Noticed yesterday on the intersate the truck has a slight "feeling" that it's surging when on cruise control. Take it off criuse, nice and smooth. No changes in and gauge readings. I can just feel it in my butt.

What could it possibly be?

Should mention this is a new problem. Never had it prior to my injector and chip mods.

 

No advice, but i have the exact same issue. it started about a year ago and would only do it occassionly. Now it is every time when i set it at highway speed and slightly more severe. i do not use the crusie any more due to the problem. i do not think mine is due to any mods, since it worked fine for many years after last modification. looking forward to any help.

 

well stay tuned! I hope someone is going to know what causes this.

 

The RABS on the top of the rear diff might be the problem. The CC uses that signal to determine if more/less throttle is needed to maintain speed. It also supplies the signal that operates your speed-o. The speed-o might be waving just a bit at the speed where you feel the surging...it needs to be rock steady.

If you have been inside the rear diff lately......the exciter ring on the ring gear may have been bumped causing it to have a little run-out. Remove the RABS and look down though the hole and watch the exciter ring while turning the drive shaft. It should be running straight and true. It doesn't take much movement to produce a 'dirty' signal which can also cause the CC to surge.

 

I agree with cuda jim ,i had the same problem for a few years and didnt know wht the problem was until i got on this site,changed out the vss and problem went away.

 

If you decide to get a new sensor be sure to ask for a RABS. (Rear Anti-lock Brake Sensor)
A VSS will get you the wrong part.....unless they fixed the parts books.

 

thanks Jim. The surging feeling occured at 70 MPH. Today headding to work cruise control at 55 mph was nice and smooth.

I'll take a look at the RABS, remove it and inspect the exciter ring. If I find the ring is not truning correctly, what's entailed to fix it?

hopefully the RABS just needs replacing. Would NAPA have the part? Idea's on what cost it should run?

 

Ok everyone. I seemed to double post this thread last night. OOPS!

I'm going to stay with this thread and abort the other....BUT Old_bird made a good point from the other thread that I would liek to move over here. He thinks it may be a chip related issue. his cruise control started this when he recently upgraded to the adrenaline HPOP.

I have another problem that just started when I put the chip in as well that may very well be corrilated with the cruise control issue. The truck doesn't start very well on all chip settings except on the high setting, the 140 hp. All other settings including stock start very odd. The motor will begin to run at 500 RPM (lower than normal idle) then lope 5-12 times between 500 and 800 rpms then smooth out at 700 rpms (norlam idle). I can stop the loping if I give it a little gas and raise the RPMs to 900 or so, then ease off the pedal, it will then go to idle quicker.

Could both of these problems possibly from my recently installed chip?

 

It's not a chip related issue... At least not on my old one. Did it with or without a chip even installed on the pcm. I never did figure out what cause it before I sold the pickup. Swapped the speedo, RABS, everything with no change. I never pulled the diff cover to see if that ring was out of wack.

Drove me insane though. So good luck.

 

drove it during lunch and set cruise at 65 and it was smooth as silk. Wonder why it only does it at 70?

I'll be taking it down to lake cumberland next week and was hoping to have the cruise fixed by then. But maybe it's going to be one of those phantom issues for a while. I wish I knew of someone around here with an obs diesel. Then I could swap their RABS out and see if it makes a difference. don't really want to through money at it until I can narrow down the problem.

 

having a spare vss in your truck is not a bad thing! buy one to test it with than throw the old one in the glove box with the cps.

 

Good point.


What does VSS stand for? I should ask for the Rear Anti-lock Brake Sensor RABS right?

according to cuda jim

 

Vehicle Speed Sensor. Some vehicles have a single VSS in the tranny or diff, and ABS sensors at the wheels. Ours use one sensor for both. I've been wondering what wrong part a counterman could come up with if you asked for a VSS.

 

RABS is what you ask for. As Jim said, if you ask for a VSS they'll give you the wrong sensor.

 

I lways order it as a vss and get the right part, but I replace quite a few of them and my parts man knows what it is.