QC Rearend Shuuder Issue after installing shims

[SlvrSnake]

Ok will try to make this short but need some advice on a possible shudder/grating feeling I am getting.

Here's the deal. Been having issues with driveline vibration which I posted before. Driveshaft was replaced as well as U-Joints. Tail shaft keeps leaking and they are going to replace the OD housing. That's another story.

About 2 yrs ago I put on Ground Force drop shackles, 1.5 inch drop. Tech who works on truck recently checked pinion angle and said it was at 5 degrees (hence reason for vibration I am now getting). To correct this I got 2.5 degree shims. Put them on yesterday. I put the fat part towards the front of vehicle to push front of the diff towards the ground. I checked the angles and they look good. I got 3 degrees off the diff and 3 degrees off the driveshaft. Before I started I got 7 off the diff and 3 off the driveshaft.

Now here is the issue the overall vibration seems better but now I am noticing this grating/shudder sensation when braking moderately at about 20 mph. It only happens when braking and is right about 20 mph not above or below. I also notice it cruising at about 60-65 mph and then letting off the gas makes it more pronounced. It is more of grating/grinding feeling more than a shudder.

Does anyone have any idea what this is? Did I go the wrong way with the shims perhaps and F-up the pinion angle? Loose U-bolts? This truck is really getting to me lately it is just one issue after another. Any insight from anyone who is good with driveline stuff would be appreciated.

Also, as far as balance goes, before we put the wheels back on after installing the shims we ran the truck on stands to look for any type of wobble in the drive line and it appeared to be true as true can be. Did not see any obvious dancing around from the drive shaft and did not feel any vibrations.

 

[spydertt]

My 05 QC is doing something simular. Driving 55-65 mph if I coast it feels like I ran over a rumble strip in the road, if I accell or let of the gas it goes away. The noise seems driveline related. A member of the forum told me to check the carrier bearing but Im to chubby to slide under it. I need to bring it to shop and put on lift (Im getting lazy in my old age). Too many honey doos lately , My son graduates from HS 22nd and the Wife has house tore apart.

 

[Yellow venom]

About 2 yrs ago I put on Ground Force drop shackles, 1.5 inch drop. Tech who works on truck recently checked pinion angle and said it was at 5 degrees (hence reason for vibration I am now getting). To correct this I got 2.5 degree shims. Put them on yesterday. I put the fat part towards the front of vehicle to push front of the diff towards the ground.

Putting the fat part of the shim towards the front? If you lowered it and want the angle back to stock,wouldnt you want to put the shim the other way to point the front of the diff up so its more straight? You want to keep the angle from the tail shaft to the pinion gear(yoke on diff) straight as possable??

 

[ZCx]

yep. like yeller said, ya want to bring the pinion/nose up. try puttin the fat part to the rear

:rock::rock::rock:

 

[Slitherbeast]

Is there any Play in the pinion at all! The vibration described , when not under acceleration or deceleration loads , leads me to believe there is pinion play!
Have you done any work on the diff. ?

 

[SlvrSnake]

In regard to the pinion being brought up. I am going by what the tech was telling me in that the pinion had to come down (nose of dif). In looking at it myself I don't disagree with you. It looks to me visually that the diff is pointing to far down when she is sitting level at this point. I was thinking this when we did it yesterday. However in thinking about the way it was stock it was further away from the body and should have been pointing more up in the air to meet the drive shaft evenly. Lowering it brought the dif closer to the body with angle still as it was stock. Does that make sense then that nose of the dif should have been pointed down to compensate for the shackles? I know you guys think it should go the other way. Just throwing out my thinking on it is all. I did contemplate this before I did it so it is why I am bringing it up.

 

[SlvrSnake]

Is there any Play in the pinion at all! The vibration described , when not under acceleration or deceleration loads , leads me to believe there is pinion play!
Have you done any work on the diff. ?

No work done to the diff.

 

[SlvrSnake]

Please excuse my retarded picture but I am trying to illustrate what I stated about the pinioin angle. The bottom one represents stock with circle being the diff and the line coming out being the drivehaft and the small perpendicular the universal. The long straight line on each represents the the body to show the relationship to the diff and driveline angle. That is why I thought the nose should come down. Stock it was further away from the body and needed a more upward angle to meet the driveshaft coming from the carrier bearing. If this is wrong then I will move the shims, just trying to make sure before I do it.

 

[ARRESTmeRed04]

try shimming the support bearing on the drive shaft a little bit, we had problems on my buddies S10 and just had to buy a bunch of washers and do it by trial and error till we found what worked for his truck, then orderd the shims.

 

[SlvrSnake]

try shimming the support bearing on the drive shaft a little bit, we had problems on my buddies S10 and just had to buy a bunch of washers and do it by trial and error till we found what worked for his truck, then orderd the shims.

I could see doing that if the vehicle was rasied. Wouldn't shimming the carrier bearing down make it worse on a vehicle that was lowered?

 

[ARRESTmeRed04]

I could see doing that if the vehicle was rasied. Wouldn't shimming the carrier bearing down make it worse on a vehicle that was lowered?

it might but it might not, the goal is to get the entire driveline back in line with each other, when you move the rearend up it changed the angle on the front shaft as well and when you shimmed the pinion angle it changed the angle yet again. so your vibration could be coming from the front shaft(and i'd think that if its tearing up the seal on the trans). we ended up having to shim the trans mount on my buddies truck up, the support bearing down and the pinion angle on the rear down to get the vibration out of it. like i said we just had to play with it.

 

[FastRam]

Been there done that but only on a lifted Chevy reg cab/short box. I chased drive line vibes forever on that truck.

I'd double check your drive shaft carrier bearing and pinon angles (with the vehicle weight applied on a level/flat surface) and make sure everything is tightened up, no leaks, all seals good, no other wear issues (including the kit that was installed).

 

[SlvrSnake]

Yellow Venom and Zcx you guys were right. For all my silly pictures and umm, thinking, I was wrong. I listened to what the tech told me and perhaps I misunderstood but I don't think so. Anyway, I reversed the shims and placed the fat part to the rear and weird sounds and shudders went away. Took out a launch shudder I was getting also, previous to, and after putting the shims in back-wards. Seems pretty good now. Hopefully, now when they tinker with the tailshaft housing it will hold a seal.

Just wanted to say thanks for chiming in and pointing me in the right direction. Basically, "Hey dumb ass! You put the shims on backwards"

 

[spydertt]

Drank a few tall boys and cranked up the tones and my noise is gone. I'm sure it will be there tomorow but sounds good tonight.

 

[SlvrSnake]

Nice...

 

[Yellow venom]

Yellow Venom and Zcx you guys were right. For all my silly pictures and umm, thinking, I was wrong. I listened to what the tech told me and perhaps I misunderstood but I don't think so. Anyway, I reversed the shims and placed the fat part to the rear and weird sounds and shudders went away. Took out a launch shudder I was getting also, previous to, and after putting the shims in back-wards. Seems pretty good now. Hopefully, now when they tinker with the tailshaft housing it will hold a seal.

Just wanted to say thanks for chiming in and pointing me in the right direction. Basically, "Hey dumb ass! You put the shims on backwards"

:rock::congrats::rock: