Do I have a problem?

[JThacker]

Thanks for all the advice guys, it's greatly appreciated. I know what is causing it, every time it vibrates it is when I have slowed down fast. The engine RPM's drop to about 600 and it rattles, I guess what I am asking is do your all's trucks do this, can you make a vibration by slowing down to 1200 RPM's in 3rd, then clutch it and stop pretty quickly with the brake. Could there be a problem with the engine letting itself idle down that low causing the vibration? This also occurred to me, could this be part of the break in, meaning the engine is getting "looser" for lack of a better term and idles down easier than before.

 

[rbattelle]

When I got home from work I checked the PDM and found on page 8 the diesel startup sequence:



1. The ECM receives the crank signal input from the camshaft position sensor.

2. The air intake heaters are not energized during cranking.

3. The ECM monitors engine speed and when the engine speed is above 650 RPM the ECM determines that the engine is running.

4. If the ECM receives a crank signal before the preheat cycle is over, the heaters will be disabled.



I interpret this to indicate "results below 650 RPM may be unpredictable".



I guess most people disagree with me that starting in 2nd gear puts more wear and strain on the clutch and engine. I'm impressed that joeyou starts in 2nd using just the idle controller. My engine lugs badly if I try to do that, so I choose to avoid it. I've driven a 4. 10 truck and that one definetly needed to be started in 2nd, but I thought others' 3. 73 trucks preferred starting in 1st like mine. Obviously I'm mistaken. I think I'll continue starting in 1st unless I'm pointed downhill or level and in a hurry. It's interesting that the owners manal specifically states you must use all gears. I'd like to hear what Peter at SBC or Jeleg think about the starting gear for a 3. 73.



For the new guys, have a look at this classic.



-Ryan

 

[JThacker]

Ryan, that makes sense, my only question is, is it normal for my engine to let the RPM's fall down to 500-600 when I clutch it when the RPM's are at 1200 in 3rd gear. Strangely, the vibration is less when I clutch it and come to a slow stop versus clutching it and coming to a fast stop, once I clutch it the speed of the truck should have no bearing on the engine RPM's. This leads me to believe that either the engine is malfunctioning letting the RPM's drop lower than they should which causes the vibration of the engine or it is doing this new thing as part of the "break in" or the vibration is purely in the clutch and the RPM's dropping is coincidental. Clutching it at 1000-1200 isn't lugging it. The lug and vibration occur after it is clutched at that RPM and it falls to 500-600, granted it is at somewhat of a load like I said it's most pronounced when going down a hill. This makes me think it is something with the clutch, I have never lugged it to below 1000 RPM's before downshifting or clutching it, considering this and my mileage is 8400 and never pulled a load what are the chances I have actually damaged something. Be honest, I can take it. Thanks Jay

 

[mberry]

... I guess what I am asking is do your all's trucks do this, can you make a vibration by slowing down to 1200 RPM's in 3rd, then clutch it and stop pretty quickly with the brake. Could there be a problem with the engine letting itself idle down that low causing the vibration? This also occurred to me, could this be part of the break in, meaning the engine is getting "looser" for lack of a better term and idles down easier than before.

Someone much wiser than me once said that it is much easier and less expensive to replace brake pads than a clutch.

 

[rbattelle]

Ryan, that makes sense, my only question is, is it normal for my engine to let the RPM's fall down to 500-600 when I clutch it when the RPM's are at 1200 in 3rd gear. Clutching it at 1000-1200 isn't lugging it. Thanks Jay

Ah ha! Now we're onto something here. I didn't realize it was dropping to 500 or 600 RPM when you release the transmission (push in the clutch) from 1200 RPM. Of course 1000-1200 RPM in 3rd isn't lugging the engine (although I wouldn't be giving it all kinds of fuel at that speed). I would have to say it's not quite normal for the RPM to drop that low when the transmission is released. Mine tends to drop down to 675-725 (verified using OBD-II monitor) when I depress the clutch pedal from whatever engine speed.



So, what could be occuring that would cause the engine to drop speed that far before recovering? I can't say for sure, of course, I could only guess. Could be a programming problem - the ECM doesn't recognize the loss in RPM quick enough. I really don't know. If it were a sensor problem you'd probably get MIL (Malfunction Indicator Lamp) illumination.



Could it be a pilot bearing or other clutch component binding up as others have suggested? I'd be curious what your % load is at idle. Do you have access to an OBD-II scanner? % load should be 1 - 4% at idle. If you had something in the clutch assembly binding up I'd expect to see higher loads at idle. Extra bind could drag the engine way down when you depress the clutch while the idle controller struggles to bring the engine back to idle.



I'm just guessing here, throwing out ideas to think about.



-Ryan

 

[InThinAir]

JThacker, Ok, try this next time you are out and about. On a slope, be a little over geared and then depress the clutch and down shift. See if you hear the same vibration. This will occur at any speed... For example approach a hill the you might usually be in 4th to climb and try 5th. If the motor boggs a little, at any RPM, then depress the clutch and tell me if the vibration occurs and the idle goes below 650...



---Doug

 

[JHardwick]

For what it's worth, I start out in 2nd gear.



If I start out with a load and on a terrain that feels like I need 1st, I'll quickly do the shift. But, this happens without thought and mostly a seat of the pants thing. I will leave a stop loaded and in 2nd if the terrain is right.



4:10 gears here, I can't do 120mph, but I can rock the hilly highways with a load

 

[rbattelle]

For what it's worth, I start out in 2nd gear.

I've driven your truck... you have to start in 2nd with them 4:10s. I've resolved to start in 2nd more often, but not all the time.



-Ryan

 

[JHardwick]

Even with the 4:10's I catch myself "burping" the throttle and then easing out the clutch as the R's are dropping while launching in 2nd.



1st is too low unloaded, IMO 1st has a purpose as does reverse ... ... ... ... don't need it til you need it

 

[InThinAir]

The Owners manual states to start in 1st gear all the time. I never do... But I would not go the the dealer asking for warranty work talking about starting out in second.



---Doug

 

[TNelson]

my truck does the same thing, when driving in traffic or coming to a stop sign in 3rd gear at 1200 to 1500 RPM when i push in my clutch my RPMs drop to between 500 and 550 then they go to 850 to 900, back to 600 to 800 and finally to 750. when they drop the truck shudders and vibrates. when i start in 2nd gear i let the clutch out and then give it fuel. the vibration was so bad my catolytic converter was hitting the crossmember. i thought the ecm would not allow the RPM to drop below 750. the truck was at the dealership 3 times and they say its normal. the problem i have is it didn't start doing this until about 18000 miles. they basically told me i' driving incorrectly. it is real irritaiting in rush hour. my truck also has miss or lope when idleing.

 

[JThacker]

Thanks TNelson, nice to know someone else has experienced exactly the same thing, mine started it at 8000 miles. I knew I wasn't bogging the engine excessively. I have an appt. on Monday to take mine to the dealership and I am going to get the head transmission guy who also drives a CTD to ride with me. I will also try to get the OBD on the truck and see if there is any problem with the sensor mechanism of the idle in some way. If you find anything out please pm me and let me know and I will post either here or pm you to let you know what happens on Monday. Thanks again Ryan and the rest of you boys I appreciate it, I'll keep you all updated.

 

[macdaddy]

Hey Thac

Man after reading the whole thread I would say it's a no brainer it's your driving habits. I am never in gear under 1000 RPM I pretty much do a 6th to 5th to 4th downshift then coast in neutral to a stop when empty. As far as towing is concerned I maybe and I mean maybe go to a 4th to 3rd downshift,

Now if you think about it consider what a trucks brakes go through with an auto coming to a stop with a stock torque converter unlocked from 60 to 0 people do it all the time! I did it with my 99 for five years and with running EGR brakes and rotors I still got over 60K on the front pads. So stop trying to stop your truck in gear and go to neutral and come to a stop. Now of course there are those who will argue but brakes are easier and cheaper to replace. than driveline components.

Mac

 

[nickleinonen]

75% of the time i start off in 2nd, and i have 3. 73 gears with 315/70 bfg's under it [so more like 3. 55 gearing?] i never give it any throttle taking off unless i am racing...



as for the idle speed, i am 99% sure the idle is ecm controlled at 750rpm [my engines valve cover sticker proves that], and below 400 rpm the ecm stops fueling [i can't find the literature that stated that ]

 

[TNelson]

as i said my truck does the same thing. my truck was in the shop 4 times and this is what was repaired. the first time i was unable to duplucate the exhaust hitting and their solution was to retorque cab mounts. i also complained about the milage and they reflashed the computor , they used tsb 18-037-04. the second time i also had a rattle from the shifter. i was succesful in duplicating the exhaust hitting the cross member and rattling. their repair was they removed crossmember to oblong holes to have clearance from the cat. convertor. they also replaced the transfer case shift lever and found a loose nut on shifter knob. the third time they roadtested with mts4100 vibration analyzer to look for any abnormal engine or driveline vibrations. they found 3rd order engine vibration which is normal inline 6 vibration. they inspected the u-joints, driveshaft and centerhanger. they performed an injector kill test on all cyls all had the same drop to 750 rpm. they performed a cyl performance test all cyl were between 98% and 103% which ok. the fourth time they did tsb 03-003-91 and road tested it and said its normal. the truck still does the same and the idle is real rough. i'm going to take it back in hopefully next week. my truck is a 2004. 5 crewcab 3500 srw 4/4 6 speed

 

[Punkineater]

What's funny about this whole thread is that there are farmers out there who have never heard about TDR that just drive starting out in second for hundreds of thousands of miles and don't give it a second thought. Sometimes I think we overthink things way too much on this board.

 

[bpenrod]

JTHacker / TNelson,

Do both the trucks have an EZ on them? I've been running one for a long time then put a Ramifier on for a test drive. After putting the EZ back on I had a similar problem, maybe even worse since mine stalled out a few times. I finally tracked it down to the MAP sensor connector not seated all the way. I tried for half an hour to get it together and could not. When I looked inside I saw the weather boot was torn and folded over. I took the weather boot out and packed it with electrical grease and put it together without the weather boot. That was back in July and I have never experienced it again.



PS, for what it's worth I start out in 1st most of the time unless racing, then usually second although I read a drag race test somewhere that stated the truck was quicker with a third gear start (on the 6 speed I believe).



Bill

 

[JThacker]

I run an EZ on mine and looking at that connector is a good idea. Tell you what, I noticed with the EZ it seemed to drop to about 550-600 when clutched like without the EZ but with the EZ it jumped higher after the drop like to 850-950 versus 800-850 without the EZ, but only recently strarted doing the vibration when it dropped and it does the vibration with and without the EZ, I will check my connections on Monday when I go to the dealer. Thanks Nelson for the info, that will help on Monday. Well, I may just have to live with it, Nelson, keep me updated as I will do the same. To clear up any misconceptions on close inspection I never normally let it get below 1200 before clutching. My only worry is this is a harbinger of something down the road which will give out, who knows.

 

[CTD 600]

I start out in second gear all the time, unless loaded. I have the same issue of the idle bouncing back when releasing the clutch and coming to a stop. I guess it is just something that is normal. The only thing I can guess is happening is the release of torque from the engine when the clutch is engaged. This would cause the rpm's to lower to idle. But... why do the rpm's go below the idle and bounce back above the recommended 750rpms?

 

[DIESELMAN]

If your dropping to 600RPM with the clutch engaged, don't do that. The engine is trying to run at idle and your lugging the engine.



As for the '04. 5's dropping to 600 then up to 800/900, then back, finally settling on idle. Its programming, its normal. The PID loop that controls the Rail pressure is slow, it needs less proportional and more derivative gain. They may have backed off for emmissions to reduce fueling quicker when the load is removed, or possibly to prevent the turbo from barking as badly since it is smaller (compressor side) than the '03/'04 was and will spool down quicker, but will also stay spooled up higher on smaller amounts of no load fueling than before.



Or maybe Cummins said thats good enough, forget about it... .....



It is annoying though isn't it?