A new tranny design.

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pdq67
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A new tranny design.

Post by pdq67 » Tue Jul 05, 2016 12:57 pm

http://blog.caranddriver.com/clutch-pla ... smissions/

Wonder if I can get one that I can manually shift?

Probably not..

And I bet the option is, "CHEAP", too!!

pdq67

peejay
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Re: A new tranny design.

Post by peejay » Thu Jul 07, 2016 1:14 pm

Sounds like the tiny "spline lock" clutches for circle track. Wish I could remember the name so I could pull up a pic.

ZIGGY
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Re: A new tranny design.

Post by ZIGGY » Thu Jul 07, 2016 3:26 pm

Sounds like you're thinking of a Ram coupler. Been around for many years but not noted for durability.
http://www.speedwaymotors.com/Shop/Ram- ... rs/20.html

pdq67
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Re: A new tranny design.

Post by pdq67 » Tue Mar 21, 2017 2:49 am

Bringing this back from the dead.

I was just looking for the 421" Pontiac Tempest drag cars from the early '60's that had two P/G's hooked together, (I think), in the back of the car on the rear end. But I don't know if the stock swing axle was used or not?? Probably could have been used because those BOP cars were small and light.

An interesting concept to me.

I would like to see how the two P/G's were hooked together just to know.

pdq67

midnightbluS10
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Re: A new tranny design.

Post by midnightbluS10 » Fri Mar 31, 2017 4:23 pm

pdq67 wrote:Bringing this back from the dead.

I was just looking for the 421" Pontiac Tempest drag cars from the early '60's that had two P/G's hooked together, (I think), in the back of the car on the rear end. But I don't know if the stock swing axle was used or not?? Probably could have been used because those BOP cars were small and light.

An interesting concept to me.

I would like to see how the two P/G's were hooked together just to know.

pdq67
I believe there's a pic on this page, towards the bottom.

http://www.jalopyjournal.com/forum/thre ... cs.427884/
Here's some info that I found on the Performance Years site, it gives details on the '63 SD Tempests and the transaxle/'rope' driveshaft used on all of the '61 -'63 transaxle Tempest/Lemans cars. These cars did not use just a common Corvair transaxle:

The 4-speed '63 Tempest automatic was called the PowerShift. It only came in the 6 Super Duty Lemans coupes and 6 Tempest wagons. (There might be a 13th vehicle somewhere). After NHRA kicked them out of a production class because of the limited production brought on by the GM "no racing" edict, which caught everyone by surprise, most folks replaced the transaxle with a solid rear. That's why Thompson had a few extra. To the right collector, a complete, operating PowerShift is nearly priceless.

It was two 2-speed planetary transmissions (like a Powerglide or TempesTorque)on either side of the Tempest final drive unit. The flywheel and either a clutch or torque converter was hung at the extreme rear end. This required shortening the fuel tank about a foot.

Power flow thru the PowerShift was interesting and complex: the "rope" driveshaft fed power into the input shaft via a splined connector at the front of the transaxle. This shaft went completely thru the front trans case, the final drive and the rear trans case to the flywheel/flexplate. From the tc or clutch output the power flowed back thru a second concentric shaft to the transmissions. From there it went back thru a third concentric shaft which was the pinion gear shaft.

First gear was about 2.43, which you get with front trans (1.76) in low and then thru the rear trans (1.38) in low (1.76 x 1.38 = 2.43). For second gear the rear was shifted into direct to get 1.76 from the front trans still in low. For 3rd, both are shifted: front into direct and rear back into low for a 1.38. 4th gear is both back into direct. While this sounds terribly complicated, that's how the old 4-speed HydraMatics worked, but with the two planetary gearsets in one housing. Clutch and band apply and release have to be timed well, especially on the 2-3 shift.

The clutch, as shown in the pic a few posts above, was a concentric hydraulic always turning throwout bearing. AFAIK, this might have been the first OEM use if this, now common clutch actuation. You can see it in the pic.

As far as the "rope driveshaft", it was an alloy steel torsion bar, about the hardness of an antiroll bar. It had a forged head at the front which bolted solidly to extra holes in the center of a Pontiac crank on the automatics (and all SDs) and to the clutch output shaft on the production manual, I believe. It was splined at the rear and approximately 80 inches long. It was bent into a gentle arc (maybe 3-4 inches max at the center)and retained in a upside-down U-shaped torque tube. It didn't really need the little bearings about 1/3 and 2/3 of the way along the shaft. They were just there to retain it if it broke or came loose from the engine and for installation purposes.

Pontiac built maybe 300,000 '61-'63 Tempests with this shaft. VERY few ever failed in the field. Producton automatics had 5/8 dia shafts and manuals had 3/4 dia. as did the Super Duty cars. You can demonstrate to yourself how it worked by putting a gentle arc in a piece of wire like 1/8 dia. music wire, and have someone turn it while it's in the arc. The rotation is transmitted smoothly without any sinusoidal variation like you find in a u-joint.

Because it's a torsion bar, it will wind up under high torque loads. In testing, I believe it wound up over 2 revolutions when a 389 or 421 WOT at hp peak was dumped into it from a clutch at the front with the rear fixed to the test fixture. It stalled the engine (and then unwound the 2+ turns). In the production Tempests, the TC was in the rear, but the manual clutch was on the engine. You could dump the clutch and feel a little of the windup/unwind. The 3/4 dia. shaft minimized that, but I think the 5/8 would have been plenty strong enough. The biggest production engine to use it was the '63 "326" HO (4 bbl dual exhaust), which you probably know was really a 336 cube engine. I don't recall if it used the 3/4 shaft for the 2-speed auto, but probably not.

Picture of the PowerShift transaxle assembly
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