Allison transmission question

[Garypowell]

2008 HD diesel with Allison. Has been almost perfect since we bought it new.

May not be a factor but we are now up in colder weather than we normally see. A few days ago for the first time check engine light comes on. And it will not shift out of 1st gear. It was in the 20's outside. Went to auto parts store and the error was something about low pressure.

We we cleared the alarm and all was well

same thing happened 3 days in a row but I realized my chip programmer would clear alarm. I would start the truck get the check engine light shut it off immediately then clear the alarm and all was well.

This morning in KY (we left rig in Nashville) no check engine but when I put in to gear to back out the truck moved a foot then seemed to start to coast. Engine was still running but no transmission

i looked at at the DIC and it said "transmission disabled put in neutral to reset". I had to do that about 10 times in order to get in front of the motel to load up the luggage.

Let the the truck run for that 5 minute period to load up and drove off like nothing was wrong.

Any ideas? What am I up against here or cost to fix if you had the same problem

or what site out their might be better?

I did check TRANS fluid and it might be a little low but well within limits.

Thanks

 

[Lynn1130]

You might want to try this question here: http://www.dieselplace.com/forum/

Go into the transmission section for your year vehicle and post the question. This site is specifically for Duramax and Allison.

 

[Majestic]

My 2007 did this, changed the oil and both transmission filters, problem solved.

My business partner had same issue in his 2008, dealers could not find the problem, a month later, blew trany just out San Fan, CA. $18k replacement

 

[porthole]

Allison's can benefit from Synthetic fluid.
Unless there was a change one issue with them was the trans pumping fluid through the cooler lines when cold. Cold oil doesn't flow well and it causes the two piece rubber/aluminum hoses to leak.

Maybe you have an fluid issue

One of the simplest maintenance procedures on the Allison once you go synthetic is to just change the spin on filter yearly, add the lost fluid. Twice a year if you tow a lot.

BTW, there are aftermarket hoses that are superior to the OEM stuff and they don't leak.

I did check TRANS fluid and it might be a little low but well within limits.

Thanks

How did you check the fluid?

Whatever brand vehicle you have you need to check the book to see if the fluid check is in park or neutral. Most every vehicle is checked in park now. Older Chrysler products were checked in neutral as there was minimal fluid flow in park.

Properly warmed up is very important, and by that I would recommend at least 10 miles or more of highway driving then a 5 minute idle before checking the fluid.

 

[Bob&Patty]

Gary, it could the shift (gear selector) module on the side of the trans. They can cause the same effect if the trans module does not know what gear its in. A sticky shift cable could do this (maybe cold weather). The other Gary might be on to something. How often do you change the spin-on and the internal filters.

 

[GMCaddic]

Check this place out also I have an 08 also http://www.duramaxforum.com/

 

[Bob&Patty]

GM transmissions are always checked warm/hot, running and in park. Its possible that trans fluid was frozen I guess. I have never fired a very cold D/A and not let run for less than 5 minutes. A very cold trans fluid will take a long time to warm...no load on it.

 

[GMCaddic]

http://www.duramaxforum.com/forum/transmission-shop/ Here is some info for you hope it helps.

 

[Lynn1130]

If it does turn out to be a fluid issue I highly recommend Amsoil Torkdrive. I use it in the transmission and transfer case. All synthetic. Nothing but Amsoil in my vehicles and engines.

 

[Westwind]

Changed my transmission cooling hoses to Alligator brand hoses when they started leaking at just about every connection. My driveway was a mess. My mechanic that put them on was impressed and if your a decent backyard mechanic there is enough posted online by Alligator fans to give you all the guidance you need.


http://www.alligatorperformance.com/Transmission-Repair-Lines-s/2444.htm

 

[cookie]

On your post you said that the error was "something about low pressure".
You might be looking for answers to the wrong question.
If the code actually was "fuel rail pressure too low", your problem would not be with the tranny.
That code will put you in limp mode as well.
If that was the error then it could be as simple as changing the high pressure relief valve. A common problem on the Duramax.

Peace
Dave

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[Garypowell]

Thanks everyone. I have posted question on Duramax site as suggested by a couple of you.

I have ave been fairly diligent iwith TRANS. About 135,000 miles on it with about 30,000 in towing. Changed both filters about 70K and changed spin on a couple of times. First with fluid change was at 20K.

Tell me me about synthetic?

is it as easy as drain and refill (I realize probably both filters have to be changed out) or is it a fairly complicated drain and fill then drain again and fill (maybe several times) to get old fluid out?

will dealership do this? I have a really good dealership in Melbourne, FL area that I trust? I usually do work in Dec/Jan timeframe while back in FL for winter. And I had planned on them changing filters again.

and tell me again what synthetic you are using.

Thanks again,

 

[sjs731]

On your post you said that the error was "something about low pressure".
You might be looking for answers to the wrong question.
If the code actually was "fuel rail pressure too low", your problem would not be with the tranny.
That code will put you in limp mode as well.
If that was the error then it could be as simple as changing the high pressure relief valve. A common problem on the Duramax.

Peace
Dave

Sent from my awesome Galaxy S5 using Tapatalk

I had the low fuel rail pressure in Tennessee this year. Pulling up a long grade it happened. I stayed on the accelerator pretty had and I had the truck go into limp mode. My programmer told me low fuel pressure code. I have relation who is a master GM mechanic and he said they see low fuel rail pressure errors all the time.

Like Dave says could this be the actual problem? I haven't seen low tranny pressure. Also like others have said watch the fluid level when it's cold. My fittings on the lines leak all over. I need to change them so I don't have to keep adding fluid in the winter.


Steve

 

[Lynn1130]

If you are leaking fluid that would be the first thing I would be checking.

 

[Gary521]

Find out exactly which code it is throwing. Low fuel pressure could be just a clogged fuel filter too. Changing to synthetic will not fix your immediate problem

 

[TravelTiger]

We had this issue last year in cold temps. Took it in, said it was a "transmission selector switch" or something like that, I have a quote back at the house. Solution for now is to let truck warm up good before moving into gear.


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[porthole]

is it as easy as drain and refill

No. Especially if your goal is to change to synthetic.

Dropping the pan only drains the fluid in the pan and some residual from the rest of the trans.

The torque converter will still retain about half the total capacity of trans fluid.

Allison does not recommend "fluid exchange machines"

Two common methods short of pulling the trans and draining the converter are:

Drop pan, drain, refill and run.
Drop pan and repeat.
It is estimated that this will yield an approximate 75% fluid change.
Synthetics can be mixed with the non syn.

Method 2 is drop and drain, refill and pull the cooler line.
While the truck runs, one person directs drain into bucket, 2nd person pours the same amount of draining oil into the filler tube.

Tricky and messy.


When I had my Allison equipped truck I did method 1. But, I had also changed to the Mag Hytec extended capacity pan (doubled the pan capacity).
And I did the drain and refill twice.

After doing that I only changed the spin on twice a year.

At the time I got a deal on Amsoil, so that was what I used.
It was a pricey way to do the change over (two drains with extended capacity pan), but my plan was to never change the oil again

 

[porthole]

Note, when changing the spin on filter, there is a magnet on the top that needs to be cleaned and swapped to the new filter.

 

[TravelTiger]

Ok, found the estimate.

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[whp4262]

2008 HD diesel with Allison. Has been almost perfect since we bought it new.

May not be a factor but we are now up in colder weather than we normally see. A few days ago for the first time check engine light comes on. And it will not shift out of 1st gear. It was in the 20's outside. Went to auto parts store and the error was something about low pressure.

We we cleared the alarm and all was well

same thing happened 3 days in a row but I realized my chip programmer would clear alarm. I would start the truck get the check engine light shut it off immediately then clear the alarm and all was well.

This morning in KY (we left rig in Nashville) no check engine but when I put in to gear to back out the truck moved a foot then seemed to start to coast. Engine was still running but no transmission

i looked at at the DIC and it said "transmission disabled put in neutral to reset". I had to do that about 10 times in order to get in front of the motel to load up the luggage.

Let the the truck run for that 5 minute period to load up and drove off like nothing was wrong.

Any ideas? What am I up against here or cost to fix if you had the same problem

or what site out their might be better?

I did check TRANS fluid and it might be a little low but well within limits.

Thanks

This sounds more like a electronics problem and not a mechanical problem. A mechanical problem like a bad clutch pack isn't going to fix itself and work correctly for a while. An electronics problem can be a hard failure or intermittent which can be a real PIA to diagnose. I would look at the transmission filters, transmission control module and shift position sensors and the engine coolant temperature sensors. I'm not sure on your 08 but on my previous Chevy the transmission module had a coolant temp input. If this sensor goes bad it can lock the transmission in 1st gear. And if I remember correctly it was not the same sensor that the gauge used. Usually a plugged or restricted filter will cause shift issues and slipping. So if you are getting solid normal shifts when it's working correctly I would say the filters are a low probability.


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