Normal Transmission Behavior??

[rcryniak]

I don't often go WOT when already at 70mph. Only if some ...um... ****... is acting dangerous and I want to move away quickly. Such a thing happened a few days ago, and I noticed that when I punched it, then let off the gas (completely) it seemed to hesitate to go from 3rd back into 6th. It's like the RPMs were being allowed to slowly drop before it would shift back up to overdrive. It sounded weird - like the high RPM whir was coming in for a landing, then eventually, a second or two later, it'd shift and go back down. Anyhow, to confirm it wasn't a fluke, I've since tried it about a dozen times; and although sometimes it was slower to "return to normal" than other times, by and large, it was sluggish to "return to normal" in any case.

Steps to reproduce:

1. Get to 65-70 mph.
2. Floor it, watching it jump quickly from 6th to 3rd gear. (Assuming you have a device that you can monitor it with.)
3. Accelerate for 1 second.
4. Take your foot completely off the gas.
5. Listen for a couple seconds as the car decides to eventually lower the RPMs and shift back to overdrive.

I don't know, it's probably totally normal, but I thought I'd ask. I would say it was trying to protect itself from going over the RPM limit, but that's not going to be the case since going back to 6th would the engine well under 3000 RPMs, so why would it hesitate to do so? Maybe its the way the tune is? (LMS 4+ atm.) Maybe it's trying to protect the transmission (rather than the engine) somehow?? Totally normal?

Any thoughts?

 

[mmh64]

Dropped my daughter at school this morning and tried this four times on the way home. 2010 non pp, lms 93, 3-bar. When I let off accelerator the rpm immediately start to sweep down until it rest about 1800 rpm. No revving. No trying to hold on to any gears. As the tach was sweeping down I felt an ever slight bump sometimes two as it touched a gear or two on the way back to 6th. I could see the tach pause for a nano second as it was doing this. This all happened almost seemlessly. I would never have noticed what it was doing unless I really paid attention and analyzed it like you asked. Hope this helps with your situation.

 

[rcryniak]

I might just log a few runs and see if LMS will let me know if they see anything off with it. (I forgot my tuner does that!!)

 

[mmh64]

Yeah, I don't think I would like it if my car held passing gear for 1 or 2 seconds after letting off the accelerator like you decribe. Just doesn't sound right to me. Your on the right track though. Logging and comparing data to what the tune is telling your car to actually do.

 

[SHOdded]

How long has this been happening, Robb? Did it happen when "summer fuel" was available? If you normally run 93, you might want to wait till summer fuel comes around again, see if the symptoms persist. Then try loading the 4x tune and testing.

 

[rcryniak]

I honestly don't know how long this has been happening. I noticed it once or twice this winter, but I don't WOT that much in the winter, so I didn't pay much attention to it until it was particularly "long to let go" the other day... leading to those tests. So, afaik, this has been winter gas only... but why would the cheaper gas make the transmission slower to return to 6th/overdrive? Honestly, I expect that the RPMs are lowering at a normal rate if I were driving manual and didn't change gears from 3rd or 4th, but just let off the gas and stayed in that gear... the slow RPM drop feels normal for that, since the car's dropping MPH equally as slow. (No faster or slower than usual.) I think it's the seemingly slow return to 6th at that has me concerned. If it were shifting back up "on time"/earlier, I'd expect the RPMs to drop in tandem with the change to the new, higher gear.

 

[rcryniak]

Just spoke to a very nice chap from Livernois. (He was from the U.K., so he's a chap, not a dude lol.) He seemed to feel, given what I described, was the car deciding to hold onto the gear due to the aggressive initial pounce to WOT. (Aggressive enough for it to drop to 3rd from 6th.) According to him, it knows that you want power at that moment, and it's holding on to make sure you didn't accidentally let off and will be pounding on it again immediately. Kind of a "hover here, let's see what the driver's really gonna do" scenario.

I'm going to hold the WOT a little longer, see how it drops then... and also try going from gas to gentle braking, see if that instructs the car differently. And also try just under WOT, see how it drops after that slightly less aggressive throttling. If it still behaves odd, I'll want them to see it then. (They're 4 hours.)

 

[SilverSH0]

Just spoke to a very nice chap from Livernois. (He was from the U.K., so he's a chap, not a dude lol.) He seemed to feel, given what I described, was the car deciding to hold onto the gear due to the aggressive initial pounce to WOT. (Aggressive enough for it to drop to 3rd from 6th.) According to him, it knows that you want power at that moment, and it's holding on to make sure you didn't accidentally let off and will be pounding on it again immediately. Kind of a "hover here, let's see what the driver's really gonna do" scenario.

I'm going to hold the WOT a little longer, see how it drops then... and also try going from gas to gentle braking, see if that instructs the car differently. And also try just under WOT, see how it drops after that slightly less aggressive throttling. If it still behaves odd, I'll want them to see it then. (They're 4 hours.)

Take a video and post it for everyone to see. If that's truly what the car is doing then they should all be the same. It's raining here or I would go reproduce your situation and video it for reference.

I've seen one person post here that their car doesn't do that so I would be skeptical it's normal. But posting a video would allow everyone to see and say yes or no their car does/doesn't do that.

 

[SilverSH0]

We had a break in the rain so I went out and took a video of my car. Here's one of the first two times:
http://vid184.photobucket.com/albums/x201/PwrRngr/20160308_185936_zpsvzgqwtwe.mp4

Here's one where I kept the throttle down a little longer:
http://vid184.photobucket.com/albums/x201/PwrRngr/20160308_190026_zpsmsct00gu.mp4

On the second one it hesitated for a fraction of a second after letting off the gas. But nothing that would catch my attention or think something was wrong.

 

[rcryniak]

Time for me to do the same I think.

 

[larrySHO01]

I'm having the same symptoms with my '10 non PP. I've found a connection to the Grade Assist option I had added to my LMS tunes. When in GA mode the upshift is fine, when in D the upshift to 6th is delayed a couple of seconds. When running stock or a non GA tune the upshift is fine. I've reported the behavior to LMS and I'm hoping they will remove the GA option from my 4 X _3BAR tunes. They indicated they hadn't heard of this issue before. Glad I'm not alone!


2010 Stl Bl Met, Loaded, non PP, LMS 4+X, K&N drop in, 170 T-stat, 3 bar MAP, SP534

 

[rcryniak]

I actually video'd it on my way to work, I'll upload it to YouTube tonight when I get home. Bottom line, reproduction steps are a little different than I thought:

1. Get to 65-70mph
2. Floor it, watching it jump quickly from 6th to 3rd gear. (Assuming you have a device that you can monitor it with.)
3. Accelerate WOT until your RPMs reach around 6500.
4. Take your foot completely off the gas.
5. Listen for a couple seconds as the car decides to eventually lower the RPMs and shift back to overdrive.

The key to reproducing the problem (and I do now believe it to be a problem unless others tell me theirs behaves the same way) is in holding WIDE OPEN THROTTLE until the RPMs reach max. Everytime I've done that, it's had that hesitation. The closer to max RPMs, the longer the hesitation (hence the variance I noticed.) The one video I took this morning is a good one. The RPMs are dropping very slowly from 6100 to 5800. Ish. I also logged it, so I'll either include logging info with the video, or if I feel up to it, I'll do a video overlay of logging data in real time. Maybe. Probably not, but maybe.

 

[mmh64]

We had a break in the rain so I went out and took a video of my car. Here's one of the first two times:
http://vid184.photobucket.com/albums/x201/PwrRngr/20160308_185936_zpsvzgqwtwe.mp4

Here's one where I kept the throttle down a little longer:
http://vid184.photobucket.com/albums/x201/PwrRngr/20160308_190026_zpsmsct00gu.mp4

On the second one it hesitated for a fraction of a second after letting off the gas. But nothing that would catch my attention or think something was wrong.

Yes, this is exactly how mine behaves. Thanks for vidio. It was hard for me to explain in words.

 

[SilverSH0]

I actually video'd it on my way to work, I'll upload it to YouTube tonight when I get home. Bottom line, reproduction steps are a little different than I thought:

1. Get to 65-70mph
2. Floor it, watching it jump quickly from 6th to 3rd gear. (Assuming you have a device that you can monitor it with.)
3. Accelerate WOT until your RPMs reach around 6500.
4. Take your foot completely off the gas.
5. Listen for a couple seconds as the car decides to eventually lower the RPMs and shift back to overdrive.

The key to reproducing the problem (and I do now believe it to be a problem unless others tell me theirs behaves the same way) is in holding WIDE OPEN THROTTLE until the RPMs reach max. Everytime I've done that, it's had that hesitation. The closer to max RPMs, the longer the hesitation (hence the variance I noticed.) The one video I took this morning is a good one. The RPMs are dropping very slowly from 6100 to 5800. Ish. I also logged it, so I'll either include logging info with the video, or if I feel up to it, I'll do a video overlay of logging data in real time. Maybe. Probably not, but maybe.

I can try to video at some point. however, I don't have my shift points up at 6500 rpm (mine is 6100 or 6200 rpm) so I cannot spin it that fast. I also find it odd that the answer is that it's holding on in case you want power again if it's already up against redline. When it's already at the shift point, it cannot go any further.

 

[rcryniak]

I was ballparking. I pulled the logs from my device to get it accurate, and it's consistent with yours, shift point wise, apologize for the inprecision. Here's highlights from the log file I pulled (I culled most entries, tried to present as LITTLE data as possible), it peaked at 6127, well, look for yourself ... however, this data looks "OK", the "weirdness" will be more apparent when I post the video.

Time (sec) MPH RPM Gear
------------------------------------------------------
6.540 70.2 1992 6
6.730 70.2 2012 5
7.021 70.8 3414 5
7.281 70.8 4366 5
7.581 72.7 5474 3
7.771 72.7 5474 3
8.011 72.7 5474 3
8.149 75.2 5643 3
8.341 77.0 5725 3
8.571 78.3 5856 3
8.811 79.5 5908 3
9.121 81.4 5972 3
9.592 83.9 6066 3
9.902 85.1 6127 3
--- let off gas completely ---------------------------
10.362 83.9 5961 3
10.673 83.2 5875 3
10.921 82.6 5844 3
11.241 82.0 5782 3
11.551 81.4 5735 3
11.781 81.4 5735 3
--- takes nearly 2 whole seconds to upshift to 4th ---
12.171 80.1 4918 4
12.421 79.5 4776 4
12.711 78.9 4298 4
13.021 78.9 4242 4
13.373 77.7 4217 4
13.691 77.0 4168 4
13.917 77.0 4168 4
14.307 77.0 4168 4
14.602 75.2 4044 4
--- another 2 seconds (plus) to upshift to 5th -------
14.650 75.2 3968 5
14.992 74.6 3768 5
15.241 73.9 3565 5
15.511 74.6 3292 5
15.841 73.3 2822 5
16.251 72.7 2802 5
16.672 72.1 2779 5
16.971 72.1 2762 5
--- another 2 1/2 seconds, finally upshifts to 6th ---
17.331 71.5 2740 6

 

[SilverSH0]

I'll have to check mine it later. I thought you were originally saying it hung up at redline for a second or two after letting off the gas before shifting.
I'll wait to see the video

 

[rcryniak]

OOOkay... so video time. Please note that I've overlaid a graph of the logging data, along with a "driver's foot" so you can see what I'm doing at the same time. The shifting is via the automatic (not manual mode), and Blue represents speed, Red represents RPM, and Green represents the gear. Note the hesitation to drop RPMs a good second or two after I lift my foot off the gas.

...and it seems I need an interior detailing. Dust particles, yuck. lol.

 

[brucelinc]

I am not sure I see anything abnormal here. It is not as though the car keeps pulling when you back off. It appears to me it is just doing this so the shift from 3rd back to 6th is smooth. Maybe I am missing something....,

 

[rcryniak]

It's the moment I let off... there's a good 1-2 seconds where it's still very close to 6000 RPMs, and doesn't need to be up there. It's not the motion it's going through, it's the timing that has me wondering about it. But as I said in the OP, it could be normal behavior. I was hoping to get others to try it to see if theirs behaves consistent with mine. If so, awesome. If not, then what's the best course of action. (Just my opinion though, that seems to hold on too long.) I just can't think of a good reason to take a full 7 seconds to shift up to the higher gears. But then, I'm a software engineer, not an automotive engineer. So, yeah, could be totally normal. Which is why I'm asking, and why the OP title is "Normal Transmission Behavior??".

 

[SilverSH0]

It's the moment I let off... there's a good 1-2 seconds where it's still very close to 6000 RPMs, and doesn't need to be up there. It's not the motion it's going through, it's the timing that has me wondering about it. But as I said in the OP, it could be normal behavior. I was hoping to get others to try it to see if theirs behaves consistent with mine. If so, awesome. If not, then what's the best course of action. (Just my opinion though, that seems to hold on too long.) I just can't think of a good reason to take a full 7 seconds to shift up to the higher gears. But then, I'm a software engineer, not an automotive engineer. So, yeah, could be totally normal. Which is why I'm asking, and why the OP title is "Normal Transmission Behavior??".

I see what you're talking about and having it kind of hang around 6k rpm would make me question it also. Have you tried switching back to stock tune to see if it does the same thing? We're still raining and it's supposed to continue until Monday or I would try another video.

Do you have the PP on your SHO? I ask because mine is non-PP and 80 mph I'm spinning about 5000 rpm and you're around 5900 rpm.