Stutter between gear shifts under WOT

[StealBlueSho]

Long story short... When I load a tune that cranks up the shift pressure such as Torrie's or LMS race tune I get a stutter between gear shifts only under WOT... the rpms don't rise like a slipping issue. Tunes that don't have the shift pressure cranked up don't exhibit this behavior at all. The car has been doing this for 18 months or so off an on. Started with Torries tunes.. doesn't seem to get any better or any worse...

Service fluid has been checked, rechecked, and swapped out on the trans and PTU. No visible signs of leaks around the casing...

I can launch the car all day at 2K RPM and she just dips and goes with any issues off the line.. no excessive wheel spin, etc.. but that 1-2 second shift will stutter then catch and go... and sometimes the 2 - 3 shift will do that same...


Thoughts? Opinions? Previous experiences?

[glock-coma]

I thought lms said this was due to fluid cavitation and to add an extra quart of trans fluid to alleviate. 

[StealBlueSho]

Agreed, and that was done as well. And it's an extra half quart...

[Brucelinc]

Does Dan Millen recommend overfilling the transmission or was that an idea from someone else at Livernois who may not have appropriate knowledge?

[StealBlueSho]

Email from Anthony at LMS.. granted, my car does this with Torries tunes as well.. though, only with the shift pressure dialed up...

Anthony M (LivernoisMotorsports)
Jan 17, 18:21 COT

Michael,
I am sorry to hear of this. While altering tunes that we know are not having this problem on hundreds of other vehicles to resolve the issue on your vehicle may be a solution, have you tried servicing the transmission to resolve the root cause of the trouble you're having? We have no problem tweaking the tunes for you, but this is an obvious sign that there is something mechanical going on with the transmission that is giving you early indications / warning signs of something worse to come. I can see on the server that there are well over 100 other SHOs running these exact tune files and haven't had any requests to lower shift pressures to fix a stuttering 1-2 shift. We have however found on other SHOs here in the shop that when they seem to have trouble with 1-2 shifting occasionally , they typically need to have the trans fluid service done and then we top them off with an extra pint over the factory fill. Even Ford has found they were having issues in stock form occasionally with the Police pursuit models since they spend a great deal of time idling and then going WOT to pursue a suspect. It's been proven that the fluid was actually cavitating and that over-filling them by a pint has helped to nearly resolve the issue almost every time. Having that extra pint of fluid helps to ensure there is much less of a chance for the fluid to cavitate. If the fluid currently has over 25,000-30,000 miles, it's suggested to drain and refill. Then it's very critical to make certain you fill the fluid, run the car to let the fluid circulate, and then check the fluid again to top it off. Then we suggest to add that extra pint once you are 110% certain it's filled completely. Many people just fill it once and don't check it afterwards which is another well known issue causing them to have a stutter from time to time.
Like I mentioned, we have no trouble adjusting the tunes for you if needed. But we would much rather help you get to the bottom of this instead of tuning around a mechanical issue possibly which may only be a temporary fix causing more harm than good. Overfilling the transmission by a pint (not quart) has been the best thing for the Explorer and SHOs having this issue.

Thank you
Regards,
Anthony
Livernois Motorsports & Engineering, LLC
Phone: 313-561-5500 Fax: 313-730-7500
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[Gjkrisa]

Hmm mine did this as well with the boostmax turnes out some how all it does is adds up to 3 psi but after a week it has been gone for couple weeks now

Sent from my Nexus 6P using Tapatalk

[StealBlueSho]

Maybe I am not giving the car long enough for the adaptive components to do their thing? Realistically I put around 3K miles on it ever 6-8 months...

[Brucelinc]

Many guys with tuned SHOs or MKSs have had the issue.  In some cases, fresh fluid has solved it -
or has seemed to.   However, the only fix I have heard of that ALWAYS works is backing off the shift pressure.

[ZSHO]

I think its a common procedure to slightly over fill the Trans and Coolant right above the Top fill line IIRC with the exception of motor oil for good measures. Z

[StealBlueSho]

Many guys with tuned SHOs or MKSs have had the issue.  In some cases, fresh fluid has solved it -
or has seemed to.   However, the only fix I have heard of that ALWAYS works is backing off the shift pressure.

From what I have read, that's seems to be 100% correct. However, Anthony made it appear that it is not common anymore, and the tunes have been revised to address this issue. So for me to ask for a softer shift version was unusual... at least according to LMS..

[TSS]

I had the 1 to 2 Shift stutter. They (LMS) gave me a modified tune to correct the problem. It had zero effect on my performance and  zero to 60 times and simply eliminated the stutter. This was probably at least two and a half years ago. It was not an indication that my transmission was on the way out. 

[StealBlueSho]

Yea, they gave me a softer shifting version... no stutter... and the tranny doesn't feel like it's going pound its way out the side of the car...

[StealBlueSho]

I had the 1 to 2 Shift stutter. They (LMS) gave me a modified tune to correct the problem. It had zero effect on my performance and  zero to 60 times and simply eliminated the stutter. This was probably at least two and a half years ago. It was not an indication that my transmission was on the way out.

Did you notice a shifting difference? Besides the obvious lack of stutter?

[Brucelinc]

I ran Livernois 4+X for over a year with no stutter.  All of a sudden, for no apparent reason, my MKS developed the 1-2 stutter.  Livernois sent me the same tune but with reduced shift pressure.  That immediately solved the issue.

My concern, however, was why was is fine for a year and then exhibit the bad behavior?  I changed out the fluid in the transmission and re-installed the original higher pressure tune.  The stutter was gone.  Was it the fluid change that "fixed" it, was it just a fluke, was it simply the reflashing?  I have no idea.  However, after that, I changed the tranny fluid annually and never again had the stutter even with their "race" tune.

As for the the transmission behavior with the reduced pressure, it was noticeably smoother at WOT.   With the high pressure tune, I always got a tire chirp on the 1-2 shift at WOT and but with the reduced pressure, I did not.  However, like Todd, my 0-60 measurement was just as good with the softer shifts. 

[StealBlueSho]

Thanks for the detailed information. It doesn't do it every time. Before I go down the path of transmission work/PTU work I wanted to see what others have done. Like I said, LMS made it sound like an oddity. Seems like to me they are dialing it up right the very edge with their race tune as far as the transmission is concerned. Torrie must use that strategy as well... as I know people have mentioned having the same issue with his tunes...

Realistically I could run the softer shift version indefinitely without any issues.