Not that ditching the shackle reversal is what you had in mind, but you might consider it. Here is a tid bid from Marks Offroad Website:
Mark if you read this I hope you don't mind me quoting it here, but what you say makes a lot of sense. Not hoping to start a debate, but if this were my rig I would quit screwing around with all that castor shim nonsense and just return it back to stock shackle setup.
Cheers,
Brian
"a. SHACKLE REVERSAL Why don’t I sell this? Read my motto: I will only sell what I would be willing to install! As far as I know, Bob Hollingsworth is the only other one that is with me on this, but that still counts! In a nutshell, I think that front axle shackle reversal is a wash at best, an accident waiting to happen at worst!
Shackle reversal is most often considered as an option by people who have handling issues with their rigs. News flash: shackles are rarely the source of handling problems. I run front-mounted extended shackles on my cruisers, none of which have handling problems. If you address your real handling issues, you won’t need this. Consider this: if the stock setup was never roadworthy, it never would have left the dealership!
Here’s the theory, which I absolutely agree with. When you hit a bump with your stock suspension, the axle wants to recoil away from the bump, which means upwards and backwards (assuming you are moving forward at the time!) With the shackle mounted at the front of the spring, the spring (and consequently the axle) will need to move forward as the shackle flexes forward. This pushes the axle and the rig even harder into the ‘bump’ causing more shock and recoil. Having the shackle at the rear will allow the axle to travel away from the bump, lessening shock and recoil.
HOWEVER, THE CONVERSE IS ALSO TRUE. If you encounter a pothole, the axle in its stock configuration provides superior performance. As the ground falls away from the front tire, the axle will drop backwards towards the ground, with the shackle flexing back. A front mounted shackle will let the axle fall forward, into the abyss, so when it hits bottom, you guessed it, more shock and recoil. Really then, its just a crap shoot whether you plan on hitting more bumps or potholes.
Now for the bad news. A. Toyota never designed the cruiser for rear mounted shackles. The clearances on your driveshaft don’t matter with an axle that only flexes away from the transfer case. With shackle reversal, you have the real potential of fully collapsing your driveshaft into your transfer case! OOPS. Maybe that’s why the companies that market them offer bump stop extensions so your axle will hopefully hit the frame before your driveshaft takes out your T-case! So now you’ve got to limit suspension travel to compensate for this “improvement”
B.Now that the axle is flexing backwards, away from the steering center arm (or traditional Saginaw box) it causes a greater pull on the relay rod, as it moves away from its parallel plane to the main steering rod. This causes a condition known as ‘bump steer” . Basically, this means every time you hit a bump and your axle compresses away from your center arm or steering box, your tires will turn to the left. NICE? NOT!
C. At an off road event a few years back, I got to see an FJ40 that had the axle flex far enough back that the lugs of the tire grabbed the inner fender skirt where it protrudes around the steering box. Guess what happened?"
