Since I bought my truck 6 mo. ago (it is an 02 and had 30k on it). I experience some "surging" (for lack of a better word) after the 1-2 shift and the 3-4 shift. This surging is the engine dropping a few rpms after the shift then recovering real quick. On the 3-4 it is more common, but 1-2 happens sometimes. This is especially true in the morning. If the outside temp. gets up in the 90's it will not do it at all, except for the first shifts in the morning. The dealership said to wait until it was cooler for a week so they can easily duplicate the problem - it is now in the shop. Before this I have tried: New fuel injectors, fuel filter, trans filter, changed trans fluid twice. The dealership has ruled out it being a driveability problem and believes it is a transmission problem. But they are not sure what is wrong. They say the clutches are not slipping nor does it seem to have any other "easy" type of problem. They have talked to GM - no other "common" problems like mine. Two questions: 1. Any ideas? 2. When a dealership cannot figure out what is wrong there is a process for getting GM involved in the problem solving/solution and that process has a name ("opening a ticket" or something like that) - what is that called? I am trying to be ready in case the dealership finally says - we can't do anything else to fix it.

Has the dealer reset all the garage tap cells? Could just be adaptive learn.


You are aware this is classified as a HD transmission and will shift like no other you have experienced.





Mac

mine has done this since i got it, it was magnified when i added the juice, it's really bad in the morning when its cold, its shifts hard and has that 'lag' after all except the 4-5 shift. goes away when warmed up. if you find something out besure to post!

Are you sure you are not experiencing defueling.
mike

good point, ill switch to defuel 4-5 locked only and see what happens. when i get the truck back from the body shop.... http://www.dieselplace.com/forum/smileys/smiley19.gif (caution, old ladies in parking lots can be hazards to your truck)

Well the dealership believes it is a adaptive learning problem, so they wiped out the "memory" and we are "learning" now. This has (so far) made things a lot better. But it does the lagging/surging about half as much as it used to do. At least all the documentation of what they have done continues to make it a warrenty issue with GM. So we will probably keep working on it.

I am experiencing the same problem, but only in OD when I get on the throttle a little and not necessarily after shifts. This only happens when the truck is cold. About 3 separate times I have run the Edge in level 5 (no more than half throttle) and the problem seems worse the next time I drive it back in level 2. Once the truck is warm, everything is fine. I agree with the transmission “learning” theory because it seems to go away after I run the truck in level 2 for a while. I believe the reason it only does it when the truck is cold is because the Egde is not adding any power yet, so the transmission is a little confused. For me, it is even a more exaggerated problem if I just came out of running in level 5 the last time I drove it.

IrvingTx.


Which dealership had your truck ?


Do you have any power adders, that might "mess" with the shifts ?

If this turns out to be something keep us posted. Mine too has done this from the beginning. Only on cold mornings (50's) and only the first shift or two. It has never seemed like it was a real problem to me as in a harsh shift or slipping and grabbing etc, just a momemtary increase in RPM before the gear ingaged.


I have no power programs etc. just stockEdited by: mightyvh

I have noticed these trucks CERTAINLY have surge due to spring wrap.
If you know what it feels like it is easy to spot.
The rear leafs wind up and unwind just a bit, but enough to make a
surge that is easy to spot. My truck has the 19.5 Ricksons which
exacerbate the problem.



Cold running makes the tranny a bit stiffer; the problem gets bigger.

Crew cab/long beds have it worse because of the interaction of frame
flex and driveshaft mount flex -- plus the motor mounts flex also.



The problem is worst in 1-2 and 2-3 because that is where the most
torque is available (torque delivered to differential, which is the
only thing that matters for spring wrap surge).



Just drive WOT in Tow/Haul mode -- you will never notice the problem.



My guess it the PCM is not tuned to deal with the resonant frequency of
the frame/leaf-spring/driveshaft deflection. If it is that is,
then the crew-cabs need a new program.



Generally speaking, this is a well-known problem. I had the same
issue with my '65 long bed and have similar problems with my '64 Malibu.

does your truck have any type of ECM power addon that you might have not known about since you bought it used?



i've driven a couple programs in the past that will do that... it goes
to shift, RPM's jump, it shifts, and they come back down... i always
called it a flare..

Frank_EP

You need to elaborate a lot more on what you just stated technicaly and tell us what program you are running because I do not buy this at all. No flame. Springs do not surge and neither do twisting frame rails. I have driven a lot of Duramaxes with every known program and not felt this surge. I have felt violent wheel hop where the pinion went up and down 6 inches ( nasty spring wind up) and not felt a surge. The only surge I ever felt was in the TTS race truck, and that was in my shorts. http://www.dieselplace.com/forum/smileys/smiley4.gif

mike

Here are the answers to some of the above questions:


The dealership is Jerry's Chevrolete in Weatherford, Texas


Options: I currently have no ecm mods, juice, tts, etc. It is stock.


Update: Since they wiped my memory and had the trans. "re-learning" it is better, (could be I just don't notice it as much), but really I think it is (adaptive learning) better. The jury is still out but it is looking good. Also I think "lag" might be a better term to describe what it does than "surge"


Thanks for the info. on this page.


Todd

Todd,


Aw...the shifting lag is definatly different than an engine surge.


Is the lag between shifts on hard accelerating. If so, that is probably the normal defuel the factory has programed for the Allison.


The annoying lag will come on hard hard acceleration... You press the fuel peddle to the floor, the truck may take off (or it may not, if it tries to go into a passing gear), but eventually it will take off, then hesitate big time between shifts, and then take off again. Mine used to really tick me off with those factory characteristics.


I don't have that problem anymore, but it ain't been cheap.


Greg McCall

I wrote a long, technical post, but Firefox ate it. Grrr.



Do some reading. Technical reading is best, but a search on "leaf
spring wrap" will get you started. Well know problem for at
least the last 30 years, with a foundation that goes back to GM chassis
research in the 1930s. Products on the market address the
problem. Rickson wheels make the problem worse because the are
HARD and tall. Frame flex, motor mount flex and 2-part
driveshaft flex are also known issues that contribute to surge.



This is the same problme as "wheel hop" -- unwanted energy storage in the drivetrain.



It helps to be mathematically specific, as there are at least 7 related
systems contributing to surge. It will be hard to have any sort
of useful discussion without getting into a particular part of reality
many people avoid -- multi-variate calculus. I do not want
to get into any hand-waving, name-calling voodo; in this instance, the
reality is rather complex, but still real. Arguments that
these trucks do not follow the laws of physics will not get you far.

Further Clarification:


My "lag" happens between shifts 1-2 and 3-4. At very light throttle. Just hold the rpms right before the shift for extra second or two and you will get a pretty good (surge, lug, lag) however it might be described. It never happens under heavy accelleration or WOT. It also happens when the outside temp is below 85 degrees. If it gets hot outside then it will only it one or two times in the morning and that is it. Rest of the time no problems. Below 85 you can get it to do it 50% or so of the time.


Todd

mine does it only if you start up and drive off, no warm up time. I figured it was due to cold temp and low psi in tranny fluid.

IrvingTx and others,


I think this is what was called a shift "flare"(quick spike in RPM's during shifts), and usually happens to me in 1-2 and 3-4 shifts in light throttle, more often when cold. It was discussed quite a bit on another diesel page a couple years ago. Seems to affect 02's mostly, or that's when it was being talked about alot. I can't remember if there was any detrimental affect of it or not, I would think not. If you wanna try to avoid it, give it a little more throttle and it will shift better. I'll try to see if the old info is still available of the other site, but it's been a while since that was talked about. Hope it helps


LA DMAX

My 05 does the same thing, I think it is normal.

With out the J/A, it seems to me that it has a "stock" defuel feature when cold and at low throttle.

Now I have the J/A, defuel in all gears, and definitley feel the backdown. (when warm) and on the throttle.

Even with the J/A it seems to do the same type of "stock" back down when cold because the juice doesn't kick in untill it is warmed up.

Mike L. what are your thoughts on this ?

Hello. Can you keep this surging going if you hold the throttle and speed steady (light throttle, low speed), or are we talking about a one time (short period of time during the shift) surg or lag. I here about some of the boxes eliminating the default defuel between shifts. Does this eliminate the surg. Thanx Geo

ttt

For me it is a lag, lug, etc. that happens either right after or during the shift. It is hard to tell exactly which one it is (right there at that time).

Also, since it is cold now here in TX mine is doing it just as much as it used to. Looks like the adaptive learning theory is out.

Todd

I just purchased an 02 and I noticed the same problem right away. It feels like the power just craps for a sec then pics back up. The dealer told me it had been all points checked when I bought it, but after taking it to another dealer and finding they didn't replace the recalled tailgate straps I may need to have things checked out.

My 02 has a rpm spike when shifting from 1-2 & sometimes 2-3 It happens when your barely into the throttle. It's kinda like a slip(the rpms spike up) then it catches & all is fine. The trans has just been rebuilt. From what i'm reading...it sounds normal.

my '02 does the same exact thing! only on light to real light throttle. i think its a computer thing about defueling, becuase it does the same thing with the stock tranny and the built one. Frank EP, are you feeling okay?? with everything turned up and pulling a sled is the only time i really can notice a "frame flex". so far to this date i have not had a problem with axle wrap and i dont have any traction bars!!!!!!! the other thing that made me smile is that your rims are HARD, i didnt know that there was a difference. aluminum is softer but dont move, steel is harder and dont move, so how do you determine a soft rim????