6 speed Allison p2723

[abgfl]

Good morning Gents.


I'm hoping someone can shed some light on the tranny issues I have. Allison tranny throwing p2723. Valve body cleaned, tested and then changed out with another - same issues. New wiring harness and solenoids. Speed sensor changed. Slipping at 2-3, then limp. Will sometimes shift fine and then limp in downshift. Have looked at all pressures through scan tool and everything looks fine EXCEPT when going from P to R, or N to R pressure goes from 230ish to 0. I've read maybe a snap ring. Maybe C3. Just looking for some more insight.


No indication of of failure. I drove it last Tuesday (Christmas Eve) to a meeting. Parked it when I got home. Went to drive it Christmas day and started having issues.

 

[Mike L.]

Scan tool cannot read pressures. Need history on trans.

 

[abgfl]

We had a MaxiCheck (MX808) hooked to it using Live Data.

 

[Chevy1925]

Scan tool cannot read pressures. Need history on trans.

We had a MaxiCheck (MX808) hooked to it using Live Data.

As Mike already said, that aint going to work. you need to hook a pressure gauge up

 

[Mike L.]

P2723 is an incorrect ratio on an apply clutch while the off going clutch hasn't fully released. Tie-up. Could be speed sensor, transfer case, voltage to the trim solenoids or bad clutches. You're not helping at all.

 

[abgfl]

First - Thank you both for weighing in.


To expand a little on the "situation"...I am by no stretch of the imagination a mechanic. I did take my truck to the company that built the tranny 100k miles ago. When it was "built" he used a PPE stage 5 kit, PPE converter, Reybestos clutch packs, and did something with the valve body. Up until Christmas eve I haven't had any issues. Using the above mentioned scan tool i did retrieve 2 different DTC's. The first was solenoid 2 stuck on. the other is solenoid 1 stuck off. after cleaning the valve body, the solenoid 2 went away. while cleaning the valve body we replaced the wiring harness and what appeared to be one bad solenoid. the tranny doesn't appear to slip while in drive. however it will not go into reverse - without throwing shift inhibited. 4-5 will hesitate. on occasion downshift will put it into limp.

 

[Chevy1925]

You will be best off taking it to a shop that can properly fix this for you.

 

[abgfl]

That's the plan for today. I was hoping maybe something easy was overlooked...but it doesn't seem that way

 

[abgfl]

We tore down the tranny yesterday and it turns out the piston blew apart, thus not holding pressure. all the PPE components looked brand new (after 100k miles). ordering replacement parts now.