Allison trans.

mountain maniac · April 28, 2023

my 2011 3500hd dually won't move. when I put it into gear there is a line under the selected gear and it flashes and I have no gears. if I unhook the battery and hook back up it will drive for a while then it does the same thing again. any ideas?

newdude · April 29, 2023

Scan for codes. Its likely a bad TCM and they've been on backorder almost a year now. Used ones are selling for $2000-4000 on eBay, its that bad right now.

Best option is to try and order one at a dealer. If its the TCM, bring your VIN down and have them order one and put a SPAC case on it. "Some" orders from last August just got filled, so hopefully this won't last too much longer. GM is expecting July but they also said January, March and May before moving it to July.

Edited April 29, 2023 by newdude

hiking_mike · April 29, 2023

While on the topic of TCM's. Can someone confirm or deny or provide insight into using OEM and Non OEM Serpentine belts. I was informed by multiple shops that using a non OEM belt can generate static electricity. Given the proximity of the TCM to the belt, this static electricity can cause damage to the TCM.

By using the OEM belt, no static charges will be generated.

mountain maniac · April 29, 2023

1 hour ago, newdude said:

Scan for codes. Its likely a bad TCM and they've been on backorder almost a year now. Used ones are selling for $2000-4000 on eBay, its that bad right now.

Best option is to try and order one at a dealer. If its the TCM, bring your VIN down and have them order one and put a SPAC case on it. "Some" orders from last August just got filled, so hopefully this won't last too much longer. GM is expecting July but they also said January, March and May before moving it to July.

We did check for codes and there wasn’t any. If it is that would it bring up a code?

newdude · April 29, 2023

18 minutes ago, mountain maniac said:

We did check for codes and there wasn’t any. If it is that would it bring up a code?

What did you check it with? Just a basic code reader? If so, they can't always read everything. It could have a U code or C code that you can't see that a higher end reader or full scan tool can read. U0101 is a popular code for a bad TCM on these.

dsr611 · April 30, 2023

TCM is shot. Mine would do the same thing...it's also temperature dependent; tried to move it one day when it was warm and it wouldn't do anything...tried again a few days later when it was about 20° cooler and was able to drive it around the yard.

My truck's been sitting in the yard collecting leaves, pollen, and bird ****** since November. If you're willing to spend upwards of $7500, you can find them on Ebay and several online performance stores. I sent mine off to Xemodex a couple weeks back and just got it back today (the 2 retainers holding it to the fan shroud broke pulling them out so I've got to find a couple of new ones tomorrow). They repair them for $1200 and reflash to your VIN...found them recommended on durmaxforum by several people. Hated to spend the $$$ on a repair, but it comes with a lifetime warranty. Spoke with 2 GM dealers here in town and they said they haven't heard anything about when new ones would be available.

mountain maniac · April 30, 2023

12 hours ago, dsr611 said:

TCM is shot. Mine would do the same thing...it's also temperature dependent; tried to move it one day when it was warm and it wouldn't do anything...tried again a few days later when it was about 20° cooler and was able to drive it around the yard.

My truck's been sitting in the yard collecting leaves, pollen, and bird ****** since November. If you're willing to spend upwards of $7500, you can find them on Ebay and several online performance stores. I sent mine off to Xemodex a couple weeks back and just got it back today (the 2 retainers holding it to the fan shroud broke pulling them out so I've got to find a couple of new ones tomorrow). They repair them for $1200 and reflash to your VIN...found them recommended on durmaxforum by several people. Hated to spend the $$$ on a repair, but it comes with a lifetime warranty. Spoke with 2 GM dealers here in town and they said they haven't heard anything about when new ones would be available.

thanks I will check into that

mountain maniac · April 30, 2023

23 hours ago, newdude said:

What did you check it with? Just a basic code reader? If so, they can't always read everything. It could have a U code or C code that you can't see that a higher end reader or full scan tool can read. U0101 is a popular code for a bad TCM on these.

Just now, mountain maniac said:

thanks I will check into that

I took it to a garage so not sure which one they have but thanks

dsr611 · May 2, 2023

Got my TCM back from Xemodex over the weekend and put it back in yesterday. Have only driven about 25 miles on it so far, but it is shifting as smooth as it ever has. Got out and cleaned all the caked up pollen and bird crap (from sitting for the past 5+months) off of it today. Will be driving it back and forth to work the rest of the week to see how it's going to act, but if it is anything like the 25 or so miles I've put on it yesterday and today, I will recommend Xemodex to anyone that is needing their TCM repaired.