Engine rotational vibration

[cowboy4123]

I couldn't find anybody similar to my problem so I decided to post.

If I have my truck in park, and keeped revved up to about 2000rpms I can feel a vibration that shakes the truck in the seat of your pants. When I look under the hood during this time I can see nothing of the obvious, but it shakes my mirrors and it causes the same vibration (multiplied) when I'm doin 65mph and more on the highway....

Its a 2wd 6.5 turbo with a 480le..i replaced the trans mount, Had the whole driveshaft rebalanced and u-joints... I replaced my harmonic balancer during the winter.... This truck has been doin this since i bought it...

Any idea's would be appreciated

[Robyn]

I will bet that the Previous Owner had the tranny rebuilt.

Likely cuprit is a poorly rebuilt torque converter.

Remove the flywheel cover from the tranny, start the engine (*** KEEP CLEAR OF THINGS***)

Have a helper rev the engine slightly to make the bad vibes come in.

I will bet that even at idle the converter will be wobbling some.

Some converter rebuilders will screw up when they weld on a new hub on the tranny side of the converter and get them missaligned.

I have seen this several times.

This issue can ruin trannies and it puts a terrible amount of stress on the engines bottom end.

The converter and flex plate should not wiggle at all while running.

Keep us posted

Robyn

[cowboy4123]

ok thank you, i will look into this tomorrow hopefully if the rain holds out.....

[midniteplowboyy]

I agree with Robyn, bad converter. Dont drive it.

Was it the balancer or the pulley that you replaced?

[Robyn]

Years ago I rebuilt a C6 tranny for a friends pickup.

We started the thing up and thought the thing was going to fly it shook so bad.

I was at a total loss as to what the issue was. We pulled the tranny back out and looked everyhting over.

Finally after failing to find the isue the second time around were were running the engine with the flywheel cover off and I noticed the flex plate and converter wobbling.

Back out with the tranny and out with the converter.

Stuck the converter hub in the lathe and run the thing. AHHHHH HAAAAAAA

The hub had been replaced (rebuilt converter) and was not welded on straight.

Not only was the hub off radially it was also crooked too.

Raised hell with the rebuilder we did. They gave us all sorts of excuses as to how we had damaged the converter during installation. :eek:

They even tried to blame us because we had ballanced the engine (also fresh)

Bottom line was they offered us a replacement converter. NOOOOOOOOOOOOO thanks.

Went to a different supplier from then on.

It is not common now but it can happen if the rtebuilder is not careful

Best

Robyn

[cowboy4123]

I replaced both

[cowboy4123]

OK , first off, i'd like to say that GM made a stupid design to make the crossover pipe go over the inspection plate so that you can't remove the inspection plate! Unless I really didn't fiddle enough, i could not get it out so i let it sit there while I shined a flash light and looked through the driver side fender....


Maybe I saw a slight wobble on the flywheel at idle from that angle, but i could not see that wobble in the converter... nor did i see any wobbling when the motor was revved to that 2000 rpm range....

I don't know if thats of any concern.. but a little more indepth... The previous owner said this was a "longblock" replacement at 83k miles, i now have 135k miles on it. I feel this vibration sometimes worse than others at highway speeds over 65 whether towing or empty, it shakes the whole truck in the seat of your pants and it feels like a wave start mild to wild through its process then after a mile or two it will be stagnant then come back a couple miles later...... very annoying because you can't ignore it....

I have elminated driveshaft, brakes, tires, rotors, drums, because like i said i will notice the same vibration parked at 2000rpm's....

This dilemma is really keeping me from saying "i love this truck"....

I also noticed my darn oil cooler lines are leaking again after just replacing them two/three months ago (about 6k miles).....


So is there another way (like a measuring device) to see if the converter, flexplate is out of round without having to remove it? Or can I remove them and be sure (by measuring not by eye) the outcome so I eliminate this?

Run it with the flywheel off?

Thanks so far!

[midniteplowboyy]

I've worked on a couple vehicles where the converter has come apart causing a vibration. If you find its the converter, pull the trans pump and inspect, it could have some damage.

Make sure your flexplate still has the counter weight on it. Pull your fan belt off and see if it still vibrates, could be a bent/going out fan clutch or something.

[JohnC]

The converter IS the flywheel. The flex plate is just there to give you something to bolt to and hold the starter ring gear. Don't try to run it without the converter.

[Robyn]

If it has a rebuilt converter then its almost a sure bet that therein lies the issue.

If the converter has had a new drive hub welded on and its out of location even as little as .010- .020" these things will shake the daylights out of the truck.

You can unbolt the flex plate from the converter and shove the converter back into the tranny and then run it to see if the shake is gone.

Be sure the flex plate has the weight on it too.

If the heavy slab of steel is missing these things will shake like HELL
These are externally ballanced engines like a 454 and have a weight welded onto the flex plate.

These engines can and will get a little whizzy without the heavy mass of the converter.

This will however narrow the issue down.

I have done this several times to trace out issues.

Also when you slide the converter back up to the flex plate, it should touch evenly on all bolt pads. If you have to pull the flex plate up on one side with the bolts then there is likely an issue.


best

Robyn

[JohnC]

...
You can unbolt the flex plate from the converter and shove the converter back into the tranny and then run it to see if the shake is gone.
...
These engines can and will get a little whizzy without the heavy mass of the converter.
...
I have done this several times to trace out issues.

(I knew she was crazy!)
;)

[cowboy4123]

I believe it haha, well for me thats a project thats gonna have to wait till july......

The whole front end feels like it shakes too from this vibration, i got new idler arm, pitman arm, inner and outer tie rod ends..... wondering if i should replace new sway bar links/bushings anyway.....

[Robyn]

Anymore I am extremely careful who I buy converters from.

Before I stuff one in a tranny and take the time to bolt the thing all up I stick the converter in the lathe and make sure thing run true.

So far I have only had one bite me in the A$$ and found two others that I would not accept.

Sad that so called rebuilders will turn out such crap.

I deal like that can waste the bottom end of a 6.5 (crank too)


Best

Robyn

[cowboy4123]

OK while these may be the wrong the wrong direction, I jacked up my truck to change the sway bar links and took notice that I "believe" i found play in my upper and lower control arm bushings... So I will post back when I can afford to buy these darn things as they're not cheap...