Honda CRV Differential Tech: How does a quick spool kit work and why do you need one?
Posted by AKDBuilt Performance on Dec 19th 2020
We get asked all the time "How does a quick spool kit work and why do you need one?" The simple answer is it is an upgrade to the CRV differential that increases how fast power and TQ are delivered to the rear wheels. But if you REALLY want know what a quick spool kit (QSK) is and what it does keep reading. To really answer this question we need to first understand how the Real Time All Wheel Drive (RTAWD) Differential works. First let me blast some basic characteristics to you so you can understand and follow along! The RTAWD Diff is a hydro-mechanical open differentials using a "Torque Control Unit" (TCU) to transfer power from the engine/transmission/transfer case to the rear wheels through the driveshaft.
WARNING THE FOLLOWING CONSISTS OF LOTS OF TRICKY TRICKY TECH STUFF:
The TCU is is made up of 3 major parts.
- Nose Cover
- Clutch Assembly
- Dual Pump Assembly (DPA)
The Nose Cover contains all of the parts of the TQ transfer unit. It seals in vital fluid required for hydraulic operation of the Differential. These differentials uses Dual Pump Fluid I (DPF-I) or II (DPF-II) which is available at any auto parts store like Napa or any Honda Service Center. It is the life blood of the entire systems and is additionally the primary lubrication system within the diff for the ring/ pinion and bearings.
The clutch assembly consists of a clutch basket which has a splined input that accepts input from the driveshaft. Inside the basket it has alignment guides for the clutches and is ventilated for maximum oil flow. There are 2 types of clutches in each clutch basket assembly. Some splines to the outer shape of the clutch basket and the others splined to the clutch guide. When power is applied a piston assembly extends from the dual pump assembly applying pressure to a dual pump pressure plate sandwiching the clutches together forcing them to lock the inner and outer splined clutches together. This sends power to the rear wheels. In most cases when someone wants to build performance from their OEM CRV/ Element/ Crosstour or AWD Swapped vehicle they get miss informed by many forums of groups to believe that these differentials cant handle power. The RTAWD differential is designed to be a fuel efficient, cost effective way of providing AWD capability when needed and allow 2WD functionality when not. Promoting fuel efficiency by reducing drivetrain loss and allowing AWD "On-Demand" when the front wheels slip. But this differential is not trash! We have been very successful in providing performance packages with power ranges from 500hp to 1000hp with the QSK and other innovations from our partners.
The DPA is the most important part of the TCU. Its sole job is to hydraulically measure pressure variances between he front pump and rear pump assembly. For a lot of you just barely hanging in there this means that it measures front wheel speed and rear wheel speed to determine conditions where the diff needs to engage. If the pumps receive a variance of wheel speed difference between the front and rear the pumps it applies hydraulic pressure to a piston on top of the dual pump assembly mechanically engaging the clutches. So now if you followed along you have the basic understanding to to know what we designed.
So what is the QSK? The QSK is a high performance hydraulic pump upgrade installed into the "Dual Pump Assembly" (DPA).
It consisting of:
- 1 upgraded x 2WD/4WD Selector Switch Spring.
- 1 x High Pressure Relief Spring.
- Corrosion Resistant Grade 12.9 Zinc Coated M8 Rear Cover Bolts.
- Corrosion Resistant Grade 12.9 Zinc Coated M6 Nose Cap Bolts.
- Corrosion Resistant Grade 12.9 Zinc Coated M5 Dual Pump Assy. Bolts.
- Corrosion Resistant Grade 12.9 Zinc Coated M6 Dual Pump Assy. Mounting Bolts.
- M6 and M8 Billet Aluminum Beauty Washers.
- RAMP Assembly Shims (if Applicable).
Optional sold separately:
- Our Thermal Switch Delete Plug with O-Ring (recommended)
The QSK increases the pressure of the 2 mechanical pumps inside of the DPA. It typically increases pressure about 30% making it safe for street and off-road applications, while maintaining a higher relief pressure so you stay in AWD longer with less pressure bleed-off. Additionally anyone going AWD or those performing performance enhancements to their OEM RTAWD equipped vehicle we included stronger hardware to replace those broken bolts and to give you a corrosion resistant and personalized finish to your project.
Depending on the differential that you are attempting to resurrect from the bone yard you will have one of the following.
- 97-04 CRV or 03-11 Element are non RAMP differentials.
- 05-11 CRV or 10-15 Accord Crosstour are RAMP equipped differentials.
Differentials with RAMP have a TCU that uses a mechanical cam assembly along with the hydraulic DPA to force the differential to transfer 20% TQ immediately. This is used in conjunction with hydraulics to supplement the remaining power handling of the differentials TCU to the rear wheels. What this means is instant TQ transfer that you can feel in your Soul the second you launch. There are differences in the kits between the RAMP and the non RAMP versions to be sure to select the one that suits your differential.
Got it? if not feel free to shoot us an email or give us a message on social media. Knowledge is free.