tylerwerrin

Hi guys,

I'm confused about the VSS outputs, and if it is possible to just swap a VSS into my 1993 T56.

From what I've gathered, the 1993 T56's VSS outputs 4000ppm via AC sin wave -- but since I'm using a 1995 PCM, I'm not getting any response from my tach -- apparently the 1994+ T56's (and even the later 1993's) output at 17pulses per revolution DC pulse. So my PCM has no idea what to do with the signal it's currently getting from the VSS.

My question is, can I just swap in a newer VSS? Or do I have to change other stuff as well?

Any help would be great!

jmd

iTrader: (4)

The M28 and M29 1993 boxes are the same as 94-up except they have an 11 teeth per output revolution reluctor ring instead of 17 teeth. It's not a different VSS.

Neither is 4000ppm; that was limited to the T5 V6 models with speedo gears.

The tach is not reliant on the VSS for signal. Troubleshoot the tach issue. If you're getting a code indicating no VSS signal, then troubleshoot that.

tylerwerrin

Oops, i didn't mean tach, i meant speedometer -- i had read on the Jags the Run VSS write up that the VSS outputted a different signal for the early 93's.

Is this not the case after all?

tylerwerrin

http://www.jagsthatrun.com/V8-chapte...ed-Sensors.pdf


1. The two-pulse (2000 pulses per mile) square wave (D.C current or direct current) used on all TBI
engines thru 1992, all computer-controlled-carbureted engines, and on 1985-1989 TPI engines.
2. A four-pulse (4000 pulses per mile) sine-wave (A.C. current or alternating current) signal is
required by the 1990-1993 TPI, 1992-1993 LT1 engines, and 1990-1993 Camaro 3.1/3.4 V6
engines.
3. A 40 pulse per driveshaft revolution speed sensor used on 1993 and newer trucks with automatic
transmission, 1994 and newer rear drive cars with the automatic transmission
4. A 17 tooth per driveshaft revolution speed sensor used on 1993-1997 LT1 engines with the BorgWarner 6-speed transmission. An 11 tooth reluctor ring is used on 1993 LT1 engines with the
Borg-Warner wide ratio (3.35 First gear) 6-speed transmission

85MikeTPI

iTrader: (9)

Your point #4 is correct and is what Matt pointed out..

You may be confusing point #2, which doesn't deal with 6-speeds and vette LT1s.

tylerwerrin

I guess i don't understand how it couldn't be a different VSS if the reluctor ring is different -- aren't there teeth on the VSS that mesh with the reluctor ring? if the teeth on an 11 tooth gear aren't the same as a 17 tooth VSS, wouldn't it not function properly?

jmd

iTrader: (4)

Pull the vss out and look at it. Or google pics or search eBay for pics of it.

It's a magnetic signal pickup sensor. You're thinking of speedometer gears.
The reluctor wheel has square-cut notches out of it for 11 or 17 teeth total. It doesn't touch the VSS.
Speedo gears are hypoid cut so they inter-mesh like a differential.

In the interest of covering all bases, JTRs description of things is blurring the issue.

tylerwerrin

Alright, thanks for the clarification -- The only problem is that now I have no clue why my speedometer isn't reading anything! Ah!

tylerwerrin

so weird, still can't get the speedo working -- i should just have a +5v output at the VSS correct?

In TunerCATS i should just change the pulses to 11, correct?

jmd

iTrader: (4)

One of the wires at the unplugged connector should have voltage, yes.

I wouldn't bother changing the tune until you have it fixed and it's reading roughly 2/3 of what it should. The tune won't fix what's broken. The tune will only cause it to read too high or low.