The venerable Ford Bronco, a true icon in the American wheeling landscape, has been out of production for--get this--13 years. It seems like yesterday that you could walk down to the local Ford dealership and pick up a fullsize Bronco, in white for those more daring trips. From 1980 to 1996, the Bronco came standard with the notorious, yet rugged Twin-Traction Beam TTB front suspension.
Ford's TTB suspension was a mainstay of 1/2-ton Ford four-wheel drive system for years, and underpins the front of countless vehicles. TTB trucks are plentiful, robust, and are still the choice of enthusiasts who require the unique qualities of TTB suspension. Roll that into the fact that Broncos are as affordable as shares in GM, and as plentiful as excess vehicle inventory on your local dealer lot, and we are seeing them reemerge on the scene again, repurposed in the hands of enthusiasts.
1. We decided to go with the...
1. We decided to go with the Eaton Truetrac for the front differential to compliment the Eaton Detroit Locker that was already in the rear diff. The Truetrac is an excellent, helical-style limited slip that won't wear out over its service life and requires no maintenance. It is fully automatic and offers smooth operation. Keep in mind there is a case split for the diff, with two different part numbers for this application.
Despite either a 5.0L or 5.8L V-8 powering these vehicles, any increase in tire size will necessitate a gear swap to get the most from the power available. The owner of this Bronco originally had 31-inch tires on 15x8-inch wheels with 3.55:1 gears. We decided that Superior 4.56:1 gears would be perfect for what he was trying to achieve with this Bronco and would be a good match for the 35-inch BFGoodrich All-Terrain T/A tires mounted on 16x8 ProComp Series 1028 polished wheels.
This particular vehicle already had an Eaton Detroit Locker in the rear, and the owner was looking forward to some high-speed driving through the desert with the occasional technical crawl. For this type of driving, we are big fans of being set up with a rear locker matched with a limited-slip front. Eaton's Truetrac helical gear differential fit the bill for our needs. The Truetrac, which provides predictable steering control at high speed without the quirky handling characteristics of a front locker, also provides enough traction to easily get over all but the hardest obstacles.
To lube up our new components, Amsoil offered up its Severe Gear Extreme Pressure synthetic gear lubricant. Severe Gear is engineered for severe duty applications, such as extreme wheeling and towing in harsh conditions and is said to inhibit corrosion, extend seal life, and offer improved efficiency, all while reducing operating temperatures.
Check out the overview of our installation on this special long-travel Bronco below.
2. Superior Gear makes some...
2. Superior Gear makes some of the best gears in the industry, and with 35-inch tires on tap, we wanted to make sure the old 5.8L V-8 had enough grunt to move the big Bronco, so 4.56:1s were the order of the day.
3. For lubrication, we went...
3. For lubrication, we went with the Amsoil Severe Gear Synthetic Extreme Pressure Lubricant in the W75-110 weight.
4. With the truck on the hoist...
4. With the truck on the hoist and wheels removed, we pulled the cover, drained the rear diff, pulled the axles, and gutted the housing by removing the bearings, ring and pinion gears and differential, all in preparation of the new assembly.
5. On the bench, the factory...
5. On the bench, the factory gears were removed from the differential.
6. On the left is the new...
6. On the left is the new 4.56:1 Superior pinion gear; on the right is the factory 3.55:1 pinion. You can clearly see the difference in tooth count and size.
7. Next, we installed the...
7. Next, we installed the pinion bearing race and pressed the new bearings onto the new pinion gear before sliding the pinion into place.
8. With the pinion installed,...
8. With the pinion installed, we assembled the ring gear to the differential.
9. Once the new bearing races...
9. Once the new bearing races were installed, we lifted the new differential assembly into the rear axle housing and tightened the bearing caps.
10. The yellow grease aids...
10. The yellow grease aids in setting up the gears by showing you the pattern that is created as the ring and pinion gears interact with each other. After a few shim swaps, we were able to get the desired pattern.
11. With the gears set up...
11. With the gears set up to our liking, we torqued the bearing caps and slid the axles in to place, securing them with a C-clip.
12. One issue that Ford 8.8...
12. One issue that Ford 8.8 owners may find is that, like us, the Superior 4.56:1 gears may contact the differential cover. We solved this by installing a Mag-Hytec diff cover. The Mag-Hytec has extra capacity, is made of aluminum for superior cooling properties, comes with a magnetic drain plug to catch any metallic debris in the diff, and has an aluminum dipstick. The special O-ring gasket requires no sealant for installation and the diff can be serviced without pulling off the cover.
13. Moving to the front, we...
13. Moving to the front, we removed the brake and hub assemblies from the TTB suspension. We then pulled the axles and removed the housing from the TTB swing arms. Because this particular Bronco has long-travel suspension, there were concerns about the C-clip axle on the short side pulling out of the differential at full droop. It turns out that in the early '80s, Ford offered a front limited-slip differential as an option, and it came with a housing that secures the axle externally, which was preferred for our application. These housings are getting harder to find, but we sourced ours from Jeff's Bronco Graveyard. Here you can see the difference between the two styles of housings.
14. In this photo, the externally-mounted...
14. In this photo, the externally-mounted axle is on the bottom, while the open C-clip axle is on the top.
15. The nice thing about the...
15. The nice thing about the TTB suspension is that the gears can be set up on the bench, so we had preassembled the Eaton Truetrac to the ring gear and bearings prior to removing the original housing from the truck.
16. This is another good shot...
16. This is another good shot of the externally secured axle being mated to the housing.
17. With the housing assembly...
17. With the housing assembly completed, we lifted it up to the truck and secured it to the swing arm using the factory bolts.
18. Next, we reinstalled the...
18. Next, we reinstalled the axles. The brake and hub assemblies were also reassembled and ready for wheels and tires.
19. As we did in the rear,...
19. As we did in the rear, we topped the front differential off with Amsoil Severe Gear gear oil.
20. After the differentials...
20. After the differentials were fully assembled, we reattached the front and rear driveshafts to the pinion yokes.
21. The last step before driving...
21. The last step before driving off the rack and doing a proper break-in procedure was to install the new wheels and tires. The polished and slick-looking Pro Comp Series 1028 with LT315/75R16 BFGoodrich All-Terrain's give a modern, functional appearance to this Bronco.