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PowerGlide Decode

34K views 9 replies 5 participants last post by  junior stocker  
#1 ·
I'm having trouble finding out what exactly the tranny I got, Is? I'm pretty sure that it is a powerglide, from the shape of the pan, but beyond that, no clue. The numbers on the side of the pan reads, C1A27D
If someone out there could help me, thanks.
I got it with a bunch of other stuff that was in a combo deal with a 67 camaro, and I don't think it's the original one, that came with it.
 
#5 · (Edited)
Powerglide

Yes. that's a POWERGLIDE. On the dip stick side of the case it should say "POWERGLIDE", and directly above that will be a square recessed pad with letters/numbers in it; LOTS of letters/numbers. They tell what the trans came in, and what engine it was used with; the letters/numbers on the pan mean nothing. Is the output shaft course or fine spline? You could pull the input shaft out of the trans and measure it's lenth; DON'T lose the brass ring on the input shaft! If the shaft is 12.625"/12 5/8" it is a 1.82 first gear unit; if the shaft is 12.875"/12 7/8" it is a 1.76 first gear model. From 62'-65 1/2' model years the trans also had a rear pump; the rear pump was deleted during the 65 1/2' model year. Your trans is also a 28" long model; the 62'-64' model year FULL SIZE cars used a 25" long trans. All the early BOX STYLE Novas/Chevy II's used the 28" model with the 4 and 6 cylinder models being air cooled; they had 4 large rectangular or round holes in the bellhousing, a sheet metal enclosure that "turbined" the air flow aroung the torque converter, and the converter had a spot welded on turbine shroud to help cool things. All other Powerglides are fluid cooled; you could add fluid cooling to an air cooled model. NOW, there is one moreTHING your trans could be, as it was apparently used in a Camaro, and that's a TORQUEDRIVE. Thats essentially a powerglide that you have to manually shift; If there IS NOT a modulator on the trans, then it's a TORQUEDRIVE trans. I think that's about all I can tell you about POWERGLIDES, other than depending on what the trans was in, and which engine was in front of it, the number of drive and driven plates in the direct /high gear drum wll be different. I think the output shaft changed to fine spline when the t-350 transmission came out. The lower first gear trans were used with 4, 6, and lowpower V-8 engines. The 1.76 first gear planetary is stronger than the 1.82 first gear trans. That help?

In decoding the set of letters/numbers on the side of the case, it's hard to find a sourse to compare to. I have a 25" glide that I found out through decoding it, that it originally came in a 63' full size car with a 409, so I guess it's somewhat of a rare piece ,and might be worth something to a numbers correct restorer.It's a 1.76:1 first gear unit. But, I built it up with a shift kit, aftermarket 5 disc direct hub, and good steels/frictions. I've thought about redoing a 28", 1.82:1 first gear model I have ,using most of the stuff from my 25"; would make it easier to use for swapping into other cars. Most use a 28" glide. Have a trans-brake coming so I've got to make up my mind. Sort of hate to use the rare trans in a drag car. If someone were to make a decent offer on the 25"it would help me decide (hint, hint).
 
#6 · (Edited)
Torque drive powerglide.

To my knowledge the torque-drive version of the powerglide never came in a Camaro. It was designed for industrial trucks. For this reason It was manual shift only, When climbing a long grade under load the trans could be kept in first gear. It is easy to spot as there is no shift modulator near the back of the case. Also the powerglide that is being asked about in the thread is a 1:76 first gear unit and the stamped numbers C1A27D that are on the pan do mean something. The "C" means it was manufactured in the Cleveland powerglide plant, the "1" indicates it is from 1971, the "A" means it was manufactured in January. the "27" is the indicator for the day of the month it was built, (in this case the 27th), and the "D" indicates it was built during the Dayshift at the plant.
 
#7 ·
Powerglide

Studebaker, Educate me here please. Is there some outward appearence to that pictured trans that tells it's a 1.76 first gear model. The only way I've learned, was that if it's not in an original vehicle or attached to an original engine, is to pull and measure the input shaft; most yards don't want you doing that, or pulling the pan. I did mag up the image and can see it does have fine splines on the outputshaft. It also looks like it may have been a "floor shift" trans by the selector lever, but I could be wrong on that. Many years ago when I first started use glides in bracket cars I had quite a few glides collected. I was looking for a Torquedrive, and even went to the Chevrolet dealer who said they could still order one; but the price was way out of my range at the time. Torquedrives were available in 4 and 6 cylinder Novas in 69'-70', and in Camaros with 6 cylinders from 69'-70'. I've only seen ONE in a car over all these years. Torquedrive valve bodies are cast with raised T D letters in the upper and lower components, and "all valves EXCEPT the pressure regualor, hydraulic modulator, and manual shift have been eliminated;I guess this means they don't have a throttle pressure valve, the so-called "kick down"-"passing gear". They may have come in trucks, but it seems they were only used in low performance Novas/Camaros. What really amazes me about the powerglide, is the number of aftermarket and seriously modified parts made by several vendors now. And when I was in high school, if you had a powerglide in your car, you were laughted at; POWERSLIDE!
 
#8 ·
Actually , you measure the diameter of the output shaft to determine the gear ratio of the OEM aluminum power glide.

Torque drive was an option for the Camaro... I doubt many were ordered though.

Also, I have seen the rear pump style power glide used up to 1967 model year.

We build glides every day with no OEM parts to them.

Eggzample below:

Notice removable bell housing and that sure looks like a FORD bell housing bolt pattern.

Image
 
#9 · (Edited)
Decode info

Junior stocker, From the stamped production code in the pan I could determine that the trans was a 1971, therefore it has to be a 1:76 ratio as they quit making the 1:82 years earlier (as far as I know, I could be wrong). . Also The 1:76 and 1:82 besides having different length input shafts, also have different size output shaft diameter. Ill get to this in a few, (note:The 16 spline shaft was discontinued in 1964) and was only the short 12 1/2 inches from the Planetary carrier to the end of the output tail shaft. The longer version is 14 11/16 from P/carrier). Although from the 1965 production run all output shafts, (both 1:76 and 1:82) have the same 27 splines there is a difference in shaft size (speaking now of Diameter) and is very Minimal. The 1:82 shaft diameter is about 9 thousands smaller in size. GM used the exact same drive-shaft yoke on both 1:82 and 1:76 27 spline output shafts. Some people with the 1:82 shaft have complained that the yoke felt loose, however this never caused any oil seal leakage problems. I have seen a lot of powerglides and never have seen a torque-drive in a camaro, but hey, it doesn't mean they did not install them. A lot of times when vehicles were coming down the production line they would install what ever was available as current stock ran out for that production shift.
 
#10 ·
Powerglides

Studebaker and Crosley, I had read/heard somewhere about the output shaft diameter differences, although minimal at several thousanths (sp) of an inch. Something that would have to be measured with an outside caliper/mic. I don't have either of those. Always just tried to pull the input shaft. Learned the hard way about the different input lenths relative to the planetary assemblies; almost never got the almost new high stall converter off the wrong shaft, as it had mushroomed at the end in the converter. Also learned the hard way about not using as gasket on the govenor support/rear pump glides. The only TorqueDrive trans I ever saw was in a 69' Nova with the 153 cid 4 cylinder engine, and it actually said "TorqueDrive" on the dash shift indicator. What also's odd about TorqueDrives is they all have the 5 pack direct clutch pack. I'm an X-Ray tech by profession and cars/drag racing is just a hobby. Most all I know is what I've learned on my own, with little bits of information from friends and fellow racers (who usually don't share too much). So, thanks for the lessons you've taught. Now, Crosley, how about sending me a couple of those glides in your pic, real cheap of course. My 71' edition of CHILTONS has a wopping 2 pages about the TorqueDrive after the Powerglide section. Thanks guys.