JHForman

Today I removed the rear shaft and went for a drive there's absolutely 0 vibration with the shaft removed so now I've at least isolated it to the rear shaft. I called tom woods today(very helpful people) and they said it's a balance issue. But apparently it's hard to get the shaft balanced with the slip yoke installed they said most shops can't do it and just balance the shaft itself. So now what do I do?

So for shits and giggles tonight I decided to take the shims out entirely, my transmission points down at 7 degrees and my pinion points up at 7 degrees, I test drove it and it's the best it has been yet!!!! Now this goes against absolutely everything I have read about pinion angles everything I have read said you want a 2-3 degree split to account for the pinion rotating upwards under acceleration and when I set my pinion that way this vibration is terrible. So my question is now do I order a set of 1 degree shims and try them? Or is it as good as it's going to get ? I have tried shims from 2-6 degrees. My vibration was from 75-90mph then would go away. After getting rid of shims all together my vibration is a very small range 70-75 mph. So what should I do?

I have not, I'm heading that route it seems though

.75" 3/4" not 3 inch lol it only changed the front angle by 1.5 degrees

I know they say not to remove the front drive shaft because of the viscous coupling, can I remove the rear drive shaft and go for a drive?

My pinion angle issue was with the rest drive shaft, I ended up using 2 degree shims on the axle and 3/4" spacers under the transfer case. The truck used to shake so bad I couldn't go over 70 mph this all happened after it was lowered now it's got a different case/trans and a different trans with a shorter rear drive shaft

Also just thinking out loud here, is there a possibility I'm getting into a resonate frequency of the chassis and maybe I'm hearing the exhaust vibrating on the frame? I have a spot where it touches it will be fixed next time I have the down pipe out

New u joints installed(moog) vibration is still there but not as bad. I thought about lifting the front of the truck back up a bit to see if it goes away?

I pumped some more lubrication into the rear joints tonight, this cured about 60% of the vibration, I will be replacing the joints. The joints have been lubricated but I'm starting to think they are just junk joints

Changes made were 4l80e/3600 stall/ 149 transfer case, right axle half changed, and front drive shaft installed. Rear driveshaft was shortened balanced and new joints installed. The vibration is most noticeable under my feet. I couldn't find a Silverado shaft locally or I woulda bought it instead of the one I did buy. It's a 5.3 not a 6.0

Transfer case was overhauled when I built the transmission, I am thinking u joint also was just wanting to hear what others thought

Pinion angles are good I already fought that battle lol, the front shaft I used is 26055995 it is 27 1/4 and the one most people use is 15182094 and it is 27 1/8 long. I don't think that 1/8 is causing this issue do you? It's just a really weird vibration/humming, it resonates through the whole truck you can see it in the rear view mirror if that tells you anything Front hubs have been checked a thousand times

Ok quick run down of the truck, it's a std cab 4l80e/awd, 3.73 gears. My issue is cruising on the interstate at 72 mph and on, I get a humming/vibration coming from the truck, you can feel it in the floor board. Is this normal for Awd? This is not a wheel/tire vibration, it does not change with load, I can shift to neutral and the vibration/humming continues, I can drive through it at around 95, but till you get through it it's kinda scary. Is my front diff going bad? Thanks for the help guys