WA580 Shift Speeds Inop?

[HackAbuse]

Has anyone else had any problems with Transmission --> Shift Speed tables seemingly not having any effect on the actual shift speed of the engine?

I have a customer with a 2006 Jeep Cherokee that recently got a 426 swap and a built transmission. Truck made great gains after the tune, ran a 12.30, customer is very happy. Anyway, the truck has a bit of an issue on it's 1-2 upshift at WOT. It will hit the rev limiter once or twice before shifting to second gear. I have tried reducing all 1-2 upshiift values on the A580 tune, but they seemingly have zero effect on the shift point itself. Even with a 30% reduction in shift speed, it still smacks the rev limiter like it's completely ignoring my changes.

I'd really like to get this guy as close to 11s as possible. Has anyone run into this issue before? The customer lives 90 minutes away, so I'd like to have a sure fix for him by the time I see him next.

Thanks for any help!
Jeff

Chiccino_Mod6.hpt

[06300CSRT8]

In what mode is it hitting the rev limit, in autostick, regular drive?

You have an EGS52 unit in the jeep, which isn't bad but I know from my experience tuning it can be a bit buggy, especially the autostick automatic shifting. It seems as though the autostick shift rpms are all controlled by the TCM limit (your tune is 6200). I think this is a fine shift rpm for this jeep, but that is awfully close to your rpm limit in drive for the motor (6450), youre only giving it 250rpms of room to make the shift which most higher power cars need more like 300-350, esp in first. I would change the RPM limit in drive to 6600, and change your TCM Limp Offset to 750.

That will make the sequence be to command the shift at 6200, hit the rev limit at 6600 (shouldn't) and not put you into limp mode until it over revs to 6950 (shouldn't).

[HackAbuse]

In what mode is it hitting the rev limit, in autostick, regular drive?

You have an EGS52 unit in the jeep, which isn't bad but I know from my experience tuning it can be a bit buggy, especially the autostick automatic shifting. It seems as though the autostick shift rpms are all controlled by the TCM limit (your tune is 6200). I think this is a fine shift rpm for this jeep, but that is awfully close to your rpm limit in drive for the motor (6450), youre only giving it 250rpms of room to make the shift which most higher power cars need more like 300-350, esp in first. I would change the RPM limit in drive to 6600, and change your TCM Limp Offset to 750.

That will make the sequence be to command the shift at 6200, hit the rev limit at 6600 (shouldn't) and not put you into limp mode until it over revs to 6950 (shouldn't).

I discovered this function shortly after posting this, thanks very much. Instead of raising the limit, I lowered TCM shift to 5950, hoping that it will shift before my pre-defined rev limit. I'd like to keep this customer's rev limit south of 6200-6500 RPM as I don't believe it's beneficial to him to rev it any higher.

I will meet with him on Sunday and try the revised TCM limit to see if it forces a shift sooner. Thanks very much for your insight!

[06300CSRT8]

Sure thing, whats his cam specs in the 426?

[06300CSRT8]

FYI as a data point, my forged but stock displacement 6.1L jeep with a smallish cam went 12.5 @112. I added 200rpms to all the shifts and went 12.3 @ 115. Some of that was better driving (had a fully manual autostick) but def helped to shift at 6200 in 1st and 6400 in all other gears.

[HackAbuse]

Sorry I didnt get cam specs for you, but we got the truck squared away yesterday and it runs great! He may be bringing it to the strip this weekend to take another crack at 11s

[06300CSRT8]

Sorry I didnt get cam specs for you, but we got the truck squared away yesterday and it runs great! He may be bringing it to the strip this weekend to take another crack at 11s

Good news, what ended up being the final fix? Just keeping track as I help the engineers work through the last bit of bugs.

[HackAbuse]

As mentioned above, I just lowered the TCM Limit down a bit. The actual tables for wheel speed RPM shift points have no effect whatsoever on his shift points (you can see where I left the 1st gear shift point pretty low in that tune posted above) - I emailed Support before creating this thread and their response was essentially that they could not help me.

[Clatall]

Good info here as I have just built a 426 for my 2006 chrysler 300 srt8 and am having the same problem. In drive it would slap the rev till I let off so I can shift and then I can get back in to it

[HackAbuse]

Yeah, I don't know why altering the shift points has no effect. The TCM Limit did the trick though

[jc052685]

2016 Jeep Wrangler with Ripps supercharger.

Cant seem to get the trans to shift as commanded. Keep lowering the shift speed and it keeps blowing right past the rpm command and hits the limiter before shifting. Also I am trying to lower the partial throttle shift points but still no luck. Any thoughts?

[oeuro5]

I've got an identical situation with my Charger, altering shift points does absolutely nothing. I'll try to lower TCM Limit. Currently TCM RPM Limit is set to 6400 RPM and Limp Offset is 500 RPM. If I lower TCM RPM Limit to 6000 RPM where do I need to be with Limp Offset?

[mxatunerjg]

2016 Jeep Wrangler with Ripps supercharger.

Cant seem to get the trans to shift as commanded. Keep lowering the shift speed and it keeps blowing right past the rpm command and hits the limiter before shifting. Also I am trying to lower the partial throttle shift points but still no luck. Any thoughts?

Any chance you figured this issue out. I am messing with a 2017 Wrangler 3.6 with a Sprintex Supercharger. It shifts fine at commanded points at WOT, but all the part throttle shifts are an issue. 1-2 and 2-3 shifts seem to be the worst. I've tried making all of the part throttle shift points the same between normal, performance, and winter and that did not make any difference. So then just to test I flat lined all of the upshift points to the output shaft speed under the 0 throttle position for normal driving. This did make it shift at lower points, but not really logical points, as it still seemed to change with throttle position. So then I took all the upshift points from my revision that had all normal, performance, and winter matched and cut them by 50%. Again, this made the actual shift points drop, but again, they are not predictable. My next move is to drop all the downshift points to a very low value to try to move them out of the way. I noticed in the stock read some of the downshift points are at a higher rpm than the upshift points, which would cause issues for the upshift. The odd part to me though is that it worked fine from the factory, so obviously those values do work. Also, this thing has what are supposed to be 5.13 gears and 38" tires. All of that has been adjusted.

Sprintex_Supercharger_Part_Throtte_Matched_and_halved.hpt
Sprintex_Supercharger_Part_Throttle_Matched.hpt
Sprintex_Supercharger_Tune.hpt

[68Camaro]

I also am tuning a 2016 Wrangler and having fits getting the part throttle shifting to work right - wants to hang and not shift out

If you come up with a solution please post it up - I am going to re-visit this tune in a week or two

[mxatunerjg]

I also am tuning a 2016 Wrangler and having fits getting the part throttle shifting to work right - wants to hang and not shift out

If you come up with a solution please post it up - I am going to re-visit this tune in a week or two

I don't really consider it a fix, but I did get it to work better. Let me first explain the specific situation...this Jeep is far from stock, it is supercharged, with 5.13 gears, and 38" tires. The suspension, body, interior and most everything else is heavily modified. I say all of this because it is getting to the point that it does not drive like a stock Jeep by any means so perfect shift points are not really what I was shooting for in doing this.

I tried quite a few different ways to make the trans do what I consider predictable shifts. Basically I made all upshift output shaft values the same, dropped downshift values to a number low enough so it would not interfere, then tested. This did cause the trans to shift drastically different, so I knew the changes were actually causing the trans shift points to change. I then went back to a stock read and studied the values. I noticed there were some accel pedal positions that had higher downshift (kickdown) points than what the corresponding up-shift points were. So knowing that normal/performance/winter shifting were not really relevant in this situation I decided to match each of the shift point maps. In my case I chose the normal maps and copied and pasted the ACC Position and the output shaft speed values from the normal shift points to the performance and winter shift points. I also did the same thing with the WOT points to WOT winter points. Then I took all of the part throttle upshift points and cut them by 25%. To be sure all of my downshift points were lower than my upshift points I cut all the downshift points and cut them by 50%. I used this as a starting point. Basically I test drove and logged everything. The upshift points were much better and so were the downshifts. The only real "hitch" I could find was on cold trans fluid it tends to get into 3rd gear a little faster than I would like, but after about 2 mins of driving that goes away.

Now I did do some adjusting to the values to "fine tune" this, but it was all done by feel and not so much data backed. WOT shifts seemed to work perfect, output shaft values matched (within reason) the shift points in the tune. Part throttle shifts always seemed to be off though. I could not find anything in the logger that would show a value for output shaft speeds that matched the speeds I had in my trans tune. I even tried subtracting the ouput speed offset from actual output speed, just to see if that made sense. It got closer but always seemed to be about in the range of 300 rpm over the commanded shift speed in the tune. One thing I did not check, but just thought about it while typing this was to see if the logged engine rpm, converter slip, and the logged output shaft speed made sense when compared to each other.

For the reasons mentioned above, I don't really feel like this is a bullet proof method of doing this tune since it is not really data backed. It also does not make sense to me why changing the gear ratio and tire size did not take care of the shift points.