05 Manual Duramax

I have an 05 Chevy Duramax with a manual 6 speed transmission. The last load of hay I hauled, I noticed while the truck was idling in neutral, the gear shifter started flopping from side to side with a rattling noise coming from the clutch area. When I depressed the clutch, the shifter stopped flopping from side to side and the noise went away. Never done it again until a few days later. The second time was after hauling a load of lumber, this time when I pressed the clutch the flopping and noise didn't stop. I actually had to put it into gear and let out on the clutch a little putting pressure on the drive line for the flopping and noise to stop.
I checked with a local diesel shop about a possible clutch/throw out bearing/idler bearing failure as the possible culprit. They had stated they have seen this scenario on other bigger trucks and ended up being a bad fuel injector. Now the truck runs fine, no misses, hiccups or smoke at 170k miles. If it is an injector wouldn't there be other indicators like hard starting or a miss while idling or under a load? If it is within the clutch area, is it a dual disc clutch assembly? There is no chatter or unusual feeling in the clutch pedal when depressed.
There is no whine when driving the truck like it could be a front housing bearing. No chunks or large debris in the oil or on the magnetic plug.
I'm curious if any of you have experienced a scenario like this because I don't want to just throw money at a hunch.
I'm heading home in a few weeks and want to tackle this job while home on R&R.
 
I have a '04 one ton with a 6.0 gas and 5 speed standard transmission. My truck has about 135,000 miles on it and I am working on my 3rd clutch/pressure plate/throwout brg, and I rebuilt the transmission once at about 100,000. I am not impressed with GM's standard transmissions and their associated parts. I have spent way too much money to keep it going over the years. I escepcially hate the plastic hydraulic throwout bearing gizmo they use. They sure don't build them like they used to. Will probably go to an automatic on the next truck.
 
I would lean towards the bad injector. I had an 06
Dodge Gummins with a 6 speed, and it was doing
about the same thing. Maybe once a month. I
chickened out and traded it. Mileage was right at
180,000.
 
Seems like they can check the injectors with a scanner.
Normally when injectors take a crap on those, you have a
little haze if bluish whitish smoke at low rpms. Then the
smoke will get worse with time.
 

R&R? Does that mean you go back again after a few months? I would think that you would have had enough after six tours.
 
It's not showing any signs of smoke at idle, can't really say when idling down the road. Would it miss or cough crank over more than normal if an injector was going down?
 
I'm only going off from an experience of two different trucks, an 01 and 02. Both ran fine, just started a little hazing. The longer it went on, there was more smoke, and both developed a tick, sounded like a small exaust leak. The one guy put all new injectors in his. Tick and smoke went away. The other guy tried getting by and eventually burnt up a piston. I'm working off foggy memory here, but it seems like the guy that had it fixed had gm scan it, and most showed bad, that's why he replaced all of them. It also seems like the earlier duramaxes, pre 04 era, were harder on injectors. The newer ones weren't so bad. I'm just thinking I'd see if they could diagnose an injector and go from there. I'm no mechanic, just speaking from experience.
 
My old Ford 6.9 diesel started flopping like that when I pulled up to a stop light one time after I unloaded a load of cattle at the stock yard. It ran rough for about 25 miles then smoothed out. Next time I changed the glow plugs,one was pretty much gone. I figured that what happened was,that piece of glow plug went in and stuck a valve.
That shift flopped around pretty bad though until the miss worked its way out.
 
What happens if you just rev up the engine a little-1500 rpm or so? Without depressing the clutch? Was it idling smooth-no fluctuation in rpm? Is it still shifting normal-no excessive travel or movement in any gear position?Mark
 
a bad injector will produce a knocking sound, and will be more pronounced with more throttle. I have experienced this a couple of times with my 2006 but put in some conditioner and just took it easy for a bit and it cleared it self. I has no real effect on starting. kinda makes a person wonder how good these fuel filters are. just takes a micron of a spec to get in the injector .
 
I had an injector failure and broke the crank on my
cummins best thing is to change the injectors every
100k miles
 
I would lean towards the crank pulley/vibration dampener. I have seen them bad that cause the issue your having. I am not around many manuals in a Duramax but it was real common on the 6.2s and 6.5 diesels. They recommend changing the dampener every 100K on them. I had a 1985 6.2 that broke the crank because if this issue.
 
They used the ZF6 behind the Isuzu didn't they?
Crawl under there and make sure you're not about to
leave your transmission in the road. Had a 10 speed
road ranger doing that once, push the clutch in and
it stopped. Had 3 bolts barely still holding it to
the engine. This was about a hundred thousand after its last clutch.
 
Those trucks used a two piece flywheel. There is a rubber damper between the two parts of the flywheel that goes bad. Most only lasted 125000 miles. There are two options, replace the flywheel and clutch with another two piece unit or there are conversion kits that use a conventional one piece flywheel and clutch. If you plan on keeping the truck go with the one piece and you won't have to replace it again.
 

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