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?

You could rebuild the alt.  I think mopar1973man had a post about where to get the parts

 

L8tr

D

CTcummins24V you might have nudged Mr in the right direction.  I replaced the accelerator position sensor because I hadn't replaced that yet.  

 

Then I noticed there was a way I could move alternator wires to give a couple more inches of clearance and after a test drive I didn't feel the problem.

 

Tomorrow I'll drag the trailer around since it's far more noticable with more drag and I'll know for sure.

Well damn.  That wasn't it either.  Now I'm considering an injector problem.  I did see a post about a cracked/sticky injector causing shuddering, more noticeable after trans lockup.

 

So, on Monday, I'm pulling the injectors and sending them to DDP for testing.

 

 

Well....  Before puling the injectors...

 

What about the harmonic balancer/damper?  I didn't realize that part is something of a consumable part in the 1999 year.  I understand later they went to a fluid filled damper but in my year they were still using two plates with a rubber separator and the rubber eventually breaks down.

 

I was reading that the stock damper is designed to damp what the engineers considered predictable vibrations.  But, as we add power, we change the vibrations and can make them more severe.  There are fluid dampers available now, for like $400.

 

Any thoughts?

Imo it would be shuddering all the time.

There's a SLIGHT vibration at other speeds, like a wheel a little out of balance, but at about 1800 it really gets noticeable and then drops out about 2100.  Fluid balancer is on order so I'll know for sure about

Thursday.

FIXED!  I have been chasing this problem for a frigging year!

 

Five mechanics in five different shops and NONE OF THEM looked in this direction.

 

There's still a slight shudder around 1800 that maybe the fluidampr can't cope with or, hopefullly not, the bearings have worn from a year of vibration.

 

MUCH easier to spin up, power is much more accessible.

That's great news! glad you got her figured out.

Man that's hard to believe, update us in few months to make sure, other than that hope it's what it is. Wired things do happen. 

I'm now almost wondering if something internal isn't screwed up and fluid damper is compensating for it, and that is why you still have a slight problem.

Great to hear and hope that is the last you have to deal with that.  

 

L8tr

D

You're right, I'm hoping the damper isn't helping to hide a different issue.  This did show up after the cam, sittings, rods and studs were added and the rods at least would change the reciprocating mass.

 

But, we'll see where I am in a month.

I would consider trading the stock dampener back on and seeing if the problem changes. If so then I would be looking at the lower end.

I already tossed the old damper.  The drive shaft has already been re-balanced and all the U joints replaced.

 

The new dampener did smooth it out but I can feel the problem still.  one thought is a cracked injector that's leaking when it's under heavy load.

 

What else were you considering I look at?  The diff looks fine inside, visually, but I'm open to external wisdom.  It does have the limited slip diff.

Edited March 13, 20178 yr by OverToyed