Banks PDA showing "Trans Slip"...Anyone experience sensor issues?

[WalterJ]

I've been noticing single digit Trans Slip #'s, and not necessarily when towing. Anyone experience related sensor issues or know of relevant TSB's?

 

[cerberusiam]

All those monitors tend to show some slip even though it is probably not really slipping. The slip percentage is a calculation the ECU does comparing rpms and output shaft speed sensor readings. Both sensors are a sine wave extrapolated to a digital signal, there is going to an error factor in them.

Like any other electronic monitor, consistency is more important than the actual readings most of the time. If the readings are all within a 10% range no matter how you are driving or the conditions it is likely good. What you would look for is a big jump in slip towing as opposed to empty, or, light throttle as opposed to heavy throttle. The slip percentage is only going to be valid with the TC locked.

 

[WalterJ]

All those monitors tend to show some slip even though it is probably not really slipping. The slip percentage is a calculation the ECU does comparing rpms and output shaft speed sensor readings. Both sensors are a sine wave extrapolated to a digital signal, there is going to an error factor in them.

Like any other electronic monitor, consistency is more important than the actual readings most of the time. If the readings are all within a 10% range no matter how you are driving or the conditions it is likely good. What you would look for is a big jump in slip towing as opposed to empty, or, light throttle as opposed to heavy throttle. The slip percentage is only going to be valid with the TC locked.

Thanks again for taking your time here. I questioned operation of these sensor inputs before & was told their source are "tone rings" with proximity pickups. If true. my experience tells me those then would be digital inputs to the ECM, et al.

Also, a query to Banks Engineering re: "units as displayed" resulted in the answer that the display units are "RPM" not %.

So I'm wondering if a 'twitchy' contact or short somewhere could be a culprit? I brought my rig to the shop to investigate any validity to these "slip readings", as my TC & transmission are still under warranty. The pressure tested the TC & transmission pump & found no leaks, etc. They replaced the TC with a new unit & sent mine to "Precision" for what they refer to as a "cut & call", meaning cut open the TC & call with forensic results showing any signs of slippage.

I felt bad bringing it in, but they agreed to investigate. Our road test had to be unloaded, so his portable 'scope' did not reveal any obvious glitches re: slip numbers. Great people I must say.

Leaving for FL in a week. We'll see. Thanks again for being such a dedicated contributer.

 

[WalterJ]

transmission slip update:

On the highway tonight, engine, etc. at operating temperature; 0 slip indicated, then I gunned it going from 60mph to 90mph & slip rose steadily from 6 to 19. I'm not liking this at all.

In addition to any input I receive here, I'm also calling my West coast friends with this query.

 

[Bob4x4]

The t/c will do that when not in lock up. wot will keep the t/c unlocked under many conditions with out an add on lock up switch

 

[cerberusiam]

If that slip number really is rpm's the displayed value is not that much in comparison to actual, less than 10% of total rpm. That could still be an error in extrapolation from analog to digital. Normally, you would see that number jump high then drop if you really had a clutch slipping. As the rpms come up the slip usually lessens because the TQ drops.

If the TC was unlocked under heavy throttle that number would more along the lines of 300-600 not 6-19, given it is rpms.