85 K10 4wd relay

[Jgonick]

I have the wiring diagrams for c10 but they do not have this portion. Can any one tell me where the 4wd relay is. I found the connector hanging by my brake pedal and can't seem to find the relay it plugs into. See image.

Thanks

 

[Jgonick]

the pigtail is short so it's got to be close.-- I'm just not seeing it

 

[nvrenuf]

There is no 4wd relay on these trucks.

 

[nvrenuf]

What year is that diagram?

 

[Jgonick]

Not sure- One I found triying to figure out what the hanging connector was. Mine is an 85- The wires are running just like the diagram. I traced them out and that's exactly what mine does-(second green wire splits off father down the line- not at the connector as shown in diagram) I just can't locate where I drew the blue arrow.

 

[nvrenuf]

I’ve never seen or heard of a 4wd relay on a square body. The tcases are all mechanically actuated so unless they put a relay on the dash indicator light some had there’s no need for it.

That said 88+ C and K series trucks are a different body style and the 4wds did have an electrically actuated IFS front differential.

 

[Jgonick]

It looks like in mainly deal with the TCC for the 700r4. it looks like you need the relay to get current coming from the low vac switch to the A post of the transmission for the temp 4-3 shift. My 4wd indicator light works- but it really never runs through the relay.

 

[Jgonick]

Well. I'm not the only one. Here is a guy trying to figure it out 20 years ago.
Drew about the same conclusions I did. but no real answer.

4WD Relay affect TCC Lockup?

I have been looking over schematics of 1985 K-10 (thanks to whoever posted that on webshots!) troubleshooting lockup on my 700R4 TCC. I found that it wasn't locking up in 3rd because the EGR Bleed Solenoid was disconnected. I find a little gizmo that the drawing called a "4wd relay" under...

ck5.com

 

[Jgonick]

Just an update on what I've found so far. It is in the wiring diagrams for 84 and 86 (later pages in a square), just missing out of the 85.
K10 trucks with auto MD8 & EGR bleed. I still can't locate the relay in my truck. I can only assume a PO removed it sometime in the past. If anyone has information on the relay itself I would appreciate it. I would like to add it back if possible.

Sort of curious what 4wd has to do with the "open momentarily on 4-3 on shift" for the lockup

 

[squaredeal91]

This is interesting. I have no clue what a 4x4 relay would even do on an 85 other than turn on a light? I could see it on an s10 but not a k10.

 

[nvrenuf]

Maybe the acronym or abbreviation is a reference to the transmission's 4th gear operation and the similarity to 4WD = "4 wheel drive" is just coincidental?

 

[Jgonick]

@nvrenuf possibly but it is right there with the 4 wd indicator light indicator and transfer case.

I believe the relay opens/close based on the indicator light being illuminated. Putting the transfer case into 4 wheel drive provides grounds to the indicator light (thus illuminating it) and to the relay.

 

[Jgonick]

Relay RY31 should work.. -

pole 1 won't be used --

 

[gdog]

The relay is used to prevent torque converter lock up while in 4 wheel drive. This will reduce damage to the drive train.

 

[bucket]

Relay RY31 should work.. -

pole 1 won't be used --

That looks just like the relays GM used on some mid 80's cars for things like fuel pump, MAF power and stuff like that. The TPI engines and the multi-port injected V6's.