Spring-Over Axle lift on an early model Isuzu.
Short Cuts
Authoring and Photography By:Dan Houlton
First Published: April 2000

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Mounting the new spring pads
New spring pads (38540 bytes)
The new spring pad on the axle and old one in foreground.

The new spring pads used were from AFCO Racing. They provide a lot of stuff for circle track racing but have a lot of suspension pieces 4 wheelers may find useful. Lou Fergers Racing also carries them. These pads are 2½" wide, made from ¼" material and fit a 3" diameter axle tube. Rather than welding on, they clamp firmly to the axle tube (hence, the need to remove the old pads) which also means they can easily be fine-tuned for adjusting the pinion angle after the lift. If you use these pads, you also have to take note of the weld seam running the length of the axle tube on the front and back. This seam needs to be ground smooth on front and back where the clamp-on pad will be so that the entire clamp is contacting the axle tube instead of just the high spot of the seam.

If you choose to use weld on pads, I'd suggest *not* welding them on at this stage. Leave them loose and bolt everything up with the u-bolts when you're trial fitting things back together and check the pinion angle. With the pads loose, you can use a jack under the pinion to get the angle correct. Once it's set, tack weld the pads and pull the axle back out to weld them up good. Also, if you're careful when removing the old pads from underneath, you may be able to re-use them on the top of the axle tube. Something to keep in mind while you're cutting them off.

One thing to be careful with: Our Isuzu Corporate 12 bolt axle tubes are not quite 3" in diameter. They're actually 75 mm, which comes out to about 2.95". Clamping down on them with these AFCO pads as-is causes the bottom half of the clamp to tighten against the upper half before getting a firm grip on the axle tube. Be sure to grind off a small portion from the ends of the upper and lower halves so they'll clamp tight to the axle tube with a small gap between the halves. It doesn't take much. Maybe a 16th of an inch or so off each of their ends is more than enough. You may want to leave a small bevel on the inside edge as well, to reduce the risk of it digging into the axle tube.

You may also want to weld the clamp on pads to the axle tube after getting the pinion angle correct and verifying that you don't have any driveline vibrations. I know one other person that's used these clamp-on pads and he had problems with the axle tube spinning in the clamps. He had not ground the ends of the clamps down however, and he had painted his axle tube after grinding with very hard, smooth and slick POR-15 (an excellent rust preventative paint BTW). He was also running 34" Swampers with oodles of traction and was trying to crest a ledge in 1st gear, low range. These all added up to the clamps not holding and the axle spun in the clamps with the pinion pointing up at about 45°. He now has them tack welded to the axle tube.

I've been running these clamp-on pads now for a little over 2 years. I have the ends ground as described above and I painted the axle tube with a regular, flat black paint that isn't nearly as slick as POR-15. I ran 33" all terrains for a while and now have 33" Mud Rovers and haven't had much of a problem. I've had to reset my pinion angle once recently as it's gradually started moving upwards over the last year, but it's never spun catastrophically on the trail. Tack welding them though is good insurance against mishap. Something I haven't done yet that might also help is to paint the inside of the clamps with high traction paint. This is the stuff that has what seems like sand in it and is used to give good traction on things like nerf bars that will be walked or stepped on. It should give the clamps a pretty good bite to hold on with, and it may be thick enough so that you don't have to grind the ends of the clamps down to get a tight fit on the axle tube.  

There is a small, curved plate that goes under the u-bolts to protect the axle tube. It spreads the load and prevents the tube from creasing when tightening the u-bolts down. You can't use these plates as is after the spring over if you decide to use the AFCO clamps or if you leave the old pads on the bottom of the axle tubes. To make them fit, cut the plates down the middle and install the halves with the raised ridge between the u-bolt and the spring pad clamp (or old pad) to protect the axle tube as before. Putting the raised edge inward will prevent them from working loose and dropping out.


Prodecting plate (19840 bytes) Spring pad assembly  (27340 bytes) Completed installation (27451 bytes)
The curved protecting plate after being cut down the middle. The complete spring pad, u-bolt and plate assembly. The completed and installed axle.

After cleaning up the axle and getting the new pads in place, tighten up the pads so they're snug and at approximately the correct angle. Eyeballing it should be close enough but be aware that it's better to have the pinion pointing down too far than up. The reason being that after you get the springs clamped to it and get the wheels on and weight on the axle, you can use a jack under the pinion to rotate it up until you get the angle you want before tightening things up for good. It's not as easy to get something up above the pinion to force it down.

After getting the axle back in for it's trial fitting with the truck's weight on it, you can use a magnetic angle finder on the output flange of the transfer case and the pinion to adjust the pinion angle accordingly. The goal is to have the pinion and the transfer case output shaft as close to parallel as you can. This keeps the upper and lower u-joints in the drive shaft in phase to prevent vibration. My pinion is actually pointed upward a little bit from parallel to the transfer case. It gives a little better ground clearance, but it's not enough to be causing any driveline vibrations.

You might want to climb in back and jump up and down a few times to make sure the springs and pads settle in completely. You could drive it, but I wouldn't recommend taking it too far unless things are bolted up tight. Once you're satisfied with the angle, torque the u-bolts and clamps down and you're done with the hard part. If using weld on pads, tack them in place and either just remove the u-bolts or pull the whole axle back out to weld them on the rest of the way. When done, slip the axle back in place and tighten the u-bolts down.


Mounting the shocks
Shock mounting (29924 bytes)
The axle in place and the shocks mounted.

The next step is to re-attach all the lines and the shocks.

For my shocks, I chose Rancho 9000s and made my own upper and lower mounts for them. The mounts that can be used will depend on how much fabrication you do and how you choose to clamp your springs on top of the axle.

Probably the easiest method is to use the stock upper and lower mounts with the stock clamping plate. The stock clamping plate that used to reside below the spring pack and served as the lower shock mount now sits on top of the spring pack. You can still use that for the lower shock mount, but the pin for the shock is now on the opposite side of the axle tube than before. This places it further horizontally from the upper shock pin in the frame. You can use the stock shocks here, but they're at an extreme angle of about 45. I can't say how well this will work, but it should at least be a good short term solution.
shocks4.jpg (36508 bytes)
A close up showing the design of a simple lower shock mount.

The next best solution is to weld some new lower shock mounts on the axle tube and use the stock upper shock mounts. This would let you use some longer shocks as well and isn't too hard to do. It's also something that shouldn't cost too much to have a shop put on for you if you're shy a welder. You could use the stock plates and shocks as described above until you can get into a shop to weld in the new lower shock mounts, then install the new shocks.

The picture on the right shows my lower shock mounts. It's just a piece of 3" i.d., steel tube cut in half to fit the axle tube. On that is welded a piece of angle to form the platform for the shock pin. On that then is a standard weld-on shock pin. You could even forego the piece of 3" tubing and just weld the piece of angle to the axle tube. I chose to use the tubing because it gave me more area to weld to the axle tube to spread the load.
shocks3.jpg (34869 bytes)
A view looking upward at the new cross member and upper shock mounts.

After welding up the lower mount, bolt the shock to it and your stock upper shock pin. Position the lower mount on the axle tube where it fits good (good clearance, doesn't bind, won't hit anything when the axle is articulating, etc), then weld the lower mount to the axle tube.

I chose to make my own upper mounts in addition to the lowers because I was making a new cross member anyways to support my new fuel tank skid plate. It also allowed me to use the longest possible shocks and mount them for the maximum amount of travel. Another benefit is that it let me orient the new shock pins 90 to the stock pins so that they're now perpendicular to the axle tube instead of parallel to it. This allows the axle to articulate more freely since the shocks will be rotating around the pins instead of binding against them like the stock mounting does.


New brake lines
Braided brake lines (23882 bytes)
The new braided stainless steel brake lines mounted to the axle.

I used Earl's for the brake lines and fittings. Their braided stainless steel hose is good for 450° F and 2000 PSI. The 'tee' on the axle uses AN fittings and metric fittings are used at the calipers and on the upper line where it attaches to the hard line above the axle.

Figuring out the parts I needed for the lines was not an easy task. You can't just go down to your local hardware or speed shop to pick out what you need. Nobody stocks metric fittings. This is further complicated because of the different flares you can use and the fact that I had no idea what the stock flares were. After several phone calls to Earl's and Aeroquip, two orders and a bunch of metric bolts to figure out banjo bolt sizes, I finally got the pieces needed. To make things easier, here's the diagram and part numbers you'll need from Earl's. Aeroquip and other makers I'm sure will be just as good, but I don't have the part numbers for them.

In the interests of saving money, there are other options. It may be possible to leave the stock lines alone. You'll have to check the line that drops from the hard line on the frame down to the axle tube for length. It may be possible to bend the hard line downwards enough that the stock line will work. Be aware though, that doing so will not allow the use of the frame mount for the end of the hard line, so the end of it will be unsupported for a fair length. Also, there is always the risk of breaking or collapsing the hard line if you try bending it. If you use the correct tools though, that risk is likely small.

A better option is just to add an extension to the flexible hose that drops to the axle. You can't replace the hose because it's permanently attached to the 'tee' on the axle. What you can do though is make a small extension of about 4" - 8" that will go between the hard line attached to the frame and the flexible line that drops down to the axle. If you look at the brake diagram, I list the fitting you'll need to attach the extension to the hard line at the frame mount. This is a female, inverted flare 10mm x 1 fitting. For the other end of the extension, you'll need the matching fitting that will screw into it. This one will "look" like the end of the hard line and the stock flexible line will screw into it. I don't have the number for this fitting, but if you call Earl's for the first one, they should be able to tell you the part number for the matching one.

The extension then is two fittings and a 1 foot section of hose cut down to the length you want. Pretty in-expensive.

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