[MEK]

Looked at a truck tonight, 91 extra cab 4x4, rear anti lock brakes. I saw a sensor on top of the rear diff but could'nt see any sensors on the front wheels to detect wheel speed. I want to buy this truck to put a solid axle in. Can't pass a VI here if you tamper with the ABS, anybody done a SAS on one with rear antilock and kept the functionality of the ABS?

Mike

 

[sickfab]

There is no front ABS on that truck. Only rear, so your good to go, as long as you dont mess with the rear.

 

[Chris Geiger]

In the USA none of the 91's had front ABS, only rear.

 

[MEK]

About to show my lack of knowledge about abs here, doesn't the front wheel speed have to be measured with sensors to tell that rear wheels are locked up?

 

[sickfab]

Well, I'm not exactly sure of how it works, but, I think it uses the ring gear as a "tone" ring to sense how fast the ring gear stops???? I'm sure someone here knows exactly how it works, and will chime in.
I do know for sure there are no sensors on the front wheels though.

 

[Chris Geiger]

It depends on the type of system. The type we are talking about here is a single channel system. The sensor reads the spinning ring gear in the diff.

My FJ80 has a 4 channel system. It reads each wheel. If a wheel stops suddenly , the computer releases the caliper for a split second. The computer than reads the wheel again to see if it has started turning again. The computer limits the caliper pressure until the wheel is turning again.

On a 4 channel system, each channel runs separately and the other wheels are not affected if one wheel is locked up.

On a single channel system like the 4Runner used, it just limits the rear pressure if there is a sudden loss in wheel speed. The computer also looks at acceleration sensor under the stereo and the vehicle speed sensor to know how fast it was going before the wheel lockup.

 

[MEK]

Thanks guys for the info.