2008 6.4 bucking/jerking violently while towing

syrupdawg

syrupdawg

GA Diesel Mafia
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Mar 16, 2008
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My friend bought a used 6.4 a few weeks ago. Its only got 117k miles on it and its a very clean truck. I got him a sct livewire and did the usual delete stuff on it. I got him some custom tunes from Eric at Innovative and they run good but he is having a problem when towing.

It wants to buck or jerk so bad that it feels like it is going to break the neck off the gooseneck. Erics street tune which is the light tow is what we were using and it was so bad that it was undrivable. We wound up going back to the SCT box tow tune. It still does it but it is not nearly has violent.

I googled and searched for this issue and found a lot people with the problem but no one really had a solution. I figured most people here are above the average intelligence of most forum members on the interwebz. Thank you in advance for any help.
 
Is it the torque converter locking and unlocking? Or is more of a fuel surging issue? Those are the 2 issues I'd look towards.
 
Gunnin said:
Is it the torque converter locking and unlocking? Or is more of a fuel surging issue? Those are the 2 issues I'd look towards.
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This, first 2 I'd look towards. Any way to monitor or record fuel pressure while it's bucking? Also does it only do it in that tune only?
 
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A friend of mine is having the same issue with a manual truck. Rcd 450 tune. Rail starts jumping real bad when it starts bucking.

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My 08 350 with Spartan tunes always did it loaded , on Spartans forum they blamed it on axle wrap. Take that however u want, my 08 sucked to tow with. Just my .02.
 
it's strange that some tuners talk about axle wrap, but some tuners don't

I'm thinking the issue isn't with the truck
 
It does it even on the canned SCT tune but its not nearly as violent. Don't believe its a torque converter issue as it will do it taking off from a light at say 10 mph sometimes. Sometimes it will do it going 60. Never really seems to have an exact formula to cause it.
 
Gunnin said:
Is it the torque converter locking and unlocking? Or is more of a fuel surging issue? Those are the 2 issues I'd look towards.
Click to expand...

It feels like you are pressing the accelerator pedal and letting off of it very very quickly. Almost like it could be a apps sensor issue but it only does it when towing
 
syrupdawg said:
It feels like you are pressing the accelerator pedal and letting off of it very very quickly. Almost like it could be a apps sensor issue but it only does it when towing
Click to expand...

Could be a pedal sensor but these trucks are known to have fuel surging issues. Might be a fuel rail pressure sensor or a hpfp starting to go bad. I'd find a way to monitor fuel rail pressure to see if its your problem.
 
Gunnin said:
Could be a pedal sensor but these trucks are known to have fuel surging issues. Might be a fuel rail pressure sensor or a hpfp starting to go bad. I'd find a way to monitor fuel rail pressure to see if its your problem.
Click to expand...

I heard the same story, they don't like to tow.
 
I have experienced different levels of this on 4 different trucks. The 08 CCLB we had was the worst. To me, it does seem like suspension issues, but they are brought to the light by the pedal being more sensitive by the tuner maybe? That is 3 different tuners, with 4 different sets of tunes as well. The 2010 450 was about the best, but it had Spartan, which on the 08 made it the worst. My current 09 cclb with a 6 speed will get into it when its loaded a certain way and its got a H&S on it. I was thinking a good set of ladder bars as the next step to see what that did.
 
on one of the forums a guy added a crossmember to his CCLB and it got rid of the bucking

some trucks do it some don't I guess
 
ACFarmer said:
I have experienced different levels of this on 4 different trucks. The 08 CCLB we had was the worst. To me, it does seem like suspension issues, but they are brought to the light by the pedal being more sensitive by the tuner maybe? That is 3 different tuners, with 4 different sets of tunes as well. The 2010 450 was about the best, but it had Spartan, which on the 08 made it the worst. My current 09 cclb with a 6 speed will get into it when its loaded a certain way and its got a H&S on it. I was thinking a good set of ladder bars as the next step to see what that did.
Click to expand...

Excellent idea.:clap::clap:
 
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