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Slip joint driveline question #1286620
Thu Nov 08 2018 08:33 PM
Thu Nov 08 2018 08:33 PM
S
Snowman51  Offline OP
Wrench Fetcher
Joined: Mar 2018
Posts: 70
Idaho Springs, CO
So I am currently trying to figure out what driveshaft I should put into my 1951 1/2 ton. It now has a 1964 SM420 open drive shaft and a 1957 HO32 chevy rear axle. I have the axle that fits the rear end so I can use that end to build a shaft. What do you recommend for the front ( I assume I’ll need a slip joint front since the yoke on the rear of the transmission is fixed). The length center-of-joint to center-of -joint is 63” and I want a single shaft. Is there anything out there that is close or do I need a front yoke and build a shaft?

Re: Slip joint driveline question [Re: Snowman51] #1286625
Thu Nov 08 2018 09:05 PM
Thu Nov 08 2018 09:05 PM
G
Gord&Fran  Offline
Shop Shark
Joined: Jul 2000
Posts: 432
Mill Bay, BC, Canada
I was advised by the local driveshaft expert to use a two piece shaft; 64" was too long in his opinion. Obviously, with a two piece shaft a steady bearing is required. Slip joint is used on the rear of the front shaft at the steady bearing. I got a core from a 68-71 GMC 4x4 and gave it to the drive shaft guy with the measurements needed.

Before I talked to the expert, I wasted a lot of time prowling wrecking years with a tape measure looking for a one piece shaft that would work. There was a Dodge one that might work, but the diameter of the tube was huge. It seems the longer the shaft, the bigger the diameter. Thinking back to my old structural engineering days, that would make sense.

Last edited by Gord&Fran; Thu Nov 08 2018 10:36 PM.

Gord
----
1954 1/2 ton 235 4 speed
Re: Slip joint driveline question [Re: Snowman51] #1286633
Thu Nov 08 2018 10:27 PM
Thu Nov 08 2018 10:27 PM
K
klhansen  Online
Shop Shark
Joined: May 2015
Posts: 846
Eagle River, Alaska
I doubt that 63" is too long for a single shaft. My Ford Supercab Longbed has a 2 piece shaft, but both halves are about 4 ft long. I can understand why they put a 2-piece under that, but 63" isn't that long.
You will need a slip joint in the shaft, typically installed at the front. Should be an easy thing for a driveline shop to fab for you, either from scratch or modifying an older one. Just find something that's long enough with the right rear yoke and let them do the rest, installing a slip yoke and spline on the front end.


Kevin
First car '29 Ford Special Coupe
#2 - '29 Ford pickup restored from the ground up.
Newest Project - 51 Chevy 3100 work truck.
Re: Slip joint driveline question [Re: Snowman51] #1286639
Thu Nov 08 2018 11:15 PM
Thu Nov 08 2018 11:15 PM
G
Gord&Fran  Offline
Shop Shark
Joined: Jul 2000
Posts: 432
Mill Bay, BC, Canada
OK, then. My advice is simple. Talk to the guy who will be cutting/welding/balancing your driveshaft(s) first.


Gord
----
1954 1/2 ton 235 4 speed
Re: Slip joint driveline question [Re: Gord&Fran] #1286646
Fri Nov 09 2018 12:20 AM
Fri Nov 09 2018 12:20 AM
K
klhansen  Online
Shop Shark
Joined: May 2015
Posts: 846
Eagle River, Alaska
Originally Posted by Gord&Fran
OK, then. My advice is simple. Talk to the guy who will be cutting/welding/balancing your driveshaft(s) first.

I agree. The real experts are the ones that do it on a daily basis. I'm just an amateur when it comes to driveshafts, but I have had a few rebuilt/shortened.


Kevin
First car '29 Ford Special Coupe
#2 - '29 Ford pickup restored from the ground up.
Newest Project - 51 Chevy 3100 work truck.
Re: Slip joint driveline question [Re: Snowman51] #1286695
Fri Nov 09 2018 05:16 AM
Fri Nov 09 2018 05:16 AM
D
delky  Offline
Shop Shark
Joined: Dec 2011
Posts: 76
Wyoming
Snowman51
Assuming you are working on a 3100 series, AD truck (short bed) and, assuming that in my 1957 3100 w/SM420 has a comparable length driveshaft, I offer the following:
my (org) driveshaft is in the neighborhood of 60"+ long. Single shaft with slip just rear of the transmission. Served me well for ~200,000 mi in 60's, 70's and 80's. I will be reinstalling it when current and long going resto is complete. Trans, shaft and rear end are as from factory.
delky dave in wyo


1957, 3100, v8
1990 Suburban
Re: Slip joint driveline question [Re: Snowman51] #1286696
Fri Nov 09 2018 05:17 AM
Fri Nov 09 2018 05:17 AM
D
delky  Offline
Shop Shark
Joined: Dec 2011
Posts: 76
Wyoming
Snowman51
Assuming you are working on a 3100 series, AD truck (short bed) and, assuming that in my 1957 3100 w/SM420 has a comparable length driveshaft, I offer the following:
my (org) driveshaft is in the neighborhood of 60"+ long. Single shaft with slip just rear of the transmission. Served me well for ~200,000 mi in 60's, 70's and 80's. I will be reinstalling it when current and long going resto is complete. Trans, shaft and rear end are as from factory.
delky dave in wyo


1957, 3100, v8
1990 Suburban
Re: Slip joint driveline question [Re: Snowman51] #1286726
Fri Nov 09 2018 02:46 PM
Fri Nov 09 2018 02:46 PM
S
Snowman51  Offline OP
Wrench Fetcher
Joined: Mar 2018
Posts: 70
Idaho Springs, CO
Yes it is a 3100 AD short bed, it now has a 1964 SM420, but has a 1957 HO 32 rear axle. Both ends have fixed u-joints so I will need a slip joint either in the front or the back. Will. A ‘57 3100 have a slip and will the shaft be enough length?

Re: Slip joint driveline question [Re: Snowman51] #1286829
Sat Nov 10 2018 04:48 AM
Sat Nov 10 2018 04:48 AM
D
delky  Offline
Shop Shark
Joined: Dec 2011
Posts: 76
Wyoming
As I see your issue, only actual measurement will answer that question.
Mine (as stated above) has slip yoke that attaches to rear of SM420. Mine is currently in my garage & not in truck. Would be happy to measure OA length between u joints & get them to you. Please advise. Good luck
delky dave in WY


1957, 3100, v8
1990 Suburban
Re: Slip joint driveline question [Re: Snowman51] #1286835
Sat Nov 10 2018 05:49 AM
Sat Nov 10 2018 05:49 AM
B
bartamos  Offline
Master Gabster
Joined: May 2005
Posts: 5,339
State48 Ranch
I believe you have a dropout style differential. Go to a driveshaft shop and tell them what you have and you want a driveshaft with a slip yoke for a sm420. They will advise and tell you what measurement they need and build it for you. One piece will work fine.

Option: there will be 55-59 trucks with dropout diff and SM420 to salvage a slip yoke driveshaft from. 57 is 114" WB and 51 is 116" WB. Shortening or lengthening an existing D/S may be cheaper.


1960 GMC K1001 (The Oreo SpeedWagon)

All I know is what the voices in my head tell me and a little from watching TV.


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