Hard upshift after using motor for decel

[Chevy1925]

So towing the last few times I've noticed something that is really concerning me. After heading down a grade and tapping the brakes a few times, the motor will down shift to slow my rig like it's suppose to. What's happening now is at 60-65mph I'm still on the brakes some, it will kick down to 3rd gear and 3800rpm. No biggy to me but the problem is, as soon as I give it a little throttle to up shift, the trans will tie up really bad. I have not really noticed it before as I use to cruise down the hills fast enough it would never kick down to 3rd at that rpm or I'd be slowing way down for traffic. Since these last few trips I've been takin it really easy and really trying to keep my speed around 60, I'm noticing this. If I'm at or below 3200rpm, it will upshift smooth as butter.

Defuel tables are all stock, trans tcm defuel is all stock and the only mod done was the lock up. Am I missing something to change for the high rpm down shift and up shift for light throttle? I don't believe factory ever went that high but my shift points at wot are 3600rpm and my rev limiter is set to 4k.

 

[onebaddmaxxx]

When I tow and get to big hills I usually play with tow haul to keel it from getting crazy....I just attest to it as 5 speeds/al5 are finicky

 

[onebaddmaxxx]

My lb7 acted worse than my lly. The lb7 had horrible grade braking....I would have to run it hard once it downshjfted to get it to upshift. Finally got it down to a quick motion of fooring it would put it back to normal

 

[Chevy1925]

There is nothing wrong with my grade braking or how/when it engages. It works awesome in slowing me down with my load, the issue I'm having is the tie up in the upshift

 

[chevyburnout1]

I noticed mine has always been slightly harsh after a good long grade brake down the east side of Eisenhower pass in Colorado. But not harsh enough to be a tie up? As in trying to stop the tires?

 

[Chevy1925]

Yeah it's bad. It's very quick when it shifts but holy heck, you think it's gunna twist the driveshaft or blow a hard part it hits so hard.

I know stock, they didn't down shift higher than the stock 3250 or where ever the rev limiter is unlike the lbz. That's why I'm wondering if there is some cells or tables that need to be adjusted somewhere for this I'm missing

 

[hondarider552]

My single cab did that the few times I towed James. 3800+ in grade brake then upshifts and shifts like a ATS trans with the copilot set on kill

 

[chevyburnout1]

With the stock trans tune in it I would think it's more than likely issues mechanically, if there are even issues though :dontknow:

 

[chevyburnout1]

Possible characteristic of built transmissions?

 

[Chevy1925]

I can't see why anything under 3200 rpm will up shift smooth as butter then under the same circumstances? Above that is like a switch and it slams

 

[THEFERMANATOR]

Grade braking seem to have tehre own shift tables that we don't have with EFILIVE. I'm wondering if this could be due to TCM changes with lockup tables. I know my upshifts coming out of grade braking are MUCH firmer than the shifts otherwise, and I've had a few that were pretty bad. But it normally smoothed itself out after it did a few of them. Also it should be of note that 02 has some of the most aggressive grade braking of any TCM OS, and I found it to shift pretty firm. This was one of the reasons I went back to an 01 OS in my bURB.

 

[Chevy1925]

its never been an issue till after raising my shift points and rev limiter. i would really hate to have to move the shift points and rev limiter back to stock. at 4k, it does a fine job of slowing me down and i really like it. not to metion the truck pulls harder at WOT unloaded shifting higher.

 

[ALLY Fox]

Mine does the same thing. It did it before and after having the trans built. I haven't noticed the same symptoms when not towing, but I always worry about the stress it's putting on the driveline when the shifts are harsh. I've tried feathering back before it shifts but that doesn't always work. Be nice to find a fix for it.

 

[Chevy1925]

found an article from kennedy diesel

https://www.kennedydiesel.com/allison_grade_braking.html

i also tried to search some more and found guys hitting the same 3600-3800rpm in 3rd gear from the grade brake with no mention of a nasty shift/tie up when hitting the throttle.

out of the 5-6 times its done this over the last two trips, i would have thought it would have started to learn/shift better if it was a learning issue. i dont know though, im guessing.

 

[Chevy1925]

So driving home today, I threw the shifter down into 3rd gear at 60 which put me at 3500rpm. Bump the shift back up to D and bam, hits as hard as it did towing. Did this another 5 times trying to see if it would learn. It got a little better but absolutely no where a smooth shift. Do the same at 3200, 3100, or 2800 and it's smooth as glass

I'm really thinking this is a defuel issue but where would I start?

 

[hondarider552]

Could start by towing me to Mikes to duplicate the problem, then you could get a refresh too. :hug:

 

[Chevy1925]

Haha boy that would fill sals day up

 

[Chevy1925]

so no ideas eh?

 

[whitetrash21]

Feed the squirrels pancakes every now and then and maybe you can convince them to match revs a little better on the upshift....???

 

[chevyburnout1]

Maybe back to the basics. New spin on filter?