A question about DRAC/VSSB modules

**Sideways** · 09-25-2014

I need a replacement for the module in my 93 Chevy K3500, 7.L, 480LE, 4WD pickup. It had pn 16158995 QWD DRAC in it, are all the QWD modules interchangeable, or do I need the exact pn? The tech working on my truck said the part had been superseded several times but he didn't know what other pn's might work.

**Six_Shooter** · 09-25-2014

Any QWD DRAC will work.

Alternatively you can modify any DRAC to have the right division, by changing the jumpers to match your current one.

Why is it you (or the tech) believe the DRAC needs to be replaced? In my experience they hardly ever fail.

**Sideways** · 09-26-2014

The tech thinks the VSS is OK because I still have Speedometer function. The truck was running fine then it made a very hard shift down to 2nd (I think), and the check engine light came on. It shows a code for VSS, I pulled the trans pan to see if the filter and pan had debris in them but they were clean as a whistle. I wiggled the wiring harness in the pan and after I buttoned it up the truck drove normally for about a week then the same failure occurred. I don't know if the tech checked everything on the DRAC but he did make sure it has power, unfortunately the dealership where he works chucked all their old service manuals, they told him he can get everything online now. He said replacing the DRAC was the next thing to try but he is not at all sure this is the problem. Is there an online diagnostic procedure to follow?

**fastacton** · 09-26-2014

Since you wiggled the harness and things got better, maybe the problem is there? Around '93, the main transmission connector was changed and most trucks were upgraded to the snap-on connector (vs. bolt-on for the original design). The vehicle harnesses that I have seen with the upgrade were spliced in with butt connectors about a foot from the trans connector, if yours is one of these, maybe a butt connector is going bad?

If it is a VSS/DRAC problem, make sure your VSS wiring isn't damaged, I think almost half of the harnesses I look at have bare wires showing near the VSS connector. I would think you should be able to swap in almost any DRAC for troubleshooting purposes to see if that fixes the problem as well. I have also seen a couple of DRACs with burned traces on the PC board and that's easy to check for. If you come up empty looking for a replacement DRAC, let me know, I might have the correct one.

**Sideways** · 09-26-2014

I'll pass this on to my tech, I've got a line on a Drac from buddrow from here on the website.

**buddrow** · 09-27-2014

Your 93 should have the "push on" type trans harness connector. If you see evidence of fluid leaking at the connector then suspect the internal trans harness/connector. Did you happen to check to see what code is setting the CEL? That will help in diagnosing the concern.

Buddrow

**Sideways** · 09-27-2014

Its been a few weeks, but I think it was code 24, (could be 42 with my memory) when I looked it up it was the code for VSS.

**Sideways** · 12-10-2014

Well it looks like my source for a DRAC module didn't come through, its been almost 3 months and the dealership where my truck is parked is getting less than enthused about my lack of progress getting them the part. Is anyone able to give me a hand so my tech can continue to diagnose the problem. I really believe it will turn out to be the harness (but they want a DRAC) and I found a place that makes them. Here's a link if it will help anyone else: https://www.wittrans.com

**Six_Shooter** · 12-10-2014

Really you can't find one at a local wreckers?

**Sideways** · 12-10-2014

Its kind of a small area and the local wreckers sent everything to the crusher, a lot of potential project cars went crunch.

**JeepsAndGuns** · 12-11-2014

I have no idea if it would work, but I have one from a 93 gmc 3500 7.4, 5 speed manual. It has 16159135, QUH on it. Maybe someone on here might know if it would work.