G56 clutch won’t disengage

[Andystransport]

Posted this in cumminsfourm but trying here, maybe someone can help.
Yesterday I pulled over at a rest area. Got back in the truck, started it and can’t get it into gear. Shut it off, put trans in first and fired it up. Let the clutch out and took off. Had to clutchless shift it the rest of the way and delivering cars. Wasn’t fun around town. I could get it into first rolling at the right rpm but the truck will want to creep forward pressing the clutch pedal. Did my dual mass flywheel take a dump on me. This trip I was loaded around 27k lbs combined. Truck is deleted but running stock tune no torque management. Hydraulics seem fine, I was getting a intermediated noise in neutral clutch not pressed. Thought it was a throw out bearing. Mostly did it after using sever engine break (down steep hill). I’ve always driven with engine brake on. This last trip truck would make a thump and a jerk when engine brake would engage letting off the gas. Thought maybe it’s my 5th wheel kingpin loose in the trailer housing again (bolt wasn’t fully tight before had a little slope) but would only do it in 5th (direct drive) and with engine brake on. Need some advice truck only has 24k miles on it. Really don’t want to be dropping the trans this earlier.

 

[GAmes]

The only way you won't have to drop the trans is if the clutch hydraulics are the culprit. Did you try "pumping them up"? If you can the issue is found. With only 24k miles isn't it still in warranty?

 

[Alan Reagan]

Sounds like the throw out bearing is bad since you mentioned the noise. Was there any vibration in the clutch pedal?

 

[TFucili]

Pilot needle bearing failure? Had that happen on a Ferd once.

 

[GCroyle]

24K on truck? Just for info, year, engine info etc. Any clutch replacement history?

24K clutch bearing shouldn't be making noise. Pilot bearing has only a few hours of actual use on it.

Can you pin down it makes a noise when I do this or conditions required to hopefully control noise off and on.

Hydro's, fluid level is where how far below top of reservoir? Adding more ain't really gonna fix this.

Engine running trans in 1st how far off of the floor before truck starts to pull?

Hydro's, use 2 finger tips only push pedal until you sense pressure being created. How far does clutch master cyl PUSH ROD move from full UP to the pressure created? Real numbers please.

Hydro's inspect full length of pressure line for moist spots = weeping in particular at connections.

Gary

 

[Andystransport]

24K on truck? Just for info, year, engine info etc. Any clutch replacement history?

24K clutch bearing shouldn't be making noise. Pilot bearing has only a few hours of actual use on it.

Can you pin down it makes a noise when I do this or conditions required to hopefully control noise off and on.

Hydro's, fluid level is where how far below top of reservoir? Adding more ain't really gonna fix this.

Engine running trans in 1st how far off of the floor before truck starts to pull?

Hydro's, use 2 finger tips only push pedal until you sense pressure being created. How far does clutch master cyl PUSH ROD move from full UP to the pressure created? Real numbers please.

Hydro's inspect full length of pressure line for moist spots = weeping in particular at connections.

Gary

Truck is a 2017 3500 2wd. Intermediated grinding noise in neutral clutch not pressed sounded like a throw out bearing. Mostly did it after using sever engine break (down steep hill), noise started after my first trip with the 3car trailer (about 28k lbs combined). Truck will creep forward if I put it in 1st then start the truck holding the clutch pedal down (like a automatic not holding brakes). Clutch seems to grab at the same pedal spot as always. Also on the highway if I push the clutch in the rpm will drop but shifting has to be rev matched. Feels like clutch drag. Ordered new hydraulics from amazon should be here tomorrow so going to try installing them. I’ll post back with the results, hopefully fixes the issue.

 

[NIsaacs]

Some info here on late model trucks with G-56 clutch issues.

https://www.turbodieselregister.com/posts/2587309/

 

[GCroyle]

The release bearing rotates continuous with engine.

The bearing has no clue what gear you are in or going to. It only knows the fork is pushing it forward or the diaphragm spring is pushing back against it and the hydraulic system is allowing it to move back.

But the force applied to the bearing changes from a slight preload with your foot off of the pedal maybe 30 lbf or so to a peak release load of 450-500 lbf about half way to the floor and then about 300lbf at the floor board this means the peak load applied to the bearing occurs while the clutch is still engaged and just after peak release load the transmission stops turning. Those are good measured numbers, not something I pulled out of thin air.

Truck will creep forward if I put it in 1st then start the truck holding the clutch pedal down (like a automatic not holding brakes). Clutch seems to grab at the same pedal spot as always.

This comment is a bit off.

Truck creeps forward means its not releasing correctly. And then clutch seems to grab at same spot as always.

You should have about 1 1/2" or even a bit more of reserve travel when you bring the clutch pedal UP from the floorboard BEFORE the clutch even starts to pull.

This hydraulic system is one of the easiest to TEST independently of the clutch to determine if it is doing its job correctly or has a problem. Remove slave cyl mechanically do not disconnect any hyd connections. NO ONE PUSHES PEDAL, YET now remove push rod and dust boot and install small steering wheel puller on face of cyl just finger snug the bolts for now, turn screw in until piston is blocked with steel. Now finger tighten puller bolts to cyl flange.

Now in cab push pedal with two finger tips only, observation is how far does the clutch MASTER CYL PUSH ROD travels before you feel pressure being created. 1/8"-3/16" would be typical for stock G56 hydro's. DO NOT USE YOUR FOOT FOR TEST!

The dual mass flywheel if it was damaged would likely created noise in all ranges and even possibly be out of balance.

Any details that control any noise could be helpful.

Gary

 

[RVTRKN]

Pilot bearing, however as GCroyle posted test the hydraulics first. 27K miles on your 2017 would normally be under warranty. Its on the boarder of a service writer claiming a wear issue anyway, however the shop who installed the solid flywheel should cover this.

 

[RT395]

I had similar symptoms when my factory hydraulics went out at 50k miles. In my case it was the slave cylinder and there was a few drops of fluid on the bottom of the bell housing. Replaced the master and slave assembly and its been good so far. Gary's test above would be a good idea.

 

[Andystransport]

Truck is deleted, No warranty. Yes that’s correct truck does creep forward in gear clutch pressed in, but pedal feels to grab where it always did (about half way out). New hydraulics should be here today. Also to my knowledge it’s still a factory clutch with dual mass flywheel (bought truck used with 12k miles) Going to install new hydraulics and see if that makes a difference. I’ll post back with results.

 

[GCroyle]

Yes that’s correct truck does creep forward in gear clutch pressed in, but pedal feels to grab where it always did (about half way out).

Andy,

That may be your story but your story is not how a correctly functioning clutch works. Reserve travel is a trait of a correctly functioning clutch system and is defined in the SAE Manual Transmission Clutch System book, page 47.

PEDAL RESERVE -- The difference between total available pedal travel and pedal travel to fully release the clutch.

If you have 6" of pedal travel and the clutch is released at 4 1/2" of pedal travel you have 1 1/2" of PEDAL RESERVE.

Your description contradicts a clutch that is not fully releasing and a clutch that is fully releasing.

The pilot bearing at your mileage should not have any significant wear on it and should not be a factor. Pilot bearing wear occurs when the engine is running, trans in gear and clutch pedal is down, released. Now the shell of the pilot is turning with the engine and the shaft it supports is not turning, = usage and wear.

Accurate observations help anyone assist in diagnosing the issue and possible causes.

Gary

 

[Andystransport]

I wish I knew what to say. What I can confirm is that it won’t go into gear if the engine is running. If I shut off the engine and put it into gear then start the engine the truck will want to creep forward. Letting the clutch pedal out engages the clutch, the truck will roll forward normally. I also am not able to shift it with the clutch unless I’m float shifting. That’s how I was able to finish my trip and do the deliveries.
One thing your right about is its not working correctly like a clutch should. It does have a dmf and I’ve read about a tsb for 2007 model year truck the would over adjust the self adjusting clutch system in the g56 transmission Which result in not being able to engage a gear with the engine running.

http://dodgeram.info/tsb/2007/06-001-07.htm

I may be wrong but to me the clutch pedal feels the same as before with the same bite spot (clutch engagement). I’ve had the hydraulics fail on me in other cars and you can feel it in the pedal. This one isn’t like that. I haven’t done the hydraulics test yet (don’t have a steering wheel puller) but like I’ve said new hydraulics should be here today. Going to install them, just maybe it’ll fix it hopefully. I don’t really like just throwing parts at something without diagnosing the problem first but because it’s amazon and I can return it if something thought I’d give it a try. Easier and cheaper then doing a clutch job if one is not needed.

 

[RVTRKN]

I'm sorry Andy, I miss read your 1st post. You have a good idea, by buying the hydraulics from Amazon. Its too bad you don't have warranty. If you do replace clutch, will you convert the SMF? I recommend South Bend Clutch for their SMF, its top notch, if you do.

 

[Andystransport]

I'm sorry Andy, I miss read your 1st post. You have a good idea, by buying the hydraulics from Amazon. Its too bad you don't have warranty. If you do replace clutch, will you convert the SMF? I recommend South Bend Clutch for their SMF, its top notch, if you do.

Yeah if I end up having to replace the clutch I’ll be doing a south bend dual disk. Sadly didn’t get the hydraulics today so hopefully they get delivered tomorrow.

 

[GCroyle]

If you have a snake camera remove the slave cylinder and start looking at the self adjusting springs there are 3 coil springs in the cover. New, these springs are almost compressed maybe 5/8" long and they extend as the disc wears down maybe out to 1 1/2" or so. At your low mileage correctly driven the springs will not be fully extended in their slot.

A disc that is not worn out and a cover that has fully adjusted will not work well together. Possible release issues from underside of spring tips rubbing the top of the clutch disc. And slippage and even noise when the pedal is pushed down engine running.

 

[RVTRKN]

Andy, if you do go to a SMF, you'll need to switch your ATF+ for a heavier, more cushioning oil. Lots of opinions here, but I use Mobil Delvac synthetic 50wt trans fluid. The DMF does well to cushion the harsh NVH, but with a DDS 3250 and SMF it will need the extra cushion of a heavier oil, and will be NOISEY.

 

[GAmes]

X2 on the Mobil Delvac 50. I do have to switch down to the thinner Pennzoil Synchromesh in the winter (recommended by Standard Transmission) in order to shift gears when the transmission is cold.

 

[RVTRKN]

I don’t live in a cold weather State, but I shift transfer case in neutral then trans in 4th gear, @ 1500 RPM, if in cold climate.

 

[GAmes]

I don’t live in a cold weather State, but I shift transfer case in neutral then trans in 4th gear, @ 1500 RPM, if in cold climate.

I've heard about that, but a 2WD doesn't have that option.