FlyDoc

here is the back story.
92 Camaro RS, 305 auto.
I did an LT1 & auto trans swap. everything worked fine including speedometer. scattered the auto on the highway. Installed a T56 and now the speedometer does not work. if some one has a diagram of how to wire the T56 and a 92 speedo may be I can figure this thing out, or some one could help me out.

vetteoz

iTrader: (13)

Doesn't the T56 have a different output signal/ VSS setup to the earlier trans?

Might need a conversion box like the Dakota unit

84redta

iTrader: (34)

shouldn't need a conversion box, that is just for pre-89 camaros and pre-86 firebirds with the speedo cable as opposed to digital dash.

travis401

iTrader: (1)

Wrong, the VSS signal from the t-56 is different from the VSS signal the stock speedo needs. You need the converter box to correct it. Or you can be like me, and use a programmable speedo and not need the box.

FlyDoc

so is the VSS signal from a 4L60E from a 94 Fire bird (donor car) than the T56 from A 95 Camaro ? the speedo worked with the auto.

84redta

iTrader: (34)

well now I know why my speedo hasn't worked, thought it did the 4000ppm out of the PCM that the dash needed, just had to route it through the factory buffer box.

travis401

iTrader: (1)

IM unsure as to the vss signal from the 4l60e, but seeing as the speedos arent diff from auto to manual, im assuming they use the same ppm.

travis401

iTrader: (1)

routing the vss through the factory buffer box will make the speedo move, but it wont be anywhere near right...take the car for a drive and youll see what i mean...

84redta

iTrader: (34)

my speedo doesn't work and my tach is eratic above 3000 RPMS like there is interference. Could have sworn I read that the PCM sends out a 4000 PPM signal for the interior of the car, you just need to select auto/manual in the PCM for it to understand the auto/manual VSS, and i know the 3rd gen ecu used 2000 ppm and the gauges use 4000 ppm in the 3rd gen cause the buffer box seperates that out and re-routes it where it's needed...i'll have to dig through my schematics.

Dyno Don

iTrader: (7)

One puts out a "sine" wave the other is a "sqaure wave".
They do not interchange with each other.

If you used the PCM from the LT1 it should work.

travis401

iTrader: (1)

you either gotta get the dakota box, a programable speedo, or have the t-56 machined to accept the t-5 vss...

84redta

iTrader: (34)

not trying to hyjack the thread, but it seems like we're on the same page, both of us are using LT1 PCM and T56's, so the PCM should be issuing a 4000ppm signal that the digital gauges will understand, mine is a wiring issue, and his is something else. One thing I can do, not sure if the OP can do, is use software to see what the PCM is seeing. I forget the name of it, it was free, but when my laptop is plugged into the port, it can read live data, of which I can see that my VSS is communicating with my PCM, it's a problem between my PCM and my gauges. Can you test any live data with laptop/serial cable? At least make sure the PCM is seeing the T56's VSS signal properly.

travis401

iTrader: (1)

I should read more carfully, i completely missed the part were youre both using the lt1 pcm's. you pretty much need the digital converter box to get the correct signal to the gauges. you just have to split the vss signal and send the raw signal to the pcm and then a raw signal to the converter box and then the converted signal to the gauges.

FlyDoc

OK my Dakota digital converter box showed up today, now which lead from the T56 VSS is the ground & which is the signal wire?
so the LT1 PCM uses 4000ppm?
I think mine is a wiring issue, must have something to do with an automatic wiring harness, for the manual. I cut out the unused leads.