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 tunetransmission-stock.tun

[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.