PTU Fluid Change D.I.Y.

[tad57]

I want to thank everyone who gave suggestions on how to refill the PTU after draining.  I did it nearly 100,000 miles ago and have been dreading the thought of having to do it again, which is the main reason I put it off so long past the recommended 60,000 mile change interval.  The first time I probably had over 5 hours getting the fill plug off and back on.  Why the plug didn't cross thread when reinstalling it I'll never know, but thankfully it didn't.  I used the fill method outlined here of filling through the vent tube.  It made the job 1,000 times easier than filling through the nearly inaccessible fill plug and I'll never put off changing the fluid again.   I made one additional tweak to the method nilohigh described.  Nilohigh inserted a 1/4 OD tube just past the opening of the vent tube.  I used a 4 foot long 3/16" OD clear vinyl tube that I inserted as far as it would go (about one foot) into the vent tube.  Ideally I wanted it to go all the way into the PTU to act as an air bleed,  but it likely stopped at the 90 degree bend you can see on the PTU diagram shown in this post thread.  I then threaded a one foot section of 1/2" ID clear vinyl tube over the 3/16" OD, attaching it to the vent tube on one end and a funnel on the other.  I used a clothes pin to hold the funnel to the hood weather strip so I didn't have to hold the funnel while I was filling it and also blowing into the small tube.   The 3/16" tube extended a few feet past the top of the funnel so I could easily blow air into it.  I poured oil into the funnel until it backed up to the top of the 12" section of tubing at the base of the funnel.  I could watch the oil level go down and when it began to slow down due to increased air pressure in the PTU, I lightly gave 3 or 4 gentle puffs of air into the small tube, taking my mouth of the end of the tube between each quick breath to relieve built up air pressure in the PTU.  During the first puff you will be blowing oil out that has risen into the small tube,  but you will then begin to hear and feel air bubbles coming out the end of the small tube.  Immediately after doing this the oil will begin flowing more rapidly into the PTU.  I think what is happening is that the air being forced through the tube briefly displaces the oil near the vent tube entry into the PTU, allowing a pathway for the built up air pressure in the PTU to be relieved by flowing back up the small blow tube.  If I blew too forcefully on the small tube, I forced extra air into the PTU and the air burped up through the 1/2" tube splashing oil out of the funnel.  I didn't time the fill procedure but I feel like it took about 45 minutes to drain 27 ounces of oil through the vent tube into the PTU.  Perhaps I shouldn't have skipped nilohigh's suggestion of heating the oil first.  I did, however, let the bottle set in the sun for an hour on a 90 degree day before filling the PTU.  Ideally you would have the small tube extend all the way into the PTU so it provided a continuous air bleed.  If someone has an idea on how to do that, I hope they post it here so I can try that next time.  Another method that might provide a faster fill, would be to not use the smaller hose at all, but instead use a hose large enough (probably another section of the same 1/2" ID hose connected between the funnel and the vent tube)  to seal against the inner wall of the funnel.  Pour oil into the funnel until it backs up to the base of the funnel, and then insert the 1/2" blow tube into the funnel until it seats against the inner sidewalls of the funnel, and then blow the entire filled 1/2"  tube and vent tube into the PTU at once.  The tube would be clear and the air would escape up the vent tube without burping up oil.  For this method to work you'd have to be able to force all the oil into the PTU in one breath, and I have no idea if that is possible or not.  No matter how you refill the PTU,  any method described in this thread is superior to filling through the fill plug!!

[KOKO]

Hi,

 

What you did with the magnet at the backside of the probe?

The magnet is actually quite important in order to collect all steel particles and debris, otherwise intensive wear will occur when they fly around between the gears.

 

BR

[TopperHarley]

I replaced my factory drain plug for that reason, to make sure the magnet is present to collect shavings. I actually used my Wife’s Turkey Baster to squeeze the oil in! 20 minutes later and it fills ! Lol 

[Yaniyanev]

Hello all. I want to change ptu i rda fluid. I'm thinking of buying Mopar synthetic gear and axle lubricant SAE 75w90 GL-5. Need I add Mopar limited slip additive?

[John/Horace]

If it makes you feel better you can. But it's not necessary, even rear diff doesn't need it. Not limited slip--trak loc  applications. Just good quality semi sun like owners manual states.

[cokey]

On 2/9/2023 at 11:57 AM, davidlb512 said:

I am putting together a plug for our PTU, that will be easier for others to put together, and requires no machine work, milling, tapping, etc. I have ordered an M22x1.5 thread male-to-1/4" female pipe thread adapter, and will be putting a grease zerk in the 1/4" pipe thread end. I will take the entire thing out of the PTU, to drain the fluid, and reinstall, and use the grease zerk to fill the PTU with 75w90 synthetic gear oil. I will add a plastic grease zerk cap, to cover, and protect, the grease zerk. I will come back here with pictures, after the adapter has arrived, and I put it together. This should be a cheap, and easy, way to streamline everyone's ability to perform routine maintenance on their PTU. I will also add the part #'s for the adapter, grease zerk, and cap, that I use, after I confirm that they perform the function that I am hoping. Wish me luck guys!

Hey any luck on this. I had the idea of "why not change drain plug with a valve that can be adjusted to 1 way.  Need to do mines very soon.