lapoolboy

Thanks. Your blocks are non-tapered and it doesn't look like you have factory shims either. Does your rear diff have a "nose-down" orientation? Mine is nose-up right now and the angle with the driveshaft is very close to zero.

Well, I took the 2.5 degree factory shims out today and the vibration/resonance is still there at around 60mph! ?. It's more of a "helicopter-like" chopping sound. It starts at 55mph and becomes unnoticeable at 65mph. What the hell am I missing here? I thought for sure that would solve the problem.

My Roll-N-Lock does. ?

Umm ok , right on there Mr. Sport Bar dude. ? I was referencing the topic at hand with my statement. While true I guess, none of your reasons for loving your sport bar so much have any effect whatsoever on the rigidity of the cab (when right-side up) as it relates to the rear window.

A bar bolted to the bed does nothing to reinforce the cab.

@jimmyboy8301

Yep. I just need to find some flat 3" blocks.

The factory shim had the pinion angled down slightly when stock. After putting the tapered ReadyLift blocks in, the pinion was brought up since I am now essentially running a flat block. And yes, blocks are oriented the way instructions state - shorter end toward the front of truck.

Removing the shims and leaving tapered blocks will shift front of diff upwards and create funky angle that would be opposite direction of last one I show in proposed setup.

Thanks. After getting under there and measuring, this makes sense. If I leave the ReadyLift tapered blocks and remove the shims, the diff pinion will be angled upward. This definitely won't be "equal and opposite" the angle at transmission. I'm thinking I need to leave the shims and just put in some flat blocks. This will push the front of the diff down.

Ok, I just crawled under and measured. The ReadyLift blocks are 3" tall at the back and 2-3/4" tall at the front. The factory shim is 5/16" So, it is confirmed the angle in the ReadyLift block is cancelled by the thickness of the shim. (Even makes the block TALLER in the front by 1/16" with it in there!). The rear diff has an upward tilt and the angle with the driveshaft appears to be very close to 0 degrees. Removing the shims will give the diff even more upward tilt.

Then the ass-end would be 3" lower than the front. I guess it "could" rule out the blocks, but the mis-match in height front-to-rear could induce other vibes. The shims are attached to the spring pack via the centering pin so I have to disassemble that to get the shims out.

The factory shims are installed with big end towards the front....so they are essentially cancelling out the taper of the blocks. The vibration is definitely coming from the rear end. I can almost hear it. The front-end is smooth as silk....the steering wheel is nice and smooth too with no vibration. The cv's are longer on the T1's than on the K2's and the front diff is narrower, allowing more lift capability. There are several other members out there who have the 4" like me and report that their trucks are smooth so I don't know what's different about mine. All of them have the factory shims still installed too.

Good luck. You'll need counsel for them to entertain that.

"Diff drop" typically refers to the front diff.

I want to get to the bottom of this once-and-for-all. Those of you who have aftermarket lifts installed (with rear blocks), please indicate if you or your installer left the factory shims in place between the spring perch and leaf spring (the shims will now be on TOP of the aftermarket lift block - see pic). My truck has less than 3000 miles on it and the ride was smooth as silk prior to installing the lift. There is now a very slight rumbling/vibrating at 55-65mph. ReadyLift says to remove the factory shim even though their instructions mention nothing of it and their own pictures in the instructions even show the shims left in place. I've looked at other manufacturer's instructions - SuperLift says to remove the shims. BDS, ProComp, etc. all specifically state to be sure NOT to remove the factory shims. No rhyme or reason - some use tapered blocks, some use flat blocks. My ReadyLift uses tapered blocks. Now to complicate things further, a member here posted a pic of his 2020 and there are no factory shims installed on his truck. I am not against removing the shims - I guess I just want confirmation that is the problem. You have to clamp the leafs together and remove the center pin bolt while holding it from spinning with ViseGrips. Never done it, but doesn't sound terrible. The angle of the driveshaft at the rear of the transmission is noticably "downward". The angle of the driveshaft at the rear differential appears to be pretty much in line with the pinion.

Post the work order

It's definitely the shift interlock solenoid in mine. It's just strange that it was dead silent for 2800 miles and now it suddenly makes the "click". Either GM uses some crappy solenoids that are sloppy/noisy or there is some grease on the contact points that wears away after a couple thousand miles?

Is that orange?

Exactly. The truth of the matter is that folks post pics on the world wide web for....wait for it....... COMMENTS! They relish and gloat in the good ones but when someone calls them out and gives them a negative comment, they get all butt-hurt. Since they can't defend their choices, they just cry and name-call.

Both possibilities I suppose but they are still outside forces. Do you notice any cracking?

Bingo. If the truck didn't leak for a while and then starts all of the sudden, it is being acted on by outside factors. It's either sealed or it's not. Let's take a poll to verify this theory...where are all these leaking trucks located geographically?

I have ReadyLift UCAs with their 4". I have about 1/4" clearance between tire and arm.

Yes, AMI and ReadyLift are sister companies. Neither are affiliated with Rough Country.

Looks good. Supposed to be near 80 here next few days so I'll be cleaning mine up tomorrow after my half day at work.