Transmission Fails to engage

[hydromax]

Tranny failed to engage in "R" or "D" after vehicle sat in garage for 6 days. Same problem as I reported earlier. Engine had run 2 minutes (time) because I was aware of conditon from previous experience. When placed in "R' and "D" only get blinking indication. Shut engine off on second attempt shifted abruptly in "D" still no "R". Shut rig off came back in 10-15 minutes restarted engine all OK. Took rig to dealer, reports finding codes PO700 & PO843. The dealer contacted tech line and they advise them that this was normal and service report instructed to start engine and allow vehicle to warm up than shutdown and restart and this problem would not occur. They also stated that GM was aware of the problem and that engineering had no solution. The tech comments are that the problem is caused by pump loosing it prime. I have a real problem accepting that this is normal. I have several fiends with Allison and none have experienced this problem. Any suggestions?

[dmaxalliTech]

hydro, I assume you have an 01 truck, these are the ones that were good for that problem. Gm is aware of these problems and tech is correct that prime is being lost. IIRC there were issues with the pressure regulator valve sticking in its bore at times and causing this loss of prime. I dont have access to the info at this time but IIRC code p0843 is pressure switch code. it sets because air is in hydrolic system and air dont push the switches like fluid does. Unfortunatly, Until GM issues us some more positive info, We will live with it for now. At this point, GM does not allow internal repairs to Allison at the dealer level.... :(

[hydromax]

Failed to identify year, it's a 2002 with 26K
Thank

[a64pilot]

Hydro,
You have several "FIENDS" with allison? Really they don't seem to be that bad to me. :D :D :D

[Heartbeat Hauler]

This happened to my 01 and it turned out to be the spin on filter. It was replaced and no problems since...5K miles then 21k miles now.
JP

[FirstDiesel]

hydromax

This is one of those known things not likely to be fixed on the older vehicles until the tranny is rebuilt.

That said I, the way I read your post I'm not surer if you followed the proceddure to prevent the tranny from having a problem.

As I understand it your supposed to idle for about 2 minutes and then shut the truck off. Restart the truck and then put it in gear.

[Buckman]

hydromax

I've heard a rumour that there soon may be a fix to address the priming issue that you've apparently experienced. My suggestion would be to have your dealer verify the problem and contact GM Technical Assistance Center regarding their findings. :D

Let us all know how it goes.

[blakmax]

Man oh Man!! If the dealer told me to live with that problem, I would drain that trans and run it for an hour at idle till it cooked!!

[Alli-max]

happened to me twice with the truck sitting at the airport for 5-7 days.

Not a problem. Actually happened on Friday last week with the truck there for 6 days. I cycled from D to R 4-5 times, and it "primed" or what ever you call it. Left the parking lot and shifted flawlessly. Took about 20 seconds for the cycle. No big deal....