Bleeding Differential on a 16-22 Honda Pilot?

[Owen Lucas]

Time to change the DPSF-II Fluid rear diff fluid on my 21 Pilot.

Anyway, after some research online (YouTube and forums) I've read that you have to "bleed" the rear differential by turning on the engine with an empty diff and let it run for a minute. Not to drive it, but just to run the engine. Supposedly more fluid will come out of the diff if you run the engine.

Is there a pump or some mechanism to warrant this operation?

Honda Manual states 1.92 qt capacity but supposedly it will take more after you "bleed" it.


(I am actually almost 3000 miles over the recommended 15k mile interval so I hope they don't use this against me if something fails in the future!)

 

[Trav]

This explains the operation of the diff. It has 2 pumps but they seem to be mechanically operated so running the engine is not going to operated them. The small amount of addition fluid you may release is not worth bothering with, drain and fill. Think of it this way, the engine has x quarts of oil fill when new but at regular OCI it is half to a 3/4 of a quart less. You could remove the engine and turn it upside down to get the rest but nobody in their right mind would even contemplate such a thing. CRV and Pilot diff are very similar in operation.

System Description15-3

 

[Owen Lucas]

This explains the operation of the diff. It has 2 pumps but they seem to be mechanically operated so running the engine is not going to operated them. The small amount of addition fluid you may release is not worth bothering with, drain and fill. Think of it this way, the engine has x quarts of oil fill when new but at regular OCI it is half to a 3/4 of a quart less. You could remove the engine and turn it upside down to get the rest but nobody in their right mind would even contemplate such a thing. CRV and Pilot diff are very similar in operation.

System Description15-3

Those are very interesting diagrams, thank you for posting them. I would assume Honda took this de-minimus remaining fluid into account as acceptable "contamination" when servicing the differential, like your engine oil analogy.

 

[Trav]

For sure they did.

 

[hrv]

I have a 21 HRV AWD and changed the rear fluid a month ago... It was nothing more then a drain and fill....easy peasy....

 

[The Critic]

Time to change the DPSF-II Fluid rear diff fluid on my 21 Pilot.

Anyway, after some research online (YouTube and forums) I've read that you have to "bleed" the rear differential by turning on the engine with an empty diff and let it run for a minute. Not to drive it, but just to run the engine. Supposedly more fluid will come out of the diff if you run the engine.

Is there a pump or some mechanism to warrant this operation?

Honda Manual states 1.92 qt capacity but supposedly it will take more after you "bleed" it.


(I am actually almost 3000 miles over the recommended 15k mile interval so I hope they don't use this against me if something fails in the future!)

I think you either misread or someone posted incorrect info. You are NOT supposed to run the vehicle with an empty differential. The process is to perform a drain and refill, run the engine to "bleed" the unit, then recheck the fluid level.

 

[Rand]

I think you either misread or someone posted incorrect info. You are NOT supposed to run the vehicle with an empty differential. The process is to perform a drain and refill, run the engine to "bleed" the unit, then recheck the fluid level.

Can you explain how does running the engine bleeds the unit or are you supposed to drive around the block too?

 

[The Critic]

Can you explain how does running the engine bleeds the unit or are you supposed to drive around the block too?

Procedure is in the second page of the PDF:

Rear Differential Fluid Change

www.piloteers.org

There is a pump in the unit that circulates the fluid.

Rear differential fluid change

www.piloteers.org

 

[Rand]

So they have an electrical pump. Trav's diagram seemed purely mechanical.

 

[Owen Lucas]

Procedure is in the second page of the PDF:

Rear Differential Fluid Change

www.piloteers.org

There is a pump in the unit that circulates the fluid.

Rear differential fluid change

www.piloteers.org

Thanks Critic, that is super helpful.

It makes sense there is an electric pump because the wiring harness going to the diff has about 10 wires or so, many more than you would expect from a sensor or 2. I guess some of the wires are to power the pump.

 

[meep]

I thought the pilot was a derivative of sh-awd, which does not use the dual pump system. The dual pump system from what I thought was their entry level system used in the CRVs. The upscale vehicles basically had a “spool” for the rear axle with individual electro-magnetic clutches on each tail shaft so torque could be sent to each axle in proportion to throttle and steering inputs. 6 amps per side, and something around 145 ft lbs of torque is the factory holding spec for each side.

you might double-check which system is in the pilot??

 

[Owen Lucas]

I thought the pilot was a derivative of sh-awd, which does not use the dual pump system. The dual pump system from what I thought was their entry level system used in the CRVs. The upscale vehicles basically had a “spool” for the rear axle with individual electro-magnetic clutches on each tail shaft so torque could be sent to each axle in proportion to throttle and steering inputs. 6 amps per side, and something around 145 ft lbs of torque is the factory holding spec for each side.

you might double-check which system is in the pilot??

The Acura rear diff fluid is also DPSF II, same part# just with an “A” added. Honda was actually selling the Acura fluids for a short while when they couldn’t get actual Honda fluid. IIRC, the previous generation was VTM. I know that the CRV also uses DPSF, that is what I was given by the parts department at two separate Honda dealers for the rear diff fluids on both current generation CRV and Pilot.

 

[Owen Lucas]

Regarding the warranty, I think I will send the fluid out to Blackstone for an analysis just in case something happens in the future. Honda could use the excuse that being 3000 miles over the recommended interval is a reason to deny a warranty repair.

I can at least have proof that the diff oil was in good condition or didn’t show any abuse, if that is the case.

 

[meep]

The true dual pump system is hard on the fluid. The interval is pretty frequent on that. The VTM and sh-awd fluid is treated nicer. Many of them probably never get changed and seem to soldier on. it would be interesting to see where haldex systems fall in the spectrum, as those get messy after a while of neglect.

 

[nthach]

The true dual pump system is hard on the fluid. The interval is pretty frequent on that. The VTM and sh-awd fluid is treated nicer. Many of them probably never get changed and seem to soldier on. it would be interesting to see where haldex systems fall in the spectrum, as those get messy after a while of neglect.

Isn’t RT4WD basically a hydrostatic system, like what Honda uses in their push lawn mowers?

VTM-4/SH-AWD is from Borg-Warner, it’s electronically-actuated system but not a “clutched” system. SH-AWD adds torque vectoring to it, but Honda is more or less rebranding RT4WD in new Acuras as such.

Yea, Haldex systems have less fluid(or a mix of fluids, one for the electrohydraulics and one for the wet clutches and diff) and a filter that should be serviced yearly.

 

[meep]

It’s not “clutched” such as a haldex or LSD, but it is a dual wet-clutch unit, electromagnetically engaged, on each side independently. Or at least the sh-awd unit in our Gen 1 mdx was. That’s how it can torque-vector between left and right, by introducing varying amounts of uneven engagement between the left and right sides independently, varying by throttle inputs and steering angle.

what sort of “got me” was how effective it was while also being limited. The mdx handles quite well and exhibits very little wheelspin, for all that “fwd power,” even over cold, wet roads. it is a very capable system in reasonably heavy snow. Yet, off-road with it and it’s got no depth. I discovered that, as mentioned above, each axle is only required to provide 145 (or something in that ballpark) ft/lbs of torque. What’s the wheel radius, 15 or 16 inches on those? That’s like 125 lbs of thrust per side, or 250 lbs of thrust total for the rear. That’s enough to do a wonderful job in rain or snow in that suv, but not when you’re looking at difficult or technical conditions. I’m guessing there could be different variants, as i‘d like to think the ridgeline was equipped with a heftier unit, but I don’t know??

 

[nthach]

Well, Honda did race the Ridgeline in the Baja 1000, but a course like that was gone through with 2WD pre-runners(which inspired the 2WD PreRunner package on the Tacoma SR5) to make sure no technical features or mud/sand is in the course. It’s a traction aid system, much like the rear electric axle on a Toyota/Lexus AWD hybrid(AWD-i or AWD-e, the main difference is AWD-i piggybacks off the main inverter, AWD-e has its own inverter).

 

[ARB1977]

On my wife’s 19 Pilot AWD the first change was 15K. Looked brand new. Did not cycle the rear diff. Currently at 47K and it’s time again for a change. Other than one winter for a few days I engaged snow mode…even in north Texas, lol. I’m curious what the condition color wise it will be.