Engine/Transmission (1998.5 - 2002) A "Hopping" feeling...

[plongson]

This is hard to describe, but when pulling my TT (load is usually 15k to 17k GCWR) up a hill, and I am really getting in to it hard before I would drop a gear, I get this feeling in the truck like it is "hopping". It only happens in 6th and goes away after going into 5th. At first thought it was the clutch slipping under the load and torque, but I got rid of the NV4500 and stock clutch and put in a NEW NV5600 and SB CON O/FE. I have about 6k miles on the trans/clutch now. This lets the clutch off the hook. I have new Bilstiens all around and air bags. It pulls like a "Raped Ape" and dosen't feel like it is really going to damage something, but it is real annoying. Has anyone else felt something like this???

 

[Boondocker]

I haven't experienced that while towing, but it sounds like axle hop. Without traction bars, the torque load under acceleration, normally at launch from a stop, rotates the axle down, the springs try to pull it back up, which can cause bucking. Maybe when you're pulling in 6th, the raped ape is making too much torque for your wheel speed.

 

[bmoeller]

Any change in fuel pressure when that happens? Or are you lugging the engine before you shift? You are lugging the engine if you give it more go pedal, but can't pick up any RPMs.

 

[plongson]

it sounds like axle hop.





GREAT thought…and that is really what it feels like now you mention that theory... That could be what it is. I see you are from Nevada... You know how the pavement gets rutted from the big rigs in the summer heat making the asphalt soft... Some of the grades (like I-15 south of Mesquite at Riverside) are especially bad and appear to be wash boarded as well. This pavement condition really aggravates the condition. HMMM. wheel hop... you could be on to something... . THANKS...

 

[plongson]

Any change in fuel pressure when that happens? Or are you lugging the engine before you shift? You are lugging the engine if you give it more go pedal, but can't pick up any RPMs.

No change in FP. Got a good LP and hold 12+psi. I wouldn't say lugging, RPM is around 1700 to 1900 but really pulling hard and probably near max torque. I honestly can't run with my foot planted because of EGT. But in the winter at lower altitudes with good thick air, it will blow about 32psi boost and only have about 1150° to 1200°.



I like the wheel hop theory... It really dosn't feel engine/trans/clutch related.

 

[SnoKing]

Lots of people report similar shudder with both auto and stick when pulling hard at lower RPMs. Would be nice to know if in is rear springs flexing to power pulses. Tractions bars would fix it then. There is one hill going to the ocean that I get it on. Road surface is also a possible cause. At any rate I will drive the same route later today with the trailer in tow. SNOKING