2014+ Lowering / Drop Kits

[keakar]

There is no one shim fits all, that's why pinion shims do not come with any kits on the market... tolerance stack ups in the frame will make each truck slightly different and some more pronounced than others. If I were you I'd buy some 2 degree shims and after you lower it see how it does. You may not need them. I ran into this on my 2013 crew cab most people with the exact same drop kit had no trouble and after much research is why I bought THAT kit, but mine was so far out of whack it was almost ridiculous. It also made me not want to lower this 2014 as much as I did my previous truck just to steer clear of issues on another brand new truck.

well then how do you measure for it?

 

do you just get a ground clearance measurements like you do for the fenders for before and after then shim to return it to the same rough measurements from front yoke of rear end to a flat spot near the rear of it?

[racerkvn]

Refer to timfactors post. You'll need a magnetic angle finder and it's measured after you lower the vehicle and get the ride height set (suspension has settled).

[whodatfan]

In regards to lowering a vehicle, if the leafs are on top of the axle, the thick part of the wedge/shim goes to the rear of truck. If the leafs are under the axle, the thick part of the wedge/shim goes to the front of truck. This will pitch the differential up toward the bed of truck back to the proper angle compensating for the downward pitch caused by installing drop shackles. Shackles change the geometry of the leaf springs and roll the differential downward towards the ground. The wedges set the angle back near factory settings restoring harmonic balance of the drive shaft. Hope this helps.

Edited September 5, 2014 by whodatfan

[keakar]

In regards to lowering a vehicle, if the leafs are on top of the axle, the thick part of the wedge/shim goes to the rear of truck. If the leafs are under the axle, the thick part of the wedge/shim goes to the front of truck. This will pitch the differential up toward the bed of truck back to the proper angle compensating for the downward pitch caused by installing drop shackles. Shackles change the geometry of the leaf springs and roll the differential downward towards the ground. The wedges set the angle back near factory settings restoring harmonic balance of the drive shaft. Hope this helps.

thanks because that picture showed the axle under the springs but the wedge was backwards for what happens when you are lowering

 

the thing is how do you go about to measure that angle? just a straight edge laid across the yoke and a set point distance out from the yoke?

 

this actual procedure and how to do it correctly and accurately is something I haven't seen anyone post or provide a link to how to do it

Edited September 5, 2014 by keakar

[nate538]

Hey guys I've been lurking around here trying to get as much info as I can, I should be ordering a RCSB 4WD (it snows here) this week and I plan on doing a 2/4 drop on it.

 

Anyway I thought this might be helpful for those of you with vibration issues

http://www.hurst-drivelines.com/files/Universal_Joint_Alignment_Proc_111606.pdf

 

Also does anyone know why you can't buy a flip kit for a 4WD? Is the rear axle different in some way?

Here's where I posted some instructions way back in this thread

[bigsapper]

well then how do you measure for it?

 

do you just get a ground clearance measurements like you do for the fenders for before and after then shim to return it to the same rough measurements from front yoke of rear end to a flat spot near the rear of it?

 

[keakar]

_{thanks guys, that looks complicated and math makes my head hurt lol}

 

_{I guess I could bring it to cottman transmission and have them check it when im done}

Edited September 5, 2014 by keakar

[nate538]

_{thanks guys, that looks complicated and math makes my head hurt lol}

 

_{I guess I could bring it to cottman transmission and have them check it when im done}

Really for what we're doing you just need to get the diff on the same angle as the trans. If you're using lowering shackles the diff is going to get turned downward toward the ground due to the rear of the springs going up. In order to correct this you need to install the shim with the fat part toward the rear. If you're using a flip kit with less than the full 7 inches of drop, the opposite is ture because they lower the rear of the spring to reduce the amount of drop so you would put the fat part of the shim to the front

[keakar]

Really for what we're doing you just need to get the diff on the same angle as the trans. If you're using lowering shackles the diff is going to get turned downward toward the ground due to the rear of the springs going up. In order to correct this you need to install the shim with the fat part toward the rear. If you're using a flip kit with less than the full 7 inches of drop, the opposite is ture because they lower the rear of the spring to reduce the amount of drop so you would put the fat part of the shim to the front

ya I got that part but I also see when the springs rotate upward the angle will change on bot sides, the tranny side and the axle side angles will be different so its more then one angle changing so I cant just restore the axle to the same as it was because it would at that point need to be set differently from the first angle it was at.

 

it doesn't look too hard but it does look hard enough that I could easily get it wrong and if I change it I want it to be right not just "good enough" if you know what I mean.

[nate538]

ya I got that part but I also see when the springs rotate upward the angle will change on bot sides, the tranny side and the axle side angles will be different so its more then one angle changing so I cant just restore the axle to the same as it was because it would at that point need to be set differently from the first angle it was at.

 

it doesn't look too hard but it does look hard enough that I could easily get it wrong and if I change it I want it to be right not just "good enough" if you know what I mean.

Yes the angle between the driveshaft and the Trans will change but that's OK because as long as there's at least .5 degree of angle between them to keep the u joint moving your ok. With the amount of drop your talking about I don't see you having a problem there. The only angles that are going to cause a vibration are the diff and trans themselves because if they aren't the same they won't cancel out the movement of the u joint

[keakar]

Yes the angle between the driveshaft and the Trans will change but that's OK because as long as there's at least .5 degree of angle between them to keep the u joint moving your ok. With the amount of drop your talking about I don't see you having a problem there. The only angles that are going to cause a vibration are the diff and trans themselves because if they aren't the same they won't cancel out the movement of the u joint

so your saying if I do the 2" drop shackle and remove the 1.25" spacer block over the axle then that's not much of a change so I don't need to recalibrate for a shim

[whodatfan]

No. That is not what he is saying. He said don't worry about the trans angle because you didn't alter it's geometry by installing shackles. It's the rear end that was rotated out of tolerance. If you get a vibration at speed, you need to shim the rear differential up to remove it. Don't worry about the front of the drive shaft and transmission. It's fine.

[whodatfan]

You need to measure the front to find out how far off the rear is though. Get the front angle, then the rear, and that will tell you what size shim you need.

[keakar]

You need to measure the front to find out how far off the rear is though. Get the front angle, then the rear, and that will tell you what size shim you need.

ok, but I already have the "built in" "chevy designed it that way" vibration so im wondering if I can fix that issue with shims before I go messing with lowering it.

[Guest]

ok, but I already have the "built in" "chevy designed it that way" vibration so im wondering if I can fix that issue with shims before I go messing with lowering it.

I also have that vibration and am hoping to fix it myself also