# allison stuck in 2nd



## nathanlacourse (Sep 13, 2003)

just bought 2001 duramax im having problems with the tranny with the plow on the temp get around 190s the tranny gets stuck in 2nd it wont go up a gear or down but will go in N and Park but when the tranny is cool it shifts fine . with the plow off the truck i dont have the problem it runs in the 150s i did put heavy duty clutch fan on any toughts thankx


----------



## Philbilly2 (Aug 25, 2007)

That seems odd. 190 degrees is high for a stock trans, but not bad. If it puts your mind at rest, my built trans runs over 200 degrees all the time. 

Here is where I would start. First thing that I would check is the NSBU. Take a look under the truck and on the drivers side of the tranny there is a little box that 2 wiring harness and the cable from the gear selector is hooked to. What colot is that box. If it is tan it has been replaced. If it is black it needs to be replaced.This is just the easy fix if this is present.

If not. it is most likley in the valve body. There are solinoids push valves in and out that allow the fluid to pass through the correct passage ways. It sounds to me that one of those valves is hanging up. I had that happen on my truck last year while I was pulling a trailer. My trans temp hit about 250 degrees and then would not downshift out of 5th gear. The only way that I could get going was to pull over and let the tranny cool down enough that the valve would move again and the truck would shif through the gears again.


----------



## Philbilly2 (Aug 25, 2007)

one more thing, i know it is stupid, but have you checked your fluid level with the tranny at normal operation temp on level ground with truck running? Just and after thought.


----------



## Lifted4x4Astro (May 10, 2008)

The first thought that comes to my mind is you bought a truck that has an almost dead tranny. I would guess the previous owner hopped up the Duramax and when the trans started to slip, he traded it in on a new one. That is the problem with buying a used diesel truck today...you just don't know. :realmad:

Trans temps in the 190's shouldn't even bother it. Definitely check the fluid level and plan to do a fluid and filter change out. Look for bits and pieces in the pan when you do it. Another option is to install an electric pusher fan in front of the trans cooler.


----------



## 02DURAMAX (Dec 27, 2006)

I hand The same Problem in june it was stuck in second and would not go up or down...and it would hit 190 and pop its stuck in 2nd....I took it to my dealer and all they did was reset or reflash the trans computer and it was good to go.


----------



## nathanlacourse (Sep 13, 2003)

plowed with trunk this morning for about three hour and shifted great temp about 150 im still going to change fluid and have them hook up to computer thanks for info


----------



## nathanlacourse (Sep 13, 2003)

put the truck on computer 3 codes
p0700-Trans control system malfuction
p1711-Trans PSI switch,solenoid E circut stuck closed
p1721-Trim solenoid "B" controlled cluch not engaged
any ideas thankx for help


----------



## lunatic81 (Sep 24, 2008)

That's the problem with all the electronic BS! I've had similar probelms with my duramax tranny. Only it did it all the time. Had to drive 25 miles with it stuck in 2nd gear to the dealership. Reset it, and drove fine.


----------



## Philbilly2 (Aug 25, 2007)

nathanlacourse;671627 said:


> put the truck on computer 3 codes
> p0700-Trans control system malfuction
> p1711-Trans PSI switch,solenoid E circut stuck closed
> p1721-Trim solenoid "B" controlled cluch not engaged
> any ideas thankx for help


P700 is a general trans code. That one pops up all the time.
the 1711 means you have problems

What is going on is the shift solenoid transfers the fluid through one passage to another. The problem that you are having is that when your tranny gets to 190 degrees, the metal expands enough that the valve that the soleniod is pushing gets stuck in the passage way for 2nd gear. The only way that I know of at the time to fix this problem is to drop the pan, pull the valve body off to get reamed. Once it is reamed it will not have the problem anymore.


----------



## LHK2 (Jan 22, 2007)

I have the opposite problem with mine. If its below 30 degrees and I don't let it warm up, mine won't even shift into first. After it warms up, no problem. Dealer reflashed the computer and it runs fine for about two weeks. I just let the truck warm up now.


----------

