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"Four Wheel", March 1, 2013

GOT 74’S?

A 60 PLUS A 14-BOLT IN THE BUDGET ’BURBAN

BY Fred Williams

PHOTOGRAPHY FRED WILLIAMS

THE CHEAPBURBAN PROJECT truck is getting stronger. I have a theory that if you break something you should try and upgrade it rather than just repair it. Take my ’87 Suburban’s front axle for example. I bent it jumping the truck at the dunes during Cheap Truck Challenge (Sept. ’12) and had to decide how best to keep that from happening. I should start by not jumping such a big truck again. I could also have tried to straighten it, truss it, and then cross my fingers, or I could just dump the ¾-ton parts for 1-ton axles. I went with the 74s (Dana 60 + Corporate 14 = 74).

Swapping Chevy 1-ton axles into a ¾-ton GMC Suburban isn’t a hard conversion, but it does take work. There is cutting, grinding, and welding, and some new parts are needed to make it go smoothly. I also upgraded to a disc brake conversion for the rear axle and replaced a few worn components to make the big Burb more reliable. I would say this swap could be done in a long weekend if everything goes according to plan and no unforeseen issues show up.

1 This type of hooliganism is not good for light-duty parts. I had a blast abusing the Suburban like this but came home with a bent and leaking ¾-ton 10-bolt front axle. A new 10-bolt could have been swapped in, but I also wanted lower gears and maybe a locker or two to deal with the 36-inch Swampers.

2 I searched the classifieds and came across a guy selling a few sets of military GM CUCV 1-ton axles (technically these are called 5/4-tons). These are Chevy Dana 60 front and Corporate 14-bolt rear, but they have 4.56 gears and a rear Detroit locker in factory form, perfect upgrades for my Burban. I brought them home for $1,600, about the normal price for a set of used CUCV axles.

3 I got lucky: The front Dana 60 was more than complete with all the steering linkage and the front U-bolt plates. These U-bolt plates are hard to find, so grab them if you’re removing a junkyard axle.

4 I put the back of the Burb on jackstands and started pulling the rear axle. The semifloating 9.5 rear ¾-ton axle in the Suburban isn’t’ a bad axle, and if it was regeared lower than the 3.73 ratio it came with I may have kept it since it is an eight-lug. I disconnected U-bolts, shock bolts, parking brake cables, and the driveshaft and brake bias lever.

5 The CUCV axles are from military Chevy pickups, not the Blazers. Blazers have half-ton axles. I knew that the full-floating Corporate 14 rear axle would need some work, specifically the spring perches would need to be moved outward roughly an inch, and the shock tabs are on the opposite side of the axletube. I used a plasma cutter to carefully cut off these parts so they could be reused, then ground the axletubes clean so I could weld them back on as needed.

6 I rolled the 14-bolt under the springs and measured to make sure it was centered. I made sure it was equal distance from the springs to the brake baking plates on both sides. Then I set the pinion angle so it was parallel to the transfer case output since I am running standard U-joints and no CV.

7 I replaced all the U-bolts and spring plates with new parts from Offroad Design (ORD). The U-bolts come extralong to accommodate thick spring packs. I needed to shorten up the U-bolts so I could get a deep socket onto the nuts and properly torque them.

8 With the pinion angle set and the axle centered, I welded the spring perch and shock tabs in place. I was able to reuse these parts, but ORD can supply replacements if you need them.

9 I also reattached the factory brake bias lever onto the new rear axle. Some drilling was required to fit the larger mounting bolts.

10 The massive rear drums on the Corporate 14-bolt aren’t bad, but mine needed all new internal parts, so I pulled them off along with the hubs to replace them with disc brakes. Tossing the drums will save about 65 pounds as well, if you are concerned about weight.

11 The ORD disc brake conversion uses ¾-ton front rotors and calipers from a 10-bolt axle with the 14-bolt full-floating hub, so I could have saved money by reusing my front axle parts, but I opted for new brakes all around. Everything bolts together except you will need to press the original wheel studs out and back into the new hub and rotor combo. I also replaced the hub seal for good measure and checked the bearings.

12 The rear brake lines were all replaced with new DOT-approved flexible brake lines from ORD. The lines have a Teflon center tube surrounded by a Kevlar braid, a second protective sleeve, a stainless steel braid, and an outer vinyl sheath. With crimped ends on the fittings and all new banjo bolt hardware I’m not expecting any leaks. I lost the parking brake but may add an ORD hydraulic brake lock eventually if needed.

13 The front axle was much more straightforward. First I supported the truck and dropped the pitman arm, driveshaft, brakes, sway bar, and shocks before dragging the “Bent-bolt” out of the shop.

14 The front steering box is retained with a new drop pitman arm from ORD. I also replaced the rag joint with a U-joint and steering shaft section from a late-model GM truck I found in a junkyard. I then added the ORD steering box brace inside the frame to keep it from cracking.

15 The steering box brace runs right next to some oil cooler lines. I slit a piece of hose and zip-tied it in place to protect the lines.

16 I added new studs on the passenger-side casting of the front Dana 60 and drilled out the center pin holes slightly to ensure that everything would go together smoothly. The front axle matches the rear with 4.56 gears but doesn’t have any locker — yet.

17 The big Dana 60 was wrestled into place, all new U-bolts added to those special spring plates, and a new steering drag link installed from a local auto parts store. The ORD shocks were reinstalled, and I finally upgraded to the ORD sway bar disconnect.

18 I also added the greasable heavy-duty shackles at this point to the front 4-inch lift springs. The front brakes received new calipers, and all the gear oil was changed front and rear as well as new driveshaft U-joints, which were the same 1350 joints on the new axles as on my old ¾-ton axles.

19 One last update was the tired clutch between the TBI 350 and the SM465 four-speed. This was a job I was dreading, as a prior owner had run the exhaust under the transmission, making complete removal almost impossible without an exhaust upgrade. I was able to just ease back the transmission and transfer case combo on a Harbor Freight Tools transmission jack to be able to access and remove the clutch and flywheel. Note the chain I used to hold the flywheel tight while I broke loose the bolts.

20 The old clutch and flywheel had seen some serious heat, so I replaced them all with new parts from RockAuto.com. With the clutch back in I also replaced the clutch slave cylinder and bled both the hydraulic clutch and brake systems before backing out of the shop with new stronger parts under the CheapBurban.

SOURCES

OFFROAD DESIGN

970.945.7777

www.offroaddesign.com

ROCK AUTO

www.rockauto.com

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