Mystery vibration (still)

[twt]

I want in on this one, My truck has what I thought was a miss & it will go away with more boost. It is more noticeable in last 2 gears, also with little pedal. Is this a converter or a trany problem? I had the converter replaced about 1 1/2 years ago, trying to get rid of this ( miss). I am wondering if the trany is slipping & catching???

 

[sagebel]

Is there a difference between TC shudder and TC slip? Can shudder occur without slip?

 

[twt]

I don`t know , but it feels like my truck has a small ( random ) miss. If you have 4 lbs of boost or more it either quits or slips so mutch you don`t notice it. I had decided to just drive until it broke ,then I saw your post. Like I said it does it in 4th gear the worst.

 

[sagebel]

yeah, canceling OD the next time it happens...
sounds like the TCC slipping to me...

Just got home. I canceled OD on the way to work and it didn't miss a beat. No slipping. On the way home I was getting on it pretty good and when I got to my test grade nothing happened! No vibration at all.

twt, Turn your chip up and run it hard (if your weather permits).

I am leaning towards an IPR problem. When a little more oil is needed it doesn't give it and is sticking. When demand is high there is enough pressure to overcome what ever is causing it to stick. Someone let me know if my theory is off base.

 

[twt]

Thanks , I`ll try that on the way home & let you know tommorrow. If that is it then I got a new, bad T.C.

 

[JLDickmon]

data log the rpm when it happens..
set it on cruise so your right foot is out of the equation...

 

[twt]

With OD off - a little better, but all that did was to raise the rpm & boost. This problem is worse with low rpm & boost . Could this be a trany pump problem ?? My DP tuner won`t let me have OD till I get to 45 mph. I have this problem from 2nd gear on up, worse when cold.

 

[sagebel]

RPMs stay constant, right around 1625 @ 60 mph. Vibration seems to be inconsistant. Sometimes it happens, others not. I am seeing a max of 8% TC slip but not during the vibration. Only see about 1-2% during vibration. ICP and IPR DC both increase but I think that is due to the hill.

Vibration seems more noticeable when cold. Over night temps here around 30. Tomorrow morning I will be engine oil get up to temp and see what it does with warm engine oil and cold trans oil.

If I wasn't driving and towing 4000 miles across country in March, I would say screw it and wait for something to break.

 

[sagebel]

To the top with some more observations:

Rough idle,sounds like it is hunting for an RPM. Engine RPM is 690+/- 8 rpm. ICP is right at 700psi, duty cycle at 14.7%

Truck also seems to stumble immediately after turning off cruise control or decelerating with CC.

When the vibration happens, it feels like the nose of the truck is bouncing. I feel it in the seat and not the steering wheel. Any help is greatly appreciated.

Scott

 

[JLDickmon]

guys, those really sound like torque converters to me..
run it by a trans shop and have their chief tech take it for a beat.. see what he says