23 GMC Sierra 10 speed trans

Jay P · August 6, 2024

3 hours ago, Edwin Grundy said:

We have a 2024 2500 Sierra that we bought off of the lot. It is a basic work truck with the 6.6L gas engine. It has 8000 miles and is currently in the shop needing a valve body for the transmission. It has been in the shop 3 weeks and the part is on backorder. GM is unable to give information on when the part will be available. At first it was between 7/31 to 8/13. The dealer now says 8/14 to 8/26. The customer service people are nice but have no authority and will not let you speak to upper management. I use the vehicle to tow and the dealer does not have a 2500 loaner. GMC will not authorize the cost to rent an equivalent vehicle. They would only state that their policy would reimburse me less than 50% of the cost and I could send them the bill for further consideration. We have averaged 11.5 - 12 mpg in the city. Highway was 13.5 - 15 mpg. Towing is another story. On a recent trip to pick up a pontoon boat in Florida we averaged 5.7 mpg at 65 miles per hour. It tows reasonably well for a gas engine. The boat and trailer combined weight was around 7800 lbs. If you are considering using the truck for towing be aware that we have had problems with the trailer brake controller. Under normal driving conditions, the truck will randomly display "Trailer wiring fault". During this time that will last from 3 to 60 seconds the trailer has no brakes. Recently with an 11,000 gross weight trailer and load, we were pushed through a red light with the antilock brakes chattering so bad that I thought that the truck was going to shake apart. GM has stated that they do not have a problem with the controller but if you search the internet you will find many articles regarding this. A dealership checked the controller and said that it was OK. I forwarded a few posts from the internet to my service advisor. A few days later when I called to check on the transmission part, he stated that they checked the controller and found a fault and that they were going to replace it.

FYI.. the 10 speed in the 1500 is not the same or related an any way to the 10 speed in the 2500/3500 trucks. The 10 speed in the 1500 and some cars was jointly developed by GM and Ford. The 10 speed in the 2500/3500 (gas and diesel as of 2024) was jointly developed by Allison and GM for the 2500 and bigger trucks (only with the diesel at first).

Edited August 6, 2024 by Jay P

redwngr · August 6, 2024

4 hours ago, Edwin Grundy said:

We have a 2024 2500 Sierra that we bought off of the lot. It is a basic work truck with the 6.6L gas engine. It has 8000 miles and is currently in the shop needing a valve body for the transmission. It has been in the shop 3 weeks and the part is on backorder. GM is unable to give information on when the part will be available. At first it was between 7/31 to 8/13. The dealer now says 8/14 to 8/26. The customer service people are nice but have no authority and will not let you speak to upper management. I use the vehicle to tow and the dealer does not have a 2500 loaner. GMC will not authorize the cost to rent an equivalent vehicle. They would only state that their policy would reimburse me less than 50% of the cost and I could send them the bill for further consideration. We have averaged 11.5 - 12 mpg in the city. Highway was 13.5 - 15 mpg. Towing is another story. On a recent trip to pick up a pontoon boat in Florida we averaged 5.7 mpg at 65 miles per hour. It tows reasonably well for a gas engine. The boat and trailer combined weight was around 7800 lbs. If you are considering using the truck for towing be aware that we have had problems with the trailer brake controller. Under normal driving conditions, the truck will randomly display "Trailer wiring fault". During this time that will last from 3 to 60 seconds the trailer has no brakes. Recently with an 11,000 gross weight trailer and load, we were pushed through a red light with the antilock brakes chattering so bad that I thought that the truck was going to shake apart. GM has stated that they do not have a problem with the controller but if you search the internet you will find many articles regarding this. A dealership checked the controller and said that it was OK. I forwarded a few posts from the internet to my service advisor. A few days later when I called to check on the transmission part, he stated that they checked the controller and found a fault and that they were going to replace it.

Your HD truck has a different 10 speed than the one used in the 1500's