Slow R.P.M. Dropoff

[D808]

Big Red the Second is an awesome truck!!!!! (2003-3500 4X4 Quad-Cab Laramie Dually with HO Cummins, 6-speed and 3. 73 axles). However, I do have one concern... Between shifts the engine R. P. M. 's drop off slower than with my previous 1996 5-speed. Although it doesn't seem to create a problem when shifting, I'd like to get some input from others out there.

 

[yogibear]

I noticed that too. I had a 00 6 spd. It sure pulls nice tho, course it should with 70 more horses under the hood.

It will take some getting used too. Don't know what caused it, must be the fueling system.



Larry

 

[JWerkheiser]

I noticed exactly the same thing and was bothered by it at first, but now getting used to it. You definitely want to let off the pedal WAY before shifting or it will rev on you when you push in the clutch.

 

[Casey Balvert]

I noticed the smoother application and release of throttle as well. Doesn't jerk the driveline like it would in my 97. I like it.



Cheers, Casey

 

[Vaughn MacKenzie]

I think CBalvert hit it, D/C likely programmed that in to keep engine speed closer to synchro speed to smooth out shifts ,and also to minimize the jerky deceleration when you let off of it while you are still in gear, in the lower gears.



Vaughn

 

[athompson]

It's probably for emission control

I had a carburated car in the early 80's that had a special solenoid that slowly allowed the engine to get back to idle. This was all to reduce emissions during decceleration.



By the way, it also had a manual transmission.

 

[JRG]

I agree, could be related to emissions.



JRG

 

[nickleinonen]

Re: It's probably for emission control

Originally posted by athompson

I had a carburated car in the early 80's that had a special solenoid that slowly allowed the engine to get back to idle. This was all to reduce emissions during decceleration.

that solonoid was also to prevent stalling on automatic transmissions. without it, if you released the throttle quickly, it would stall from the drag the automatic transmission causes. if i can find my papers from school last year, i can get the name of that solonoid. . *edit* throttle return dashpot or anti-stall dashpot are/is what that little solonoid is called



i don't see how slowly coming off the throttle will reduse emissions. getting into the throttle slowly does reduse the soot produced, but coming out of it slowly... i can't see what emmission it can help reduse. like above people have stated, most likely to ease in shifting

 

[Pat@BD]

The slow drop in RPM was done for emmisions purposes. It ensures a cleaner burn of all the fuel while returning to idle.

 

[nickleinonen]

i guess i was wrong... oh well. . i just don't see why they do not turn off the fuel and cut it back in when it is at idle speed. even less emissions if there is no fuel being burned and it would slow down a bit quicker too.

 

[D808]

Thanks Guys! I'm glad to hear that the slow R. P. M. drop-off is normal for the 2003's. I don't believe the drop-off is actually as slow as it seems though. Perhaps the sound from continued fueling is a little deceptive.