4th & 5th Converter Lock = bucking/slipping

[cRaZy8]

Ok, so I thought this was originally an engine issue.
My stupid @$$ didnt put the two together to realize its a trans issue.

Heres what happens-

-only on the highway
-noticeable on flat ground, but more so on a hill/incline
-only happens with slight throttle input (20-50% throttle, roughly)
-only after trans is up to 140* or higher
-only in 4th with lockup, and 5th with lockup (via Edge Insight)
-truck lunges/bucks/shakes with slight throttle application
-smash the throttle and it screams, no issues
-if you hold the throttle just to maintain speed (or decrease speed as you inclince), it wont do it
-much more noticeable with my boat in tow, higher load on engine/trans (boat, trailer, gear weighs about 5k)
-no codes
-all engine parameters stay solid during the bucking
-FICM 50V+
-RPM does not flicker
-ICP voltage solid
-HPOP psi steady
-Fuel pressure never drops below 59psi, usually steady at 61-63*
-ECT never above 195*, 205* max towing
-EOT never above 195*, 202-203* max towing
-Both near 189* while around town

Recent maintenance or upgrades since the issue started-

-Trans fluid drained around 75k (91k on clock now), new pan gasket, filter, and TP filter, Mercon SP, fluid level dead nuts in the middle the "H" when around 160*
-8 new injectors
-new frame mounted fuel pump
-BPD 53V FICM, 6phase unit
-BPD tested Logic board FICM
-IDP FICM tuner
-FICM wiring harness
-Shell T5 Rotella
-Shell Rotella ELC
-Fuel filters every 5k miles
-Front & Rear diff fluid changes
-Transfer case fluid change
-New HG's (Black Onyx failure)
-ARP's
-New OEM Ford turbo (not a rebuilt)
-IDP long Y-pipe (EGR delete pipe)
-Riffraff Diesel intercooler boots

You can see my sig for other mods.

As far as running goes, this truck is beast. Cold starts awesome, never misses a beat. Tons of power, never smokes. I get a puff of smoke on start up, but it clears up in 2-3 seconds. She blows a little haze on a hard run up the highway ramps, definitely not a cloud of smoke. She can handle around town towing in 100* temps with a 30ft Grady White (about 15k with trailer/gear) with no issues.

I am bringing it to a local tranny shop this week.
I went to the dealer a little while back, and brought a boat with me, and he hooked up the scanner for the test ride. I drove he watched. It acted up, and he said it was a fuel issue. Seeing that I have since replaced everything in the fuel system besides the tank and lines, I highly doubt that.

Seeing that the problem is only in 4th & 5th during converter lock, I am ruling this to a trans issue. Also, having no codes, and a dealer tech in the truck with a scanner, and not seeing anything.

Ideas?

[cRaZy8]

No tranny experts out there?

[06DZL]

I would find someone with a scanner who can run a cylinder contribution test. It actually sounds like a bad injector.

[spoonfedblue]

^^^That's what I was thinking, I see that all the time with gassers. As soon as the converter locks up, any load increase on the engine, ESPECIALLY light loads without a downshift, will make a misfire show up almost immediately. Cylinder contribution test should be your next step. I bet you'll find you've got a cylinder dropping out, those are classic symptoms of a misfire on any vehicle.

FWIW, I'm a trans tech at a Chevy dealer , so I can back that up

[cRaZy8]

I cant rule out a bad injector.
But the problem was there before I changed all 8 injectors.
And its still here after changing all 8 injectors.
How likely is it to be an injector issue on two different sets of injectors?
I didnt have mine rebuilt, I bought new units.

I installed a new ICP sensor, problem still there.

ICP voltage & ICP psi are both jumping back and forth when the shake/shutter happens.

The HPOP builds 4000psi when you smash the throttle.
When this problem is happening, I am thinking the IPR valve (which is a stepper motor) is sticking at that one area it is trying to regulate the pressure.
When the problem occurs, the ICP V goes from 3.0/3.1 down to 1.5/1.6V.
Pressure drops about 300-400psi, somewhere around 1800-2200psi.

[cRaZy8]

And yes, my thinking is like this: HPOP is gear driven from the crank, the STC fitting connects the pump to the branch tubes, branch tubes connect to oil "logs" on top of the injectors, o-rings seal the logs to the injectors, dummy plugs and stand pipes are sealing the logs to the branch tubes. The IPR is regulating the oil flow to the system. If the pump builds 4000psi, the system is sound. If I have fluctuating pressure, the only item telling the HPOP to deliver the needed psi is the IPR. The ICP is only checking the the IPR, to make sure its delivering the specified psi to the system.

Right???

[Galaxie]

I think this is a trait of your tune. Will it do this on stock or with your tow tune?

[Ropegun_1]

I just posted a thread in the performance discussion board with the same problem. I was advised to check VGT plug as it can work lose. I am interested in if you find a cure. The post regarding the issue being tune related is also interesting. I am running Eric's Tow Tune but dont remember it doing it stock......

Kris

[Face Down]

Got the same problem.....subscribed!

[Face Down]

Just found this...I can say my truck does not "buck" when I am using the cruise.

2005-07 Bucking/Jerking when Towing:
Trucks that exhibit a bucking/jerking sensation at steady speeds in tow/haul when towing large/heavy gooseneck trailers that typically goes away when the accelerator is completely released or depressed fully, and does not occur when using the cruise control, may be caused by movement of the driver's foot after hitting a bump in the road or triansmission upshift in combination with the particular trailer load. There is a revised computer program to make the computer less sensitive to minute accelerator pedal inputs. If reprogramming does not resolve the issue, the problem may be due to the hitch, the trialer or the loading of the trailer. TSB #07-6-9.