Rear Leaf Springs and Hangers

The rear All Pro leaf springs I will be using are 56" long and provide about 5.5" of lift. These springs are 9" longer than the stock rear springs and due to the extra lenth and spring design are very flexable. To install the springs the stock spring mounts need to be relocated to accomidate the extra lenth. I also wanted to move the rear axle back a bit to increase wheel base so I factored that into where I placed the hangers.

I cut off the rear hangers with a die grinder. I removed the rear frame crossmember that normally holds the spare tire and replaced it with one I made from 3" X 2" tubing. I notched a hole into it to accommodate a receiver. Later supports will be added from the frame to receiver.

The rear shackle hangers went back on at the extreme rear end of the frame 4" back from the stock location. The front spring hangers needed to be moved forward. The factory front hangers are a little thinner than I would like and on my last truck both factory type rear springs hangers failed after allmost two years of trail use. New larger and stronger All Pro hangers were used to prevent the this. These were mounted 4.5" forward of the stock ones. With the hangers mounted as I have the rear axle will be moved back 1" and the shackles should rest at about 20 degrees when the truck is loaded for trail use. The old front spring hangers were removed. The leaf springs were then installed using 1.5" longer shackles, poly bushings and greasable 18mm bolts.

Over all the combined shackle and spring lift will raise the rear suspension about 6". WIth this amount of lift it's common to have driveshaft vibrations at freeway speeds. To prevent this a CV style drive shaft will be made for use in the rear. To completely eliminate vibration the rear housing will be rotated up so the differential points toward transfer case. This also has the added effect of moving the pinion shaft and U joint up higher for better clearance.

To rotate the housing the stock spring perches were torched off and replaced. One way to make new spring perches is to take square tubing and drill a hole through the side of it with a hole saw. Set it on top of the axle and weld in place. For this project I am used a new prototype U bolt elimination kit. This is a combination of new spring perches and flip plates that bolt together. These spring perches are 6" long, 2" longer than stock. This extra length helps reduce axle wrap by spreading the attachment point out over a longer section of the spring. The longer spring perches combined with the torque leaf design springs provide plenty of anti-wrap control without the need for additional control arms and links. The spring perches are only tacked into position for now as I may need to fine tune the amount of rotation. Later they will be welded into place and a plate added to the top of the spring. The perch and plate will then be bolted together. With this arrangement U bolts are not needed.

Rear Axle Housing

My original rear housing was a 49 3/8" wide (measured flange to flange) pre IFS style (79 - 85). I have chosen to use a later model (1986 - 1995) as they are 51 3/8" wide. With the narrower axle in the rear the super flexey rear springs I am planning to use would allow the 35"+ tires to rub the frame. Using the wider axle will resolve this problem and add some stability off-road with out making the truck so wide that I would have problems with the highway patrol.

To increase ground clearance under the housing All Pro Off Road has a neat trick, cut off the bottom of the housing and replace it with 1/4" thick plate steel. This gains about 3/4" of ground clearance over a stock housing and makes the bottom of the housing much stronger. The drain plug (famous for falling out on the trail) has been eliminated. To drain the oil out of the housing it will be necessary to remove one of the third member studs bolts. Welding a nut onto the lowest stud results in a "drain bolt" that is as easy to remove as a stock drain plug.

The spring perches were removed. There are two reasons for wanting to replace the perches. The first is wanting to use longer perches to control axle wrap. Adding two inches to the length of the spring perch greatly reduces the wrap up of the rear axle that can cause wheel hop on the trail. The other reason for wanting to change is to rotate the 3rd member up so that the drive shaft points up toward the transfer case. To reduce the vibration associated with lifting the truck I will be using a rear drive shaft with a CV on the transfer case end. For this to work correctly the pinion needs to point nearly straight toward the transfer case. Another advantage of rotating the pinion up is that it moves the pinion up a little higher, helping to prevent pinion and U joint failure as a result of impact with rocks.

Upgraded Third Member A popular rear end upgrade for older 4cyl Toyota pickups is a later model V6 3rd member. When Toyota started producing the V6 motor they totally redesigned the rear third member and made several improvements that make this rear end much less likely to fail like the rear end pictured left. Below are listed some of the specific differences between the two units. The 4Cyl housing weighs 16 lbs, the V6 housings weighs 23 lbs.

One factor that contributes to ring & pinion failure is housing flex. As gears turn under a load they are driven apart, the more power applied the more they want to come apart. It is the job of the housing to keep them in place and a stronger housing helps reduce flex that can be fatal to the gears. The V6 unit on the right has 8 thick fins along the side of the housing. The 4Cyl has 6 thin fins and is less ridge.

At the same time Toyota reinforced the housing they also enlarged the pinion gear used. In this picture you can see the 4Cyl and V6 pinion gears next to each other. The V6 pinion on the left is 1/8" longer than the 4Cyl on the right. Many different gear makers now only create the 4Cyl gears and do not make the V6 sets anymore. To install the 4cyl gears into a V6 housing spacers are used to push the 4cyl gear up further. Precision Gear is the only manufacture other than Toyota currently making V6 after market gears.

V6 third member Improvements: Larger pinion gear More ridge housing Much larger pinion bearings Larger side bearings Thicker mounting flange

4Cyl and V6 bearing races

For my project I have chosen to use the V6 rear third member with Detroit soft locker and 5.29 Precision V6 ring & pinion gears. I also choose also to use a solid spacer instead of the crush sleeve that came with the setup kit.

I took a little experimentation with the spacer shims before I choose a set that worked. The idea is to make it tight so the pinion has some resistance to it but not so much that it causes binding. Over the years I have watched several third members go together and even installed a set of lockers myself but never attempted a full setup from scratch on my own. I read through the factory manual, some online setup guides, and read install instructions from gear makers. With the help of Jon and Jay at the shop I was able to do most of the setup myself. It took me about 3 hours to do the setup.

Toyota uses at least 4 different drive shaft flanges on it's trucks. My truck came with the smallest size flange. For more strength installed a 84/85 style flange on the rear diff. Both ends of the tcase and the front differential will also get the same flange. These flanges are a little larger and used a larger bolt size than the earlier 79-83 style. Keeping all four flanges on the truck the same will allow me to build a single spare drive shaft that will fit on the front or rear of the truck.

Related links:

Project Trail Toy Main Page