2003 HR Neptune Cummins 5.9 Allison 2000 Having jerking problems first gear/accelerat

[Evugrandtour]

Hi.

I have a 2003 hr Neptune with Cummins 5.9 Allison 2000 tranny. It’s jerking when take off but only the very beginning when it’s given too lil gas. Once pass the 1500rpm at first gear it’s fine.

Would this be a tranny issue or something else?

Thanks

[Gary RVRoamer]

Before you start into diagnostics, have you changed the fuel filters? Poor fuel delivery can cause a lot of flaky performance issues, including the one you described. And to a lesser extent, so can a dirty air cleaner. When a diesel isn't performing normally. new filters is always the first step.

[Evugrandtour]

Hi. Yes the fuel filter was changed. So I thought about that too and when cruising on the free way 45-50 and barely tapping on the gas it doesn’t have that issue. It was sitting for a month and when first started up the check trans light was on with the stop engine. It didn’t have any power. So we shut it down for a minute and start it back up and the light went away. It drove fine (but with that jerking problem on beginning of first gear)

[153stars]

I would still lean toward fueling or motor issue. Look for leaks in boost side air from turbo are you getting normal boost pressure.
Try to see if you can retrieve any stored Allison codes using key pad diognostic and engine code if you can. More common is low voltage or bad ground to TCM or VIM triggering issue with Allison. A few times reseating plugs fixed an issue. There are few and far between real internal problems with Allisons. The most common is internal issue with internal wiring harness.

[wolfe10]

And, on that chassis be sure to check the REAR TRAILING ARMS. The originals and the replacements made to OE specs FAILED.


There are much more robust trailing arms available. If you have the OE design, replace them!


And, a broken trailing arm that allows the rear axle to move around will sure cause vibration.

[Evugrandtour]

Thank you everyone for your input