For those running the older 4L60 trans on their LS swap

[droopyzda1]

I also dont know if it matters, but there is a plug that was cut off from my original harness that I left all the wires there just in case. I was able to trace tha lt harness to the red and blue connectors. Some of the wires were for one of the O2 sensors in which I soldered a new pigtail to it. The other wires I labeled and tucked them away. Those were for the digital gear shift indicator. But in my case, its mechanical. Could it be that I missed some of those wires? As far as my trans wiring from yhe ls stand alone goes, I only connected the round plug and the vss.

[Mickeymotormount]

Not sure if the PCM uses the shift switch on the side of the trans to allow the trans to shift out of first gear automatically. It could be a possibility though. I retained my selector switch not kinowing if it would work without it.

Another possibility, although remote, is that the VSS is defective or the harness to the VSS could be at fault.

I had a similar problem with my swap when I first started to drive it, no upshift from 1st to 2nd. Turned out I wired the VSS to the PCM and the DRAC box to allow the speedo to work. After removing the wires to the DRAC box and leaving the PCM wires on the VSS, the trans shifted perfectly.

[droopyzda1]

Thanks Mickey. I will double check the harness going to the VSS and will check to make sure it is working. As for as a DRAC box is concerned, isn't that for cruise control? If it is, I don't have it on mine cause its a plain jane trim, work truck.

[kewljay223]

im pretty sure it is used for both. it reads the pulses that the vss from the transmission sends out. it then deciphers it and sends a new signal to the speedo and also to the crusie control module. on the newer trucks there is no drac box because the pcm now does the deciphering. so you have two options to control the speedo on our older trucks (which i didnt find out until later) either by the new pcm or the old drac box like original.

but im not sure why mickey had that problem because im doing the same thing he did originally. i kept the wires from my vss going to my drac so it could control the speedo and cruise like its supposed to. but the pcm needs signal also so it can control the transmission. so i just spliced into the vss wires and ran them to the new pcm also.... and both my 60e (worked) and my 80e i have now work just fine hooked up that way.... so i dont see how that could have messed up his shifting....

im willing to bet its the 4 gear shift wires that you dont have hooked up. they also go directly to the pcm.

[droopyzda1]

I meant I have a plain Jane work truck. It does not have cruise control so I think I do not have a DRAC box. Where would it be located? By the way, this pass weekend I ran all the wires from the engine bay to the cluster. My speedo works, oil pressure, voltage, and coolant temp. I ran a 3 wire camaro temp sensor but it reads 40 degrees below what it should be

[kewljay223]

glad you got it all working. but i want to say that you have to have a drac box because that is what controlled your speedo before. ACTUALLY to be correct you have a VSSB (Vehicle Speed Sensor Buffer). the DRAC (Digital Ration Adapter Controller) came on 90-91 trucks and the VSSB came on 92-95 tucks. They both do the same thing and control 3 things. the speedometer, cruise control and antilock brakes. it is located behind the glovebox next to the old pcm. i dont remember off the top of my head if its sitting on top or hanging below it... i want to say underneath....

[droopyzda1]

I never new about the DRAC box. I learned something new about the obs. Thanks.

I still have to go over the VSS and trans wiring though. I did not have a chance to look over the trans issue this pass weekend. But I do have to clarify the problem I am having again. Whether on low 1 or 2 its on 2nd gear. If on overdrive or drive, its on first gear and never shifts to 2nd. I can drive it on OD or D then have to manually shift on low 2 to get to 2nd gear but I can never get 3rd or 4th gear.

[Mickeymotormount]

Interesting. Not sure why my initial parallel wiring of the VSSB and PCM didn't work. After doing some research, I found out exactly what 'Jay had said. The new PCM does all the deciphering so I wired the speedo directly from the new PCM. My cruise control still functions although I feel the my rear ABS has have been compromised by eliiminating the DRAC/VSSB box.

[bobbylog]

Don't want to hack the thread but does some of you know how to wire my rear ABS? According to LT1SWAP the my 2005 PCM output 129K mille on the PIN 49 and

Digital Ration Adapter Controller (DRAC) and Vehicle Speed Sensor Buffer (VSSB) are both electronic devices that simply convert the input AC signal (from the VSS) to a calibrated digital DC signal. The DRAC sends 2,000 digital pulses per mile to the ECM (Electronic Control Module), 4,000 digital pulses per mile to the cruise control module, and 128,000 digital pulses per mile to the ABS (Anti-Lock Brake) computer. The DRAC and VSSB units are pre-calibrated from the factory according to the vehicle's stock gear ratio, and tire size. But, it can be re-calibrated by simply moving jumpers around. 1990-1991 vehicles should have the DRAC, and 1992-1995 vehicles should have the VSSB unit. The main difference between the DRAC unit and the VSSB unit (from what I can tell) is that the VSSB unit has an extra "bank" of 7 jumpers in addition to the same bank of 7 jumpers that the DRAC unit has. I would assume this extra bank of jumpers is for the electronically controlled transmission that GM started using in 1992.

(from TBICHIP.com)



Do you think if I wire the pin 49 green connector to the white wire (D)going to the ABS module on the diagram if it will work?
Thanks