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2 1/2" shackle flip questions

jonathon

jonathon

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Well I'm thinking I'm going to have to replace my fuel pump soon on my Suburban(it's cut out for a brief moment on hills twice now), and I had planned to do this eventually and since I'll have to drop the tank why not sooner than later :D

I'm only going for ORD's 2 1/2" shackle flip right now, mainly because the burb is a daily driver and I only want to clear 33's(after I decide to replace my current tires) and have a little more aggressive of a stance. My concerns are mainly the pinion angle. Will it need to be changed?

My plan is to run it with the stock suspension and the 2 1/2" flip for now and later on do 2" springs in the front. Will running the stock front suspension be a problem for the time being? I figure if anything it'll look mostly level with a slight rake to it :crazy:
 
Yep, pinion angle will change and effective caster will change up front due to the rake. Suggest matching suspension height front/rear and adjusting pinon as necessary with a shim.
 
on my Burb the pinion angle was off by about 5 degrees with the shackle flip and then another 1 - 2 degrees with the added super shackles.
 
rcamacho said:
Yep, pinion angle will change and effective caster will change up front due to the rake. Suggest matching suspension height front/rear and adjusting pinon as necessary with a shim.
Click to expand...

Well if that's what I got to do then that's what I got to :D Good excuse to get some 2" front springs.. now as far as the front, do I need a raised steering arm and/or a drop pitman arm?
 
PsRumors said:
Not for 2" of lift.
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Well that makes it easy. Same with brake lines I suppose? Mine are in good shape, don't see a reason to replace them if I don't have to.

Now for another question, if I toss a zero rate in the rear to level it out when full of fuel will I have caster problems or no? I'd really like to nix saggy butt.
 
Are you sure it's the fuel pump cutting out? When I'm low on gas and take a sharp turn the gas will slosh around and the engine won't get enough fuel. It will run really rough for a few sec and almost stall. I'd imagine a hill would have similar effects.
 
pinion angle shouldn't be a big deal. mine is fine with a 4" lift. i wouldn't run the stock shocks though. they'll come apart really fast after they hit their max travel on the street a few times.
 
SLO C5 said:
Are you sure it's the fuel pump cutting out? When I'm low on gas and take a sharp turn the gas will slosh around and the engine won't get enough fuel. It will run really rough for a few sec and almost stall. I'd imagine a hill would have similar effects.
Click to expand...

I wish, but it was a full tank :crazy:

vortec said:
pinion angle shouldn't be a big deal. mine is fine with a 4" lift. i wouldn't run the stock shocks though. they'll come apart really fast after they hit their max travel on the street a few times.
Click to expand...

Good to know. Shocks are pretty inexpensive.

It's looking like what I'll need is:

The Shackle Flip
Shims for the rear
2" springs for the front
6 new shocks
Zero rates for the rear
New u-bolts all around

So far looking good? Any other recommendations?
 
I don't know that you're gonna need to shim the rear. On my K5 I did a 4" shackle flip and my pinion angle is okay; with a Burb you have the longer wheelbase, i.e. the pinion angle change will be reduced, and it's further reduced 'cuz you're doing a smaller lift. [I don't see how the front will change the rear pinion angle; the angle is a function of the rear suspension and its relation to the frame, i.e. t-case.]

If it were me, I'd set it up and measure the various angles (cheap tool link below) and do the math, and then if you really don't like it, THEN add shims of the specific angle you need. (They come in various sizes ya know.) It's not that much work to pop the U-bolts off, clamp the springs, and add the shim, if the thing is already up on stands. (Now, if you only have the one vehicle to drive it's a bit trickier as you have to reassemble it while you wait for the Brown Santa to bring the shims =))

http://www.harborfreight.com/cpi/ctaf/displayitem.taf?Itemnumber=34214

Also, umm, why do a 2.5" flip AND zero rates? Seems like you could just do a 4" flip and be done with it -- cheaper, anyway.

If you want to tune the rear ride height after that, you could add/remove leaves from your springs (hassle, but cheap) or get shorter/longer shackles.

And if you're replacing the front shocks, just get two good ones. The factory dual setup uses softer shocks than the singles... one good aftermarket should be just fine.

As for steering, you might or might need to tweak it, but that's best done after you've got the suspension set up. Raised arm is definitely preferable -- the dropped pitman is a PITA to adjust. Anyway, after you've got the springs dialled in, if you have bad bumpsteer, then scrounge for a used steering arm. The for sale forum here is great, 'cuz you have LOTS of people upgrading to crossover. I bought mine here and sold it a year or two later when I went crossover; I think I paid $40 for it shipped (and sold it for the same, since they're not really a wear item =))

Another item to consider is spring bushings. Especially if you're gonna replace the front springs, you might as well remove the rear ones. I *really* like the poly greasables... not like you need the flex for a DD, but they don't dry out and crack like rubber, and IMHO if the bushings have room to turn, then your springs will see less thrashing on the smaller (but higher speed) bumps and turns you would get DD'ing (as opposed to the greater travel, but slower speed, you get 'wheeling.)

Anyway, just some thoughts. Worth every penny of what you paid for them. (Maybe :D )

-- A
 
That is some good information! I'm thinking a 4" shackle flip would be too much for a 2" lift in the front, but maybe I'm wrong(and I'd really like to do it right the first time). The big thing for me is that I want it to sit level with a full tank of fuel. Will the flip move the axle in the wheel wells?

Spring bushings sound smart, adding that to the list :D Ditching the extra shocks sounds good too :crazy:
 
jonathon said:
That is some good information! I'm thinking a 4" shackle flip would be too much for a 2" lift in the front, but maybe I'm wrong(and I'd really like to do it right the first time). The big thing for me is that I want it to sit level with a full tank of fuel. Will the flip move the axle in the wheel wells?

Spring bushings sound smart, adding that to the list :D Ditching the extra shocks sounds good too :crazy:
Click to expand...

Ride height is tricky to judge... but consider that if you do a flip, you'll have old (i.e. saggy) springs in back, and in front, new (i.e. stiff) springs. It would seem as though our trucks are prone to sagging in the back, so I would *guess* that ~2" springs up front and a 4" flip in the back would about balance. (Especially yours being a Burb, it's gonna be butt-heavy, more so than a K5 or even an unloaded pickup.)

While the flip does move the axle forward, I don't think you'll see it. IIRC on my truck it was less than an inch.

-- A
 
Thanks!

Now if I do a 4" flip in the rear and 2" in the front, will I have castor issues? I was think it seems like I almost should already since it sits well over an inch low in the rear already, but I don't know :confused:
 
With a wheelbase that long, I can't imagine that your caster/castor angle would change materially. The trig makes my head spin, but it would take a couple of degrees before you'd notice, in my experience, and a slight difference in ride height shouldn't cause that much change.

In any event, the only way to tell is to do all the suspension work, and then take it to the alignment shop and have it clocked on the machine. If at that point you need shims, get them then. (Didn't we do this already? :D )

-- A
 
dremu said:
I don't know that you're gonna need to shim the rear. On my K5 I did a 4" shackle flip and my pinion angle is okay; with a Burb you have the longer wheelbase, i.e. the pinion angle change will be reduced, and it's further reduced 'cuz you're doing a smaller lift. [I don't see how the front will change the rear pinion angle; the angle is a function of the rear suspension and its relation to the frame, i.e. t-case.
Click to expand...

Do get your pinion angle correct you will need to shim it unless you plan on going with a double cardon driveshaft, commonly reffered to as a CV.

Your pinion angle must be the same angle or a degree below that of the transfercase. When You do a 2 1/2" Shackle flip this is going to send the pinion to about 5 degrees up, your transfercase should be sitting at about 2 degrees down, so at the very least you need to bring the pinion down 3 but prefferably 4 degrees.

While I know that does not seem like alot when you add in axle wrap you will receive a lot of vibration from the drive shaft.

Now if you are going to use a CV shaft you may end up right on with your pinion angle but with a burb and 2 to 4 inches of lift there is no need for the extra expense.

Of course, this is all depending on what you are looking for and will tolerate. In my burb build I would not tolerate any vibrations or harmonics coming from the drive line so I did it right and adjusted the angles to achieve such an effect.


And your pinion angle will not be reduced by the longer wheel base, the angle between the drive shaft and pinion will but pinion angle compared to the horrizon has no bearing on wheelbase.
 
Good info.. I'll be playing with it for sure. I do not want vibes. Fortunately in the summer I won't be driving the Sub as much :D
 
Okay, I got an ORD 2.5" shackle flip inbound from ThatK30Guy :D Also got new u-bolts for the front and spring bushings from him.

Do you think I'll need new brake lines right off?

I'm hoping to tackle this at the end of June. Gather parts slowly. Next thing to get will be Zero Rates and a Steering Brace from ORD.

Edit: Just measured it.. with a little more than half a tank of fuel it sits 1" low in the rear. I have a 37 gallon tank so I'm thinking the zero rates + the extra half inch on the flip paired with 2" springs in the front should level it out.
 
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