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You haven't received a response so I'll give it a try. The 56 power glide had a coarse spline yoke. I believe all chevy's did until about 1965. Then they switched to a fine spline. I think most of the regular parts vendors should be able to sell you a fine spline yoke. Ecklers, Corvette America, Long Island Corvette, Mid America.
You may have to have a slightly longer driveshaft made for use with the 27-spline TH350 yoke; the C1's all had a 4-1/2"-long yoke due to the extreme driveline angles (and how that affected fore-aft yoke position on the output shaft with rear axle vertical motion), and I suspect the TH350 yokes you find will have the standard 3"-long tubular section. Don't know that for sure, but keep it in mind as you hunt for 27-spline yokes.
What!! And miss the puking on the garage floor and the wonder of the 2 speed?? I had a turbo 350 and a very nice 350 small block in my '55 when I first rebuilt it in the 80's.. How I miss the 3rd gear and the 300 horsepower...
You may have to have a slightly longer driveshaft made for use with the 27-spline TH350 yoke; the C1's all had a 4-1/2"-long yoke due to the extreme driveline angles (and how that affected fore-aft yoke position on the output shaft with rear axle vertical motion), and I suspect the TH350 yokes you find will have the standard 3"-long tubular section. Don't know that for sure, but keep it in mind as you hunt for 27-spline yokes.
John----
I think he'll need to have a new driveshaft made (or modified) in any case. I think the original C1 cast iron Powerglide was longer than the Chevrolet version of the THM-350. If that's the case, he'll want to have the forward yoke of that driveshaft match the transmission yoke so that there's no need to use a conversion u-joint. I THINK the Corvette style transmission yoke that would work would be the GM #376747. It's discontinued but I think it's available from Spicer. This yoke uses the 1330 series u-joint. This u-joint has wider fingers than the 1280 series u-joint used on C1 and C2 Corvettes. So, the driveshaft will have a 1330 series u-joint yoke at the front and a 1280 series u-joint yoke at the rear.
I do not know of a THM-350 transmission yoke that uses the 1280 series u-joint but that does not mean there isn't one.
I was wondering about the length of the yoke as well. The original yoke on the C1 driveshaft is right at 6 inches center of u-joint to end of yoke. The adapter plate I am using for the starter moves the transmission back 1/4 inch, so something like 5.75 inches SHOULD work OK.
Joe has me wondering about the overall length of the short tail th350 compared to the powerglide. I was thinking they are pretty close in length.
Worst case, I have a drive shaft made up. Not a big deal.
I was wondering about the length of the yoke as well. The original yoke on the C1 driveshaft is right at 6 inches center of u-joint to end of yoke. The adapter plate I am using for the starter moves the transmission back 1/4 inch, so something like 5.75 inches SHOULD work OK.
Joe has me wondering about the overall length of the short tail th350 compared to the powerglide. I was thinking they are pretty close in length.
Worst case, I have a drive shaft made up. Not a big deal.
I'll figure it out as I go.
Thanks guys.
Ed---
My information shows the cast iron Powerglide used for 1956 to be 29.25" in overall length. The short version of the THM-350 (i.e. Chevrolet) is 25.25" overall length. The long, dual pattern version is 34.75" overall length.
My information shows the cast iron Powerglide used for 1956 to be 29.25" in overall length. The short version of the THM-350 (i.e. Chevrolet) is 25.25" overall length. The long, dual pattern version is 34.75" overall length.
Joe;
Check this web site out. I am thinking the cast iron powerglide is the "short tail" powerglide. If so, the cast iron powerglide is 25 23/64 inches .vs 27 11/16 inches for the TH350. That would make the TH350 about 2 1/3 inches longer. THis may NOT account for the transmission adapter on the 56 powerglide. Your thoughts on this?
Check this web site out. I am thinking the cast iron powerglide is the "short tail" powerglide. If so, the cast iron powerglide is 25 23/64 inches .vs 27 11/16 inches for the TH350. That would make the TH350 about 2 1/3 inches longer. THis may NOT account for the transmission adapter on the 56 powerglide. Your thoughts on this?
I don't know what to make of this. I thought the information I had was accurate. On the other hand, I would think that TCI's is accurate, too. So, I guess it will take actually measuring them. Automatic transmissions are certainly not an area of much expertise, for me.
I measured my cast iron powerglide. It measures roughly 26 inches, plus 1.5 inches for the transmission adapter. Total is about 27.5 inches.
I don't have the TH350 yet, so I can't measure it.
I think I understand that the 1280 series u-joint has been replaced by the 1310 series u-joint.
I have found plenty of 1310 series transmission yokes for a TH350 on Ebay. They vary in length from 5.5 inches to 7.5 inches (center of u-joint to end of tube).
I should be OK in finding an input yoke. I'll wait until I get the TH350 in place to determine what I need.
I measured my cast iron powerglide. It measures roughly 26 inches, plus 1.5 inches for the transmission adapter. Total is about 27.5 inches.
I don't have the TH350 yet, so I can't measure it.
I think I understand that the 1280 series u-joint has been replaced by the 1310 series u-joint.
I have found plenty of 1310 series transmission yokes for a TH350 on Ebay. They vary in length from 5.5 inches to 7.5 inches (center of u-joint to end of tube).
I should be OK in finding an input yoke. I'll wait until I get the TH350 in place to determine what I need.
Ed-----
Yes, the 1280 series has been replaced (long ago) by the 1310 series. I just can't extract that 1280-series nomenclature from my brain for what reason I don't know.
I don't think the length of the transmission typically includes the adapter. Regardless, it looks like my information on trans length is inaccurate UNLESS they are using some sort of measurement protocol different than the conventional and commonly used.
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