Allison Automatic on 5 ton M923A2

[Afterburn]

I recently bought the truck and not sure if the transmission is up-shifting correctly. From a stop, the first up-shift seems fine. After that, I have to lift off the accelerator a bit for the remaining up-shifts. Trans oil looks clean and the level is okay at 70 degrees when checking it. Trans temps are just under 200 deg.

 

[simp5782]

I recently bought the truck and not sure if the transmission is up-shifting correctly. From a stop, the first up-shift seems fine. After that, I have to lift off the accelerator a bit for the remaining up-shifts. Trans oil looks clean and the level is okay at 70 degrees when checking it. Trans temps are just under 200 deg.

adjust the modulator cable. it is up on the motor just below the throttle linkage on the injection pump. you have a shoulder bolt there that you can loosen and adjust the arm bracket accordingly you may have to play with it a few times

 

[cucvmule]

Welcome from Missouri to Steel Soldiers Afterburn!

 

[Afterburn]

Thank you mule

 

[Afterburn]

Thank you. I looked up this adjustment in the TM dated 2012, the illustration shown is not the same as what's on my truck, but it's not hard to see what's going on. With the throttle wide open, is the intent to have the modulator cable fulling extended as well?

 

[86m1028]

From what I understand the answer is NO.

 

[74M35A2]

Start by lubricating this modulator cable first. I used WD-40 and the straw directly down into the cable housing at the top by the throttle connection. You can freely pull on the cable and release it while doing this, to work it in. Makes a huge difference. You want to make sure it is moving freely as possible before any adjustments are made. The cable is spring loaded in the pull direction on the transmission end. It should very cleanly "snap" back to its home position when released. You do not have to disconnect anything to perform this.

By lubing this cable, it should cause the 2-1 downshift to be butter smooth. I know this was not your concern, but when mine because harsh, this was the cause of it. As reference, my cable is in the middle of the adjustment on the throttle lever, and seems to have perfect shifting and shift points, both up and down.

 

[MAdams]

Make sure the cable slides easily and aim for 3/8" slack at WOT

 

[Afterburn]

Thank you 4-star. With the throttle fully open, I was able to pull the modulator cable out by hand almost a half inch. I''l lube up the cable and adjust to 3/8.

 

[MAdams]

If you have a 1/2" now, adjust it until its tight at WOT and go from there. Its trial and error until you get it to shift where you like it.

 

[Afterburn]

Today I extended the modulator cables length a little, transmission now up-shifts to third gear normally. A few more threads on the cable and it should be good. Thank you everyone for your input and help.