Seriously bummed with this drivetrain setup right now :(

[SquareRoot]

Don't forget, the national speed limit for the majority of the squarebody years was 55mph.

All of the 4.56 + 4-speed combos I've seen have either been regular cab tow trucks, CC ramp trucks, box trucks or camper special CC dooleys.

Were these longbeds with one piece shafts?

 

[nvrenuf]

It’s long gone but a friend had a LWB ‘77 K10 350/4spd/205 with a 1pc 3.5” dia rear shaft, the 4spd is in my Blazer now. He used the rear shaft in another truck.

 

[SquareRoot]

Update - Mystery solved. I pulled the output housing from the 205. Pulled it apart on the bench and couldn't see anything unusual. When I put it back together, to make it easy I used an impact on the yoke nut. After I got it back together I realized the excessive end play was gone. If I had to guess, it might be 2-4 thousandths at most. Everything turns nice and smooth. Afterwards I went for a drive. Smooth as butter up to 85 mph.
Apparently a bearing wasn't seated, which is odd given the output shaft bearing is a caged needle bearing. That bearing is pressed into a "hole" that goes all the way thru the webbing it's cast into. I had pressed it in until it was flush. It seems using the impact may have pulled it in tighter and self adjusted, eliminating the free play. Whatever the case, I'm very relieved and happy it's working as intended.

 

[SquareRoot]

Hmmm...I wonder if I just solved the mystery?
Exceeding the Critical Speed DESPITE being balanced will cause vibration according to Spicer Website. My vibration starts at 60 mph and I can feel it thru the clutch pedal at that speed. Starting to make sense.

Funny, I had a thread about a one piece vs two piece given the length I was dealing with and somebody Flamed me. I guess if the shaft is 5+ inches in diameter it would work? @Keith Seymore

This was not the case. When I pulled the shaft and got actual measurements, it was 58.5 inches between joints. My theory is busted.

 

[SquareRoot]

Thanks all who contributed. This was a learning experience. Hopefully someone in the future can benefit from it.

 

[Redfish]

Thanks all who contributed. This was a learning experience. Hopefully someone in the future can benefit from it.

I know I learned a lot from it. Thank you for posting the fix and not leaving us all hanging. I am really happy you got it figured out and all that time and money spent is now doing what you want.

 

[TotalyHucked]

Glad you got it figured out! Sometimes it's something so small and simple that will create the largest headaches.

 

[TotalyHucked]

Were these longbeds with one piece shafts?

Most of what I was referring to were either very long box trucks (like Finnegan's race car hauler) or ramp trucks, so 2 piece shafts. I can think of maybe 2 CCLB dually camper specials I've seen over the years with a one piece shaft and 4.56 gears, one SM465 and one TH400. However, I did not look for evidence of a carrier bearing, so who knows if they were original or not.

 

[Craig Nedrow]

Way to stick with it SquareRoot aka Mike. I have been on here three weeks watching, and glad you got it fixed, cause this winter I'm gonna swap stuff around and will need new shafts. Thanks for the great pic. Carry on!!