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Allison 1000 Transmission Flush Instructions

Using the "Hoot" Method.

AMSOIL Technical Bulletin DT-2005-09-28

Parts Needed:

• Transmission Fluid (five gallons)
• Spin-on filter

Tools Needed:

1. Two feet of 5/8 heater hose
2. 13mm & 15mm socket, and 3/8 ratchet or equivalent
3. Torque wrench- 3/8”
4. Empty three gallon containers—2 ea
5. Safety Glasses
6. Plenty of rags
7. Very small screwdriver


Remove and replace spin on filter—prime if you like.
Don’t forget to transfer magnet from old to new filter, wipe magnet very clean before installing in new filter.

Keep track of what you drain out of the trans. This will come into play later.

Install drain plug and tighten to 25 foot pounds.

Pour approximately 11 quarts of oil in transmission.

Disconnect upper line from trans cooler at the transmission. These lines are on the passenger side of the transmission, near the torque converter. The lines are also identified on the side of the transmission

Quote from Hoot: “In case you haven’t seen the Jiffy-Tite style connector before: Slide back the plastic cover over the c-clip-shaped spring, then use a small screwdriver to pop the spring out of it’s groove. KEEP A FINGER ON THE SPRING AS YOU DO THIS, because those springs love to go flying off into some dark hole where you’ll never find it. Once the spring is out, just pull and wiggle on the line until it comes out of the fitting. As soon as you have the line out you can put the spring back into its groove so you don’t lose it-the line will snap right back into place when you’re done, even with the spring there. Be careful not to damage the o-rings when re-installing.”

Attach the two foot hose to the line you just unhooked and run into your other container. Make sure to push the hose on far enough to go past the ridge in the line. Have one person hold the hose while another starts the truck (unless you have remote) and a third person pour oil in the filler tube.

Turn the truck on and off until you run about one and a half gallons out of the line.

You will have empty containers (if you bought the one gallon size) that you can set inside of your second container, which you can run the hose directly into to measure your progress. Be careful the oil comes out pretty fast.

At this point check how much oil you drained initially and how much you drained in the flush. Subtract how much you drained from how much you added and shoot for a difference of 3.2 quarts. In other words you want 3.2 quarts more in the transmission then you drained out. If you have too much in the transmission run a little more out of the cooler line.

Once you are satisfied the oil level is close, reconnect the cooler line and make sure the line is firmly attached.

You should have the c-clip back in its original position before reconnecting the line.

When reconnecting the line it will “click” in position and may squirt you in the face with a touch of oil.

Start truck and look for leaks, then run the transmission through the gears a few times.

Put truck back in park and check level with dipstick. Should be full cold-if not add fluid.

Drive the truck enough to get the transmission warmed up and then check again-should be to full hot mark.

Once you know you have the fluid level correct you are good to go. NEVER OVER FILL THE TRANSMISSION WITH FLUID!

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