Just wondering if anyone had any advice as to what my problem might be. I just got done with my rebuild. I built a blower motor out of my stock ls1 with a forged bottom end and poly-motor mounts, 13-16lbs. of boost. I also got a locker 9-inch rear-end and replaced my random tech torque arm with a UMI (which did not come with an angle finder, but I used a friends and I think we have it set.) I'm have a heavy vibration at around 1500-1700 rpm. It's really bothering me and I don't know what's doing it. Any ideas? (feel free to move this if it's in the wrong forum) -Andy

 

Check to see how much wobble you have on your harmonic balancer. If it's excessive replace the balancer, and your vibration may disappear.

Do you have a polyurethane transmission mount? I took mine out because it was giving me a funky vibration at close to the same RPM you're describing.

Ben T.

 

I do have a poly tranny mount but I had it before the build to and didn't have this problem. the balancer is a new ati balancer, i had the crank keyed for the procharger.