I've noticed this since I've had the truck (a year). But lately it's really starting to bug me because it does not make sense. Driving the truck normally there are no problems (Generally because I never go above 2400rpm). When I give the truck a little gas in 3rd gear I believe... when I hit about 3000-3200 rpm the rpm's drop about 200-300 rpm. I think it might even happen in 4th gear. I'll check tomorrow... Also, the engine doesnt stutter or anything either it just drops 200rpm and keeps on pulling... weird.

Yes I've listened to the engine and it's not a speedometer problem and NO it is NOT the transmission shifting gears because a couple seconds later I hit 4th gear and it doesn't drop 200-300rpm it drops like 800. Any ideas?

Summary: Give the engine a little gas in 3rd gear let the rpm's spin up... BOOM in a microsecond the rpm's drop 200-300.

Thanks in advance.

 

Sounds like your rev limiter is set very low do you have a performance chip in it .

 

No I don't have a performance chip... you misunderstand though. The truck performs PERFECTLY NORMAL other than the slight drop in rpm once in awhile if i give it gas (or floor it)... if i floor it obviously it does the small rev drop and revvs all the way up to 5400 before it switches gears...

 

so it Hesitates a little is that what you are saying????

John

 

If I understand what you are describing, you may be seeing it go into OD. I see mine do what I believe is similiar behavior.

 

No, when it goes into OD it drops about 900rpm... its only dropping 200... ill videotape it sometime this week... then you will know exactly what im talking about.

 

when ur truck reaches a certain speed/rpm/load etc, the pcm locks the torque converter up for improved gas mileage. Yes, it drops about 200 rpm. When i first got my truck i thought i had a tranny prob, took it to Ford and everything. I discoverd that this is perfectly normal. Anyway, when u give it a little gas, it unlocks ur torque converter, almost unnoticed. And once again when u gain a specified amount of speed, it will lock up and thats what ur feelin.

 

I know exactly what you are talking about. When you are crusing at normal speeds and you apply just a little more gas, the rpm goes up, then drops off just a few hundred rpm almost immediately. My 99 w/ 4.6L has done this consistantly since it was new. It is related to the transmission but don't ask me why. I haven't tried to see if it does it with the OD off. Maybe I will just for kicks. Anyway, I would not worry about it. If you watch it while on the highway it will make you nuts. Everytime you put your foot down just a little it tachs up and then immed. drops off a couple of hundred. If you find out a definative answer let me know

 

mine does the exact same thing, basically what happens is when I am standing on it, around 3000rpms or so, it will drop off a few hundred rpm's, did it without a chip and with a chip, its not a hesitation, becuase the truck still pulls, my best explanation is like silver and blue said, torque converter going into lockup for economy reasons. I think its normal and only those of us that are super sketchy about our cars notice it.

 

what you're describing sounds to me like normal automatic tranny operation, There is no mechanical link between engine and transmission, there is only a fluid coupling, your torque converter. when you step on it then your engine revs up and a second later your torque converter kind of spins up to catch it and the load comes on your engine again and your rpms drop a bit. Don't know if this is explained very clear, but thats about the best I can do.

 

tater, what u described is perfectly right except for one thing. In certain circumstances there is a physical link between the engine and transmission. With the torque converters (tc) we have in our trucks they are equiped with a clutch inside of them. When ur truck satisfies this set of circumstances, the tc is locked ( i mean the flexplate is physically locked to the input shaft on the transmission thru the tc. This is only for improved economy and only happens in third and fourth gears on our trucks. So instead of fluid driving the input shaft on the tranny thru the turbine, stator and impellar it is actually linked directly to the tranny. Kinda weird, but it is pretty cool how it works. Anyway, thought i would try to clear it up a little more.

 

I do know about the lockup torque convertor also but it is not locked on hard acceleration, that's why I did not mention it. I thought it would only complicate my explanation, which I didn't think was very clear to begin with. I guess that's why I'm not a teacher.

 

Alright thanks guys that seems to explain it.