A Glance into the Honda RT 1st and 2nd Gen. All wheel drive rear differentials!
So in this brief documentary I want to give you all the opportunity to see 1st hand the Honda first and 2nd Gen. RT-AWD rear differentials from the Honda CRV and Honda Element! Using Norman and Shilo’s differentials we have a rare opportunity to show and contrast the differences in design of these 2 differential designs as I await the carrier cases return from powder coating! Lets Dive In!
I chose these 2 as a comparison because there is a lot of misconception being thrown around about corrected gear ratios and about the actual functions of these differentials.
So utilizing these 2 generations of rear differentials I will give you the option of learning as we explore during our build process for these differentials while waiting for the differential housing has to come back from powder coating. So some brief comparisons.
From the naked eye both differentials appeared to be exactly the same even down to the diameter bearing diameter and thickness but newer slight changes in bearings design between generations. The trunnion gears are exactly the same amount of teeth, diameter, and metal thickness with the same over all design but again I wanted to engage you all in this discussion. The differences come in when you get to the Ring Gear and Pinion!
The 97-05 Honda CRV/Element differential carries 38 teeth on the ring gear and 15 on the pinion. So I guess it’s time to get into some math! Getting into it the ring gear ratio divided by the pinion ratio will give you the total gear ratio for the differential. This is the equation for the 97-05 CRV/ 03-11 Element rear (15 /38 = 2.533:1). Driven by a transfer case that sends 2.542:1 ratio to the rear differential this means that the older CRV/ Element differentials are over driven by the transfer case forcing the differential to build hydraulic pressure faster for clutching gagement in the rear differential.
However the newer style RT-AWD differentials for the 06 and up CRV and Cross-tour use an opposite method of engagement! Operating with a 16 tooth pinion and a 41 tooth ring gear they come in at a 2.562:1 ratio (16 /41 = 2.562:1). For the newer generation to increase performance and response Honda further opted to use further underdriving with a mechanical RAMP assembly consisting of 2 roller bearings, pressure plate, RAMP cam assembly and a new dual clutch assembly giving the 2006 and up CRV/ Crosstour rear differential much more response and immediate TQ power on demand capability while in operation. This one way CAM assembly aids in transferring 20% mechanical energy to the rear wheels instantly. In the imagine below is the 2006 and above CRV Torque Controlled Differential (TCD) nose assembly. It shows the base components and orientation of the ramp assembly its components! Think of it as a progressive style one way cam inside of a limited slip differential. As the ramp assembly spins it pushes on a series of ball bearings fitted in groves that roll inside of the cam forcing separation of the cam and pressure plate assembly forcing pressure to be applied to the dual clutch assembly.
The ramp assembly applies 20% torque immediately to the differential through the clutches to the rear wheels allowing instant torque application, faster engagement and response from the rear differential. The one thing that has been missing from the entire equation is a clutch kit that was capable of transferring more power with less heat and less wear. Innovations like our dual pump quick spool kit use shims under each snap ring to apply additional pressure to the clutches and ramp assembly forcing preload.
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