Allison 3000 Series question

[Andy Clark]

Not sure what's going on with my trans. After sitting unused for more than about a week, the following occurs: I start the engine and let it run to air up the bags and get the engine temp off the pin. When I press the "D" button on the pad, nothing much happens. There is not the firm shift into drive that I get when the engine has been run more recently, (the same happens in "R",btw). It doesn't seem to matter how long I leave the trans in drive, it doesn't change much. The coach will move slowly forward if I raise the rpms very slightly and then gradually, over a few feet (10-20?) the trans will begin to operate normally and is then fine until the next extended "sleep". After 3 or 4 or 5 days at a park, the normal slight "thump" (not the right word?) will occur when going into "D" or "R" and the trans shifts normally.
What can the experts offer regarding this? It feels to me based on my car experience that the torque converter may be draining back over an extended period of inactivity. Oh,boy. I sure hope not!!!!!
Thanks for any insight you can provide.
Andy

[Dave Atherton]

Andy, just answered but something happen again after review, I do have with me the Allison
tech service and troubleshooting manuals for the allison 3000. I also have allison program on
computer along with the packard connector to connect to your transmission. Can help you out
later tomorrow a.m. Dave Atherton Retired Cat Mechanic

[Dave Atherton]

Good morning Andy, Back with you on your allison problem. Sounds like you have electrontic
problem not giving shift solenoid in transmission correct voltage to engage shift. looking at allison
troubleshooting manual everything keeps pointing power either going to transmission off the J-1939
data cable from transmission to engine ( loose connector or dirty connector or shift touch pad.)They
have came back with the shift touch pad jell touch under the cover and shift keys. Talking possible
cause with touch pad in sunlight and heat inside of motorhome when standing longs periods and
possible age getting hard. tapping or pushing on keys after while will make correct contact. Can be shifting pressure in transmission but in this case allison will need to go inside with test pressure gauges.
do not think you have self test off touch pad in 1995. Dave Atherton Retired Cat Mechanic

[Edward Buker]

Dave, Andy,

Because Andy gets the shift indicator to change from N to D or R and when he adds RPM the coach moves and then seems to fully engage in some short distance I think the mechanicals of shifting (pad and control circuit are working) has actually occurred but the fluid flow in the transmission has not been fully engaged through the right channels. I am not sure how this all works regarding the valves in the transmission.

I say this because I have a 99 Suburban which shares some of the Allison heritage from its GM days and if this vehicle sits I get the exact same symptom. I shift but in this case it is with a direct mechanical lever system. I do not feel the thump shift engagement, I add throttle and for the first 20 feet it rolls slowly and then at that point all proceeds normally for the rest of the day. It has been doing this for several years, has not gotten worse or better on its own. There must be a knowledge base regarding this issue at Allison shops or possibly those that service GM truck automatics. A wild guess is an ageing or sticking valve body in the transmission. The transmission does not slip pulling loads once it has been driven a few feet and operation becomes normal again.

Later Ed

[Andy Clark]

Edward,you are exactly right in your interpretation of my problem. The issue never used to happen, however now it is repeatable. My old Mercury used to do something similar, and it turned out to be torque converter drain-back. Since that trans had a front pump, running the engine at idle for a while refilled the converter. I don't know if the Allison has a front pump, a rear pump, or both.
I have not yet had an opportunity to check the fluid level warm to see if it's low.
Thanks to you and Dave for the responses.
Andy

[Dave Atherton]

Good morning , ED and Andy, the shift of the Allison is via: electric shift solenoids that allow fluid to
pressure clutch packs. Just pulled info as I'm typing. sounds like Ed you have experance the shifting
area with Andy and you both agree what is happening. Ed are you going to be in Branson if so will
have chance to meet you Dave

[Edward Buker]

Dave,

We are traveling visiting family in the western states and will head back home in late September so we will not be in Branson. Love to meet you and some of the folks but just not in our path and timing.

Later Ed