Shifting issues from 6-7

[toddarama]

I am currently running 37" tires with the factory 4.10 gears on my 2022 JTR with the 3.6 and automatic transmission. I have 9,000 total miles on the truck wiht 4,500 since installing the lift and 37s. I did reprogrammed the tire size using a Tazer mini when the were installed.

I am experiencing odd behavior when highway driving with the shift from 6 to 7. The issue is pretty consistent every time the shift to 7 occurs. It feels like the transmission attempts a shift from 6 to 7 but remains in 6, then within the next 5 seconds or so it cleanly shifts to 7. I can feel some slight hesitation when the transmission attempts the shift but remains in 6. Other than this one issue, the transmission is butter-smooth with all other shifts (including downshifts with no harsh transitions).

Is anyone else experiencing the same or anything similar? Should I be worried that this is an indicator any bigger problems emerging?

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[Hootbro]

I had a similar issue on my Willys with 3.73 gears and 35's.

In my opinion, there is only so much margin you can adjust for tire size and speedometer before you need to look at regearing.

 

[toddarama]

I had a similar issue on my Willys with 3.73 gears and 35's.

In my opinion, there is only so much margin you can adjust for tire size and speedometer before you need to look at regearing.

Yeah, I am working on the savings account to prep for a regear to 5.13's .... but that's still a little ways off.

 

[Hootbro]

I do not know about the Tazer but I used JScan that has settings for both tire size and actual percentage "%" error adjustment for the Speedometer. I played with the tire size input setting within a +/- 1/2" of actual and then set my Speedometer error rate at like a +1%. This seemed to eleviate it for the most part.

 

[ShadowsPapa]

I do not know about the Tazer but I used JScan that has settings for both tire size and actual percentage "%" error adjustment for the Speedometer. I played with the tire size input setting withing a +/- 1/2" of actual and then set my Speedometer error rate at like a +1%. This seemed to eleviate it for the most part.

Yeah, these devices and software don't allow the granular adjustments that the system can handle. That's a good find.
These transmissions are made to determine if the shift up or down is one that is best done one at a time - "would I spend enough time in the next numerical gear to be worthwhile, or do I jump 2 gears instead". A lot of downshifts under certain conditions skip a gear - I go a lot from 8 down to 6 or 5, for example. Likely this is doing the same shifting up.
Also - could the Tazer tire size settings be tweaked to improve this? Maybe it's "close enough" on the speedometer reading compared to GPS or radar signs, but could be better. Took me two tries to get a number that actually was not only very accurate, but helped shifting.

I did reprogrammed the tire size using a Tazer mini when the were installed.

My question would be - what number did you use? Did you compare odometer/GPS or speedometer/GPS when done, or just assume a number was good for your specific tires?

 

[Lunentucker]

I'd try manual shifts just to see if it feels any different in those transitions, 6-7, 7-6.
That may help to ease your mind, or not, about it being mechanical and not computer related.

 

[toddarama]

My question would be - what number did you use? Did you compare odometer/GPS or speedometer/GPS when done, or just assume a number was good for your specific tires?

My tires are Mickey Thompson Baja Boss A/Ts, and I used the specs from the M/t site (36.7") and I think I set the Tazer to 36.5". Speedometer is dead on according to the work zone speed signs and speed calculated by Waze (completely disconnected from the Jeep - no USB and no bluetooth). So I think it's pretty close..

 

[ShadowsPapa]

My tires are Mickey Thompson Baja Boss A/Ts, and I used the specs from the M/t site (36.7") and I think I set the Tazer to 36.5". Speedometer is dead on according to the work zone speed signs and speed calculated by Waze (completely disconnected from the Jeep - no USB and no bluetooth). So I think it's pretty close..

Just curious as I wasn't able to use the tire maker's online number. It was a starting point but the rolling circumference ended up being different. It's spot-on now (radar and Waze)
Well, then I'd go back to @Lunentucker's thinking - try manual shifting. That will tell if there's a clutch pack or band issue, or certain hydraulic issues. It won't catch ALL issues because the automatic shifts are handled different ahead of the clutch packs and so on, but it will at least confirm or deny some items.

 

[Lunentucker]

I don't know Tazer, but ECRI allowed me to input the actual tire measurement (floor to center X2) and it pretty much nailed the MPH with my phone's GPS.

 

[toddarama]

Lot's of good input from everyone. As soon as it stops raining I'll do the floor to center x2 measurement and compare to my current setting in Tazer. I have a trip to Canada coming up at the end of this week, so I'll get some good mileage in to try out any adjustment to tire size and to see how it behaves under manual shifting.

 

[ShadowsPapa]

Lot's of good input from everyone. As soon as it stops raining I'll do the floor to center x2 measurement and compare to my current setting in Tazer. I have a trip to Canada coming up at the end of this week, so I'll get some good mileage in to try out any adjustment to tire size and to see how it behaves under manual shifting.

PLEASE SEND RAIN! We're in a drought. Again.

Anyway, good luck. Issues with these automatics are rare, but can happen.

 

[toddarama]

PLEASE SEND RAIN! We're in a drought. Again.

Anyway, good luck. Issues with these automatics are rare, but can happen.

Today is the first time we've had any appreciable rain in several weeks, so I am not complaining.

I am hopeful that I'll be able to tune this away with some more precise tire size setting.

 

[jjdustr340]

I had found that my JT, and both my wife’s and daughters JLUs had the speedometer set from the factory to read 1 mph over the speed shown on radar (between 25 and 35). So I played around with tire diameter in Jscan until I was able to achieve the same thing. This has resulted in very good shifting and driving for me.

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