JHForman Posted June 30, 2016 Report Share Posted June 30, 2016 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 Quote Link to comment Share on other sites More sharing options...
1BAD2K Posted June 30, 2016 Report Share Posted June 30, 2016 Have you checked pinion angles, or possibly backlash on the gears? Quote Link to comment Share on other sites More sharing options...
eberhama Posted June 30, 2016 Report Share Posted June 30, 2016 What do you have for a driveshaft? When my front diff was going bad, it seemed to make noise under load. Maybe a bad front hub? Quote Link to comment Share on other sites More sharing options...
JHForman Posted July 1, 2016 Author Report Share Posted July 1, 2016 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 Quote Link to comment Share on other sites More sharing options...
Doughty08 Posted July 1, 2016 Report Share Posted July 1, 2016 What about the output shaft bearing in the transfer case? Shouldn't have but around an 1/8" of play in it. Just a thought is all Quote Link to comment Share on other sites More sharing options...
EXGM Posted July 1, 2016 Report Share Posted July 1, 2016 You sure you don't have a bad u joint? Quote Link to comment Share on other sites More sharing options...
JHForman Posted July 1, 2016 Author Report Share Posted July 1, 2016 Transfer case was overhauled when I built the transmission, I am thinking u joint also was just wanting to hear what others thought Quote Link to comment Share on other sites More sharing options...
1BAD2K Posted July 1, 2016 Report Share Posted July 1, 2016 What changes were made when it started? Quote Link to comment Share on other sites More sharing options...
eberhama Posted July 1, 2016 Report Share Posted July 1, 2016 I was wondering more about the rear shaft, if it was a junkyard piece, or something you had made? on the front shaft, the yard where i work we sell allot of the blazer shaft you used. Don't know if its wimpy u-joints or what, but the seem to get torn up behind a 4.3 with part time 4x4. Cant imagine what 6.0/awd would do to it. We don't sell nearly as many of the silverado ones(second part #). Maybe swap one of those in to see if it help. Looks like they for around $50 used. Quote Link to comment Share on other sites More sharing options...
JHForman Posted July 1, 2016 Author Report Share Posted July 1, 2016 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 Quote Link to comment Share on other sites More sharing options...
EXGM Posted July 2, 2016 Report Share Posted July 2, 2016 Just because it's a new u joint doesn't mean it's good. I had a u joint go on a S10 I had. I bought the best NAPA had total junk it vibrated worse then the junk one I took out. I bought a spicer one and was smooth as glass..... Quote Link to comment Share on other sites More sharing options...
JHForman Posted July 2, 2016 Author Report Share Posted July 2, 2016 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 Quote Link to comment Share on other sites More sharing options...
Downeast Johnny Posted July 2, 2016 Report Share Posted July 2, 2016 Just because it's a new u joint doesn't mean it's good. I had a u joint go on a S10 I had. I bought the best NAPA had total junk it vibrated worse then the junk one I took out. I bought a spicer one and was smooth as glass..... I have given up on NAPA. In my experience 40% of what they sell is junk, maybe more than 40%. Quote Link to comment Share on other sites More sharing options...
EXGM Posted July 2, 2016 Report Share Posted July 2, 2016 I have given up on NAPA. In my experience 40% of what they sell is junk, maybe more than 40%. Yep I gave up on Napa several years ago. That u joint was the last straw. 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 Spend the money and get spicer ones. They are worth it. Quote Link to comment Share on other sites More sharing options...
JHForman Posted July 3, 2016 Author Report Share Posted July 3, 2016 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? Quote Link to comment Share on other sites More sharing options...
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