Hey guys/gals(?), I've been wondering for a couple of weeks about this. Maybe someone else has had or is experiencing the same thing.

Basically anytime that I am decelerating like coming up an off ramp, up to a stop light or stop sign, once it reaches about 1000 or 900 rpm it will surge up about 100-200 rpm and then continue decelerating down to normal idle speed. Just a little blip in engine speed, but it happens EVERY time without question.

The 'scary' part is that it does require a little extra braking pedal to overcome the acceleration of the truck. I don't recall the truck doing this when I first got it, and since I've added the MagnaFlow. I don't believe its related but could it be? I did have the battery disconnected for three-four hours while installing the exhaust.

Anyone hear of this? Any help would be aprreciated!

 

I haven't run across this with my 06 QC but if I did I would try a little test.

Lock the shifter into D1 and drive. Run the rpm up to say 3k and coast. See if it repeats the action you describe.

I suspect it is the auto trany downshifting as you slow. Locking it in 1st gear prevents shifting. If the symptons repeat, it is an engine thing; otherwise it is in the shift pattern of the trany.

Perhaps a few others may be able to shed a little light. IMO

 

Your vehicle is downshifting.

 

Well you guys are right. I locked in D1, D2 and D (Tow/Haul aka OverDrive Off) and in all cases the engine/transmission didn't do the idle bobble thing.

So now I know it only does it if in D and from higher speed decels. But, I guess I still don't understand why? Shouldn't it happen when in D "tow haul" or even form D2?

Trest - Does your truck/engine do the same thing?

Would disconnecting the battery again possibly reset the adaptive memory and cause new shift points to be re-learned?

 

Cause its downshifting in normal auto mode the shift pattern is designed to be smooth, making it downshift yourself it doesnt give a rats *** how smooth it is.


And yes mine does. I noticed on my 3.9 after the ehxuast it seemed more noticeable tho. Havent done it yet on this truck to tell tho =)

 

I guess I was thinking that even when in D - Tow/Haul or in D2 the transmission downshifts eventually to 1st gear but will only upshift as high as the manually selected gear, correct? Thus the similar downshift event should still be happening from any gear?

Now I've noticed (I think) it will only happen if I am decelerating from top gear (maybe 4th as well) while in D - normal. For whatever reason it doesn't appear to happen from 3 or 2 to 1. Is it possible that durring decel the trans is attempting to go from 5 or 4 straight to 1 which it wouldn't obviously be doing if in 3 or 2 and decelerating?

You are also correct that it is probably just much more noticable with the exhaust since it is now much more audible.

 

yes you computer is telling your tranny to slow down and it is locking up the convertor. next time you come to a stop turn your radio off and listen to the dash board. there is another computr in there and when it makes a signifigant noise you will fell the truck lock up

 

i have the same problem on my 01 4.7 durango automatic. i've had borla exhaust from the begining, just started noticing it recently (80k). i have changed the plugs to ngk a while back. i'm going to change them back to stock. i'm running out of ideas what it could be.

 

It probably is the trans, but I noticed something similar after getting my magnaflow.
My truck takes a few extra seconds to drop rpm whenever I clutch it. Like it wants to keep running at 2k or 3k rpm.
It didn't do that with the stock exhaust.


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