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Shuddering at the 18s

OverToyed
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OverToyed

OverToyed

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Ok.  Quadzilla is installed and now I'm chasing the problem that I think started when I had the Hamilton cam put in.

 

The truck shudders, like it's in some kind of harmonic, when:

*  Towing uphill (under load - it will do it when not towing but it's barely noticeable)

*  4th gear in TC lockup (I have a switch to force lockup and it makes no difference if forced into lockup)

*  Starts at 1800 RPM, about 21# Boost, IQuad says 18 timing

 

If forced into third and TC lockup problem seems to go away (but RPM boosts to about 2200)

 

I've tried increasing ans decreasing timing at the 1500 and 2000 mark.  It seems less if I set the timing to max allowed, but if thats the solution its not enough.

 

It could be a compression stall and the moter just cant consume that much air at that RPM but I'm hoping I can solve this.

 

Any ideas?

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OverToyed

OverToyed

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Driveshaft re-balanced and all u joints replaced.  I haven't actually blocked the wheels and aped the shaft sideways to test the center bearing support.  I suppose I could get dirty and do that.  But I would think I'd have the problem in a lower gear at the same speed and load since the torsion would be the same on the shaft?

 

But, after not listening to you guys on the grid heater issue, I better shut up and test. :)

 

Thinking gets me into trouble.

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OverToyed

OverToyed

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Me78569 - Looks like I have a one piece drive shaft and no center support bearing?

 

Mine is the quad cab - short box model.

 

There's about 1/4" of play when I twist the shaft with my hands (on jack stands in neutral).

 

Mopar1973Man - Are you thinking AC noise causing the TC to lock/unlock? Wouldn't the bypass switch eliminate that from suspicion? I did replace the alternator just for grins and it had no effect.

 

Edited by OverToyed
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Mopar1973Man

Mopar1973Man

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4 hours ago, OverToyed said:

Mopar1973Man - Are you thinking AC noise causing the TC to lock/unlock? Wouldn't the bypass switch eliminate that from suspicion? I did replace the alternator just for grins and it had no effect.

 

I wasn't figuring that was torque converter lockup per say. Maybe the AC noise is disturbing a sensor for the engine function and creating the shutter issue? 

 

Now re-reading the post again and thinking possibly is the clutch in the torque converter getting tired and slipping only in 4th gear while towing?

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Dieselfuture

Dieselfuture

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I would check ac noise and next thing would be injectors in my mind. Had something similar happen and I believe it was both, exessive ac and injectors out of wack. Pull fues for alternator and drive it on batteries, carful with ratchet not to hit ground. Assuming fuel pressure is good, coold be injectors but that one not sure how to tell for sure without pulling them out and testing them. Maybe good time to upgrade if they have over 100k on them.

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CTcummins24V

CTcummins24V

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2 hours ago, Mopar1973Man said:

 

I wasn't figuring that was torque converter lockup per say. Maybe the AC noise is disturbing a sensor for the engine function and creating the shutter issue? 

 

Now re-reading the post again and thinking possibly is the clutch in the torque converter getting tired and slipping only in 4th gear while towing?

 

What do you have for a torque converter? Single? Triple?

 

I had a billet single slipping (grab and slip grab and slip) in 3rd lockup and 4th lockup. Felt like slight shuddering, especially up hills.

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dripley

dripley

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Not trying to speak for Mike but he does have a 5 speed manual, but he does help folks with these issues quite often.

 

Me, I have a manual also but have been experiencing something similar of late. Occasionally a vibration at idle. Almost like an injector or cylinder not firing completely. Hard to describe though it seems to disappear under throttle for the most part but not always. When it happens, under hard throttle, it seems like the shudder you describe. Just installed new injectors and I believe it is gone. Not sure yet because I have only made one good run in it and due to the smokiness I did not pay attention to the other problems. I just kept trying to tune out the smoke. As I remember all was smooth under throttle no matter how hard I got into it.  

 Anyway, not sure that is part of your problem just my experience.

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Cowboy

Cowboy

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I've never personally had this issue, but I've talked with a couple guys that have.  After installing a cam, the turbo would bark while cruising with some boost.  IIRC, Hamilton suggested trying to loosen up the exhaust valve lash slightly and tighten up the intake valve lash slightly.  May not be your issue, but thought I'd mention it.   

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OverToyed

OverToyed

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It did seem to start with the cam, but I hadn't towed for a long time before I put the cam in so it could have been there all along and I didn't notice..  I've talked to Hamilton and all they could offer was to install a less aggressive cam, because, you know, changing a cam is just like changing an oil filter.  Right?  They didn't say anything to me about changing the valve adjustments.  First I've heard of that.

 

It will do it under those conditions without towing but it's harder to generate the problem then.

 

TC is a triple disk from Suncoast with about 200 RPM lower stall. Managed to talk Suncoast into a warranty exchange so it's actually on it's second one with no change in symptoms.  TC has less than 15k miles on it.  The TC was the first thing I suspected.

 

Injectors have about 30 k on them.  Is it possible that at a certain RPM/Fueling one of them has a problem and that one cylinder having a problem is what I'm feeling?  It does seem that if I dial down the fuel from 1800 to 2100 the problem decreases so it could be a fuel problem and nothing to do with timing?

 

As for disconnecting the alternator I think I already tried that once with no effect but it's such a simple test it couldn't hurt to test that again.

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OverToyed

OverToyed

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Standard gears, Just bought new rims and tires two months ago - no  effect on the problem though they are about 4" taller.

 

It seems to go away if I can shove it through about 2100 RPM.  Putting it in third with TC lockup (turning OD off with TC lockup switch on) sets it to 2100-2200 RMP and no problems there.  That's why I was considering compression stall since the motor can consume more air at 2200 RPM.

 

Problem with the overdrive?  Complete guessing.

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OverToyed

OverToyed

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410s(?) 355(?).  That's about 65mph?  I think?

 

I did not get the lower geared diff for towing.  Seemed like overkill way back in 1999 since after buying the truck I couldn't afford to buy anything to tow anyway.

Edited by OverToyed
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OverToyed

OverToyed

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By Me78569 in Axles, Suspension & Brakes, January 26, 2016

      You can use this Spreadsheet to change the Gear ratio and tire size on your Cummins powered Truck  You will...

 

I shudder to even start down that road until I have this problem worked out and I'm really rich and really really bored.

 

:)

 

Edited by OverToyed
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OverToyed

OverToyed

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I'm not quite ready to surrender on it just yet.  I think I can feel it waffling at the 1800-ish RPM range at other times now.  Maybe that's because I screwed up my tuning, but the electronic noise affecting something else is an intriguing thought .

 

CTcummins24V's thoughts have my interest on that piqued.  Now, if there's was only a smart way to test....  Where did I put my oscilloscope and my knowledge of how to use it..... 

 

I guess disconnecting the alternator and running on batteries for a while would be the best way.  I swear I've done it before but its such an easy (cheap)  test I might as well try twice.

 

Edited by OverToyed
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