4l80e swap VSS issue

[titan101]

Hello I have a issue with my truck that I have been trying to figure out for about a year now. I have a 1993 Chevrolet 2WD C2500 truck with a 4.3L TBI in it and a 4l60e (I think). I swapped to a 1994 7.4L tbi 4l80e 4WD. I drove this donor truck before I took everything out. So all I had to do was change the output shaft to work with 2wd and my drive shaft witch I did. I used the donor Engine,Wire harness, Transmission and PCM. Both these trucks have the 7060 PCM. I had a reluctor ring and VSS sensor added to the 4l80e for 2wd use. My issue is that I am getting is the PCM is not picking up the output shaft speed (VSS error). I tried 2 other sensors and I get the samething. BUT when I put the 4.3 tbi PCM in the transmission shifts perfectly just no OD and the engine runs like crap. Is there something I am missing? Is it having a issue because it was originally 2wd? With the 7.4 TBI ecm the engine runs amazing but goes into limp mode.

[Six_Shooter]

4.3L/4L60E with a '7060? Are you sure? I've never seen that combo run by a '7060.

Do you have a DRAC installed, if so, is it calibrated for the gears and wheel size?

The only other thing I can think of is that the VSS input is in a different position for each application.

[titan101]

Yes I believe I have a DRAC (the small box by PCM) im guessing its not calibrated. It was a 1993 2500 truck with a 4.3 tbi.. if it isnt a 4l60e what could it be? It working on the 4.3 PCM makes sense because the drac is programmed for the truck. How would I calibrate it?

[titan101]

Shouldn't mine be a VSSB since its 1993? The 7.4 tbi truck WAS a dually too.

[titan101]

wouldn't the VSSB I have in the truck work? Its calibrated for the wheels and gear ratio the truck currently has. Does the 7.4 PCM have something different programmed?

[Six_Shooter]

Is the DRAC/VSSB white or yellow?

I haven't personally tried swapping between them, but I recall something about the output signals being different. If I had a VSSB I'd test it to see.

[titan101]

Is the DRAC/VSSB white or yellow?

I haven't personally tried swapping between them, but I recall something about the output signals being different. If I had a VSSB I'd test it to see.

I believe its white Ill have to check. Would I need to get a diffrent one or? They both use 16147060. here is the PCM information




Prog ID BCC Size Year Release Date Eprom ECM PromID ScanID Platform

AZJA 1992 33529 16169737 16147060 9738 9381 C2 (old 4.3tbi)

D8 AXRD 32.00 KB 1992 33253 16162295 16147060 2296 2061 K2 (new 7.4tbi)

[fastacton]

I've never seen a truck with a '7060 in it from the factory that had anything but a 4L80E in it. Both of your BCCs show MT1 as the transmission type on the lookup and I know that means 4L80E on the 7.4 so it should for the 4.3 as well. I've seen a few '7060 4.3/4L80E trucks around.

For the DRAC/VSSB (both should be white in a '7060 vehicle), I've been noticing lately that any truck '93 and older in the junkyards seems to have a DRAC in it. I've only been finding the VSSB in the '94-95 trucks. I haven't come across a '7060 truck lately, so that might not hold true there, though. When you're using the 4.3 PCM, do you still get the VSS error? Have you tried swapping the 7.4 MEMCAL over to the 4.3 PCM and see what happens? Besides calibration, I don't know of anything that would be changed speedo-wise.

If by some chance you do have a 7060 that ran a 4L60E, maybe you're missing the ISS or VSS wiring in the body harness. I believe that one of them runs uninterrupted through the TBI harness on the passenger side while the other runs through the firewall connector on the drivers side and then to the DRAC/VSSB or PCM. If it was different on the 4.3, then that wiring might not be there. The more I think about it, this probably isn't the issue, but it's worth checking if nothing else pans out.

As for VSSB/DRAC interchange, I'll try to remember to check that out tomorrow. I have a modded VSSB sitting on my desk that I can swap with the DRAC in my 280Z and see what happens.

[1project2many]

VSSB and DRAC should be interchangeable for this. Even if it's not calibrated correctly it should provide a speed signal
MT1 option code is 4L80E. Same for either engine.
Where is "speed sensor" on the new trans? Where was it located on the old trans? Did you have to change any connectors or modify the wiring to the sensor at all?
Start with basic diagnostics at the trans to make sure sensor is providing signal. Even new parts can be faulty.

[titan101]

Its using the harness that came with the 7.4. I get no vss error with the 4.3 PCM hooked up. The vss used to be on the 4x4 transfer case of the 7.4. The 4l80e has a rear speed sensor location for 2wd models and that is where I put the sensor. I changed the sensor 2 times. I did try swapping the MEMCAL and nothing changed. I didn't have to modify the wiring at all.

[titan101]

I was reading something about The 1993 4.3 TBI uses a 2 pulse sine wave VSS. The 1994 7.4 TBI uses a 4 pulse VSS with a 40 tooth ring. I am probably using a 2 pulse VSS with the 40 tooth ring, which is why the transmission shifts OK with the 4.3 ECM, but doesn't when using the 1994 ECM.

[1project2many]

Both of the calibrations you listed above are for 1992 trucks.

Did you use the entire harness from the 7.4 truck? Including the ecm and under dash portions? Do you still have access to the 2wd truck harness? Is the trans output speed sensor connected directly to the ecm in that harness or does it go to the white adapter box?

Service information here at the shop is limited for that year and my memory for the early trucks isn't so good. Without a bunch more time to hunt this down, it looks like 2wd rucks use trans signals for shift control and speed information while 4WD uses 2 trans signals for shifting and additional speed signal from DRAC. If so, solution closest to factory is to get 2WD 7.4 calibration and to route trans speed sensor wiring directly to B5, B6 at ecm. Solution that *might* work is to add wires from speed signal to DRAC (light green/blk and ppl/white) and connect them to B5 and B6 at the ecm. The VSS is 40 pulse per revolutions. The internet seems to think the trans sensor also produces 40 pulses per revolution.

I would like to find better information to confirm wiring. This question has come up before.

Good luck.

[fastacton]

I think I have a few '7060 harnesses here, I know I have both 5.7 and 7.4 versions and hopefully I have 2 and 4wd versions. If I have time in the nxt day or two, I'll dig them out and see what they look like as far as VSS wiring goes. I think I remember one a while back that had two sets of twisted pair wires coming off of a single VSS connector.

[titan101]

Both of the calibrations you listed above are for 1992 trucks.

Did you use the entire harness from the 7.4 truck? Including the ecm and under dash portions? Do you still have access to the 2wd truck harness? Is the trans output speed sensor connected directly to the ecm in that harness or does it go to the white adapter box?

Service information here at the shop is limited for that year and my memory for the early trucks isn't so good. Without a bunch more time to hunt this down, it looks like 2wd rucks use trans signals for shift control and speed information while 4WD uses 2 trans signals for shifting and additional speed signal from DRAC. If so, solution closest to factory is to get 2WD 7.4 calibration and to route trans speed sensor wiring directly to B5, B6 at ecm. Solution that *might* work is to add wires from speed signal to DRAC (light green/blk and ppl/white) and connect them to B5 and B6 at the ecm. The VSS is 40 pulse per revolutions. The internet seems to think the trans sensor also produces 40 pulses per revolution.

I would like to find better information to confirm wiring. This question has come up before.

Good luck.

I just used the 7.4 engine and trans harness. I have the 2wd engine and trans harness still. I have to check if its directly connected. I know on the f2 and f3 plug schematic its shows that its empty on the 2wd harness. Both of those PCMS I listed really came from a 1993 4.3 and a 1994 7.4

[titan101]

I think I have a few '7060 harnesses here, I know I have both 5.7 and 7.4 versions and hopefully I have 2 and 4wd versions. If I have time in the nxt day or two, I'll dig them out and see what they look like as far as VSS wiring goes. I think I remember one a while back that had two sets of twisted pair wires coming off of a single VSS connector.

Really appreciate the help. Ill go over my 4.3 harness and check it vs my 7.4. Eventhough im using the engine and trans harness that came with the 7.4.