"How-To" RDU Fluid Exchange - glock-coma

S

SHOdded

Moderator
Staff member
Originally posted by glock-coma

Changed RDU fluid today
#1
04-14-2013, 08:40 PM
Just thought I would post some pics

Here are some DIY 2"x12" car ramps I made.
Found these over @ evolutionm forum
http://forums.evolutionm.net/evo-x-g...bout-40-a.html
15247f96ae632b547180a06711f6ddd5.jpg


I used a Hydro-Turf oil extractor and a quart fluid pump both found on amazon.
http://www.amazon.com/Hydro-Turf-Oil...sim_sbs_auto_1
e3b533df28eb2b2d5cffc8b847ae2d4e.jpg



Pic of RDU fill plug....I used a 3/8 drive ratchet to remove it. The hole is pretty shallow, so the ratchet will not go completely in. Anyone know why that exhaust hangar is there?
There is not a bracket on the pipe below it
0bb8561846c9aab2be1da9df6f5dc581.jpg


Drain plug before cleaning, and after. Some metal filings, but nothing to worry about
414d721c2f39ebd3ca684204400b6e02.jpg

8a926ac4c7dcbebd86d51997e657dd1f.jpg


I couldn't completely warm up the fluid for easier extraction, I didn't want to deal with a hot exhaust while under the car. It was moving very slowly through the tube.
4f76d3b3f810dc7c4e92d77fe067cb31.jpg


I got out as much as I could, about 32 ounces by weight.
The fluid was pretty nasty. It was the consistency of syrup, maybe a little thicker
a0529e0b50122927870e6a4e27b179ad.jpg


Here is a side by side of old fomoco "lifetime" fluid and new redline 75-w90
0c0638f3a66e9abd60fc32ea9aa6f92e.jpg


Wasn't that hard of a job, the pump just took awhile because of the thickness of the fluid.
While I was waiting, I also changed the spark plugs to the new updated part number CYFS-12Y-3. Probably going to do the PTU fluid next week.

Last edited by glock-coma; 04-14-2013, 10:49 PM.

12/4/2015:  Thanks for the re-linked images, glock!  Much appreciated :thumb:
 
Lovely how-to. How'd that extractor pump work? I think I'll pick one up.

So, to be clear...

The RDU has a fill plug only. No drain. Thats where a pump or suction device comes in.

How about the PTU? Aux cooler (Perf. package) equipped SHOs have a fill AND drain on the PTU, correct? Both accessable by removing one or both primary cats. But those without the aux cooler do NOT have a drain, thus require a suction device as well. Is that correct?
 
I just popped the cover when I changed mine. Just have to buy some RTV and you can wipe out more old fluid with a towel.

ALso meant to add awhile back when I changed my PTU the fluid looked ok but it was only at about 5K miles. People were wondering what relatively new fluid looked like since people were seeing bad fluid at 20k. I wanted to change mine before it had a chance to turn bad.

And I'm not sure but I don't think it would do any good to drive the car to try and heat up the Rear diff because I think the clutch pack that activates the rear is in the PTU and only comes on when needed. I don't think the driveshaft spins until needed.
 
I would think the driveshaft would spin as long as the engine is running/ trans is not in neutral or park to avoid the startup inertia, no?  Should still take longer to warm up the RDU though.
 
SHOdded said:
I would think the driveshaft would spin as long as the engine is running/ trans is not in neutral or park to avoid the startup inertia, no?  Should still take longer to warm up the RDU though.
Click to expand...

Now that I think of it I think you are right, the clutch packs in the PTU just engage to link the 2 when needed.
 
That not correct. The clutch is a part of the RDU. The PTU is always engaged and the drive shaft is alway spinning. The electronically controlled clutch engaged RDU when needed.  There is no clutches in the PTU what so ever.
electronic clutch circled in red.



Sent from my iPhone using Tapatalk
 
How did y'all stick that ratchet in there? My standard 3/8" drive ratchet won't fit because of the exhaust hanger and that IRS cradle. I'd have to get a really slim ratchet in there?
 
metroplex said:
How did y'all stick that ratchet in there? My standard 3/8" drive ratchet won't fit because of the exhaust hanger and that IRS cradle. I'd have to get a really slim ratchet in there?
Click to expand...

You need to go from the top and fish the ratchet down and into the plug.  It's tight, but it will fit. 
 
I used several 3/8" extensions through the passenger side wheel well maybe a crows foot wrench with a 3/8" adapter would work
 
I tried going from the top, it almost fit. I have a Gear Wrench pass-thru wrench set that I should have thought to try, it's like 1/4" thinner than my normal ratchet.

Is the RDU just an open differential? Is there any merit in using some Lubegard Gear Fluid additive (which is supposed to help reduce temperature and reduce friction) to help out the RDU and the PTU given that we don't have a lot of oil to work with?
 
The RDU uses a electronically controlled clutch so I wouldn't use anything that reduced friction.

sent from my speak n' spell using tin cans and string
 
metroplex said:
So the electronic clutch mechanism is in contact with the RdU gear oil?

It doesn't seem to be actually part of the differential fluid system: http://www.shoforum.com/index.php?threads/how-does-the-awd-work.119781/
Click to expand...
Here some info on the AWD for your reading pleasure.  Z  Police-only Cooling
The police version of AWD has three unique features to improve durability during severe use. First, the Power Transfer Unit on the AWD system uses a police-only auxiliary cooler. The retail AWD unit is air cooled, i.e., the aluminum housing dissipates heat to the surrounding air. When the vehicle is stationary, the amount of cooling is obviously less than when the vehicle is moving.
On the police AWD unit, the front housing of the Power Transfer Unit has a special water jacket cast into the assembly. The integral PTU auxiliary cooler is part of the water cooling system. That means the cooling remains “active” since the cooling water is constantly circulated, whether the police vehicle is moving or stationary. The PTU cooler is plumbed into the bottom of the radiator, where the water is cooler than at the top of the radiator.
Second, the Power Transfer Unit uses an internal temperature sensor, not found on the retail unit. A module keeps track of oil temperature in the PTU and the amount of time spent at that temperature. An electric clutch pack engages and disengages as torque is transferred to the rear wheels.
Both the PI Sedan and PI Utility default to FWD under normal conditions. As the front wheels slip, torque is selectively diverted to the rear wheels. A time versus temp logarithm activates an Oil Minder light in the driver message center if and when it is time to change the PTU fluid. The special synthetic oil may last 100K miles in normal police use.
Third, the Rear Differential Unit on the police version uses a fluid-filled clutch pack, while the retail version uses dry clutches. The fluid-filled RDU can withstand more severe duty.
The cooling ability of the police-only auxiliary radiator-water jacket combination was tested in 110 deg. F weather. Hard driving—where power is constantly shifting from front to rear, back and forth—can take many different forms.
Think aggressive driving during a city pursuit: hard throttle for a city block, 90-degree turn, hard throttle, where torque definitely shifts from front to rear. Also think getting unstuck in desert sand. Even though the vehicle and wheel speeds are not high, torque is constantly shifting between the front and rear spinning wheels.
Under the worst conditions of high-torque, clutch engagement and disengagement, the synthetic oil reached temperatures around 195 deg F. The special lube is rated for temps just over 500 deg F. The air-to-water cooler works.  http://www.hendonpub.com/resources/article_archive/results/details?id=5091
 
FWIW the Gear Wrench pass-thru ratchet worked perfectly, it was slim enough to slip between the cradle and fill plug either from the bottom or from the top!
 
Called my dealer the other day to get a quote on having the PTU and RDU fluid swapped out and they said they wouldn't do it.  Claimed there is no drain plugs to do so.  Guess I'll do it myself one weekend when I have time.
 
I suggest finding out where the Police service their Interceptors and try them.  Other option is a Lincoln dealer.  My wife works at a Lincoln dealer and they don't see anything odd with the request.
 
You must log in or register to reply here.

Similar threads

C
my 2017 SHO w/PP
2 3 4
Replies
65
Views
28K
SHOdded
S
S
Water pump, timing chain and unsolicited info
Replies
1
Views
9K
SHOme
S
P
How to Use Whatever Rear Spring You Want
Replies
10
Views
12K
Thomks
T
L
PTU Vent Leak - How to fix?
Replies
10
Views
12K
LipschitzWrath
L
C
Coolant
Replies
3
Views
5K
mrhighcaliber
M
Back
Top