7427 Rev limiter / 4L80E question

[brian617]

I like where you are going with this, but did the 7060 come in any trucks that had 4wd? If it did, I would assume one pin would go to ground when you shifted the lever into 4lo....

Looking for the same answer on 427 PCM. Never found anything in the wiring diagrams to support this theory. The 4wd 4L80's use the speed sensor signal from transfer output and have the transmission output shaft speed sensor hole dummy plugged. Something has to tell the PCM your'e in 4low but I couldn't ever find it.

[1BadAction]

I like where you are going with this, but did the 7060 come in any trucks that had 4wd? If it did, I would assume one pin would go to ground when you shifted the lever into 4lo....

Yes. 91 Crew cabs 2500s and Suburbans.

[RobertISaar]

Looking for the same answer on 427 PCM. Never found anything in the wiring diagrams to support this theory. The 4wd 4L80's use the speed sensor signal from transfer output and have the transmission output shaft speed sensor hole dummy plugged. Something has to tell the PCM your'e in 4low but I couldn't ever find it.

94 K2500 5.7 4L80E diagram



would this have been a 7427 application?

[Nasty-Z]

Yes , Pin F8 on a '7427 is the 4X4 Low range signal , X-fer case has a ball switch that sends a signal to the PCM when in 4 low , thereby modifying the shift firmness .

At least that is the way I understand it , works that way in my '93 3500 .

TOM

[brian617]

I think you found it! My ShopKey has F8 blank, but when I looked at the 7747 to 427 conversion chart F8 is listed as 4wheel low input for 427. Drove my self crazy looking for that couple months ago. THANK YOU!

[brian617]

Yes , Pin F8 on a '7427 is the 4X4 Low range signal , X-fer case has a ball switch that sends a signal to the PCM when in 4 low , thereby modifying the shift firmness .

At least that is the way I understand it , works that way in my '93 3500 .

TOM

The ball switch is for front axle lock. Must be another source for 4 low???

[Nasty-Z]

The ball switch is for front axle lock. Must be another source for 4 low???

There is a pin switch that is supposed to be for front axle lock (not used on my truck as I use a different setup to lock the diff) , there is a ball switch for the indicator lights and there is also a ball switch that only comes into effect when 4 low is selected. Possible different Xfer cases use different switch configurations ? Mine is a BW 4470

TOM

[brian617]

There is a pin switch that is supposed to be for front axle lock (not used on my truck as I use a different setup to lock the diff) , there is a ball switch for the indicator lights and there is also a ball switch that only comes into effect when 4 low is selected. Possible different Xfer cases use different switch configurations ? Mine is a BW 4470

TOM

I'll have to do some more looking. Most of the manual shift transfer cases 88-94 maybe 95 use the two wire ball switch on the t-case to send power to front diff two wire metal actuator, as I have fix several of "no 4x4" problems this way including my own truck, after 96 they started using the black plastic front actuators that were 5 wire I believe and they may differ. Maybe there is a three wire ball switch? Cant remember any of the manual shift cases having more than one switch on them, but i'll dig around tomorrow and see what I can find. Come to think of it, i've even fixed a 98 model 4l60e manual shift transfer replacing the two wire ball switch same situation.

[Nasty-Z]

I'll have to do some more looking. Most of the manual shift transfer cases 88-94 maybe 95 use the two wire ball switch on the t-case to send power to front diff two wire metal actuator, as I have fix several of "no 4x4" problems this way including my own truck, after 96 they started using the black plastic front actuators that were 5 wire I believe and they may differ. Maybe there is a three wire ball switch? Cant remember any of the manual shift cases having more than one switch on them, but i'll dig around tomorrow and see what I can find. Come to think of it, i've even fixed a 98 model 4l60e manual shift transfer replacing the two wire ball switch same situation.

I will double check as well, I do know that when in 4 low Pin F8 sees a ground , when I did the conversion I thought the signal came from the ball switch on the transfer case . It has been a few years since I did the swap , BBC in place of the 6.5 Diesel and '7427 to control it all. CRS is acting up again .........

TOM

[1BadAction]

Well at least we have one question answered. I guess I'll need to drop my old hard drive in this computer, pull up the service manuals for the MT1 trucks and see what I can find.

[brian617]

Well at least we have one question answered. I guess I'll need to drop my old hard drive in this computer, pull up the service manuals for the MT1 trucks and see what I can find.

One answered and five more asked

[brian617]

Turns out the 4L80 uses a three wire ball switch on the transfer case with the third wire making the ground input to F8 for low range.

[Nasty-Z]

Turns out the 4L80 uses a three wire ball switch on the transfer case with the third wire making the ground input to F8 for low range.

You beat me to it, but you are correct , that is the way my 4470 works . Checked this morning.

TOM