dcmodels

I have been using RedLine brand ATF-D4 in the rear differential of a 2009 RDX for the following reasons:

Ø My empirical testing shows less wear with D4, than with either Honda ATF-Z1 or DPSF.

Ø D4 is a full synthetic ATF which is advertised as ATF-Z1 compatible. ATF-Z1 is the original specified OEM Acura rear differential fluid for pre-2011 RDX. I believe that the original SH-AWD differential was designed to use Z1, and not DPSF, which is the current “acceptable” fluid.

Ø D4 is rated as a GL4 gear oil, and the RDX rear differential contains drive-gears, as well as the electronically controlled clutches.

Ø D4 is thicker at 100C and thinner at -40C than other ATFs – better protection at high temperatures, and better flow (and protection) at low temperatures.

CAUTION: use this information at your own risk.

The thread in the following link also discusses the use of RedLine ATF-D4 in the SH-AWD rear differential of various other Acura/ Honda vehicles:
https://acurazine.com/forums/showthread.php?t=806911

WHICH FLUID DOES ACURA RECOMMEND FOR THE RDX REAR DIFFERENTIAL?
Acura/ Honda originally specified ATF-Z1 for all years (and models) for the SH-AWD rear-differential, excepting early MDXs. But since Z1 was discontinued, Acura now says that DPSF is “acceptable” for all years (and models), again excepting early MDXs.

Acura DPSF is approved for use in the SH-AWD differential, but not for use in the transmission. Note that the official Acura chart states that DPSF is “acceptable” for the SH-AWD, not that it is “recommended”.

Since Honda no longer has an ATF that is acceptable for the SH-AWD differential, it has decided to use second best: DPSF. I believe that the RDX SH-AWD system was designed to use an ATF type of fluid, such as ATF-Z1, but not to use DPSF. If Acura thinks that DPSF is better than ATF-Z1, it could have originally specified DPSF. Honda DPSF has been used in Hondas for years.

p/n 08200-9001A – Honda ATF-Z1 – red
p/n 08200-9002C – Honda DPSF (Dual Pump System Fluid) – amber (before 2007)
p/n 08200-9007 – Honda DPSF-II (Dual Pump System Fluid) – pink (new in June 2007)
p/n 08200-9007A – Acura DPSF (all-wheel drive fluid) – pink

Also, the early Acura MDX SH-AWD system still requires VTM-4 fluid. Don’t you wonder why? Could it be because the MDX is heavier that all other models which use the SH-AWD? A heavier vehicle would exhibit more severe force against the gears and clutches in the rear differential, especially when towing.

COMPARISON OF ATF VISCOSITY:
I have not been able to find any viscosity information for Acura DPSF p/n 08200-9007(A) or Honda DPS-II p/n 08200-9007. The closest data I found is for Australian made Penrite HDPS (Honda Dual Pump Service), a semi-synthetic.

100C/ ..40C/ -40C .... cSt at Centigrade/ Brookfield cP @-40C
7.70/ 34.00/ ...... = GM OEM Dexron III-H (Petro-Canada)
7.50/ 34.00/ .5,200 = RedLine D4 (for Honda ATF-Z1) (Synthetic)
7.40/ 36.30/ 10,040 = Mobil-1 Synthetic, Dexron III-H/ Mercon
7.06/ 29.49/ ...... = Honda OEM ATF-Z1 (discontinued)
7.00/ 37.00/ ...... = Penrite HDPS (semi-Synthetic for Honda DPSF)
6.83/ 25.09/ ...... = Honda OEM DW-1 (Idemitsu Lubricants America)
6.40/ 30.70/ .4,500 = RedLine D6 (for GM Dexron-VI) (Synthetic)
6.00/ 29.80/ ...... = GM OEM Dexron-VI (Petro-Canada)
6.00/ 29.50/ 12,500 = Valvoline licensed GM Dexron-VI (Synthetic)


NOTE 1: Honda DW-1 is a replacement for Honda Z1 in the transmission, is thinner (than Z1), but not as thin as the GM DEX-VI. That is why DW-1 is too thin to be used as a replacement for Z1 in the RDX rear differential, and why Honda DPSF is now recommended instead.

NOTE 2: RedLine ATF-D4 is thicker at 100C and thinner at -40C than other ATFs, including the synthetic Mobil-1 DEX-III and the synthetic GM DEX-VI.


SERVICE RECORD FOR MY OWN RDX REAR DIFFERENTIAL:
The following is drain mileage service data for my own 2009 RDX rear differential. Since I reset the MID early in most cases, for oil changes, I have not noted a second MID report for (#6) rear differential oil change. If one was reported, I simply missed it.

.6,060 30 Oct 2009 / 6,060 /... Honda ATF-Z1
12,625 29 Jun 2010 / 6,565 /... Honda ATF-Z1 ... MID A16
18,044 03 Apr 2011 / 5,419 /... Honda ATF-Z1
22,421 22 Nov 2011 / 4,377 /... Acura DPSF
27,034 08 Jun 2012 / 4,613 /... RedLine D4
40,466 14 Nov 2013 /13,432 /... RedLine D4


DIFFERENCE BETWEEN GEN-1 and GEN-2 REAR DIFFERENTIALS:
The 2007-2012 RDX rear differential is the SH-AWD system. The later gen-2 differential is not. Basically, the SH-AWD system can control drive-torque to each rear wheel separately, using two separate control clutch-sets. The gen-2 differential has only one clutch set, located on the input drive shaft from the front transfer case, so that both rear wheels are driven together. That explanation is rather simplistic, so anyone desiring more detailed information, should research further.

The gen-2 RDX rear differential operates similar to the Honda CR-V rear differential. The CR-V differential has always specified Honda DPSF, followed later by DPSF-II.

The gen-2 RDX rear differential has always specified Acura DPSF. I do not know how RedLine D4 would work in a gen-2 rear differential. And because I have not tried it, cannot personally recommend its use in a gen-2 differential.


DRAIN PLUG MAGNET:
The magnet on the RDX rear differential drain plug, is a large cylinder. The two halves of the cylinder are the two magnetic poles. Most engine drain plug magnets will have the two poles at the ends of the cylinder instead.

By having the two magnetic poles comprise the entire two halves of the cylinder, the entire cylinder can attract magnetic particles, instead of just one end (tip) of the cylinder.

PICTURES of the gen-1 RDX DRAIN PLUG:
The pictures below are for general reference only. Because of different driving conditions, it is not practical to compare directly what you see on your own drain plug, against the pictures below. You can compare your own drain plug for a given oil change interval, against what you see for another OCI. That will help you to decide how often for an OCI, and how the oil is working for you.

The drain plug from my own 2009 RDX rear differential, is from the drain at 40K miles and an interval of 13K miles. The pictures are the four sides/ quarters of the drain plug. The amount and appearance of material is significantly less than that from the other (shorter) drain-intervals, as reported in my service record above. Don’t be confused by the bright straight vertical lines – those are ambient light reflections. The actual wear material is “wrapped” horizontally around the cylinder.

In fact, there is only a trace of silver material visible. There is some material on each side of the drain plug magnet-cylinder, on each pole, but no material on the cylinder sides between the two poles. Heavier deposits will cover the entire cylinder.

The color of my rear differential magnetic material is silver, I assume because the material is steel. By contrast, the color of magnetic material which collects on my transmission drain plug, is black – I assume that is because the steel particles are mixed with trans clutch material.

PICTURE of the gen-2 RDX DRAIN PLUG:
The drain plug from the 2013 RDX rear differential, is from an initial drain at 20K miles. I would expect more material on the plug for an extended initial drain, during break-in, as seen. That is the very reason why I followed the recommendation in the 2009 RDX owner’s manual, and changed my rear diff fluid early.
https://acurazine.com/forums/showthread.php?t=899684
---eof

wifesRDXtech

Love this info , you are making my want to put redline my rear diff on next fluid change makes sense when you put all the facts and figures on one page. I use redline 75w90 on my front and rear diffs on my BMW.

Question you ever send out your fluid for testing?

dcmodels

No, but I do check and compare deposits between fluid changes. And I have magnetic drain plugs everywhere but in the front diff (that's next). And I have magnetic inline filters in the trans and PS systems, and magnets in the engine oil filter. I am not convinced that the typical $20 oil test/ check has any absolute value, only a relative value over a period of time - and I prefer my own direct check of depostis as just described - JMO

Anicra

Would you recommend D4 for 2013 TL SHAWD rear diff? I stumbled on this while looking for DPSF fluid.

CSmoney28

Wrong thread 🧵 this is for first generations RDX’s ...