Allison Transmission Questions Hi there Armstrong, Sorry it took me so long but it has been a busy week. I would call Clarke Detroit Diesel Allison in Memphis @ 901 396-7320. They will not be able to work on your pick-up but may be able to tell you which GMC dealer in your area. There is another option which is General Truck Sales & Service Inc. in Memphis @ 901 345-3270. General seems to be the big GMC dealer in Memphis and they do have authorization to do Allison maintenance. If you have a problem and the dealer does not know about the Service Information Letter, have them call me @ Pacific DDA 360 887-7400 and ask for Rick F in the Allison shop. Thanks and have a great day!