Manually shifting M1087 transmision while driving

[Duckworthe]

Just a general question concerning manually shifting the truck with up/down arrows while moving. I have always wondered what would happen if while pulling a hill and just wanting the truck to drop one more gear instead of lugging. I know the truck has to be STOPPED to be shifted into Mode. But pushing the up/down arrows seems ok to me. But I will ask before pushing it and breaking something.
Thanks everyone,
Eric

 

[Suprman]

I have not tried it. But the computer should not allow a shift that could/would cause damage.

 

[coachgeo]

Manually downshifted to 6th on a steep curvy highway hill with no issue. Found it a bit cumbersome to reach around the turn signal arm and steering wheel though.

Remember the transmission is a typical Allison 6speed used in many many many vehicles. Only different about ours is the AWD box tagged onto the arse end of it. Thus would think??? using the transmission in most situations should be pretty much the same as any other auto tranny when using the gears "in the transmission" (First gear is in the AWD box)

 

[DiverDarrell]

The controller won't let you mess it up. The computer will only down shift when the Rpms will be in the accepted range for the lower gear.

 

[dmetalmiki]

Just a thought, Even 1950s cars (and now others) Had (have) a governor that won't allow shifts before governor pressure is correct. ( for the selected gear ratio)

 

[Duckworthe]

Very nice. Now I can reach over and give it a push with out the fear of dollars flying out of my wallet!!! Fingers crossed of course. Thanks everone

 

[tennmogger]

Duckworthe, in that lugging situation, can't you press the accelerator pedal to force a downshift? Can on mine, unless the engine would go too high rpm after the desired shift. The tranny knows. In that case the trans won't downshift.

You can certainly force a down shift with the down arrow without worry. It just might not shift yet, until road speed drops a little more.

On a downgrade the trans can be manually set to lower gear to assist holdback. Still have to brake though unless you have the exhaust brake. If the trans senses too high engine speed, a shift will be made anyway, to a higher gear. Example, push down arrow to 5th, but when road speed increases from lack of braking, the trans will shift to 6th to protect the system even though you manually set 5th. That was an eye opener the first time it happened to me.

Does anyone else have trouble estimating engine rpm on these FMTVs? The turbo whine is mostly monotone so no clue there, and that tone covers engine rpm hints. Need a tach!

 

[Duckworthe]

Tennmogger,
Thanks for your response, as well as everyone else . I can obtain full throttle as I have adjusted my throttle cable correctly. I seem to run full throttle most of the time. Just at times while pulling a long hill it feels like it could shift down sooner to keep it moving. I wish I had a tach!

 

[Suprman]

I have universal tachs that are compatible. You can get the tach signal at the ste ice harness, big round plug lower left under drivers dash or behind the heater box. And you should be able to use the alternator AC output on the regulator to drive a tach also.
Will