Allison 6sp: trans pressure codes

[greygoose08]

My 6 speed automatic keep wacking out on me. putting it into reverse or drive sometime makes the underline on the selector blink and sometimes goes out completly. sometimes i get the common shift range inhibited as well on the DIC. some of the codes i remembered before clearing were p0700 and like 2 to do with trans pressure sometime..... (didnt write down or remember before i cleared) anyone know what is going on here? low fluid, too much fluid, the internal nsbu???? need to get this taken care of!! thanks

 

[Mike L.]

Nsbu?

 

[millerman04]

I've also thrown the "shift range inhibited" before as well. Always wondered what that may mean?

 

[greygoose08]

i was told the 6 speeds have an "internal" nsbu switch compared to the 5 speeds. im not sure just going off what i was told! i will get the codes as soon as it does it to me again! it just kinda kicks itself in a nuetral and will just rev up when the issue happens. i will keep you posted

 

[greygoose08]

sorry, or the internal "IMS switch" i beleive it is now

 

[JoshH]

Could be a number of things. It isn't common for the 6 speeds to have the selector switch go bad, but it isn't impossible either. You need to write down the codes next time it screws up.

 

[greygoose08]

happend last night when i went from reverse for Drive. here is what i pulled.


P0751, P0877, P0700 (some of them were duplicated) but those are the codes i got. i found out that i think its something to do with trans fluid in it?? when i installed my DE downpipe, i only got 1 nut back onto the flange on the trans dipstick holder. and i checked fluid yesterday and it virbrated off there so its not even mounted securly to the trans anymore. im thinking it may have popped out of the trans and i lost some fluid? i didnt crawl under and look cuz it was raining here yesterday.

 

[Mike L.]

Those codes indicate that the TCM is not getting the feedback it's looking for from the PSM. Low fluid or sticky valve?

 

[greygoose08]

i am thinking its low fluid. im assuming since its not bolted to the trans anymore it moved around going down the road where that o ring seats into the trans pan and im loosing/lost fluid. i am gonna get it bolted back up to the trans and get an accurate reading and fill if i need to.

 

[Mike L.]

Take 3 or 4 readings and look at both sides of the stick. Always use the low reading ( if there is one ) as your true reference.

 

[greygoose08]

thanks for the help Mike!!! ill keep posted on what i find out here