Aw4 Vss Question

[ParadiseMJ]

I have questions about the VSS (Vehicle Speed Sensor) mounted at the rear of the AW4 tranny...as touched on in this thread.

 

http://comancheclub.com/topic/40598-91-speedometer-issue-does-not-read/page-2

 

How crucial is this particular sensor to the shifting "timing" of the AW4.  Mine is shifting too soon. Other than it shifting too soon...once it gets up and going it seems to run and lock/unlock/downshift properly.  As Hornbrod mentioned the testing is not all that reliable.  So how would one know if it is functioning properly or not, short of just throwing a new one in there??

 

 

[cruiser54]

You fixed the wiring to it?

[ParadiseMJ]

I fixed the wiring that I found broken, but found that the wiring I fixed goes from the end of the harness on the tranny, plugs in to the transfer case. It's separate from the VSS.

 

http://www.novak-adapt.com/images/pics/transmissions/aw4_transmission.jpg

 

If you look at this picture, there are 3 "plugs" on the end of the tranny (to the right). One is the VSS, One is the harness adapter, the third goes back to the transfer case (for the dash light?) it's a 94 tranny and case. So the wiring I fixed has no bearing on the VSS. It's nice that it's fixed but it didn't change anything.

 

I'll likely put the thing on a jack this weekend and see if I can test the VSS like Don outlined in the noted post.

[ParadiseMJ]

Would it be possible to check the speed sensor and it's input/output information from the plug/connector at the firewall. I'd like to check to see if that particular information is making it UP to that connector. I'd also like to check it up on a jack/block with the engine running, in gear, with the rear wheels rolling and I don't particularly want to lay under the vehicle while that's going on.

 

Any ideas??

[neohic]

...I'd also like to check it up on a jack/block with the engine running, in gear, with the rear wheels rolling and I don't particularly want to lay under the vehicle while that's going on.

 

Any ideas??

 

I jacked up the rear of mine and put the trans in neutral. Took two hands to keep everything lined up with my meter so I just kicked the driveshaft around to get things to turn.

[cruiser54]

This help?

 

http://forums.off-road.com/gm-standard-ifs-trucks-suvs/173327-speedometer-problems-how-test-vss.html

[ParadiseMJ]

Thanks but not really, since the VSS on the AW4 has absolutely "zero" to do with the operation of the speedometer when the speedometer is run solely by a cable. The link, and the location, type of sensor all point to an electronically controlled speedometer. It does not address the VSS that tells the TCU how fast the output shaft on the AW4 is turning.

 

Does that sound right???

 

The TAN wire

[cruiser54]

Tan from C3 on the TCU. Goes wht/br at connector c114, 8 pin connector at right rear of rocker cover..

Shares ground (blk) with the solenoids at dipstick tube stud after going through C104, a 10 pin rectangular connector near the RH shock tower.

[ParadiseMJ]

Thank you.  I'll check that out this aft.