Allison 5sp: po872 and limp

[Tbo88]

had an issue the other with the truck towing and just confirmed that it does it with no trailer just driving after it gets over 185 degrees it throws p0872 and goes in limo mode.. let it cool down clear the codes and its fine again until it goes over 185 trans has maybe 3000 miles on it since rebuild new suncoast valve body new nsbu... only think I can think of is the first valve boby I got from suncaost did the same thing sent a new one put it in and its been working since then till last friday

 

[Mike L.]

E shift valve is sticking. You have something grinding up inside the trans.

 

[Tbo88]

that would be temperature related ? it works great till it gets to that temp then it limps

 

[Mike L.]

that would be temperature related ? it works great till it gets to that temp then it limps

It could be electrical, but I doubt it. I've never seen temperature cause a solenoid to act up. Usually it's floating debris.

 

[Tbo88]

its weird casue the first valve body did the same thing out this one in and it worked great 5 or 6 hooks to the sled and plenty of street driving then all of the sudden it decided to limp the other night.. I guess ill drop the pan and change the fluid again

 

[Mike L.]

its weird casue the first valve body did the same thing out this one in and it worked great 5 or 6 hooks to the sled and plenty of street driving then all of the sudden it decided to limp the other night.. I guess ill drop the pan and change the fluid again

I would find out why this is happening. Changing fluid is not the answer.

 

[Tbo88]

what could be the cause no metal in the pan no clutch material in the pan I had a stock valve body in the trans and its fine suncoast valvbody and it shits the bed 500 miles after I put it in

 

[Mike L.]

what could be the cause no metal in the pan no clutch material in the pan I had a stock valve body in the trans and its fine suncoast valvbody and it shits the bed 500 miles after I put it in

OK then you fix it.

 

[Tbo88]

idk how haha im not sure were to start other then taking the valve body part and cleaning it again

 

[Chevy1925]

E shift valve is sticking. You have something grinding up inside the trans.

idk how haha im not sure were to start other then taking the valve body part and cleaning it again

he gave you the answer

 

[Tbo88]

I understand what the code means.. I'm asking what could be causing the valve to stick on mostly brand new parts

 

[Mike L.]

I understand what the code means.. I'm asking what could be causing the valve to stick on mostly brand new parts

You're assuming everything in the trans is perfect. That is probably not true.

 

[juddski88]

I have seen temperature effect solenoids at right about the temp he posted. I documented at least one of the cases here.

 

[Mike L.]

Cool. So now it's a simple fix. Change the solenoid E and you are home free. Funny how the last valve body did the same thing.

 

[juddski88]

i didnt say that. I just said I have seen solenoids affected by hot fluid. I'm not an electrical engineer who can explain why, just stating what i've seen Mike.

I do know coils get weak, and that they get even weaker when temperature rises. Those are facts. Beyond that, I couldn't really tell you without looking into it further.