interesting new problem

servantsalesmen · December 14, 2014

I just replaced my flexplate and got the truck running today! The truck has developed a shake/vibration at idle then again at 2200 rmp. I'm guessing it's torque converter. Any input? Also, the new flexplate is bigger and stiffer than oem. The truck cracked two oem flexplates at 35,000 miles each. My thought is that the new stiffer plate made the shake from the torque converter more pronounced.

8.1HD/ALLISON · December 14, 2014

Very possible. Remove and have balanced? Or checked.

servantsalesmen · December 14, 2014

What's the worst case if I let it go? Will it harm the tranny or the crankshaft? If it will hurt the trans, I'll leave it till it dies then replace the trans and converter. My hope is to build a performace truck out of it. Just crazy fast in a straight line lol

8.1HD/ALLISON · December 16, 2014

Hard to say. If bad enough it Could take crank and rear main out? Trans issues?

servantsalesmen · December 17, 2014

How would you define bad? In your opinion, how violent of a shake is really bad? I.E. a small vibration vs felling it in the seat vs the dash shaking vs. Steering wheel shaking vs. Consol shaking etc. I'm going to tackle it this weekend

j-ten-ner · December 17, 2014

I guess that any vibration caused by a rotating part is bad enough to be concerned.

And you don't know for sure where it comes from.

Could also be a bad spark plug or valve or camshaft or even the drive shaft. Or a low compression on one cylinder.

so long

j-ten-ner

servantsalesmen · December 17, 2014

I can rule most of those things out. It happens when the truck isn't moving. It's definitely either flexplate or torque converter. It seems to be worse in reverse though.

8.1HD/ALLISON · December 17, 2014

I can't describe a vibration. That's a seat of the pants thing. I'd say by your concern I wouldn't drive it.

servantsalesmen · December 18, 2014

Yup, I'm gonna pull her off the road this weekend. I'll post back with what I find. I have a feeling it could be the torque converter bolts. I had to sand them down on the heads just a hair to clear the bell housing (really stupid, I know) and I think that might have been enough to throw off the weight cause I'm sure they didn't all lose the same amount of weight.