Need some help on 727 parts interchangeability

dsd1967 said:

I have a 1978 big block 727 that came out of a class A motor home. It has the short tailshaft housing with a drum brake on it. The transmission only has 285 miles on it (there's a story behind that), so I would like to use the transmission.

The issue is that I need the standard car/truck tailshaft. I had a 727 that I scrapped several years back and in the process kept the tailshaft and output shaft. Problem is that I don't know the year or application of that transmission.

My question is.....am I that lucky that the output shafts were the same throughout the years and applications....or am I going to run into an issue on splines or something like that. What would I need to look for? Any help would be appreciated.

Thanks
Dave

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Lefty71 said:

I think '76 is the breaking year.... meaning there is an earlier spline angle and a later one, and then they did change again years later... ill look for the particulars...

***EDIT***

62-75
76-93
93-on

Three different spline angles.
Do you have any other parts from that other trans? No case ##'s to lookup?? No idea what year it was?? No gearsets to go along with the shaft you saved??

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dsd1967 said:

Thanks Lefty!

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dsd1967 said:

I wasn't smart enough when I parted the one to look for year information. I'm sure it is the first generation so I'll have a spline angle issue. At least it gives me an area to closely evaluate to verify. I'm not in a big rush to get this together, so if I find they don't match I'll post a WTB for the second generation output shaft. I appreciate the help.

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Lefty71 said:

I think '76 is the breaking year.... meaning there is an earlier spline angle and a later one, and then they did change again years later... ill look for the particulars...

***EDIT***

62-75
76-93
93-on

Three different spline angles.
Do you have any other parts from that other trans? No case ##'s to lookup?? No idea what year it was?? No gearsets to go along with the shaft you saved??

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1 Wild R/T said:

The spline count is the same so the parts will fit but the angle is different so they will fail...

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dsd1967 said:

So when you are talking the spline angle....is it the included angle between splines....the V portion? In other words is one more truncated than the other like an ACME thread vs a UNS thread?

At first I was thinking the spline angle was referring to the spiral around the shaft, but looking at the shaft that I have out the only spiral is for the speedo gear.

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dsd1967 said:

So when you are talking the spline angle....is it the included angle between splines....the V portion?

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1 Wild R/T said:

It's along those lines.... BTW the late shaft has a groove to ID it... See the pointer at the bottom..

View attachment 1039190

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Dipstick said:

I have seen the front planetary spline angles expressed both ways, pressure angle or included angle. Included angle is the angle of the open V.

The included angles are as follows:

'62-'75= 90°

'76-'93= 75°

'94-on= 60°

The pressure angle is half the included angle (45°, 37.5°, 30°)

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dsd1967 said:

What is the best way to tell what year the motor home transmission is.

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