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Old 12-04-2019, 01:58 PM
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Trans not downshifting soon enough.

Is there a way to change the downshift characteristics of the W5A580 trans?

I have a 2016 JKUR with 35's, 4:10 gears, Superchips Traildash 2.
My Jeep and 2 other friends Jeeps all seem to be reluctant to downshift at low RPM and light throttle, that is they hold the gear too long. On the street it's not too bad except when there is a slow person in front, the trans up shifts (too far) because of very light throttle, the engine lugs and when you need to apply a little bit more power, it does not want to down shift unless you give it a lot more throttle. Although annoying, I can live with that.

We recently went on a trip to the High Sierra's and while climbing some very long steep grades in low range we found that if you were running along at say 2000 rpm in 3rd or 4th gear and then the grade got a little steeper the trans would not downshift until around 1000 rpm, at that point you are experiencing pretty severe tortional driveline vibration and pretty poor engine performance. Several times we got a P0734 code, probably indicating that whatever clutches are associated with 4th gear had slipped a little bit. I am assuming at that rpm the pump can't make enough pressure to hold the torque.

Superchips says that the trans programming is encrypted seperately from the engine and that they are not going to break the encryption to make it possible to change anything on this trans. I really don't know all of the parameters the computer looking for when determining a downshift. I am hoping that there is a way to externally modify an input to the computer or something to trick it into downshifting sooner.

So, does anyone know a way to make the trans downshift sooner under light throttle?

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Old 12-04-2019, 02:35 PM   #2
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A Pedal Commander will take care of that.

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Old 12-04-2019, 03:05 PM   #3
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I downshift manually 1 or 2 gears, otherwise it would climb at 40 mph in 5th or at 25 mph in 4th.
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Old 12-04-2019, 03:21 PM   #4
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This is one of the main reasons I think that our Jeeps feel so sluggish. Very reluctant to downshift without really pressing the pedal to the floor. I have got into the habit of just tapping the shifter to manually downshift which is a much better driving experience for me. I plan on getting a Pedal Commander in the future to address this.
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Old 12-04-2019, 04:44 PM   #5
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I am very skeptical of electronic performance stuff. When I first installed the PC I set it on Sport and it was just way too much, very touchy. I backed it off to City and 0 and it really helps performance in just about any place. I am surprised but I like it. It doesn't add HP but it almost feels like it does. The PC, some downshifting and possibly a re gear and it's not too bad.
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Old 12-04-2019, 06:03 PM   #6
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Do you have the tire size set correctly? Since the computer relies on the wheel speed sensors to determine trans output shaft speed, programmed tire size and diff gearing affects trans shift points. Easiest way to check that the programming is spot on is to compare your speedo reading to a GPS measured speed. I know that I had to fine tune my programmed tire size, even after setting the size based on the physical tire measurement as instructed. Not sure it would be off enough to make a difference or not.


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Old 12-04-2019, 08:22 PM
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dwtgolden: Yes, I originally set the tire size to 35". I have played with the numbers a bit to no avail on the downshifting. I have settled on 33.75 that makes my speedo read correctly.

On the pedal commander: So you guys think that the more agressive initial hit on the throttle makes your down shifting work a bit better? I think that I am only having problem when driving gently.
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Old 12-04-2019, 09:17 PM   #8
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I just got 4.88 gears to replace the stock 4.10s, and don’t have this problem anymore. It runs in the higher gear and doesn’t need to downshift to speed up. AT and 35s.
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Old 12-05-2019, 07:26 AM   #9
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I notice it as well. It makes me wish there was an 'OD OFF' button or some way to keep the TC locked up. It seems to shift way too low to always ride around 1000k rpm. Big difference from my MT where I like to be 2-3k. I hop in the AT and it feels sluggish until downshift which is too late for my taste . I also wish we had some control over it...
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Old 12-05-2019, 10:26 AM   #10
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A Pedal Commander type widget might help with that. We have one (an iDrive) and like it. But after we re-geared the throttle widget did not make as big an impact on how well it drove.
Using the manual shift mode should also help with that. That is what we call a "work-around".
But the best thing to help with that would be proper gearing. 4.10 gears can work with 35" tires. But it sounds like for how you are using it 4.10 gears aren't enough and a re-gear should eliminate the issue.
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Old 12-05-2019, 12:39 PM   #11
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I think that diff gears multiply torque. So with a base torque at engine of 240 when the lower gears are installed more torque is at the tires. Not more HP. Back in the 70's we would spin v8's on the freeway all day at 3K RPM's. That 3.6 will easily spin at 3K all day.
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Old 12-05-2019, 01:24 PM   #12
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Have you tried using the manual mode on the transmission?
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Old 12-05-2019, 04:19 PM
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Both of my friends have 4.88 gears and 37's. Overall their gearing is still lower than mine with 4.10's and 35's. They are having the same problem, in fact they are the ones that have had the P0734 code and one of them went into limp mode once. I have only been annoyed by the late down shifting. All of this was while driving the same road at the same time. Our work around is to manualy shift into a lower gear, and that keeps the violent driveline vibration and the codes away, but the engine is so smooth and quiet that sometimes I forget to upshift and find that I have been at 3500 rpm for 5 minutes, that makes me feel bad.

I would imagine that the trans programming is optimised for the original gear ratio and tire size. I have only changed my tire size and they have changed their tire size more than me and changed their gearing. Like many other things, it seems like the farther from stock you get, the more things get messed up. I'll bet all it would take is to change a few values in a lookup table to fix this. Hopefully someone a lot smarter than me will come up with a fix.

Thank you to all who replied
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Old 12-05-2019, 05:59 PM   #14
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Chase down P0734 before anything else. I'm wondering if the root cause is because the ECU has the incorrect final ratio or tire size. But my guess is a speed sensor.

Quote:
Originally Posted by Redass View Post
Superchips says that the trans programming is encrypted seperately from the engine and that they are not going to break the encryption to make it possible to change anything on this trans.
I use HP Tuners to program the transmission tables so it is possible.


Edit: read the OP and note that you were is 4LO. It could be the TCC slipping.
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Old 12-06-2019, 05:26 PM   #15
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Quote:
Originally Posted by rgreen65 View Post
Have you tried using the manual mode on the transmission?

I think this is really the most basic solution and is how i typically use my Jeep on the trails.




Quote:
Originally Posted by Redass View Post
Both of my friends have 4.88 gears and 37's. Overall their gearing is still lower than mine with 4.10's and 35's. They are having the same problem, in fact they are the ones that have had the P0734 code and one of them went into limp mode once. I have only been annoyed by the late down shifting. All of this was while driving the same road at the same time. Our work around is to manualy shift into a lower gear, and that keeps the violent driveline vibration and the codes away, but the engine is so smooth and quiet that sometimes I forget to upshift and find that I have been at 3500 rpm for 5 minutes, that makes me feel bad.

I would imagine that the trans programming is optimised for the original gear ratio and tire size. I have only changed my tire size and they have changed their tire size more than me and changed their gearing. Like many other things, it seems like the farther from stock you get, the more things get messed up. I'll bet all it would take is to change a few values in a lookup table to fix this. Hopefully someone a lot smarter than me will come up with a fix.

Thank you to all who replied
I have 5.38s and 37s and I get what you are saying. I experience it somewhat as well, though it doesnt seem as bad as youre describing. I dont think its a gearing issue. I would be very curious to try a pedal commander, or similar device. I genuinely think that the electronic throttle just doesnt operate efficiently when you get bigger tires and re-gear or are offroad. What feels like a lot of pedal input probably barely opens the throttle.

I find myself frequently feeling like i "give it a lot of gas" in order to "force" a downshift. The reality is probably that it only "feels" like im giving it a lot of gas, but the electronic throttle is not opening up as much as i perceive it should.

I'll try and pay more attention next time i run the torque app connected to the Jeep, it shows the throttle percentage and might expose some interesting behavior.
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Old 12-06-2019, 05:52 PM   #16
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You're right, it's a gearing thing. Not enough gears. The 8 speed takes care of that. Try a pedal Commander. It's got a 30 day moneyback guarantee. You'll be keeping it. I keep getting $50 off e mails from them.
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CJ7, 304V8, auto, loaded, Detroit rear, and more.
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Old 12-09-2019, 02:50 PM   #17
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You're right, it's a gearing thing. Not enough gears. The 8 speed takes care of that. Try a pedal Commander. It's got a 30 day moneyback guarantee. You'll be keeping it. I keep getting $50 off e mails from them.
Hadnt really considered THAT type of gearing issue, was only thinking of differentials. But yea, 3 more transmission gears would surely take care of it.
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Old 12-09-2019, 07:49 PM   #18
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one sure fire way to get the transmission to downshift is to trade it in for a manual and downshift it yourself........
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Old 12-10-2019, 08:59 PM   #19
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Reflash your TCM

I had shifting problems on my 14 JKUR with 37ís and 4.88 gears and E-Force supercharger.
Sent in my TCM and had it reflashed for $300. Made a world of difference. Now it up and down shifts much more normal. This is who I sent it to:
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Old 12-11-2019, 02:00 PM
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Thanks, Big Red Rubi. That is exactly the kind of thing I was really hoping for! I will probably give them a try.
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Old 12-12-2019, 09:34 AM   #21
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Smile TCM reflash options

Not sure what type of driving you do, but there were 2 different reflash options, from what I remember. An off-road aggressive reflash, and a street use reflash. I took the street use reflash, since most of my driving is on the road.
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Old 12-12-2019, 03:24 PM   #22
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Any recommendations for throttle controllers? I see Pedal Commander has been mentioned. Anyone familiar or had experiences with the iDrive throttle controller or the HIKEIT?
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Old 12-12-2019, 03:30 PM   #23
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Any recommendations for throttle controllers? I see Pedal Commander has been mentioned. Anyone familiar or had experiences with the iDrive throttle controller or the HIKEIT?
We have the iDrive. It works as well as the SprintBooster we had before it, and it works the same as the others.
I will say that the support I received for the iDrive was really good considering they were out of Oz. They were very helpful with their support of their product.
We mostly use the iDrive on its lower settings, especially in the dirt where it can help slow down throttle response (we are re-geared, so throttle response can be pretty strong, especially in 4L).
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Old 12-22-2019, 11:17 AM   #24
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[QUOTE=Big_Red_Rubi;34616577]I had shifting problems on my 14 JKUR with 37ís and 4.88 gears and E-Force supercharger.
Sent in my TCM and had it reflashed for $300. Made a world of difference. Now it up and down shifts much more normal. This is who I sent it to:
[/QUOTE

WE have been running one of his Modified TCM's in my daughters 15 sport. Mike is amazing and was able to dial in the program remotely with the data I sent him. Night and day difference in the shifting strategy.
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