strange jolt

So while cruising at around 60mph in O/D, if I let off the gas pedal quickly, I sometimes feel a slight jolt.

Then while coasting at around 60mph if I press the gas pedal quickly, I almost always fee the same jolt but now a bit more sharp.

However if I press the gas pedal gently while coasting at around 60mph, the jolt does not occur.

What is causing this? Anyone else have this? I have the 4 speed AUTO.

 

Are you running stock rear springs?

 

stock rear springs yep! However, the situation I'm talking about is not coming to a stop.. I'm still coasting at around the 60mph range.. it's just letting go off the gas completely causes the jolt. Then stepping on the gas quickly creates the jolt again.

If I ease the gas pedal, the jolt does not occur.

 

None the lees, "wrapping" is still occurring.

Both of those actions, hard acceleration and deceleration, apply and release torque. Weak springs twist and release excessively which you are feeling.

 

It seems that more and more of our wonderful trucks are falling victim to axle wrap...

 

Is the truck shifting gears when you fell this jolt? Could be stiff gear changes that cause this slight jolt and slightly more of a jolt?

I'm not sure, could be something else, like mentioned up above.

 

You mite have on of these in your cup holder! haha sorry bored!

 

Hmm the acceleration and deceleration I'm referring to is not hard.

I merely let go off the gas as if approaching a yellow and preparing to stop.

When I step on the gas, the pressure I apply barely results in RPM increase, not enough to increase the speed.

At lower speed range such as 35-45mph.. the same action on the gas pedal does not result in the jolt. Would axle wrap explain this?

Finally, I've applied the U Bolt mod on my rear springs which has effectively rid of the axel wrap jolt at dead stop around 85% of the time. The jolt with the gas pedal at 60mph occurs almost all the time and feels different than the typical axle wrap

I don't think it's shifting gears since the speed remains at around 60mph.. I can recreate the jolts consecutively simply by letting off gas and then stepping on it. Speed doesn't change much during this time.

 

just a thought, is your cc cable kinda loos on your throttle? maybe when you let off of your pedal the accelerator cable is tight but if the cc cable has slack in it. When it catches, that might cause the jolt?

 

CC = Cruise Control cable? How does that affect it?

Just did more testing... the jolt when letting go of gas is MUCH less obvious than stepping on the gas with moderate pressure...

 

the cruise control cable and the accelerator cable are both attached to the throttle. If the cable for the cruise control has a good bit of slack in it, i.e. it isn't tight with the throttle sitting closed, then that might affect when you activate the cruise control. When the cable finally gets tight from the cruise control activating, that could be the jolt you feel when it pulls the throttle open suddenly. It could be less of a jolt when you push on the gas pedal because the cable is already tight due to the cruise control being on.
have you looked at your accelerator/cruise control cables to see if they're adjusted properly or snagging anywhere at all?

 

Well unlike everybody else here that jumps straight to the conclusion that its axle wrap.
I'm going to say how about checking out your motor and transmission mounts, maybe one of them let go.

 

my 03 doesn't have cc cable i think. it's got a throttle sensor unit... only the cable linking the pedal to the sensor.

the sensation is just like the shift jolts you feel thru the lower gears when you accelerate rapidly from dead stop.

what are signs of failed mounts?

 

you have to look at them and see if they are cracked or broken.
Also pop the hood rev the engine, if you see it moving with the brust of gas its motor mounts

 

Okay revved the engine and the motor does rock a bit.. looking at this video.. the engine also rocks a bit but it's hard to tell how much he had it revved since he's not running a muffler.. but this video shows the same type of movement in my truck. Is this sign of failed motor mounts?

http://www.youtube.com/watch?v=6bsFMJ8f-gg

 

sounds like the torque converter locking/unlocking