Transmission slip on inclines/declines 2001 S80 T6

[Tannhauser]

Sooo... Since I've had this money pit, I've had an issue with it seeming like the transmission slips on certain gradient inclines and recently felt it going down a hill as well. I basically have to feather the accelerator when this happens until it clicks into gear. I pretty much know exactly when it will do it as I travel the same routes alot. My driveway is steep as sh*t and no issues going up it.

I know the tranny is made out of glass and elmers glue, but I have no issues with gear changes otherwise. I drive mostly in geartronic because I'm under the impression it uses a higher line pressure. Trans was drain and filled multiple times a few months ago with some Lucas transmission conditioner and a shift kit thrown in to boot. No CEL's or codes in VIDA.

Someone mentioned similar issues with the uphill thing and it was a faulty brake position sensor. But I'm not having any issues with cruise control. Before I fork out for a new sensor, does anyone have any ideas?

[Vova585]

I would try to ask dealer to install updated software and maybe reset the fluid counter in transmission. No other ideas.

[Tannhauser]

Thanks. I reset the fluid counter myself when I flushed the trans.

[Cees Klumper]

FWIW my 2002 T6's was starting to have difficulty shifting down on long uphil climbs (not particularly steep, just loooong) to the point I got a new filter and fluid to 'one day' attempt to address it. To my surprise however, the issue has gone away without me doing anything, after about 3 years. It's been fine for the past 2 years. Your mileage will most likely vary.

[StevenS]

Sooo... Since I've had this money pit, I've had an issue with it seeming like the transmission slips on certain gradient inclines and recently felt it going down a hill as well. I basically have to feather the accelerator when this happens until it clicks into gear. I pretty much know exactly when it will do it as I travel the same routes alot. My driveway is steep as sh*t and no issues going up it.

I know the tranny is made out of glass and elmers glue, but I have no issues with gear changes otherwise. I drive mostly in geartronic because I'm under the impression it uses a higher line pressure. Trans was drain and filled multiple times a few months ago with some Lucas transmission conditioner and a shift kit thrown in to boot. No CEL's or codes in VIDA.

Someone mentioned similar issues with the uphill thing and it was a faulty brake position sensor. But I'm not having any issues with cruise control. Before I fork out for a new sensor, does anyone have any ideas?

If the problem has persisted since purchase and only occurs on certain hills, I wouldn't immediately blame the transmission. If the clutch were indeed slipping, it would usually also manifest itself under hard acceleration on smooth roads, and the problem would typically worsen.

First, I'd check the fluid level (at the correct temperature), then record real-time data using VIDA, reproducing the problem. Pay attention to the brake switch status, the selected gear, the actual gear, and torque reduction requests. Sometimes the sensor will provide inconsistent data without an error code.

I wouldn't replace the brake pedal sensor just because someone else had a similar symptom, especially if the cruise control and brake lights are working properly. It's a relatively inexpensive part, but it's better to confirm the signal disappears before replacing parts. I always check to make sure everything is working properly, and I use the same principle at https://mostbetbd.asia/. Real-time data usually points in the right direction much faster than guesswork.

[plumage]

Solid diagnostic advice