Log In

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!
  • Students Click Here

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Students Click Here


Cam and pawl differential, continued...

Cam and pawl differential, continued...

Cam and pawl differential, continued...

thread78-313320: Cam & Pawl Differential

As it happens I've been researching this type of diff as a variation is used as the center differential in the 2006 through 2012+ 4WD Suzuki Grand Vitara, I have a '10 model and per my usual habit am trying learn every technical detail about it, as I do with every vehicle I own.

There is some, but not too much information on the web about this. It was invented by ZF in 1930 and used on certain VWs. It was intended as a limited slip axle differential and later appeared on some low volume UK vehicles. These applications were known to have high wear. The path gets blurry but it appears to have been developed further by Automotive Products LLC (called APTRAC) then passed on to Eaton and was once known as a Suretrac, before that name was transferred to a more conventional clutch-pack LSD design. It was used on the 2004 Subaru WRX (at one axle only) but received bad reviews.

OK, enough of that. The main thing is to clarify that it's nothing like a Detroit Locker. No slippage occurs nor is there any ratcheting action. It's more like a harmonic drive. The cams have a differing number of teeth on each side so the pawls can slide axially in-between the cams. There is a lot of axial sliding going on for very little speed difference so the friction provides an "LSD" effect. A Subaru technical description can be found here.

It's interesting that there is an inherent uneven torque split, in my case 47/53 as a center diff, but this did not seem to discourage axle diff applications. I have not discovered where Suzuki sources this unit (pic below) but the geometry has been refined from earlier versions, presumably for ease of manufacture. When I do a U-turn I can hear (feel in the steering wheel) the pawls sliding back and forth. Because it doesn't work that well as a limited slip Suzuki adopted brake-type traction control from 2009 and possibly even revised the cam angles in the unit to reduce noise and wear yet still provide an open center diff function in a small package.

RE: Cam and pawl differential, continued...

It's axial cam and pawl diff, but I'm intrigued a bit about opting for wedge profile for cams and pawls... I would think it's supposed to give some 'preload' i.e. to increase torque difference between wheels required for diff to unlock (I'm still of the opinion I think I've expressed in older thread that the natural 'state' of those diffs is locked).

Thanks for the technical description- will look into it.

RE: Cam and pawl differential, continued...

Why is there an inherent uneven torque split? It appears to be symmetrical in every respect.

RE: Cam and pawl differential, continued...

RossABQ, the reason for this assumption is the different number of lobes on each of the cams (IIRC the radial diffs typically had 13 lobes on inner cam and 15 on outer- so this type would have different number of lobes on left and right cam)- but the way I see it cam & pawl diff does not work like a gear, so the different number of lobes or 'teeth' does not come into play. I'd say, although I've seen a few mentions of uneven torque split, I do not subscribe to that theory. With diff in 'normal' operation it's locked and transmits torque evenly, and should it begin to slip the torque split will be a complex function (position dependant) and the friction will, when it's designed properly, prevent it from excessive wheel speed difference (not allow it to function like open diff).

Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members! Already a Member? Login


White Paper - The Criticality of the E/E Architecture
Modern vehicles are highly sophisticated systems incorporating electrical, electronic, software and mechanical components. Mechanical systems are giving way to advanced software and electronic devices, driving automakers to innovate and differentiate their vehicles via the electric and electronic (E/E) architecture. As the pace of change accelerates, automotive companies need to evolve their development processes to deliver and maximize the value of these architectures. Download Now
White Paper - Model Based Engineering for Wire Harness Manufacturing
Modern cars, trucks, and other vehicles feature an ever-increasing number of sophisticated electrical and electronic features, placing a larger burden on the wiring harness that enables these new features. As complexity rises, current harness manufacturing methods are struggling to keep pace due to manual data exchanges and the inability to capture tribal knowledge. A model-based wire harness manufacturing engineering flow automates data exchange and captures tribal knowledge through design rules to help harness manufacturers improve harness quality and boost efficiency. Download Now
White Paper - Modeling and Optimizing Wire Harness Costs for Variation Complexity
This paper will focus on the quantification of the complexity related costs in harness variations in order to model them, allowing automated algorithms to optimize for these costs. A number of real world examples will be provided as well. Since no two businesses are alike, it is the aim of this paper to provide the foundational knowledge and methodology so the reader can assess their own business to model how variation complexity costs affect their business. Download Now

Close Box

Join Eng-Tips® Today!

Join your peers on the Internet's largest technical engineering professional community.
It's easy to join and it's free.

Here's Why Members Love Eng-Tips Forums:

Register now while it's still free!

Already a member? Close this window and log in.

Join Us             Close