Grinding noise after lowered

[Slimtwitch]

So never did a forum before so hopefully not starting it wrong. I’m looking for some thoughts on issue I’m having with my 2017 Silverado z71 crew cab after 4/6 drop issue is a grinding like noise only on highway maybe 60 mph and up just when coasting it doesn’t last long and seems to take about 10 minutes or so to start doing it. I raised tranny mount 3/8 inch and helped but still not completely right plus think it’s creating vibration is situate was t there without the shim. I know there’s lots of info on driveline angle issues on lowered and lifted trucks but seems it’s all on vibrations and not a noise like I have I’m currently trying to measure my angles to see what I have. I seem to have plenty of room for yoke in tailshaft so not sure it’s botttoming out. Thanks for any help

[1SLOW1500]

Drive shaft on floor. Of truck. Maybe. Slide under and see. Where it is hitting. Then at. Least get a. Air bag helper. Worlds of difference.

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[Slimtwitch]

Thanks I wish that was that was the  case but seem to have plenty of room everywhere pretty sure my drive angles are off just weird I haven’t found anything about this issue. I’ve been checking everything with suspension loaded I think driveshaft clearance issues is usually after 8 inches and more 

 

[Slimtwitch]

I also used chassis ears and seems noise is at tailshaft area just don’t know exactly why other than maybe drive line angles 

[1SLOW1500]

Angle or axle. Wrap do to angle.

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[Slimtwitch]

I’m not sure exactly what axle wrap is I’ve heard of it 

[1SLOW1500]

I’m not sure exactly what axle wrap is I’ve heard of it 

Angles can be in spec of each other but when you hit the gas or under driving load the operating angle jumps many degrees. Adds a stress on joints and bad for the pinion.
Zero and in some suspension - 1* is the loaded ride height. Or like me traction bars.

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[Slimtwitch]

Makes sense thanks my tailshaft is 5.1 down and axle is 2.3 up that’s with 3/8 shim under tranny and no shims in rear end 

[Darmichar]

Did you drop it enough that the pinion is shoved up against the rear of the trans housing?

[Slimtwitch]

Makes sense thanks my tailshaft is 5.1 down and axle is 2.3 up that’s with 3/8 shim under tranny and no shims in rear end 

[Slimtwitch]

I can push the drive shaft forward about an inch and half wilth suspension loaded so seems ok I will admit the sound it makes sounds like maybe if it bottomed out against the bearing  It also seems little worse when warmer outside we have crazy weather so one day it’s 20 degrees next day it’s 40-50. Raising the tranny definitely helped so that also makes me think it’s in the angles I have a 4 degree shim for axle ordered them I will see what effect that has

[Slimtwitch]

Makes sense thanks my tailshaft is 5.1 down and axle is 2.3 up that’s with 3/8 shim under tranny and no shims in rear end 

[Slimtwitch]

I was thinking most people needed to shim the rear axle down to get correct angle but since my tranny is around five degrees down and axle is 2 degrees up I may need to shim my axle up more to get closer to 5 degrees up to match the front just feels wrong cause thought guys usually set rear pinion down a little to have a good angle when under load but if I shim mine down the rear would be down just like the transmission 

[1SLOW1500]

Axle should be zero or negative do to the axle wrap and oil to the pinion. Then correct the trans. Other option that in my opinion is a great mod for all of us is new small diameter 2 piece drive shaft then you can set it to anything you like and go lower also. These trucks have super week shafts and the large diameter can also hit the body.

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[Slimtwitch]

thanks I am planning to try 4 degrees down on axle this weekend the part that was confusing me is after my axle is maybe little negative down then I I won’t have opposite angles since transmission is down and not enough room to make it have upward angle and everything I read says you want opposite angles between the two and I’ll have tranny down and axle down a little