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| | | | Joined: Jul 2015 Posts: 18 New Guy | | New Guy Joined: Jul 2015 Posts: 18 | Hi,
I picked up a 1970 chevy 12 bolt rear axle with 3.73 that I want to install under my 1950 3600, replacing the 4.56 and hucks. Anyone know if I can use the existing spring perches on the 12 bolt rear? The 41 1/2" center to center match up to existing, but not sure of pinion angle | | | | | Joined: Apr 2005 Posts: 7,441 Bolter | | Bolter Joined: Apr 2005 Posts: 7,441 | Grinder, welder you can make it work. Should be easy. 
Martin
'62 Chevy C-10 Stepside Shortbed (Restomod in progress)
'47 Chevy 3100 5 Window (long term project)
‘65 Chevy Biscayne (Emily)
‘39 Dodge Business Coupe (Clarence)
“I fought the law and the law won" now I are a retired one!
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USAF 1965-1969 Weather Observation Tech (I got paid to look at the clouds)
| | | | | Joined: Mar 2010 Posts: 10,310 Renaissance Man | | Renaissance Man Joined: Mar 2010 Posts: 10,310 | Is the axle from a half ton truck? Is the donor truck a coil spring setup?
1952 5-window - return to "as built" condition | 1950 3100 with a 235 and a T-5 transmission
| | | | | Joined: Jul 2015 Posts: 18 New Guy | | New Guy Joined: Jul 2015 Posts: 18 | Axle numbers indicate it is from 1969 0r 1970 1/2 ton, Looks like with leaf springs, 3.73 open carrier. | | | | | Joined: Mar 2010 Posts: 10,310 Renaissance Man | | Renaissance Man Joined: Mar 2010 Posts: 10,310 | I had a '69 1/2 ton and it was a coil spring rear end.
1952 5-window - return to "as built" condition | 1950 3100 with a 235 and a T-5 transmission
| | | | | Joined: May 2001 Posts: 7,438 Extreme Gabster | | Extreme Gabster Joined: May 2001 Posts: 7,438 | If it has leaf spring perches it no doubt came from a truck with leaf springs. You might be able to use the existing spring perches but you won't be able to use the existing mounting holes in your springs. They will be way too far forward. Once you get the new mounting holes drilled in the proper place, mount the rear and check the pinion angle. You might get lucky. | | | | | Joined: Jun 2011 Posts: 5,096 Crusing in the Passing Lane | | Crusing in the Passing Lane Joined: Jun 2011 Posts: 5,096 | GMCs came with leaf springs, Chevys came with coils certain years.
Ed
'37 GMC T-18 w/ DD 4-53T, RTO-610, 6231 aux., '95 GMC running gear, full disc brakes, power steering, 22.5 wheels and tires.
'47 GMC 1 ton w/ 302, NP-540, 4wd, full width Blazer front axle.
'54 GMC 630 w/ 503 gasser, 5 speed, ex fire truck, shortened WB 4', install 8' bed.
'55 GMC 370 w/270, 420 4 speed, grain, dump bed truck from ND. Works OK.
| | | | | Joined: Jul 2015 Posts: 18 New Guy | | New Guy Joined: Jul 2015 Posts: 18 | I believe it to be chevy:
id numbers on axle.
11" x 2" brakes
NF3896838 Axle cast #
TDA 0109 W Axle tube code # (indicates 3.73 1969 W shift 1)
Built K148 1--14-68
Rear could be closer to 1969, if anyone knows a difference btwn it and 1970
if these codes where shared between chevy and gmc, i guess that would be code to know. Again, i believe it to be Chevy
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