'15 PIU not shifting into Low "L" gear when driving

[TTIntercept0r]

I couldn't find any info elsewhere about my issue, when stationary I can go into low gear by pulling the column shift down past drive, or by pressing the button at the end. But while driving, it will not shift into low gear. ATF is fine as far as I know, just checked it tonight and its still pink ish color, not brown or charcoal. Not sure how to precisely check the level due to the dip stick being under the air box. I had to totally remove the air box and filter to reach the cap. (EB engine, 3.7 is easily accessible)

Anybody else ever had an issue or thoughts?

 

[Jeep driver]

My 2014 PIU Owners Manual states:

• Low Gear button will downshift to the lowest available gear for the current vehicle speed; allows for first gear when vehicle reaches lower speeds.
• Is not intended for use under extended or normal driving conditions and results in lower fuel economy.

I have owned my 3.7L PIU for about 6 months, and have not found a use for Low Gear. I suppose it would be helpful for towing heavy loads.

 

[goots]

I suppose it would be helpful for towing heavy loads.

It is NOT for towing AFAIK.

Ford Owners Manual states:

When driving at slow speeds in deep sand under high outside temperatures, use a low gear when possible. Lower gear operation will maximize the engine and transmission cooling capability.

And:

Provides maximum engine braking. Will downshift to the lowest available gear for the current vehicle speed; allows for first gear when vehicle reaches lower speeds. Is not intended for use under extended or normal driving conditions and results in lower fuel economy.

 

[FruztalProjects]

I have no use for low gear, so I'm not sure. Probably vehicle speed has an effect on the button.

 

[TTIntercept0r]

It is NOT for towing AFAIK.

Ford Owners Manual states:

And:

Yep, I am not towing. I need it for engine braking so I dont destroy my brake pads and rotors on our mountain roads.

I have no use for low gear, so I'm not sure. Probably vehicle speed has an effect on the button.

Ive always only needed it for downhill grades where my speed is never more then 40mph anyway.

Something must be wrong with it, thats the only explanation I can think of...

 

[Jeep driver]

The ECM/PCM may not see the parameters that make low gear safe for the transmission to shift or operate. How often are you needing engine compression braking ?

 

[TTIntercept0r]

The ECM/PCM may not see the parameters that make low gear safe for the transmission to shift or operate. How often are you needing engine compression braking ?

Basically every time I go to work/town. Its about 11.5 miles to town and Id need to use low for around 2 miles of that. That section of the road is steep with lots of tight turns which Id like to stay 40 mph or under. You never know when a deer might jump in the road where I live.

What youre saying does make sense, but I know its safe for the transmission to downshift since the car is under 2000rpm. This is why I like manual transmissions lol, much finicky. Or atleast something with selectshift

 

[FruztalProjects]

Basically every time I go to work/town. Its about 11.5 miles to town and Id need to use low for around 2 miles of that. That section of the road is steep with lots of tight turns which Id like to stay 40 mph or under. You never know when a deer might jump in the road where I live.

What youre saying does make sense, but I know its safe for the transmission to downshift since the car is under 2000rpm. This is why I like manual transmissions lol, much finicky. Or atleast something with selectshift

I've tried the Low Gear button today. It does downshift pretty aggressively at high speeds. Not sure if it's a programming thing or it's downshifting to the "lowest available gear". Hopefully not being first at 60 MPH.

 

[TTIntercept0r]

I've tried the Low Gear button today. It does downshift pretty aggressively at high speeds. Not sure if it's a programming thing or it's downshifting to the "lowest available gear". Hopefully not being first at 60 MPH.

Yep, it downshifts to the lowest possible gear without over revving. It can also be used to get a quicker downshift if your on the highway for example and need to get up and go quick. That way you dont have to wait for the computer to figure out what tf it wants to do.

 

[Jeep driver]

Its about 11.5 miles to town and Id need to use low for around 2 miles of that. That section of the road is steep with lots of tight turns which Id like to stay 40 mph or under.

My Dad always told me brakes are cheaper than transmissnions. I do not think that slowing gently to 30-40 mph is stressing the brakes. The PIU does have heavy-duty brakes. Some slight extra wear, but no stress. Go for a ride-along with your local PD if you want to see some hard brake usage.

When I drive my lifted Jeep Cherokee to and from Moab, it is loaded with skid plates and off-road bumpers, camping gear, tools, and spare parts. On I-70 west of Denver, some of the grades are real serious, and my Cherokee picks up speed and needs to slow down. The brakes get some hard use, but I have made this trip 5 or 6 times and never had any issues with the brakes.