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Torque Converter vibration after bolts tightened?

92DripCherokee

NAXJA Forum User
Location
Tampa, Florida
I tightened up the loose torque converter bolts, now the engine vibrates.

The vibration peaks at 1500 rpm, phases out at 2000 rpm.

What could have happened?
 
I replaced the transmission mount, vibration is still there but damped by the stiffer mount. I'm going to find the cause sooner or later. I've ruled out fan clutch, water pump and harmonic balancer. It still might be a lost balance weight on the flywheel, warped flex plate, or worse a dying torque converter.

Still have to pull the inspection cover again to have another look.


I removed the old transmission mount without pulling the CM, but the new mount was too tall to fit in the gap. I had to jack the CM up against the new mount to get the bolts started. The underside of the NP231 transfer case has a perfect spot to position a floor jack.
 
Did you have all the bolts loose at one time? It's possible, if the converter was slid back, that it got cocked in the back of the crank while snugging the bolts back down. I always alternate bolts to pull the converter back forward if I know it's not all the way seated in the crank.

Hopefully the flexplate's not cracked, also, I'm not seeing how a bad mount could have anything to do with this.
 
Uh oh. Thanks for the warning, I didnt realize i should have criss-crossed the torquing. Its so much more work to keep turning the engine over by hand for each bolt.

I only tightened the 2 loose bolts, and retorqued the rest. I must have a crooked converter now.
If the flexplate wasnt cracked, its probably warped now.
 
Last edited:
-after new trans mount, new rear diveshaft Ujoints, and new TC to flexplate bolts...

Smooth driving, slight idle vibration, and slight vibration on acceleration.

Not perfect, but good enough for government work.
 
update-

the idle vibration was a misaligned torque converter, pulled the inspection cover to find it was wobbling away. no cracks in the flexplate thank god.


I pulled all the TC bolts, and turned the flexplate 45°, one bolt position away, for good measure,

Then I did what two different pro mechanics neglected to do and cross-torqued the bolts in opposite pairs, in three separate stages. That meant barring the engine over and over while watching the hole in the harmonic damper for reference.



Just like stretching a sheet across a bed, you have to pull diagonally to have equal tension. On TC bolts, tightening the nearest neighbor can pull the converter off-center, and create a fairly nasty vibration. So X-torquing is the new rule

The engine purrs now, hasnt been this smooth before.

thanks all for your input.
 
A useful hint:
Taking out the spark-plugs allows you to rotate the crankshft by hand... Yes, it takes a few more moments to take them out and put them back at the end of the day, but still, worth it. Also, I ussualy use the opportunity to replace or clean them... Just make sure you mark the spark-plugs-wires and know which goes where.
Oded
 
I did consider pulling the spark plugs, so I didnt have to fight against the compression stroke. Fortunately I had a three foot breaker bar, no problem. With a 3 foot breaker, anyone can generate some serious torque.

The plan was to keep unbolting, rotating, and rebolting the flexplate to the next position on the converter, until the vibration stopped. With all the cross-torquing, it was possible I'd have to bar the engine dozen of times looking for the sweet spot.

I lucked out and it ran smooth after one 45° clockwise rotation. Phew!

If the plugs were out for barring the engine, and it vibrated again after the plugs were back in, it would have gotten old, taking them out over and over for each new rotation. Good thing the harmonic balancer bolt is hardened as hell, so it's none the worse for wear.
 
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