Part 3 Honda CRV differential rebuild
Comparing Notes for the Nose Caps Old Vs New!
So in Part 2 we discussed the disassembly of the CRV nose cap, removal of of the clutch pack assembly, and prepared for the brake down of and we went over some of the So as we take these differentials apart we notice a lot of the similarities between the 2! One disassembling the nose cap of the 2006 to 2011 Honda CRV reveals that the nose bearing is much larger diameter than the older Honda CRV. However the inner diameter of the bearing races exactly the same diameter. At 1st glance the older 1997-2005 Honda CRV differential nose bearing uses NACHI-5206 Bearing which carries a 62 mm outer diameter With a 30 mm inner diameter and a 5 mm bearing race with a total thickness of 23.7 mm.
The 2006 to 2011 Honda CRV differential however utilizes a 64.2 mm Bearing outer diameter with a 30 mm inner diameter bearing and a 9.6 mm bearing race with a 14.6 mm total bearing thickness making the 2006 and up Honda CRV differential superior to that of the element and predecessor Honda CRV rear differential.
So for most people thinking about these builds they would imagine that a lot of these components are cross compatible because that is just the nature of Honda. And dealing some of the research for you documenting the build of these rear differentials we notice a lot of the similarities and upgrades in design that highlight some of the key features of additional performance put him to some of the newer Honda all will drive differential components.
RT-AWD Dual Pump Assemblies!
Moving from the RT-AWD nose cap assemblies its time to look inside and see what makes the system transfer power! This part is what most of our customers have been waiting to see. So lets Dive in! The initial look of both dual pump assemblies show vast differences in size and diameter! This technology didn't change much from the old style RT-AWD differentials to the new other than the system was made shorter and wider for the newer differentials with the RAMP Assembly!
RT-AWD Dual Pump Assemblies
I can imagine that this is to allow a more consistent increase in pressure supplied by the dual pumps and a more gradual and stable transition into applying TQ to the rear differential through the clutches. More surface area with the added benefit of the RAMP assembly allows more power to be transferred quicker with let work from the hydraulics in the dual pump assembly. Well the only way we will know for sure is to take it apart and do some investigation! So lets dig into the Dual Pump Assembly!
Disassembly is pretty strait forward. There are 3 - 8mm 6pt bolts on the back of the Dual Pump Assembly that will need to be removed to begin this process. Turn the Dual Pump upside down so that the piston assembly is facing down and remove the 3 bolts from the bottom of the Pump Assembly. Note: The Dual Pump Assembly has several Springs and 9.4 mm and 12.6 mm ball bearings internal that change and or block the flow of hydraulic fluid transfer throughout the pumps. When removing the hardware the assembly is under spring pressure. Maintain downward pressure on the assembly during removal of the hardware so that the pumps do not separate!
While maintaining downward pressure on the pump assembly remove the 3 - 8mm bolts and place them in a safe area. Slowly lift the bottom portion of the 3 part pump assembly carefully. For my customers doing the dual pump quick spool kit installation this is the information you need to see! The spring visible to the lower right is the pressure relief spring for the dual pump assembly.
2006-2011 CRV Rear Pump Removed
2006-2011 CRV Dual Pump Oil Drive Gear
Inside the Dual Pump we find the oil pump drive gear for the secondary pump, the 9.4 mm and 12.6 mm ball bearings that control flow through the dual pump assembly. Take these and place them in a small zip lock bag with the springs for each corresponding bearing. Remove the Oil Pump Drive Gear from the assembly and inspect it for cracks or damage from normal use. You want to look for scoring, cracks, debris, dents etc all that will reveal that the differential has been starved for oil like your engine oil pump. if these parts are damaged replace the dual pump assembly immediately.
Secondary Oil Pump Drive Gear 2006-2011 CRV
Inspect the Oil Pump Drive Cavity for Scores and Damage 2006-2011 CRV
Next separate the Primary Dual Pump from the Dual Pump Piston assembly. Remove the bearings and springs from the assembly and place them in labeled zip-lock bags with their corresponding springs. Inspect the Pump Drive gear and the Pump Drive Gear Cavity for damage as you did above.
In the image above I am inspecting the 1997-2005 CRV/ 2003-2011 Element RT-AWD Differential Dual Pump Assemblies (Bottom) compared to the 2006-2011 CRV Dual Pump Assembly (Top).
Honda didn't really change the internal design and components of these pumps much over the years between generations of the V but they did change the size of the pumps themselves. What I discover during my tear down of these 2 differentials is that the old style RT-AWD Differential is under-driven by the T-Case and the newer style with the RAMP Assembly is over-driven by the Transfer Case. I Part 2 we discussed the difference in size of the dual pumps from the external but not how they function. So for those of you who do not know what makes this work here is the flow diagram for the CRV Non Ramp differential.
Non Ramp CRV Differential RT-AWD Dual Pump Assembly
The dual pump assembly is made up of 4 major parts. The primary and Secondary oil pumps, Clutch Piston Assembly and the Rear Oil Pump Cover. How this system works is relatively simple but follows the principals of Bernoulli's theory of Fluid Dynamics where he states that an increase in the speed of a fluid occurs simultaneously with a decrease in pressure or a decrease in the fluid's potential energy. This compounded by Issac Newtons
Second Law of Motion stating If a small volume of fluid is flowing horizontally from a region of high pressure to a region of low pressure, then there is more pressure behind than in front. This gives a net force on the volume, accelerating it along the streamline. The RT-AWD Differential uses a Hydro-Mechanical Tq Control System that allows a series of flow controls to (spring and bearings) that regulate the flow of hydraulic fluid supplied to the Clutch Piston Assembly. The Dual Pump Quick Spool Kit increases the pressure and flow of hydraulic oil supplied to the Clutch Piston Assembly thus increasing the pressure and volume of oil supplied from the Primary and Secondary Oil Pumps to the piston assembly. The shims decrease the amount of distance between the clutch Piston assembly and clutch engagement.
RT-AWD Dual Pump Assembly Flow Characteristics
The main thing people forget to do in the installation process of the Dual Pump Quick Spool Kit installation is to take the 2 - Oil Orifices in the Differential and Open them up to allow more flow increasing the volume of the newly modified pumps. This is a rubber O-ring with a 12.2 mm diameter x .5 mm thick orifice with a small "0.5 mm" hole in the center that allows hydraulic oil to pass from the primary and secondary oil pumps to the clutch piston assembly to engage and disengage the clutches. For the Dual Pump Quick Spool kit to work correctly you must drill the hole in the oil orifices open to 3.175 mm or 1/8th" and chase the holes til smooth so that fluid travels smoothly with no obstruction. Clear away any debris from the oil Orifices and reinstall them into the rubber o-rings.
Once this is done its time to install the modified Springs into the Dual Pump Assembly. In our kit we supply 2 spring replacements for the dual pump Assembly that increase hydraulic pressure and hold your V and decrease pressure bleed-off while in AWD operation.
Honda RT-AWD Dual Pump Pressure Relief Spring (Top Left) and 2wd/4wd Selector Switch Spring (Bottom Left), Dual Pump Quick Spool Kit Upgraded Pressure Relief Spring (Top Right) and Upgraded 2wd/4wd Selector Switch Spring (Bottom Right)
These pieces for the 2006-2011 CRV are a direct swap! Remove the old springs and replace them with the upgraded ones. However for the 1997-2005 CRV and 2003-2011 Element owners out there you will need to trim your spring slightly to allow proper fitment. Take your factory Pressure relief Spring and trim to the desired length of the factory Pressure Relief Spring. For those of you just doing the quick spool install this is the end of the road for you. Reassembly the dual pump assembly after your parts have been inspected and cleaned. For the rest of you we will continue our rebuild later this week with the pinion removal and bearing replacement. Thanks everyone for participating and following along! Like/ Share/ Comment!
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