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Old 04-03-2019, 10:57 PM   #475
Old57
Registered User
 
Join Date: Apr 2015
Location: Wichita Kansas
Posts: 455
Re: 57 GMC, frame swap, 4wd, 454 big block, 4 speed

Yes, it is a nice change to have the good weather lately.

I posted earlier about having a drive line vibration at 60-70 mph... I rechecked my pinion angle, and ended up changing it 2 degrees. That helped some, but I still had pretty heavy vibrations on the highway. I checked my drive line again, but it was set just right so I was trying to figure out why I still had the vibration. I decided to get a new rear shaft made with a double cardon joint and a custom flange on the transfer case from High Angle Driveline. When I called and talked to them, and explained what I wanted to get, he asked why I needed to do all of that for my application. After I told him about the vibes, he asked a lot of questions about how the truck was set up, and said it was all correct and shouldn't be having this issue. Then he asked if I had new motor and transmission mounts, and I told him everything was brand new. He asked what mounts I have, and I told him they were Prothane polyurethane mounts... he said that right there was my vibration problem. I changed out the motor mounts for new USA made factory rubber mounts, and now it doesn't have the vibrations. So if anyone is chasing weird vibrations while using polyurethane mounts, try changing them to rubber mounts.
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My 57 GMC build
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