I noticed this a couple of days ago and has been happening since. Crusing on the freeway lets say 65, I turn on my cruise control and set it. My RPM's are at ~1800 (dont remember exactly) As I am driving my rpm's shoot up and down, not much 1800, 2000, 1800, 2000. But the vehicle maintains constant speed. It happens for a bit, goes away and comes back. Happens @ 55,60,65 etc mph. I believe it's the TC locking up and unlocking. I dont understand why, the road is level and flat for the most case. If I was driving through some hilly roads, then ok. My fluid level is normal... Could it be the TC, electrical? Questions, comments, suggestions. Take it to a dealer?


DakaDan

 

Wouldn't the TC unlocking have more like 400-500 rpm jump? My 93 jeep GC 5.2 had about that. My current truck just stays locked almost all the time when in 3rd & 4th gears and is really hard to unlock the TC... when it does, it is just before a down shift. Does this only happen w/cruise on?

 

Could be the Air Conditioning kicking in and out.

 

"Could be the Air Conditioning kicking in and out. ".... good point, but wouldn't you only see a change at idle & not higher rpm's? Are you thinking the load of the AC is draging the rpms down?

 

It also happens why I driving normally/constantly with the Cruise off. A/C is off, btw.

 

When the air conditioning is off but the defroster is on, the air conditioning compresser will still cycle to dry the air. I'm not sure how much if any cycling it does while in heater mode or off mode. Anyway this was just an idea to throw into the pot, it could be something else all together.

 

I just noticed the exact same problem on a long trip this weekend. I have a 02 5.9L Quad Cab. It's independent of whether the AC is on or off. My RPMs would show a 200-300 RPM fluctuation and the tach would bounce up and down ittermittently. I noticed that if I gave the truck more gas and caused it to up-shift, the problem would disappear for awhile and then return.

Any luck on your inquiries?

 

I have had the exact same problem on my 01 Ram. I have had the trans fixed and the TC fixed and it still does it. I have tried to have Dodge look at it but they never notice the problem when they road test it. Try it with the Cruise Control on, it seems worse that way. I believe it to be something with the Towing package and the clutching in the trans, but I can't be certain. Mine's under warrentty so I'm not that worried about it yet.

 

Mine is doing the same thing - 02 5.9l.

I brought it in on Saturday - they think it is tranny related since there is a sensor between the transmission and cruise control.

It never happens when off cruise - and can be prevented by putting a bit of pressure on the gas pedal while cruise is engaged.

I told them that is seems that whatever grips the throttle wire is slipping - and fix that.

Unfortunately - this will be another multi-visit problem.

It's a good thing the truck looks to nice...

Dave

 

Please let us know when/if the dealer diagnoses the problem. Since you mentioned you're only having the problem on cruise, I thought I'd mention that I first noticed the problem on cruise control, but since initially noticing it, I've found that the same problem occurs at constant freeway speeds when it's not on cruise. The one thing that seems to temporarily solve the problem is forcing the tranny to shift by pressing on the accelerator.

I'm wondering if it's a bad sensor in the tranny, because every time I have the problem the vehicle is within about 500 rpms of an up-shift. Interesting to note that we're all driving 02 5.9L trucks.