6l80 Low speed low load slip

[cessnageek]

Hi,
I notice my scanner is reporting transmission slip at low speed and low load in 1st gear. Typically when I'm on the brake. Is this normal for a stock trans? Only way I can think this would be normal is if it is the low sprag is doing something here? I've poked around some other 6l80 logs I've downloaded off the forum, and haven't seen the same behavior. I've got a million and one channels logged, but unfortunately I don't have commanded pressures. I can grab a log with those if that is useful.
Log and tune attached. Can see it at 17:31 in the log.

Thanks!

[verlon]

Automatic neutral, but it is strange to see it on a truck. I used to meet it on Opel cars.

[cessnageek]

Good to know. Thanks!

[TransGo Robert]

The log did not include most of the transmsision parameters making it really hard to tell what is going on. If you can take another log using this list of channels it would be great. 6L80.Channels.xml

I am also not clear at what you are concerned with, is it the negative slip when you are coasting down in first gear?

[cessnageek]

I'll grab a log with those channels. Probably won't be able to do it today, though.
Yes, the negative slip in 1st gear. I'm assuming it's the low reverse clutch not being engaged and so the sprag is letting the output free wheel? I guess a log will probably tell if that's the case. I'm a little confused what the logic for the low reverse clutch is, e.g. when should it engage in 1st and when should it disengage in 1st? I found something saying it engages under engine braking - if so when does the truck go into engine braking mode?

[TransGo Robert]

I'll grab a log with those channels. Probably won't be able to do it today, though.
Yes, the negative slip in 1st gear. I'm assuming it's the low reverse clutch not being engaged and so the sprag is letting the output free wheel? I guess a log will probably tell if that's the case. I'm a little confused what the logic for the low reverse clutch is, e.g. when should it engage in 1st and when should it disengage in 1st? I found something saying it engages under engine braking - if so when does the truck go into engine braking mode?

In OD range, the low reverse brake only applies on take off to help the sprag when and it releases at about 3 mph. You will be able to see that looking at PCS 3 command when you take another log with all the transmsision parameters selected. If you put it in manuals low or TUTD then it will keep the low reverse applied up until it makes the 1-2 shift so that you can have engine braking and or to assist the sprag during the whole 1st gear pull when pulling something heavy. When you come to as stop, the low reverse only start to gently re-apply around 2 mph and only really fully apply just as you come to a complete stop. That's done so that you don't get a clunk on the 2-1. So yea, with the LR not applied the wheels cannot drive the engine so you get a calculated negative slip which is perfectly normal and desirable.