Hipirihop

On a 2009 GU 813 Iam having a little trouble with the allison transmission, not always, the problem just comes and goes intermittently. Sometimes when I start the engine, select D, add gas the trucks moves but you feel instantly a rough feeling (like if you have selected LOW in a 4x4, it kind off jumps), and the next gear takes a long time and the engine starts rev up and the gear enters with a very rough movement and so on the next gears, but if you stop the engine and start it two, three or four times and it is all gone…. it has never been the other way around, if you start the engine for the first time and no roughness it continues ok for the rest of the trip. There are no codes on the gear case. I've heard it can be air in the fuel system is this possible or should be looking at something else? thanks!!

mackpro68 thanks for the information!!!

Hello Iam from Chile and new in the forum, I would appreciate if some can help me with the following: have a strange noise on a GU 813 2009 at cold start up (5 to -5 Celsius) the engine starts ok, but suddenly an air blowing noise is heard out of the exhaust and behind the turbo, some times like a whistle, the engine comes down in rpm's and then up again (only once), like if a exhaust brake is on (it has no engine brake). If I push the main air parking break off, it all comes back to normal, and the engine comes back again, it feels lighter, what can it be??? thanks.