clutch pedal vibration

[JLinn]

I have an '07. 5 6. 7 3500 6 speed 4wd with 4600 miles. It has always had a very annoying vibration in the clutch pedal each time I push the clutch in to shift. It will sometimes vibrate when I push the clutch in and rev the motor in neutral but not always. Took a tech from my only dealer for hundreds of miles for a ride. He said something is wrong but did not know what and he would need to remove the trans to find out. When I called two weeks later they told me they could not duplicate the problem. I have been a professional mechanic for the last 20+ years and have never encountered a similar vibration but do not know what new clutch, throw out bearing, t ransmission setups they might have in this truck. The clutch itself works normally with no vibration with the clutch pushed all the way in or while driving. Anyone have any ideas?

 

[GCroyle]

JLinn,



Reading your post, 2 issues come to mind and to comment further, I have a couple of diagnostic questions for you.



1. We need to determine if it it being caused by the diaphragm spring tips not being uniform and the bearing is actually pulsating and pushing the fork in and out? The frequency of the pulsation would increase with RPM.

2. Engine running, select neutral, foot off of the clutch pedal, increase engine RPM up to say 3000. Do you feel a vibration in the truck body? This type of imbalance vibration MIGHT be due to the DMF secondary F/W to primary bushing failure. This has been commented on here by several G56 transmission owners.



Teardown inspection points.



1. Inspect the diaphragm spring tips BEFORE removing the clutch from the DMF. Inspecting or measuring the clutch cover by itself on the bench does not yield very valid information.

2. Inspect the Self Adjusting Clutch mechanism, visible components exist on the top of SAC covers issues. These components compensate for disc wear and control the diaphragm springs height, worth looking into.

3. DMF in the center, just out from the pilot bearing is a thin bushing, CLOSELY examine it for wear and try to move the secondary relative to the primary radially, not rotation, but IN and OUT, look for movement that causes balance issues.

 

[JLinn]

No body vibration, a slight roughness @2800-3000. My vibration is in the pedal as you get about half way in with the pedal as you make the shift and continues until the clutch is released. When engine is warm it will vibrate in neutral with clutch in and rpm @1800-2000 but it is in the pedal.

 

[GCroyle]

JLinn,



1. Any chatter on engagement? Could you put a hot cup of coffee on the dash and pull away and not spill the coffee?



2. If you are not aware of any engine related vibration (think tire balance) then I vote for an irregular diaphragm spring presentation relative to the release bearing. This would also fit nicely if the clutch was not as smooth during engagement/friction zone usage as it could be.



Armchair diagnosis is tough sometimes, we don't have fault codes for clutch issues, need good detectives and symptoms to work with.

 

[sag2]

As noted above they need to inspect the fingers after removing the transmission. Using a dial indicator (works best with a wheel end like when checking tire run out) they need to rotate the engine and the fingers should be less than 1mm out of flat. If they are not the clutch does not need to be replaced. Just loosen the clutch bolts and torque them to 20 ft/lbs. Then loosen them all the same number of turns, say 5-8, and then re-tighten in a star pattern one turn at a time to tight, then torque to spec. Dial indicate again and see if it made an improvement.

The other thing to check if that is not it, and even if it is, is the flex plate to crank bolts. Tighten them to the 2008 spec in either case, or replace flex plate and bolts if they are loose and tighten to 2008 spec which is higher than 07 spec.

All the above need to be done with a wrench, not an impact. You need to stress this to the writer/manager/technician, or they will just use the impact and you may be right back where you started.

 

[JLinn]

Clutch engagement is dead smooth except for this vibration. My gut is it is like an engine balance thing. Isn't it some kind of wierd new flywheel? Or maybe a funny vibration damper deal? Can you imagine trying to get my dealer to retorque the pressure plate! Wonder how many hours they give you to r&r the trans? Maybe it's just a square ball in the TOB?

 

[GCroyle]

G56 DMF and Clutch System

JLinn, before I try to add any more, we need to pat sag2 on the back for his spot on comments about inspecting the cover on the truck, his technique of using a dial indicator, actual values, and tips about re-tightening were very good. One of the big things that I get concerned about is the use of impact guns to install clutch covers, the staggered pattern, 3/4 turn at a time, torque to spec approach is correct.



Nice comments sag2.



The DMF has additional features and functions, it has been discussed here previously. The attached image is that of a used G56 DMF. The other image is of the OE clutch system. One additional note concerns the clutch cover.



This cover is known as a Self Adjusting Cover, they have been out since about 1995 in the Ford Ranger. My Dodge service manual CD didn't cooperate this AM, but I checked it on ALLDATA and this procedure is valid.



IF you remove a SAC and then attempt to re-install the same (used) unit you need to re-set it prior to installation. This lets the SAC start over in the adjustment process.



Re-setting involves pressing down on the diaphragm spring (hydraulic press or even a threaded rod approach) until you can reposition the three exposed fingers (compressing the three small coil springs) we have just used screwdrivers and then hold them in position while you slowly allow the spring to return to its relaxed position as you release the pressure on the spring.



JLinn, to get back to your truck, it might be time to spend some more time listening to and observing the pedal assy, possibly getting it on a lift and listening to and actually feeling the gearbox, clutch area and slave cylinder trying to get more truck feedback. Be careful, good luck.

 

[sag2]

The reset procedure is outlined in the factory service manual and is exactly as described above. This should only need to be done when installing a new clutch plate with a used cover. Unless you have a press or large arbor press you will not be able to do it at home.