8.1 Engine Bogging

ClawSS · December 6, 2001

Before I take my truck to the dealer for them to say that they can't reproduce the problem, I wanted to run it by you guys.

In the mornings I start the truck, let it idle for about 30sec. to a min. before pulling out of the driveway. Intermitantly (not every day) when I get to the end of my street and turn left the truck will bog...meaning that when I press the go pedal the rpms want to rise, but do not and the engine labors to increase speed but doesn't. Then, after about 5-8sec. of this it starts picking up rpms like nothing happened. It definately isn't a neutral drop since I don't rev at all...just bog down. ???

It only happens first thing out, never when it is hot. I have been thinking about running some drygas through it in case it was water, but am not sure if it could be something more serious.

Truck Model: 2002 8.1/Alli CC 4x4 w/ 1200mi. on the odo

Thanks in advance.

Chris

chane · December 6, 2001

Could this be the Alli warming up?

ClawSS · December 6, 2001

chane wrote:

Could this be the Alli warming up?

I dunno, maybe. Would/Could the tranny keep the engine from increasing rpms?

Chris

chane · December 6, 2001

chane wrote:
Could this be the Alli warming up?

I dunno, maybe. Would/Could the tranny keep the engine from increasing rpms?

Chris

When the Tranny is cold in the morning it shifts slower until it warms up witch causes the engine to rev higher. With the engine reving higher and the Alli downshifting I could see how it would be 'Bogging'.

ClawSS · December 6, 2001

When the Tranny is cold in the morning it shifts slower until it warms up witch causes the engine to rev higher. With the engine reving higher and the Alli downshifting I could see how it would be 'Bogging'.

True...I can grasp that. I am pretty sure due to the length of my street that I do not exceed 1500 rpm before comming to a stop. Most of the time the Alli will shift to 2nd but doesn't have time to shift out. I come to a complete stop at the end of the street usually due to cross traffic, but it is possible that I roll thru the sign and the tranny may still be in second. If this is the case, wouldn't the engine increase in rpms when the go pedal is depressed even if just a little. This thing goes the other way with zero engine reaction to the accelerator.

Sorry, I'm not doubting you at all...just you are really assisting me in describing the problem and working through the scenario.

chane · December 6, 2001

Sorry, I'm not doubting you at all...just you are really assisting me in describing the problem and working through the scenario.

I'm just saying that's mine does and what I think is the cause. I am definitely not a mechanic..

Anyone else have an idea?

chane · December 6, 2001

Sorry, I'm not doubting you at all...just you are really assisting me in describing the problem and working through the scenario.

When I bought mine the dealer introduced me to like everyone on the lot. When I met the Service Manager I asked him if he had seen in of the HD 8.1/Alli's in w/probs yet. He had only seen one and they flashed a new program on the Alli. You might see if you need that update.

ClawSS · December 6, 2001

When I bought mine the dealer introduced me like everyone on the lot. When I met the Service Manager I asked him if he had seen in of the HD 8.1/Alli's in w/probs yet. He had only seen one and they flashed a new program on the Alli. You might see if you need that update.

That's cool...I can call the dealer and see what the Alli reprog will do.

Please don't let that be the end of this thread, though. I need all the input I can get.

Thanks again Chane.

4x4man · December 13, 2001

With 1,200 miles on your truck, the tranny could still be in its fast learning mode. What I would try is this: as you are coming to a stop (3-4mph) manually shift down into first and then stop. Put it back into drive and then drive on. Try this a couple of times as you are coming to a stop at a red light or any other spot where you need to come to a complete stop. This will help teach the tranny to shift into first around that speed.

I had an issue with my truck when I first got it, that I after I got to a stop it would bump...I mean it would feel like someone tapped me from behind. As it turns out it was the tranny shifting into first at that point. It was suggested to me to do the same thing as I described above a few times to take care of it. Sure enough that did the trick!!

Give it a shot, you have nothing to lose!

Good luck!

Bob

ClawSS · December 13, 2001

Thanks, Bob....

I will definately try that. It would make more sense as I can feel that it is staying in a higher gear and eventually shifts.

Well, gotta go drive my truck.

The horrible things I have to do...

Thanks again

gandolphxx · December 14, 2001

Is that unique to the Allison?

ClawSS · December 14, 2001

gandolphxx,

I believe that the learning aspect may be. I am not aware of any other tranny computer that learns the shifts in this way, but I may be wrong.

Did you have a chance to read this bulletin? I think that it gives a great account of how this thing "thinks".

Info - New Product Information - Adaptive Control Feature of Allison 1000 Series Transmission #01-07-30-025

CMNTMXR81 · December 14, 2001

Claw, you have an 8.1L V8 with 455lbs-ft of torque, do you REALLY think that a cold transmission will generate enough force to stop that amount of torque?

If it is in the transmission, it could be in the torque converter. I'd check into a TCC (Torque Converter Clutch) solenoid as well as lockup speed.

If it is in the engine, without having a TechII or AutoTap program on it, it could be either fuel or ignition. It's kinda hard to tell.

I will tell you though that twice now, when the truck has been cold/still warming up, it has stumbled after coming to a stop then starting to accelerate again. I began to think of the Torque Converter immediately.

Another possiblity I though of after that is the live by wire throttle control we have. We don't have the old fashioned cable connecting our gas pedal to the throttle body. It's like the Corvette where it has a signal sent to it from the PCM, then an electric motor/solenoid opens the throttle. Perhaps this is sticking, not getting a correct signal, etc, etc.

rola76 · December 14, 2001

Well here's a change of pace; I have the 6.0L and mine does the exact same thing! So as for those wondering if it's exclusive to the 8.1, I'd have to say no. As far as the first description, mine does the EXACT same thing, at low rpm's. I have to actually get on the gas so it doesn't bog down. Hopefully this isn't anything detrimental!!