[cjcrashesalot]

Hi,

I'm getting a strange behavior from my truck's transmission, but I've only owned it a few weeks so don't really have a frame of reference for what is normal.

Living in a hilly area and coming from a manual transmission, I've been manually putting the Titan into 4th, 3rd, etc. when coasting down steep hills to maintain speed without having to brake.

However, if the RPM's are below ~2500, the transmission does a weird pulsing thing where the engine speed raises and lowers by ~300RPM over and over. It feels like someone is sitting there lightly tapping the gas pedal on and off, but my feet aren't touching anything. Obviously the transmission will disengage a manual gear if the RPMs get too low, but it seems like the 1500-2500 range should be fine for coasting downhill.

This happens in manually selected gears 1-4 but hasn't happened when in D. Transmission seems to shift fine and function normally otherwise, which makes me think this is some sort of software/programming issue. If I shift or tap the gas/brakes, the problem generally goes away for a brief time.

Has anyone experienced this before? Any tricks to try? I searched but couldn't find anything.

 

[LUBECAKES]

The transmission will downshift automatically in D if you use light brake pressure going downhill. Mine seems to do it when the brake switch is on and the truck gains speed going downhill.
The thing you're referring to is normal...at least for my truck.

I would stick to using the brake normally, since brakes are cheap.

 

[dubyam]

You could have a throttle position sensor issue. Not likely but a TPS relearn won't hurt anything.

More likely is your torque convertor is locking and unlocking, which might indicate you should consider a fluid change.

 

[LUBECAKES]

When you downshift manually the engine will hold you back only to a certain rpm then it "let's go" if you will. This is the point at which the Op's Rpms are fluttering up and down. I know exactly what the op is referring to because mine also does this. If it was the tpms, you'd get a code.
It will not do it in "D".....or at least mine hasn't yet.
One thing I've found that does help my trans operate better, is before I drive away, I always make sure the Rpms come down in gear before I pull away.

 

[cjcrashesalot]

When you downshift manually the engine will hold you back only to a certain rpm then it "let's go" if you will. This is the point at which the Op's Rpms are fluttering up and down. I know exactly what the op is referring to because mine also does this. If it was the tpms, you'd get a code.
It will not do it in "D".....or at least mine hasn't yet.
One thing I've found that does help my trans operate better, is before I drive away, I always make sure the Rpms come down in gear before I pull away.

Glad to hear I'm not the only one who has experienced this! I haven't noticed the transmission doing much voluntary downshifting under braking, but it may still be learning my driving style.

I changed the transmission fluid shortly after getting the truck, and the issue didn't seem get better or worse.

Sounds like I just need to adapt to the transmission's way of shifting, rather than forcing it to adapt to mine. Maybe I miss driving a manual a bit too much.

Thanks for the help!

 

[LUBECAKES]

These trannies are quirky to say the least.