I am new to ZF Tuning and I?m having a problem deciphering the files. All I?m wanting to do is lower the 2-1 coastdown shift speed or soften it up in an attempt to correct a clunk. Dealer says it?s a normal characteristic in a 15 Grand Cherokee 3.6L. Myself nor the customer like it. Any help would be much appreciated.
2nd to 1st downshift is "always" an issue...Originally Posted by Truefordguy
The way to fix it is:
- Reset adaptation (to see if it helps... drive for a while... I mean, a couple of days). If the issue persists, the solution would be a combination of torque converter opening point, shift RPM, pressure and timing.
Hard to say the exact value. However, fully possible to get it fixed!
DO you have a flare 3rd - 4th upshift under light throttle? THis is also a common issue for this model...
Thanks.
DodgeBoy.
YouTube: https://www.youtube.com/@dodgeboy2785
Thanks for the response!
No flare or any issues on upshifts. Vehicle came in with a SEVERE 2-1 downshift issue. Fluid and pan was full of aluminum. "A" clutches were completely wiped out. Overhauled rebuilt T/C from Precision. w/ new clutches and pistons in every cylinder except "D" clutch. That cylinder air tested good and clutches were fine so only replaced clutches there. Installed low mileage known good VB w/OE TCM. Initial test drive after resetting adapts at operating temp of about 170, the harsh downshift on 2-1 was still there. Had dealer reflash with latest Cal. That did help the down shift a lot but did not eliminate it. I am studying the tune file trying to make sense of their terminology and am hoping someone can enlighten me.
tuned by tank [email protected]
Is this a possible fix for harsh 2 to 1 downshift?
yes
just play around with the oss values in the cells i circled
(lower them)
DFCO speed can also be an issue. Try raising it and note the effects..
If in doubt, multiply everything by 1.1.
Thanks I tried this and it worked great, no more harsh downshift to first.
Any recommendations for minor adjustments to improve shift speed and firmness? Not looking for any major changes from stock, just minor improvements.
I?m new to the ZF as my last car had a NAG
sorry
that information is proprietary
i'll throw you a couple bones tho
1) when it comes to speed and firmness: not all the shifts require the same pressure settings or timing settings. some gear changes do not need to be tweaked as much as others, especially at WOT. part throttle and light throttle the difference is there, but it is not as noticeable
2) this is the biggie: tuning one of these things is like tuning anything else, all trial and error... But it is hard to feel the difference between a shift that you get spot-on, firm and quick, vs one that is slightly binding. if you do not know what you are doing and the transmission is running itself over, those clutch packs will not be long for this world.
its an expensive transmission. sipple gets $11k each, and that does not include billet input or output shafts, just a billet E drum. i charge $600 to tune one. it should be 3x that but i am a nice guy : )
tuned by tank [email protected]
Look under Shift timing tab, and then Upshift and Downshift. You can also play with the Shift pressure. If you're new to playing with one of these look at other files that use a ZF as a reference. IE, Charger 5.7, Hellcat, Demon, And Just play around, Make small changes one at a time. And most of all do some research, use your Brain and logically think about what you're changing before you change it. Its not black magic.
But if you're not comfortable doing that, by all means go get it done professionally.
if you do not have experience DO NOT start adjusting your shift pressures
you do not need to jack shift pressure to get the desired effect
tuning a zf 8 speed may not be black magic... but the tcm is smart, and it is doing it's own data logging and its own adjusting
fuck around and find out : )
Who said anything about jacking shift pressures?
you did
post #11
Jacking would mean to just raise Pressures, thats not what i said ; )
jacking = raising
correct
so you are going to "play with the pressures" without raising them???
how so???
lower the shift pressures is a very bad idea
Increasing or decreasing shift pressure depends on the issue you are having or the desired outcome.
Max out pressure values will be as bad as having them very low
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