Transmission hard upshift

[fpchief]

There seems to be alot of posts on the Allison shifting hard on downshifts. But not finding much on hard upshifts. The shift from 1-2 is pretty hard....shakes the seats and may be normal but I am looking for a way to make it a little easier. A shift that hard cant be good for the joints.

 

[Kbarnes0]

There seems to be alot of posts on the Allison shifting hard on downshifts. But not finding much on hard upshifts. The shift from 1-2 is pretty hard....shakes the seats and may be normal but I am looking for a way to make it a little easier. A shift that hard cant be good for the joints.

What fluid are you running? How long since the service? I've had had a few that were soft shifters and ran Delo 15W40 in and it helped out. 1-2 soft was pretty stout, especially when cold. Maybe a lighter oil may help soften it up.

 

[Elijah95]

My M923A2 had the same issue, adjusted the TV cable for the tranny and properly lubricated it, big difference but still snappy. These trucks weren’t meant to be driven unloaded, and shift substantially different with an actual load on them. Just don’t be one of the guys to swap to ATF trying to coax a smoother shift out of the truck, it’s not the correct route.

With the truck off, The TV cable should be adjusted correctly and snap back immediately if you crack the throttle by hand and let off, if it doesn’t, spray it with Aerokroil, PB or something and work it, spray, repeat. It took me over 100x to get mine loose and when it did it made all the difference in the world


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[fpchief]

Fully serviced it when I got it about 8 months ago. Put in dex III.

What fluid are you running? How long since the service? I've had had a few that were soft shifters and ran Delo 15W40 in and it helped out. 1-2 soft was pretty stout, especially when cold. Maybe a lighter oil may help soften it up.

Fully serviced it when I got it about 8 months ago. It had dex in it (was brown but smelled like atf) so that's what I put back in it. It does act about the same hot or cold.

 

[fpchief]

My M923A2 had the same issue, adjusted the TV cable for the tranny and properly lubricated it, big difference but still snappy. These trucks weren’t meant to be driven unloaded, and shift substantially different with an actual load on them. Just don’t be one of the guys to swap to ATF trying to coax a smoother shift out of the truck, it’s not the correct route.

With the truck off, The TV cable should be adjusted correctly and snap back immediately if you crack the throttle by hand and let off, if it doesn’t, spray it with Aerokroil, PB or something and work it, spray, repeat. It took me over 100x to get mine loose and when it did it made all the difference in the world


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I will definitely give it a shot, the one I rode in pulling M198's around back in the day definitely did not shift like this...loaded or not. But I dont know if it was an A1 or A2...didn't care to know back then.

 

[Hulk5T]

My M923A2 had the same issue, adjusted the TV cable for the tranny and properly lubricated it, big difference but still snappy. These trucks weren’t meant to be driven unloaded, and shift substantially different with an actual load on them. Just don’t be one of the guys to swap to ATF trying to coax a smoother shift out of the truck, it’s not the correct route.

With the truck off, The TV cable should be adjusted correctly and snap back immediately if you crack the throttle by hand and let off, if it doesn’t, spray it with Aerokroil, PB or something and work it, spray, repeat. It took me over 100x to get mine loose and when it did it made all the difference in the world


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[Hulk5T]

What is a tv cable?

 

[simp5782]

What is a tv cable?

Modulator cable. It controls the flow of transmission fluid pressure to change gears with throttle. It runs from the rear drivers side of the transmission to the throttle arm

It is called a TV cable on smaller cucv and hmmwv more commonly.

 

[Mullaney]

Modulator cable. It controls the flow of transmission fluid pressure to change gears with throttle. It runs from the rear drivers side of the transmission to the throttle arm

It is called a TV cable on smaller cucv and hmmwv more commonly.

Wes, Since there is a Modulator Cable - does that mean there is a valve on the side of the transmission that looks like what used to be called a "Modulator Valve" on an old GM or Ford (passenger vehicle) transmission?

OR is it all mechanical on the Allison?


Tim

 

[simp5782]

Wes, Since there is a Modulator Cable - does that mean there is a valve on the side of the transmission that looks like what used to be called a "Modulator Valve" on an old GM or Ford (passenger vehicle) transmission?

OR is it all mechanical on the Allison?


Tim

Yes but these are non adjustable springs in the stock ones. Ccc cables in Houma, LA makes an adjustable spring type.

 

[fpchief]

I lubed up the cable as suggested, made no diff on it. That shift is the single thing that sucks about driving that truck.

Is there anything else to check? I am hoping to work on it this weekend. My damn fuel pump is leaking yet again. No gasket this time, just the correct RTV. Not sure what the deal is, never had an issue sealing something so easy to get to.

 

[Elijah95]

Lift pump or main injection pump?


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[fpchief]

Lift pump or main injection pump?


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Lift

 

[Elijah95]

Mine had the same problem, never could get it to seal correct without gasket. I put Indian head shellac on the gasket, both sides, cure to tack, then mount up, snug bolts, then torque in a few hours m


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[fpchief]

Will give it a shot!

 

[simp5782]

I lubed up the cable as suggested, made no diff on it. That shift is the single thing that sucks about driving that truck.

Is there anything else to check? I am hoping to work on it this weekend. My damn fuel pump is leaking yet again. No gasket this time, just the correct RTV. Not sure what the deal is, never had an issue sealing something so easy to get to.

Replace the cable with one from ccc. It fixes the issue