Growl noise in 'Tow Mode'

[ensoniqman1]

Guys -

So when I go through mountain passes without towing, I will occasionally enable the 'Tow Mode' button to activate all 8 cylinders (out of Eco mode).

When I do this, I can hear a distinct growl from either the driveline or rear end.

Any thoughts?

It goes away if I disable the tow mode.

Note, that I am NOT actually towing anything or have a heavy load.

 

[kurek]

Tow mode doesn't deactivate MDS, pretty sure that one's been beat to death at this point

Tow mode changes the shift map and likely increases line pressure.

Does the growl happen constantly? In all gears and on acceleration and deceleration?

 

[ensoniqman1]

Growl just in acceleration, going on an upward steady incline

 

[kurek]

Can you manually downshift (while not in tow mode) using the ERS function and see if the same thing happens?

 

[ensoniqman1]

Tried that, and yes..no growl when manual downshifting with the ERS

 

[kurek]

Tried that, and yes..no growl when manual downshifting with the ERS

Got it. So this becomes difficult to diagnose.

I don't believe your concern is related to MDS in any case because it's been stated by enough people who seem to know their stuff that tow/haul does not disable MDS, but manually operating ERS does disable MDS. So at least you can cross that off your list.

This is purely a guess, so take it for what it is: I suspect that the main mechanical difference you'll find with tow/haul is in commanded line pressure inside the transmission. I don't have inside knowledge from Chrysler about it but it would make sense that they would program a lower line pressure when it's not needed, for softer clutch engagements and reduced heat and fuel consumption. High pressure isn't "free", in other words. But under towing conditions you would want the clutches held as tight as possible and shifts to occur more quickly so they don't slip and wear as much.

So if tow/haul bumps up line pressure you could encounter a few possible noise generating failure points; for example a failing torque converter can "balloon" and grind against the case, or a leak at any of the connection points or end plate of the valve body could cause cavitation as the fluid jets out of it which may make a roaring or growling noise. Even the pump assembly itself could be undergoing failure and produce a growling noise in complaint when it's asked to raise pressure.

Sorry I don't have more than that but hopefully it gets you closer to a solution.

 

[turkeybird56]

Delete

 

[ensoniqman1]

Ok, thanks.

Had a tranny pump fail in my 2002 with 445 trans...after towing with a full load and trailer (287 engine).

Did not growl, but maybe idea is the same.

Thanks.

 

[jws123]

How many miles on it?

what your describe reminds me of rear end pinion noise EXCEPT you say you only hear it in tow mode not reg so thats weird but all jeeps/dodges do this at some point mine in a high gear under lil load if you give it lil gas rear will growl. Its been doing this for long time its just normal tbh all my dodges/jeeps did it at some point if you find that to be the cause turn radio up and drive it or replace rear end pinion bearings.

When is last time you changed fluid in rear axle? you could try that.

 

[Ribtipram]

Are we talking a 1500 or 2500 here. Mds is not active on a 2500 in tow haul.

 

[savage_46]

Do you have a cold air intake? I'm curious cause maybe the engine is under more load & sucking in more air through the open filter creating the noise

 

[Texram155]

My 2010 makes a noise from the tq at 14-1500rpms. Guess there was a tsb about it.

 

[ensoniqman1]

Miles just turned over 160k. No cold air intake, all factory. Basic 1500 ST model 4WD truck.

Never any problems before...