BlackBear tune issue, Truck is short shifting

[AlohaOBS]

Im officially stumped. I’ve had the BB tune since 2018 and opted to raise my WOT shift points to 5500 rpm. Recently the truck has been acting like its back to the factory shift mapping. Under WOT, its shifting at 4900 RPM, not 5500. Sometimes unplugging the PCM for a few minutes will fix the issue and the truck will go back to shifting normally under WOT, but then the problem comes back. Now the problem will not go away at all, I tried leaving the battery off overnight, changed my TPS (throttle position sensor), and the issue still continues. It wants to upshift before it even reaches 5,000rpm. If i hold the trans manually in 2nd or 3rd, it’ll hold the gear to 5500 rpm untill i shift it to the next gear with the column. However first gear will never let me exceed 5,000rpm if i select (1) manually, it’ll kick me into 2nd gear even though i am manually selecting 1st gear. When the tune was working correctly, the truck would shift at 5500 rpm thru every gear when left in drive, no manual selecting needed, which is exactly what i want... except its not doing that anymore, the computer is acting like its running off the stock shift mapping. Any ideas as to what could be causing the trans to shift so early? I contacted black bear and am waiting for them to get back to me...

4L60E/Vortec 5.0L RCSB
Small bolt ons/deletions/BB tune

 

[df2x4]

IIRC, the RPM limit of the stock Vortec black box PCMs is somewhere around 5500 RPM. Maybe your tune is right on the edge of that limit and causing some issues as a result?

Obviously I'd way to hear back from BBP but that's my completely uneducated hypothesis.

 

[Supercharged111]

Stock limit is 5600 unless he bumped that too. My question to the OP is why the hell do you want such a high WOT upshift? The motor is done at 5k.

 

[AlohaOBS]

Stock limit is 5600 unless he bumped that too. My question to the OP is why the hell do you want such a high WOT upshift? The motor is done at 5k.

The shift points are raised because the motor falls on its face with my 33x12 tires and long gearing when shifting at the stock 5k to the next gear under WOT. With the higher shift points, it brings it closer to 3600 Peak torque when going into the next gear than it does with the stock shift points which drops me into the next gear around 3,000 rpm.

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[Supercharged111]

Gotta love that overgeared 4L60 life.

 

[SuperTramp]

I’ve noticed a couple times when I’m needing to move quickly while merging that my 5.7 winds to 6k before shifting into 2nd or into 3rd.

 

[AlohaOBS]

Update, BBP responded to my concern and told me to check the throttle position sensor, and to make sure the throttle is opening fully. TPS is brand new, swapped it with the old one and no difference at all, throttle opens fully as well. The problem persists. Im starting to think I have a faulty ECU, because the problem used to always go away when the ecu was unplugged and then plugged back in, leading me to believe it was an issue within the computer. The problem would also show up immediately if accelerating hard While (1) first gear was selected on the column. It would never let me hold it to redline manually in first, always shifted itsself to 2nd right before 5,000rpm... BBP stated that the factory tune should be completely overwritten by the BBP tune, which i hope is the case, but it still doesnt answer why the ECU is defaulting to shifting at less than 5,000 rpm at Wide Open Throttle if its been programmed to shift at 5,500rpm. Reasons and arguments for the higher shift points aside, I would really like my 5,500 shift points back, it makes a great difference when accelerating in my vehicle, and Plenty of people have raised shift points on their vortec powered gmt400’s so its not an issue of the shift point being too close to the rev limit. Note the hardwired max rpm of my motor is 5800rpm due to the ECU being a black box. However my programmed rev limiter is set to 5,600rpm. If anybody has any idea what could be causing this annoying short shifting issue, please chime in, im all ears!

 

[Supercharged111]

No, it's programmed to shift WOT at 5500 so it should be doing that. It has different patterns for if the cruise is on or the trans is hot, but that's only if it's really hot. The reason he asked about the TPS is because, at a certain TP, the PCM hits a WOT threshold and switches from part throttle shift values to WOT shift values. Do a Google for a TPS relearn and do that. Simply swapping in a new TPS is only part of the job.

 

[AlohaOBS]

No, it's programmed to shift WOT at 5500 so it should be doing that. It has different patterns for if the cruise is on or the trans is hot, but that's only if it's really hot. The reason he asked about the TPS is because, at a certain TP, the PCM hits a WOT threshold and switches from part throttle shift values to WOT shift values. Do a Google for a TPS relearn and do that. Simply swapping in a new TPS is only part of the job.

Will definitely look up how to relearn the TPS, thankyou for the quick reply! Its hard to find help out here in hawaii, literally nobody out here knows anything about these trucks, they all live and breath toyotas and nissans LOL

 

[AlohaOBS]

Attempted a TPS relearn, truck is still short shifting. Is there anything else that could be causing the shortshift issue? This is gonna make me loose my mind if i cannot figure it out