Question periodic shudder during idle

[Tx_Atty]

Here is a new one to me - this week I was sitting at a light and all of a sudden the engine shudders and I hear (at the same time) a metallic sounding rattle. The rpm dipped just slightly. Whole thing lasted only a couple of seconds then goes away. It now does it fairly regularly but still only for a couple of seconds at a time. If I hold the idle up just a little, it does not happen and it does not do anything weird while driving. I have also noticed that when I shut it down it does not make the same sound that it always has. Hard to describe but it seems to shut down more softly if that makes any sense. No codes being set either.

Ideas please?? I can't afford another repair.

Thanks!

 

[BJS]

check for play in the dual mass flywheel, would be my first guess and sorry but that's not going to be cheap

 

[Tx_Atty]

ok, great. How do I do that? Im not a mechanical idiot but Im not very knowledgeable about these things either.

 

[Patrick Feeley]

Remove the flywheel inspection cover. If you fool around a bit, you'll figure out how to counter-rotate the two masses against each other. Measure the distance (at the outer edge of the flywheel) of this "play" and it should not be more than about 5/8". Also look up in there at the dampening springs in the flywheel and make sure they're all there along with the plastic pieces at the ends of the springs. Cheers!

 

[Tx_Atty]

Well, I'll try to take a look this weekend. Assuming it is the clutch, I am looking at the South Bend Con O (rated for 350hp & 750 ft lbs). I do not have that kind of power yet but hope to in the next year or so. Any reasons I should go with something else or will this support a consensus?

Also, here is the indication of my abilities, where is the flywheel inspection cover?

Thanks!

 

[Tx_Atty]

Well, I ordered a South Bend Con O today. It's being shipped to the shop here in Lubbock and will go in whenever they get it. Nice $1400 kick in the nuts. I might switch to a damn bicycle.

 

[BJS]

yeah I was afraid that was your problem as that seems to be the culprit for vibrations at idle with the 5 speed trucks.

I've read very few who were unhappy with the Southbend clutches and the Con-O is a good one for your power level and some somewhat significant upgrades in the future.

 

[Tx_Atty]

I still don't know where the inspection cover is so I did not ever get to look at it but from everything I've read and from what the South Bend guys told me, y'all were right on your diagnosis. $775 for the clutch shipped and another $600 labor. Yippee. Just what I needed.

I appreciate the input.

 

[BJS]

I can't remember specifics on the ZF but in general the inspection covers will either be a section around the bottom of the flywheel or they will be a port in the side of the transmission bellhousing.