help me, alison 4-3 downshift

[latemodel68]

i need some more help.this truck has me so pissed off.when i tow my camper and i hit the slightest of hills,my truck downshifts from 5th to 4rth,and is ok,but right after that it goes into 3rd.then i loose power because the rpm's are so high.if i let off the gas a little,it shifts to 4rth and picks up speed.so long story short i am trying to prevent the 3rd gear shift with speeds above 48mph.i have altered D5007 and D5037,but no matter what i set it to,it still has too agreasive downshift.can someone please look at this and tell me what i am doing wrong.
as alway's thank's

[minytrker]

You shouldnt lose power with your rpms high, you should gain power. I would adjust the motor tune not the trans tune. I tow my 17,000lb race car trailer every weekend and the on hill when it downshifts the rpms get real high and I max max boost I gain speed going up the hills. Whats your boost and egt's doing when your rpms climb?

If I make mine stay in 4th vs 3rd my egt's will climb real high because it wont make alot of boost. I think its in your motor tune not trans.

[latemodel68]

i should have been more specific with my post.
my truck is a chevy 2500hd with an 8.1 and allison 5spd transmission.
justin at blackbear performance tuned the engine.
if i could get the transmission to hold 4rth gear when pulling it would pull better.
he said at the time he could not alter transmission shift points.
thanks

[ScarabEpic22]

Are you using T/H mode? I know T/H has more aggressive shift timing (hold gears longer before upshifting, and holds them longer before downshifting). What speed does this occur at, thats what needs to be determined so you can adjust the tables for the right speed.

[minytrker]

Yeah disregard my first post since you a 8.1. Why couldnt he adjust shift points?

[latemodel68]

i would like to stop the 3rd gear downshift at speeds above 50-55 mph.if it would only shift to 4rth gear it would have a lot more torque.my engine doent make a lot of power at 4500 rpm.like i said,i can back off the throttle and it will shift up,and when it does the truck takes off.i don't understand why the adjustments(see attachment above) don't change anything.

not in tow haul mode.seem's the same as far as the downshifts are concerned.

thanks

[Big Mike]

I dont have a stock 02 trans tune to compare yours to (post yours if you can) but running on memory it appears you adjusted only the 3-2 downshift settings in the 4Lo row. Is that correct?

[latemodel68]

here's the stock tune10900

[Big Mike]

What I'm seeing comparing the two tunes is that you made most of the adjustments in the 4-3 downshift table in those columns OTHER THAN the normal mode column. The only change made in that column is a MPH decrease at 100% TPS which doesn't do any good anyway, because at 100% TPS the trans is using the WOT tables {D5037}, not the part throttle tables.

So if you want it to stay in 4th longer you need to lower the MPH in the normal mode column in the TPS area where you're having the premature downshift problem. Say from 50% through 100%. And....

I've also found it's best to keep the 100% TPS MPH the same as whatever the MPH is in the WOT table {D5037}. If they aren't the same it seems to cause oddities with how the the trans works. So what ever MPH you use at 100% TPS in the part throttle be sure it matches the MPH in the WOT table, which again would be {D5037}.

[killerbee]

see post above.

Also, what column are you adjusting? They are mislabeled in many cases. Column D is not what it says it is.

[latemodel68]

thanks guy's,
this is what i did.i have adjusted all 4 part throttle tables to max out at 45mph.then adjusted wot speed to 45mph per Big Mike's advice.so far it shift's perfectly.at 50mph part throttle or wot,it shift's to 4rth only.the test will come thursday when i pull my camper to myrtle beach(300 miles).i will get back to everyone when i get back on monday.thank you, everyone, for taking the time to help me work this problem out.i will also post my final bin,maybe it can help someone else out one day.

[latemodel68]

ok,made it back from vacation.here's how everything worked.with nothing hooked to the truck,it shifts the way i like(no 3rd gear downshifts above 50mph).but with the camper hooked up and a golf cart in the bed,it still downshifts into 3rd gear at speeds as high as 62mph.i am at a loss here.no matter what speed i put in the wot and part throttle downshift tables,it still dowshifts.here's my final transmission tune.maybe i am just doing something wrong.
thanks for all the help.

[latemodel68]

just wondering if anyone has a clue here.my personal feelings are that the allison controller has a way of determining load somehow.must be a setting there that is unavailable with efilive.i really would like to solve this if possible,but i have tried everything i know.

anyone??
thanks

[killerbee]

Is it a 4-3 "locked" shift? Does the TC stay locked throughout?
Does the same issue exist in normal and T/H?
Are you using cruise control?

[latemodel68]

thanks for the reply killerbee,
not sure exactly what you mean by 4-3 locked,but if i let off the gas slightly,the transmission shifts to 4rth,then a short time later the converter locks up.same thing in tow/haul mode.also will still do it in cruise as well.

[killerbee]

on the possibility that cruise control has it's own schedule, don't use it.

My question is, on your log, is the TC staying locked on your 4-3 observation? In other words, are you sure you are experiencing a shift, and not an unlock event? Just throwing this out. It can feel similar.

[latemodel68]

well killerbee,
i am not going to lie about it.i havent done a log.i guess that's what i am going to need to do.i am pretty sure it's shifting into 3rd gear.to solid of a shift to be lock up.i even thought for a second it could be 2nd gear.i will do a log and post it here.only problem is i am going to have to hook the camper to it.maybe this weekend before i can do it.
thanks for trying to help me out.i will post my log as soon as i get it.

[Big Mike]

I doubt it's the converter releasing (but a log is still helpful) as on the 8.1/Allison trucks once the converter locks they don't want to release. I'd be more incline to believe it is actually down shifting. Why it is though is a tough call. Even with the shift tables set to hold a gear they have enough strategy that we can not see in the tuning software so other things can be going on, such as a forced (unwanted) down shift for other reasons.