Grade Brake-Downshift in Normal drive - Allison

[reelbob6.6]

I have a 2001 chevy duramax with allison transmission. Do these allisons downshift from 5th to 4th on grades when the brake is applied on steep hills in normal drive position? According to a chevy bulletin #02-07-30-004 I have it should down shift from 5th to 4th but mine does not and the dealers I have taken it to say nothing is wrong with mine. It shifts down great in the tow/haul mode but not in the regular drive mode?? I posted this on the 2500HD site. & thought I would try this one. THANKS FOR THE INFO IN ADVANCE - Bob

2001 2500HD
EXTEND. CAB.
6.6 DURAMAX
ALLISON TRAN.
15,000MILES LITTLE TOWING

[glclary]

Mine DOES downshift in normal drive when I am going down a steep hill with the brakes on. It does not happen as quickly as when in T/H though. Seems like the brakes have to be applied lightly for 2 or 3 seconds on a pretty steep grade before it happens. It doesn't downshift on every hill. I am sure its a computer thing and that somebody else on here can give you the scientific answer.

Have a nice day!

Lee ;)

[Dave_WB3FYV]

I read someplace that you have to have your foot off the accelerator (zero throttle position input to the computer) AND apply the brakes for 7 seconds before it downshifts to 4th. Note that 'any' throttle input, even resting your big toe on the pedal, will change the downshift pattern.
Mine does it fairly well, but I notice that after I have run in T/H mode for a while, it will downshift sooner.
You may want to try the tranny reset sequence explained in other posts to get it to learn how you drive. Then it may act better.

[reelbob6.6]

Thanks for the feedback. I did the 50mph - fifth to first sequence and hope the advocants are not ford owners getting a kick out of allison owners doing the crazy think??? I will try to see if I can get it to shift down as you both pointed out on my next trip out of the valley. I would think the dealers could reprogram the tcm & ecm without the drastic downshift sequence? but mine don't have a clue - did not know what "grade braking" is??
Thanks Bob