Bucking/shuddering while towing at 30psi ?

hashim

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Hello all, I have a 6.4 with the gear head tunes, the truck also has the afe stage 2 si setup, dpf/egr delete, cac pipe, running the street tune. It's lifted with stock gears 3.73 iirc and 40 inch tires. Stock trans , stock motor etc.... Problem I have is when I tow the truck starts to buck and shudder like it's cutting in and out around 30psi or whenever it hits a hill/incline or load I am usually doing around 65-70mph and my rpms are around 1800. When this happens I have to let it down shift then it will go away and I can speed up but when it up shifts again into od and hits the same rpms and boost it does the same thing. I have zero cels no codes or anything. Truck has 44k on motor. What are your thoughts?
 

Phiber Optik

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It's either the fuel rail pressure fluctuation or torque converter slip, both can be monitored with a tuner/scan tool...
 

Powerstroke Man 6.4

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Same problem here but instead for the GH tunes the truck has spartan tunes its a F-350 CCSB drw W/ 4.30's and it bucks when daily driving and towing. When lock in TC and just switching though the gears go up a hill or flat smooth road. trans got 30k on it. Fuel filters got 5K on them.
 
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Tree Trimmer

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with your tuner, moniter rail pressure, and mass fuel desired when its doing your bucking.

i had same issue, and he tweaked a few things, and it went away.
 

Rubenk

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Are you in cruise control when it happens? Mine will slightly buck if the CC is trying to lightly maintain speed up a hill. I have to foot control it to smooth out.
 

hashim

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I have traction bars, replaced u joints shimmed the driveline etc... It does the bucking/shuddering with cruise control on.....is there anyway besides using my foot to smooth it out?
 

Rubenk

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If its the CC doing it then youll need tune tweaking I believe.

I'd say we're lucky, heard of others having cruise go WOT to accelerate on races tunes lol.
 

TheRobenator

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It truthfully sounds like your torque converter. Your torque converter goes into full lock-up in OD and if it is slipping or your TCC Solenoid is going bad, it will go in and out of lock-up and promote symptoms acting like you have a bad injector or a skip. Check it with a scanner to make sure you are going into FULL lock-up and staying in lockup in OD.
 

BigPSD

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This used to happen too me all the time when I towed. Hit a bump and the bucking would start and not stop till I park it again. I racked my brain for months, thinking I needed traction bars, full leafs to get rid of the rear blocks, etc. Thought it was my tune, I know Spartan has got its fair share of blame out of it on other sites...

Wanna know what it was? Play in the hitch, there was about 1-1.5mm of play in the hitch receiver and the ball mount. I was also using an adjustable drop hitch. The slider also had a tiny bit of play. I guess at those speeds, and with certain amounts of weight, once you let the setup slack and introduce motion, it just goes thru the whole truck...

It could be the other things posted but its worth a look...

Now if I could just figure out the 2-1st gear slam shift at low speed...:cursing:
 
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hashim

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guys, thank you for your inputs well the bars I am running are the fabtech ones. I don't think these are solid type? The bucking and shuddering I am having feels like the torque converter or trans slipping. It's not a weight issue I don't think. I have an add a leaf plus the Firestone airbag kit in the rear. I'll monitor my slippage and report back.
 

Breaking Habits

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guys, thank you for your inputs well the bars I am running are the fabtech ones. I don't think these are solid type? The bucking and shuddering I am having feels like the torque converter or trans slipping. It's not a weight issue I don't think. I have an add a leaf plus the Firestone airbag kit in the rear. I'll monitor my slippage and report back.


Fabtechs are absolute junk.

On my truck all they did was eliminate uneven wrap. They do not help to control pinion angle. On my truck with add a lead and fabtech it wrapped more than a stock truck we compared to.
 

hashim

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Ah that sucks! Well I have a block and add a leafs. Does the ouo bars offer a clamp style setup around the axle vs the traction block setup? I really don't want to buy new blocks if I don't need too.
 

BigPSD

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Please check you ball mount...It was something that easy for me... Mine would get violent, like the truck was coming apart...
 

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