Duramax Wont Run Over 2000 Rpm

warrens2500hd · April 3, 2010

hey since ive gotten my 05 lly back from the dealership ive installed a edge juice and 4 in exaust well im a guy that loves power and so i was out and about messing with the truck my word i never knew a 8700 pound truck could run so fast with minor installs. however i noticed my trans temps creaping up quickly started backing out of the truck and on the way home the truck wouldnt turn up over 2000 rpm. for those of you who know anything about it is that a safety feature that defuels the engen till the trans temps cool down? im curentlly been browsing around trying to find some answers letting the truck cool off tried to call edge but they only work 5 days a week. need some help!!

brims · April 4, 2010

Did you try driving it after it cooled off? If it's still not working well, try setting back to stock?

Silverado4x4 · April 4, 2010

You have "limped" the tranny, it is a safety feature to prevent tranny damage as you slipped the clutches and I believe 3-4 restarts should reset it but once you limped it for the first time it will go into limp mode easier the next time.

The Allison will handle about 60-70 more HP but as you keep stomping on it the trannys life is greatly reduced. In stock form the tranny is bullet proof.

warrens2500hd · April 4, 2010

yea not long after i wrote the message i went back outside and cranked the truck to see if the trans temps had fallen yet and they had so i took the truck down the road and it ran fine but i most definatelly have set the truck to stock and im debating on taking the edge off till a later date so i dont get any urges untill i can do some trans upgrades maybe even look into building a stronger allison

masterp2 · April 4, 2010

as I recall, a limped LLY trans is not limited to limp home 2000 rpm defueling. It was more likely a fuel pressure code. This, and many other codes, will trigger limp home mode. Trans temp was incidental, not causal.

warrens2500hd · April 4, 2010

well i most definately need to do something about my allison. went to drive it this morning and with the edge set on stock i was reading at some times up to 45% slip soooo..... i done screwed up!!!!! gona baby it for a while and try to doctor it up untill i get my funds together so i can get suncoast to build me one unless anyone has any other ideas.

masterp2 · April 5, 2010

Hopefully you realize that "slip" is what an automatic transmission does. Lockup should not be expected at all times. You seem to be convinced you have trans problems, but you haven't said anything that suggests that compellingly.

brims · April 5, 2010

Hopefully you realize that "slip" is what an automatic transmission does. Lockup should not be expected at all times. You seem to be convinced you have trans problems, but you haven't said anything that suggests that compellingly.

My Aeroforce gauges show trans slip speed. The tranny slips plenty, at heavy throttle it doesn't slip until it shifts, and I think at a couple of miles an hour it won't slip if I'm easing it along, and of course after the TCC locks it doesn't slip. Other than that it slips anywhere from every last RPM (at idle) to 1/2 the RPMs while accelerating normally.