Rear control arms and lowering: Thinking off the deep end

[iamdub]

Spohn arms are too expensive and I don't want such stiff bushings on the control arms.

With my planned rear drop of 4"-5", I'll need to set the axle back to center it in the wheel well. I have relocators but this doesn't do anything for the upper control arms. So, wouldn't this roll the pinion downward? I know many people have bolted these on and I don't recall anyone ever saying anything about checking or adjusting the pinion angle.

Does the pinion even change that much with this amount of drop and the relocators not only center the axle but also set the pinion angle where it should be?

I'll probably end up at least replacing the rear lower arms just to have new bushings- they're only ~$32 each. I could even extend them to center the axle and forego the relocators. I'd plate the bottoms so they're fully boxed regardless of extending their length or not. I'd either build some adjustable uppers (DOM tubing, rod ends,etc. can be had for well under $100) or splurge on the Spohn uppers to fine-tune the pinion angle, if necessary.

I don't intend to overthink this, but I'd like to be 100% prepared as well as upgrade where feasible. I know some aftermarket parts manufacturers will cut relatively insignificant corners to keep their products as simple as possible for the average DIY-er. So, maybe they figured the pinion angle/U-joint life wasn't sacrificed enough to be concerned with designing an upper control arm extender? But if I can make a few small mods to ensure everything remains and operates in the factory design- then, why not?

 

[swathdiver]

I don't know much about this Chris, but this thought did cross my mind. Do the PPV/SSV and or XFE Tahoes have different parts because they sit lower?

 

[iamdub]

I don't know much about this Chris, but this thought did cross my mind. Do the PPV/SSV and or XFE Tahoes have different parts because they sit lower?

Good point, but I doubt it. They're only what- 1"-1.5" lower, suspension-wise? I'd say that's well within any standard truck's normal range of travel and not enough to engineer an alternate design. Maybe even at 3"-4" the pinion angle still isn't thrown off that much. Or maybe, at that point in the articulation, the pinion is actually rotated upwards and the relocator brings it back down?

 

[iamdub]

Grrr... Site issue causing multiple posts again.

 

[iamdub]

... And again.

 

[FrankU]

Id be cautious when lowering the rear as the suspension travel is very limited. The "free suspension travel mod" isn't the best IMO. Lowering 2" would be the max I'd go if I had to do it again. I did the 2-4 drop kit and now wish I didn't.

 

[iamdub]

Id be cautious when lowering the rear as the suspension travel is very limited. The "free suspension travel mod" isn't the best IMO. Lowering 2" would be the max I'd go if I had to do it again. I did the 2-4 drop kit and now wish I didn't.

These things have plenty of travel once the bump stop and bracket is removed. Aside from some lowering springs being too stiff or, as most are for that amount of drop, too soft, it should ride nicely with no bottoming out. I know not many people realize the panhard bar or it's bracket will hit a frame cross member with larger drops. They assume that banging they're feeling is the axle bottoming out on the frame and it's just part of having a big drop. Did you ever notice or address this with your 4" rear drop? I'm pretty well-versed with lifting and lowering cars and trucks and I'm taking every precaution I can to have the suspension operate just as it does in stock form. Spring rate is mostly out of my control but that can be adjusted with load bags (which are included in my pile of parts). Maintaining proper articulation and geometry is my only real concern which is my purpose of his thread.

Now that I'm thinking on this, I may go out and cut off those bump stops today...

 

[FrankU]

I was told that when the bump stops are cut off the tires will hit the inside of the rear wheel wells. We all ready had the tires hit the inside of the rear wheel wells with the stock bump stops in place. I'm very cautious about cutting the stops off. Next week I'll take the 1" rear spacers out and put 2 1/2 inch spacers in the rear. To gain a little more travel for the rear axle. Post up when you cut your stops off .

We should have just put in a coil over setup in the rear.

 

[kbuskill]

I was told that when the bump stops are cut off the tires will hit the inside of the rear wheel wells. We all ready had the tires hit the inside of the rear wheel wells with the stock bump stops in place. I'm very cautious about cutting the stops off. Next week I'll take the 1" rear spacers out and put 2 1/2 inch spacers in the rear. To gain a little more travel for the rear axle. Post up when you cut your stops off .

We should have just put in a coil over setup in the rear.

What size wheels/tires are you running???

 

[Ilikemtb999]

My rears rub on the inner fenders every once in a while but it’s usually when driving over something very uneven like a driveway or a water runoff drain.

 

[iamdub]

I was told that when the bump stops are cut off the tires will hit the inside of the rear wheel wells. We all ready had the tires hit the inside of the rear wheel wells with the stock bump stops in place. I'm very cautious about cutting the stops off. Next week I'll take the 1" rear spacers out and put 2 1/2 inch spacers in the rear. To gain a little more travel for the rear axle. Post up when you cut your stops off .

We should have just put in a coil over setup in the rear.

Can't say for sure that I've ever heard of this happening with stock diameter tires. My initial thought is maybe this is caused by a large drop with stock panhard bar. I'll certainly check around everything for clearance when I lower it and I have an adjustable panhard to re-center the axle once it's at it's new ride height.