Dmax/Ally owners question

[rhidalgo]

My transmission did a couple of odd things recently and was wondering if any of you have experienced anything similar and what was the outcome. I have a 2009 LMM engine with 6 speed Allison 114000 miles. Had one occasion going from coast to throttle on that the trans acted like it was in neutral, engine sped up, trans didn't. I let off throttle and the trans caught. Another occasion just prior to a stop I felt a jolt almost like someone rear ending me, apparently the trans shifting to first a little prematurely. The truck has been acting completely normal since these two incidents?? It's time for a fluid change so I'm doing that now but was wondering if any of you have had any experiences that might help. Currently not alarmed, but not comfortable either.

[rohrmann]

We have had an occasional burp, thinking it is just the computer. We are close to 100K miles, and am thinking of changing the fluid with an Allison approved Transynd fluid. From what I've read on another forum, a drain and fill with the new fluid, run about 100 miles, then another drain and fill, this time with a change of the spin on filter, and the fluid is good for the life of the transmission, with only topping off when changing the spin on filter, which I do already every 30K miles. This change procedure is supposed to give a fill of about 95% new fluid, according to a retired Allison engineer. They also do not recommend a flush on these transmissions, as it can damage the pump. Also, the screen in the pan is just that, not a filter, and is only serviced at a major overhaul. You may want to have the unit checked out, but if it's working OK, it's your call.

As a PS, at the last service on our truck, at over 90K miles, the Dexron fluid looked just as pink and clean as new fluid. I am thinking those spin on filters must work really good.

[bethandkevin]

Unfortunately, with todays modern transmissions, there are many things that could cause your symptoms. A sticking roller or sprag clutch, sticking valve body valve or check ball, electrical solenoid sticking, the list goes on. When you do or have the maintenance done look or tell your mechanic to look for anything in the fluid pan that doesn't look right. Also, have the transmission module scanned for codes-this can't be done at the local Autozone, their readers are just too generic. A good transmission technician can also look at shift data from the module and detect issues as well. The more information you provide the technician about when it happened the better too. Good luck.

[TLightning]

Call the Allison tech line, they are very helpful.

[ckwizard]

Once in a blue moon when I am coasting up to a stop light mine will shift into first and it feels like a bump from behind, I wouldnt worry about it.
I have 173.000 miles on mine and switched to Transyd a long time ago.

[jlb27537]

For what it is worth. My pusher had a Allison 3000MH tranny. It used Dextron in it. It did what you are describing, usually when cold or very hot.

I changed the 2 internal filters and switched to Trans/syn. It held 5 gallons of fluid.

Perfect after that. So, if you are running the original fluid for 100K miles, yes it will probably be pink, but the additives are gone.

Jim

[knighton91]

I also did the fluid change to Transynd. Made a world of difference in the smoothness of the shifting. I have a 2008 GMC HD2500, but have not experienced any real problems. Did get a recall or should I say advisory on the transmission lines. Mine had already been changed. You will be pleased if you swap the fluid. The retired Allison engineer's name is Tom Johnson if i remember correctly. His information is on the Duramax forum. Happy Fourth to all.

[rhidalgo]

Thanks for all the comments. Fluid changed and pan looked very good. This was it's second change and performance is still normal so I won't worry about it unless it happens again. Thanks again guys.

[nowinter]

I have the same 2009 and have never experienced anything like what you did. Please keep us informed of how this proceeds. I just had my transmission fluid and filter changed at 36,000 miles. Been a great truck so far without one problem. It still looks as good as the day I bought it. Oh yeah, I am on my third tailgate.

[TLightning]

Once you put Transynd in it, and get it tested annually, as long as the tests come back WNL, it is good for life.

[rhidalgo]

Update. It ran without incident for about a month then went totally bananas. Would not go into any gear and would display random messages. Could stop truck and restart and get different results. When problem occurred was able after several tries to get truck to engage in drive and started home. Quickly found out that it would not shift out of first. Once home I tried different things again and got similar random messages with truck mostly not moving. Replaced TCM (transmission control module) and all is back to normal.

[hunts800]

I had a 2009 which I traded on the 2015 dually. At about 60k, transmission was suddenly shifting erratically, no prior problems. Dealer had it towed in, and ended up replacing what they said was the transmission control module. They covered it under warranty. No problems after that.

[dpam]

The service manager at a GM dealership told me that if the computer senses a problem
with the Allison transmission it will put the truck in to a limp mode or it will simply shut the transmission down and you will be sitting on the side of the road.