4L80E speed sensors

[myburb]

My understanding is with a 7060 in the early years they installed the reluctor at back of trans whether 2 or 4 wd and just plugged the rear speed sensor hole on 4wd and sent the transfer case output to b5 and b6. If it was 2wd the signal went to a drac and was then sent to b11. I think the signals are the same so probably could sent the tcase signal to a drac and as long as you weren't using 4wd the 7060 wouldn't know the difference.

[1BadAction]

My understanding is with a 7060 in the early years they installed the reluctor at back of trans whether 2 or 4 wd and just plugged the rear speed sensor hole on 4wd and sent the transfer case output to b5 and b6. If it was 2wd the signal went to a drac and was then sent to b11.

This is correct according to the schematics, and a switch (in the schematic I posted for an early 7060 truck) would tell the PCM when the T-case is in low range so it would shift correctly. I've never seen a 4L80/205 combo out of a 91 square with 3 speed sensors, the couple I've seen had an extension harness to the VSS in the tailshaft of the transfer case.

[Nasty-Z]

Depending on how many of the outputs are currently used you might be able to find a 1:1 output from the DRAC?

The only 1:1 on the DRAC is at C13 , it is already used to input to B11 on the '7060. I don't think there are any others .

Maybe i'll try to piggyback the VSS and input to B5 and B6 , whats the worst that can happen.............

This is correct according to the schematics, and a switch (in the schematic I posted for an early 7060 truck) would tell the PCM when the T-case is in low range so it would shift correctly.

Where would this be inputted to the '7060 ? I have never seen a schematic that correlated to a pin on the '7060 such a switch would be inputted to.

FWIW , the '91 V3500 Ex railroad truck that my 4L80E/205 combo came from was a 3 speed sensor truck , It was a '7060 PCM also. That combo was supposed to go in my S10 Blazer , but I used the 700R4 / 205 instead.

TOM

[1BadAction]

FWIW , the '91 V3500 Ex railroad truck that my 4L80E/205 combo came from was a 3 speed sensor truck , It was a '7060 PCM also. That combo was supposed to go in my S10 Blazer , but I used the 700R4 / 205 instead.

TOM

Intredesting. The 7060 is slow, yet they are doing that extra calculation, makes sense that it would work though.

I can't find pinouts online, other than the "to ecm" on that above. I think it may be time to fire up my old hard drive with the GM SI software so I can pull some schematics.

[Nasty-Z]

Intredesting. The 7060 is slow, yet they are doing that extra calculation, makes sense that it would work though.

I can't find pinouts online, other than the "to ecm" on that above. I think it may be time to fire up my old hard drive with the GM SI software so I can pull some schematics.

I went through my old (key word there , "old") books last night with the early square body wiring diagrams in them , no mention in '91 R/V books of an input to the PCM for 4 low.

I'll have to look at my old PC also , I have the old fiche (sp) copies from GM for the 73-87 (and 88-91 R/V) trucks , maybe something will pop up.

TOM

[Nasty-Z]

Well,

FWIW , and for anyone who might search for the same topics that I did , splitting the output of the VSS on the tailshaft of the T case to feed both the DRAC and the TOSS input at B5 and B6 works fine , no problems in 2WD , 4WD or 4WD low range . Rock solid output and accurate to 75+ mph which was all we ran it up to.

Thanks for all that responded , I appreciate the help

TOM