Mystery vibration (still)

[sagebel]

Vibration occurs in OD at the bottom of an incline when the engine loads up a little (generally a 1-2 psi increase in boost). If I give it more pedal the vibration goes away. I started noticing this last December when I drove North on some of the larger hills. I have been noticing it here in GA on smaller grades over the past 6 months.

Replaced carrier bearing and all U-joints
Greased slip yoke
Shimmed carrier bearing 3/8" and 3/4"

The vibration is very inconsistant. Some days it is very noticeable, other days I don't even notice it.

Looking for ideas. I'm not sure if it is the engine, TC, Trans, driveline, or rear end.

 

[JLDickmon]

cancel OD next time it happens and get back to me

 

[sagebel]

Truck down shifted and no more vibration. Downshift was smooth, nothing out of ordinary. I can also make it go away by giving it more fuel. Did a little more testing. I can also get the vibration on flat road by very slowly increasing speed. It is easier to do with with cruise control. Vibration seems to happen right around between 55 and 65mph (1700-1850 rpm).

I have an AE so if you need me to data log something, let me know.

Scott

 

[DaveBen]

At 55 mph, I have found, in the past, that it is associated with U-joints.

Dave

 

[sagebel]

Dave,

I replaced the U joints less than 10,000 miles ago along with the carrier bearing. No change. Everything is still tight.

 

[sagebel]

Pulled the rear drive shaft. Good news: The vibration is not coming from anything behind the transfer case. Bad news: I still don't know where the vibration is coming from!

 

[DaveBen]

You have a multiple of trucks shown. Which one are you referring to? I would guess the Torque Converter.

Dave

 

[sagebel]

Dave, Just one truck. Many years of parts. Is there anyway to pinpoint the TC? The only other thing I think it could be is a miss in one of the cylinders. I can make the vibration stop by pressing on the pedal.

 

[JLDickmon]

Dave, Just one truck. Many years of parts. Is there anyway to pinpoint the TC? The only other thing I think it could be is a miss in one of the cylinders. I can make the vibration stop by pressing on the pedal.

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

 

[sagebel]

I'll hook up the AE next time. Haven't seen any slipping once the TC locks on other runs. Didn't think to take on the last test run.