Harsh 3rd - 4th gear upshift while towing

[markrinker]

While towing ~14K lbs in tow/haul mode, driving a bit aggressively, I noticed that the 3rd to 4th upshift is very harsh. All others smooth - RPMs about 2800. Feels like a momentary slip, then bang its hooked up with a strong thump through the drivetrain (and through the seat of my pants).

If I baby it, its not there, but starting out from a dead stop with about 1/3 - 1/2 pedal, its nasty, and repeatable.

Anyone else experiencing this while towing?

2001 LB7/DA 74K miles. Should I be concerned?

[More Power]

It can take a while for the Allison adaptive learn to catch up with a particular driving style. It might be a concern if towing more or less continually for several days, and the Allison continues to shift harshly.

Jim

[markrinker]

We might be on to something. In this particular scenario, the truck was driven (by me) for about 600 miles before I noticed the rough upshifts. These were all loaded miles ~14K lbs. I was nearing my destination, in heavy traffic, and a bit late - all adding up to a heavier foot that this truck has seen.

My theory is the adaptive learn was not prepared for this throttle level, RPMs, and loading during 3-4 upshifts, and it resulted in 'flare' shift. Once my right foot returned to a more conservative approach, the shifts were smooth as silk once again.

MP - Does 'adaptive learn' take into consideration Driver 1 and Driver 2 on the newer trucks? (I don't think the 2001 has that concept, anyway.) The truck will regularly have two different drivers, with different driving styles. Trailers and loads will be the same.

[ 09-17-2005, 04:56 AM: Message edited by: Mark Rinker ]

[Kennedy]

It seems that some times the Allison just learns bad habits. They will eventually "learn out" these hard shifts. I typically use my Tech 2 to reset the individual adaptive on the particular shift and it seems to do well after this. My 2005 began a harsh 3-4 not long after I put in the Suncoast kit. I reset the adaptive on the 3-4 and it hasn't bucked since.

If you look back you will see this has been a not so common occurrence, yet over the years we'll see a few complaints regardless of model year etc. My 2002 did this for a while heading out to the Rendezvous or maybe it was the Pull Off one year...

[REDTRUCK05]

Originally posted by kennedy:
It seems that some times the Allison just learns bad habits. They will eventually "learn out" these hard shifts. I typically use my Tech 2 to reset the individual adaptive on the particular shift and it seems to do well after this. My 2005 began a harsh 3-4 not long after I put in the Suncoast kit. I reset the adaptive on the 3-4 and it hasn't bucked since.

If you look back you will see this has been a not so common occurrence, yet over the years we'll see a few complaints regardless of model year etc. My 2002 did this for a while heading out to the Rendezvous or maybe it was the Pull Off one year... How do you rate a good shift and a bad? My tranny still seems alittle mushy in shifting. I set the edge to not defuel and it seems alittle better, too early to tell. first is strong as is second, third seems confused as does fourth and fifth. This tranny is the best out there, But seems confused often. What happens when the "talked about 10 speed" comes out?

[Kennedy]

I like a firm shift that gets hooked in and goes with a little nudge. So long as it does not slam...

My 02 and 05 have slammed in the past, but as stated earlier this seems to be gone now.

[Steve Rapp]

My 04.5 shifted pretty firm when I returned form a cross country trip (towing 6000lbs in tow-haul mode the whole way) at the end of July but now seems to have smoothed out.