Allison Transmission Removal Guide

Online pdf Allison Transmission Removal Guide

This is a guide to removal and installation of your Allison transmission.  This is on an 03 Extended cab short bed truck so some things may differ on your truck. Also this truck is a 4x4 model so many of these things will not apply to 2wd trucks. It is meant to be a guide that somebody that knows which was to loosen a bolt can use so if it seems dumbed down a bit at points I apologize.  

However even though this guide may make it look easy, you do need to have some mechanical knowledge, things can go wrong and I know this write up will not be complete as there is so much to remember.  But I will do my best for you.  I apologize for not having perfect pictures or pictures for everything, but once you get in there you will be able to figure it out.

Tools you will need.

  1. Car lift, or buddy with one, or some jack stands
  2. Transmission jack of some sort
  3. 13mm and 15mm Deep and Shallow Socket
  4. 13mm and 15mm combo wrench
  5. 18mm socket and wrench
  6. 8mm wrench
  7. 7/8” socket
  8. 11mm socket
  9. 3/8 Ratchet and a couple extensions of different sizes
  10. Impact wrench
  11. A LOT OF Extensions for the impact wrench
  12. ½”-3/8” adapter
  13. Small flat bladed screwdriver
  14. Body clip removal tool, or your own method of removing them.
  15. A BIG adjustable wrench
  16. A Heat gun
  17. Some brakleen (optional)
  18. Some penetrating lube.

Now for the removal.

  1. First things, first. You need to get your truck in the air.  Use one of the methods above to get the truck off the ground so that you have enough room for your tranny jack to lower the tranny out and roll out from under the truck this isn’t a tranny you just lift in and out on your belly.  I am fortunate enough to have a car lift in my shop and used that.  If you are a first time car lift user, the lift points on our truck are the front leaf spring shackles for the rear arm, and for the front arm use the frame.  If using the style pads like mine use the big step in the rear with it angled in, and use the small step in the front angled to the rear of the truck.  Now lift it in the air and make sure its sturdy. Also disconnect your batteries as well.
  2. Now you need to gain access to the torque converter bolts.  The only way to do this is to go through the starter motor housing on the passenger side of the engine.  It is a PITA, but so is everything in life these days.  To do this you must first remove the passenger side wheel with the 7/8” socket and impact wrench. 
  3. Next you need to remove the fender liner, which is where I recommend spending 50 bucks on a set of body clip removal tools they make it so easy.  Otherwise you can pry up in both slots with two small screwdrivers and grab it with a needle nose. A PITA and you’ll probably slip and cut your fingers a few times. Not all of the clips hold the liner on. You will see more but they are for the fender flare and do not need to be removed.  Once you have all of those clips removed there will be a Christmas tree push in plastic thingy in the corner of the fender liner. It has a big head so you cant miss it.  It too needs to be removed.  Now some wiggling and the liner will be free but there are 3 wires that are fasted to the back.  To remove these use the small flathead to release the clips.
  4. Now you will see the starter and need to remove it, you can leave it lay against the frame rail but I choose to remove my exhaust front pipe and completely get the starter out of the way as it makes removal of the torque converter bolts.  You will see two wires running onto one post of the starter, use a 13mm wrench to remove that nut.  The other little wire you will need an 8mm but BE CAREFUL it is an odd design and can rip a chunck of the solenoid off with very little pressure. I know, mine did it.  Now with the wires disconnected you will need to remove the two bolts that hold it on with the 15mm wrench.  I choose the remove the bottom bolt first because leaving the top bolt in keeps pressure off of the bottom bolt so you can thread it out by hand.  Otherwise it’s a PITA because the oil pan extends out underneath the bolt and you have very little room to work.  The top bolt can be removed with either the wrench or socket.  Now the starter is free
  5. If you choose to remove the starter completely you will need to remove the front pipe.  However depending on your exhaust system your experience may differ.  In my case I have a seal clamp where my front pipe connects to the exhaust, which makes for easy removal. On most trucks you will have a 4-bolt flange.  Let this soak in penetrating lube for a while then carefully remove them. They like to break. Next you will see the V-Band clamp where the down pipe connects to the front pipe.  This uses a 11mm deep well or a 7/16 if you don’t have an 11.  Simply loosen the nut so that it is nearly off of the threads. Then you will mostly likely need to work the three sections of the clamp off with a screwdriver.  Now just push the threads back and the T-section will slide out of its holder. Now remove the front pipe and snake the starter through the opening.
Online pdf Allison Transmission Removal Guide

Allison Transmission PDF Manuals