Flip the Trailing Arm Mounts on Crossmember

[ecgate]

Im doing a 5 or 6 inch drop spring and a 2 inch lowering block and was wondering if I am going to run into problems with the angle of the pinion. Would flipping the trailing arm mounts on the crossmember benifit me to correct the angle? Am I over thinking this and there wont be a problem at all? Will I need a shim kit? If so how many shims would I need? I like the idea of flipping the trailing arm mounts but I dont want to do it if i dont have to. I have a 1967 swb if that helps.

[lolife99]

I would lower your truck first.
Some people do the flip to help with the pinion angle.
I have never done it myself.

I assume you have a 1-piece driveshaft?

[ecgate]

At the moment I have a bare frame and I thought this would be as good of time as any if it needed to be done. And yes I plan on having a one piece driveshaft.

[Robznob11]

well I don't know for sure what is the best. I bought a cpp drop member and the mounts are flipped on it and welded in place, ece drop member comes with them in standard position. Hotchkiss markets a kit known as the anti squat kit that supposedly helps the truck hook up and not blow the tires off. id does this by raising the position of the front mounts just like flipping them. I took a measurement with my cpp drop member and my pinion angle on my rear end is up 6 degree's I think that's a bit much so I think that I might cut them off and flip them back. I bought a set of bolt on brackets from ece to do this. hotrods to hell told me it would be better to lower them because you want the angle of the arm them self to be about 1 degree up, factory is about 11 degree's . I have not come to a conclusion yet either so im just waiting till later I hate to cut up a pretty powdercoated member and find I did not need to. over all the pinion angle is most important to keep u joints in etc. it just makes more sense to me to reflip them as opposed to running a 4 degree (thick and unsafe for power) shim

[69gmcc10]

I converted from leafs to trailing arms and when I did I flipped my mounts to change the anti squat and increase traction. It made a huge difference in putting the power to the ground (engine kinda bogs now) and the science says the lower you go the more important it is to flip the mounts for traction, but if you are just gonna cruse in it the benefit is the pinion angle. Going that low you might need some shim regardless, I think the math is a 4" spring and the mount flip will counter most pinion angle change, but I dont know how dramatic a 6" spring and blocks will effect the situation.

My vote is do it, from my limited experience I dont think it can hurt and you are there anyway.

[ecgate]

You might have just talked me into it 69gmc. Tell me this, its definetly not going to hurt anything, it can only help. Right?

[69gmcc10]

Originally Posted by ecgate

You might have just talked me into it 69gmc. Tell me this, its definetly not going to hurt anything, it can only help. Right?

It wont hurt anything because regardless of what you do you still need to check the pinion angle and shim accordingly if necessary.

Think of it this way, when you lower the truck the trailing arm mount drops and the more the tire wants to try and drive over the mount. If you move the arm mount up the tire tries try to roll under the mount and the mount pushes against the body of the truck to increase traction. Auto-crossers use adjustable mounts for tuning there chassis to get the amount of force they want to the tire (anti-squat).

if you don't like it flip it back over