82, 1.76 and 1:1.
Shifting from the 1.82 2nd gear to the 1.76 3rd gear requires shifting both transmissions, simultaneously from low to high and and the other from high to low.
Not smooth easy or fast. Not very practical gear splits.

So for practical use you'd have to choose how to shift it as you'd have 2 slightly different 3 speed transmissions 3.20 1.82 1.00 :1 OR 3.20, 1.76 1.00 :1

Not much practical difference between the 2 different shifting modes.

You'd be much better off adding a Gear Vendors OD to a power glide.
Now you can split shift on the fly with much more practical and usable ratios splits
of the 4 forward speeds this gives you. The Gear Vendors OD ratio is .78 to 1
now you got 1.76, 1.37, 1.00 and .78:1 OD

Or with the 1.82:1 version PG and GV OD the 4 forward speeds are
1.82, 1.42, 1.00 and .78

More practical gear ratios spreads and can be split shifted on the fly fast using their
optional electronic (split) shift controller on the GV OD.

Also much more practical total Trans+OD length.


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