Junk Yard VSS

[EagleMark]

Anyone ever found an easy VSS to remove from the JY? Like an inline unit?

Most I have seen are built in trannys or dashboards...

[cmaje72]

Any Jeep grand wagoneer with cruise control has an inline VSS. Some of the mid-late 80's Cherokee and Wranglers had them too. They are 8 pole VSS's though. So if you cannot change the road speed constant to match they won't do much good.

As an example I have a LT1 in my wagoneer. Factory the road speed constant was set to 4060 (for a 4 pole vss). So using the 8 pole vss my speed was doubled. I doubled the road speed constant to 8120 and now it reads correct.

[Six_Shooter]

Nice, I'll have to look into that. :D

[EagleMark]

Can't get any autp parts stores to find a VSS for those vehicles. Do you happen to have an exact year or?

I did look through a lot of pictures on AutoZone website and found these are all screw into speedo line, but don't know the K per mile or"

Duralast/Vehicle Speed Sensor

Part Number: SU5456

Availability: Ships within 2 business days.

Warranty: 2 YR
$41.99



Duralast/Vehicle Speed Sensor

Part Number: SU2115

Availability: Ships within 3-5 business days.

Warranty: 2 YR

$42.99

Duralast/Vehicle Speed Sensor

Part Number: SU2259

Availability: Ships within 2 business days.

Warranty: 2 YR

$77.99


Duralast/Vehicle Speed Sensor

Part Number: SU5455

Availability: Ships within 2 business days.

Warranty: 2 YR



$63.99


Duralast/Vehicle Speed Sensor

Part Number: SU2113

Availability: Ships within 3-5 business days.

Warranty: 2 YR

$49.99

[EagleMark]

Also a PDF from Jags that run on VSS. ut they say the four pulse is sine wave? 2 pulse for TBI is square wave? Which one is needed for 427 PCM?

[JeepsAndGuns]

I was wondering the same thing. I had noticed that the speed was not reading when datalogging with my new7427. I could have swore I remembered it working the first couple times I datalogged with it, but I may have been paying too much attention to all the other cool data on there to notice. I was starting to think mabey my vss had stopped working, but now I read this, I think the 7427 might use a diffrent one.
The one I currently have is #1 from here:
http://www.jagsthatrun.com/Pages/SpeedS ... meter.html (http://www.jagsthatrun.com/Pages/SpeedSensors_Speedometer.html)

Aftering reading through it, we may need #3. It says its a 4 pulse sine wave, where the #1 for tbi is 2 pulse square wave.

You can read a little more in their manual, but its rather vauge.
http://www.jagsthatrun.com/V8-chapters/ ... ensors.pdf (http://www.jagsthatrun.com/V8-chapters/V8-tpi-Speed-Sensors.pdf)
It appears these trucks used a 40 pulse reluctor ring and a drac module,and this module reads and splits up the signal to go to the spedo, ecm, abs, and cruise. But it made no mention of how many pulses and and what type of signal it sends to the ecm. Is it this 4 pulse sine wave?
I really want to know too, as I want the correct vss and signal for the pcm.

[1project2many]

Time for a little history lesson. :)

Cable driven speedometers are typically calibrated to register 1000 cable revolutions as a mile. At 60 mph, or one mile per minute, the cable turns 1000 rpm. Cable driven VSS's will generate pulses which are 1000 times the number of "poles" or pulses the VSS generates in one revolution. An 8 pole VSS therefore delivers 8000 pulses per mile. The earliest GM VSS were optical sensors built into the back of the speedometer head. A disc with two notches was attached to the speedometer cable inlet and would rotate with the cable. When a notch was aligned properly, an infra-red LED would signal an infra-red sensor which would trigger a 5V output. When the notch was not aligned the 5V signal dropped to near 0 V. So two pulses per revolution, 2k pulses per mile, square wave output When GM started switching to all electronic speedometers they replaced the speedometer based sensor with gear driven VSS units on the trans. These units used a system similar to the pole piece and pickup coil inside a distributor with four "poles" to generate a signal. The sensor was geared to turn 1000 revolutions per mile, so the signal generated was about 4000 pulses per mile. Due to the way the sensor used magnets to generate a signal, the output was an a/c signal. During all this time the ecm / pcm circuitry and code for handling speed signals was very similar across different pcm families. Why spend time and money redesigning a circuit that works? So the 1000 rev per mile cable calibration carried over into vehicles which never had a cable. mid to late 90s 4X4 trucks, for example, were all electronic with a 40 pulse per driveshaft rev signal. But the ecm expected a 2000 pulse per mile speed signal so the DRAC was used to convert the speed signal into an ecm friendly signal 2k square wave. Even when the signal wasn't adjusted before being sent to the ecm, it often was changed in the ecm to a multiple of 1000 pulses per mile before being sent to to cruise and speedometer. Many fwd cars using tone rings on the trans output shaft and magnetic sensors use this design.

IIRC the 7427 cals are like others in that they have a magnetic / optical VSS select bit along with a pulse per mile road speed constant and a speedometer signal IP divisor. Choose magnetic for a/c sine wave and optical for square wave. Square wave inputs cannot be adjusted before being sent to the speedometer however signals input on the magnetic terminals are affected by the IP divisor (think of how the first signals were produced).

Many service manuals will mention the speed sensor output if you look into diagnosing a failed speedo or a code for "no speed signal."

HTH

[1project2many]

Tried attaching DRAC calibration info but same problem as attaching Bithoist... file too big (just over 2 Mb).

[EagleMark]

Just rasied the limit to 3mb for you! :wtg:

[Six_Shooter]

In OEM applications the PCM receives both a 40 PPR and 4 PPR signal.

The PCM uses the 40 PPR signal for tranny controls on pin F12. It uses the 4 PPR on F13 for speed and other speed reference functions.

You can use the 2 PPR JTR VSS to the PCM, but it will read low, and can cause some control issues.

In my case I am using a 4L60E, and found out the hard way that I had to use the 40 PPR tone ring and DRAC. For non E tranny applications it would be best to use a 4 PPR, a VSS buffer may be need to condition the signal.

I believe the flag to change from Optical (square wave) to Magnetic (Sine Wave) is called "Output Speed Not from DRAC" in most XDFs.

[EagleMark]

OK, spent some more time looking and did find a listing for a 1987 Jeep Grand Wagoneer, but no picture... so my kid is going to see if they have one in stock where he works at Oreillys auto parts.

Then someone may know how to test it with DVM?

They are CHEAP too! See if this link brings them up for you.
http://www.oreillyauto.com/site/c/searc ... vi=1182350 (http://www.oreillyauto.com/site/c/search/Transmission+Speed+Sensor/03247/C0033.oap?keyword=speed+sensor&year=1987&make=Jeep&model=Grand%2BWagoneer&vi=1182350)

[JeepsAndGuns]

Good info six shooter. I found the flag you speak of and set it. I'm gonna datalog some tomorrow and see if the speed works. If so I guess its gonna be about half what it should be. I may still order the 8 pulse one from the link I posted. I'm gonna try and do a little digging on that waggy vss. My system is in a 79 cherokee, aka, a 2 door waggy.

[1project2many]

In OEM applications the PCM receives both a 40 PPR and 4 PPR signal.

The PCM uses the 40 PPR signal for tranny controls on pin F12. It uses the 4 PPR on F13 for speed and other speed reference functions.

That's a trans specific issue. The 4L80E has an input shaft speed sensor but the 60E does not. So cals intended for use with an 80E trans will expect multiple signals. Might be a good idea to isolate the specific cal differences related to this issue, maybe when the snow gets deeper.


Just rasied the limit to 3mb for you!
Did I miss a deadline? Message still says
"The file is too big, maximum allowed size is 2 MiB."

[Six_Shooter]

In OEM applications the PCM receives both a 40 PPR and 4 PPR signal.

The PCM uses the 40 PPR signal for tranny controls on pin F12. It uses the 4 PPR on F13 for speed and other speed reference functions.

That's a trans specific issue. The 4L80E has an input shaft speed sensor but the 60E does not. So cals intended for use with an 80E trans will expect multiple signals. Might be a good idea to isolate the specific cal differences related to this issue, maybe when the snow gets deeper.

Just talking VSS input, not tranny control related issues. ;)

[EagleMark]

Just rasied the limit to 3mb for you!
Did I miss a deadline? Message still says
"The file is too big, maximum allowed size is 2 MiB."[/quote]
No I changed it for good! no reason to have a place to put stuff if it won't fit.

Looked at your permissions and you were not in a user group? You are now and have attachment privledges. For some reason registered users had no role assigned? Anyway should work.

Posting it in forum right? don't think attachments are allowed in PMs...

[JeepsAndGuns]

There is a couple of pictures of a waggy vss in this thread. Seems one guy modded a 4 out buffer to work with the waggy vss.
Though, looking at the pictures, I dont know how easy it would be to adapt this vss to other applacations, as it appears to have male threads on both ends, with one being smaller than the other.

http://www.ifsja.org/forums/vb/showthread.php?t=112561

[EagleMark]

Doesn't look like that would be a good conversion part with 2 differant size ends...

i have read a lot on that site but never joined. ou can tell those guys the buffer he is talking about is called a DRAC on early models and VSSB on later ones.

I solder in DIP switches on them to adjust for tire and gear changes, don't know if it could be modded to comensate from 2 pulse from 4? They have differant outputs for speedo, ABS and cruise.. I think 1ProjecttoMany or someone here had mentioned exact specs?