2004 8.1L Reverse Serge

JetNoiz · February 16, 2005

Has anyone experienced a throttle surge when shifting to reverse? This most always happens when I first start the truck in the morning. Is it temp related (i.e. outside temp or engine temp), or do I have a PCM problem?

Sorry if this is an old topic. I am new to the forum.

knez · February 16, 2005

You know my 8.1l does the same thing from time to time .Anyone?

dewfpo · February 17, 2005

I've got an 2005 that I park in a garage at night so in the morning, I start it, wait about 10 seconds then throw it into reverse and LEAPS..... almost scary. It doesn't do this on cold starts into Drive. A quirk I guess. I know that the reverse gear is 4.49:1 vs. 3.01:1 for 1st gear but I wouldn't expect it to leap like it does and my foot is always on the brake.

DEWFPO

knez · February 17, 2005

Hey DEWFPO.Thats kind of what my does put it in reverse and its like im goosing the throttle then it goes down 200-300 rpm or so then back up then back down and so on and then kind of tapers off wheather I put it in drive or not i see what your sayin about the gear ratio does yours just surge when put in gear and stop or keep going up and down?

BADHD · February 17, 2005

Mine does this also.It will surge up and down mainly in reverse and sometimes in drive.The engagement is fine its just when you start to move and its only on a warm restart.

Was going to take it in soon.

Daubs · February 17, 2005

My 8.1/Allison has always jumped in to reverse quickly. I don't notice a "throttle surge" per say. It does go into reverse more quickly than going in to drive.

Wonder if it's an Allison thing?

dewfpo · February 17, 2005

I hadn't paid any attention to the rpm surge, I am always looking backward when it jumps with my foot on the brake so that I can have some semblance of control. I will look next time and let you know. I haven't really noticed it in D or on warm start. I'll pay more attention. The cold reverse leap is REALLY noticeable.

DEWFPO

EASTCOASTER · February 17, 2005

Mine has the same surge, but not all the time.

Polak · February 18, 2005

Mine two.

I bowl with a guy that works for Allison here in Indy. Talked to him about it, waiting to see what he comes up with.

JetNoiz · February 18, 2005

Wow! I guess I am not alone. I'm pretty sure it's ECM related because it's the throttle that's surging as evidenced by watching the tach fluctuations. I don't think we can blame the Allison for this one. You'd think there would be a service bulletin out on this one since there is a potential for an accident.

Megawatt · February 22, 2005

My new 04 with the Allison does the same thing. I just got it back from the dealer to check it out along with some other issues. They say nothing is wrong and couldn't reproduce the problem. Yea right! I have only noticed this about 10 times. The truck now has 7k miles. When it does surge in reverse, it's definitely noticeable and does it the moment I shift to reverse. I have to really stand on the brake to get it stopped! This is going to cause an accident eventually. What's going on here?????

04 2500HD CC 8.1 Allison