6.2D to 350 TBI conv. VSS/DRAC needed?

[MartinAro]

Hi,I'm at the final stages of converting my '90 K2500 Silverado from a 6.2 diesel to a 350 TBI from a '94 burb. One thing I didn't realize before sending the donor to the scrapyard is the VSSB/DRAC module that's supposed to be in there some where.
Is that really a signal that's needed by the PCM (which is a 7427 btw)? The tranny is a 700R4, and the lockup is controlled by vacuum (kit by TCI). During the first startups I experienced some rough idling, just as if a cylinder wasn't firing. And on the test run it hit the rev limiter at 4000RPM, would at least expect it to rev closer to 5. Could this be the PCM stopping it prematurely because it thinks the car is stationary?

If a VSSB/DRAC is needed, what parts am I looking for? Where on the car is it located? Is it just a case of inputing the signals from the VSS from the back of the transfer, and then it splits the signal into one going to the PCM and two to the speedo?
The fuel vapor thingy is also missing (the black box connected to the intake with a line going back to the fuel tank). Will that have any side effects?

Kind regards,
Martin

[Six_Shooter]

For best results with any Delco EFI system, a VSS is needed, which means a VSSB (DRAC) may or may not be needed depending on the actual VSS output you are using.

Have you tuned out all of the transmission control stuff of the PCM? If not that's the bigger issue. Without the PCM seeing the transmission inputs (and outputs) the PCM will be in a limp mode.

The PCM can control your lock up, and would recommend doing it that way.

[MartinAro]

I don't know what kind of VSS I have. I have the instrument cluster that I think is known as an "all electric"? I've attached some diagrams of the original wiring. The OE part number for the sensor is 15547452.
Looking at the one for the instrument cluster, I do see some speed signal outputs from the cluster at 437A and B. Can these be plugged straight to the ECM, or do they still need to be converted in some way?

No, the transmission controls are not programmed out of it. I actually didn't think it was that smart to be honest, nor have I got any clues on how to do so.

[ony]

I think on that model the vss is built in the speedo cluster.

[MartinAro]

That would be great if that's the case. Then I'm sure that wire to the PCM is part of the old harness behind the glove box. That I'll figure out.

Then the next issue is programming out the transmission control. Guess I'll need to get my hands on an old Windows laptop and an ALDL cable, and get my hands dirty. Unless there's an easier/cheaper option.

[Six_Shooter]

ALDL cable isn't exactly what is need to do that, you need a programmer and an EEPROM (or two) along with a MEMCAL adapter (or modify your MEMCAL).

The trans controls need to be PROGRAMMED out via a modified BIN programmed to the EEPROM.

There are details in threads on this site how to do it.

You don't need an old laptop, just one that runs windows. Tuner Pro RT will run on everything up to Win10 I believe (I only have 7 on my systems, and only tested 10 briefly when it was in public beta). I know I've read discussion of using Win10 with Tuner Pro RT.

Using an ALDL cable will help to see what the PCM is doing and seeing, but won't on it's own help you get rid of the trans controls.

Look at moates.net for the hardware that you need.