71 Gmc 2500 14 bolt disk brake rear end swap

[RR440MAN]

For you experts out there I am soliciting your brain! I have a 1971 GMC 2500 Sierra Sport Truck long bed, 350 / 350 TH front disk brake long bed White/green father and son project. The best thing about this is my son gets high school credit for his FFA Ag Mechanics SAE project in doing this hands on resto. It is undergoing a slow frame off restoration. The truck has the 10 bolt drum, 8 lug 4.10 ratio rear end. The 350/350 TH is being swapped for a 6.0 LQ9 engine and 4L65E tranny. Due to the age of the rear end, drum brakes, and 4:10 ratio it would seem fiscally prudent to switch a full rear end with disk brakes 3:73 ratio over converting a 73-87 14 bolt to disk brakes. Does anyone know a good swap for a leaf rear end that is of close measurement in width? I am willing to grind off the perch welds to line up with the correct OEM measurement. I cant seem to find any measurement data on these newer rear ends. I read somewhere that a 99-06 Chevy Gmc 1500HD 14 bolt rear might swap, but I need to confirm what will work before making a correct search. Any experts out there who can advise of a complete 14 bolt disk brake rear end that will work? 8 lug or 6 lug is ok. I can fit different front 6 lug rotors to the front, but I’m also good with the 8 lugs also.

[71blksuper4x4]

A 77-91 c30 or K30 SRW 14 bolt should be a bolt in.

[57taskforce]

If you want factory disks on a 14 bolt 99-10 are the years to go for. They are a little wider. After ‘10 the lug pattern changed to metric. I’ve got two of these on a cart in the shop waiting to go into my trucks. Keep in mind that the late models trucks can have 2 different 14 bolts. Basically anything with an Allison has the bigger 11.5” ring gear and the 6.0 trucks have the 10.5 ring gear. The 10.5 based off the old school 14 bolt but isn’t identical in every way. The factory disks will not bolt up to an old 14 bolt. either of these late model axle will work but like you said you’ll have to strip the housings and re weld the perches and shock mounts. Also The late model disk brakes have Parking brakes far superior to the disc conversions on the old 14 bolts. There also is the AAM 9.5 in the 6.2 equipped late model 1/2 ton trucks that is six lug and based off the old gm semi float 14 bolt if you wanted some disk brake beef in the 6 lug variant.

[RR440MAN]

Thanks for the reply guys! This clarifies the cost factor will be in favor of the 99-2010 14 bolt model rear ends. I was aware that the older 14 bolt conversions with the Eldorado emergency disk brake calipers were not quite reliable and have some issues. It isn’t as cost effective to spend more money converting an older 14 bolt to disks since most kits range from $400-$600 alone.

[57taskforce]

Originally Posted by RR440MAN

Thanks for the reply guys! This clarifies the cost factor will be in favor of the 99-2010 14 bolt model rear ends. I was aware that the older 14 bolt conversions with the Eldorado emergency disk brake calipers were not quite reliable and have some issues. It isn’t as cost effective to spend more money converting an older 14 bolt to disks since most kits range from $400-$600 alone.

Your exactly right there. Your money ahead to just buy the factory setup.