Need Help with New CUCV-2 - Vehicle End Trailer Connector

[Andercomm]

Hi All...

I own one of the rare 1999 Chevrolet Tahoe 2-Door 5.7L (CUCV-2) which I bought in 2011 with around 116,000 miles and it has served me very well over the last several years.

It has a steel bumper with tow ring bars cut into the face - and a military trailer connector socket mounted on the center right side. The socket has not worked since I bought the truck...looks like some of the wiring got clipped underneath. I have not taken the time to try and trace and test the wiring to get this plug working - and being retired don't really have the extra money to pay a mechanic to do it.

I would really like this year to be able to tow a civilian trailer with my Tahoe - and was thinking of how to install a GM OEM style trailer connection plug under the left side of the bumper like my civilian Suburban has. I thought I had read that the original GM OEM trailer wiring was present, and when the truck was re-built into a CUCV it was just modified for the military plug...?

I have never dabbled much in trailer wiring - and was hoping someone here might give me some pointers on what trailer socket component might work well - and how I would actually mount it to the Tahoe bumper - and how it would wire up. A photo or two of an example would go a long way...!


Thanks in advance...!

 

[MWMULES]

I have a former USAF flight line van with a receiver and pintle hitch. It had a buggered up trailer connector and the wiring was a rats nest, it was hot and did not want to lay in the gravel jacking with it. I took it to U-haul and 15 mins later and $20 lighter, I was on my way with a new 4 wire connector mounted to the step bumper. I did also tell them I was going to be back on the weekend to rent one of their little trailers.

 

[NDT]

My '00 Chevy 3500 has some kind of aftermarket harness that plugs in between a GM harness plug at the left rear of the truck and has a trailer connector at the other end. I think you can buy these at auto parts stores.

 

[Andercomm]

I watched one YouTube video that installed a steel mounting bracket for the cable socket connector box into the underside of the bumper with "self tapping screws".

I have never used these before - but I suspect they will not penetrate the thick chrome plated steel rear bumper...maybe I am wrong...?

 

[Andercomm]

I had also wondered if I could just remove the CUCV military trailer wiring socket (I already bought the military to civilian conversion cable for prior use on another civilian truck) - and if a new civilian 7-pin round socket would just drop right in the existing hole in the bumper...?

 

[xenocath]

self tappers will penetrate the bumper and there should be an adapter for your wiring for four way flat trailer connection and you would need to add the brake/ aux power wires yourself as well as a 7 way rv style plug if needed.

 

[Stonepicker1]

On my CUCV-II's, I installed the 7 blade/4 flat connector.

The wiring was already there from the fuse box to the rear bumper from factory. Just had to un-tape the ends and hook the wires up.

 

[Andercomm]

Based on the comments you guys made - I got under the Tahoe today to check the available trailer power wiring.

I only found one run of 6 wires running inside black plastic conduit - from the left rear fender to the military trailer connector mounted on the center right of the rear bumper.

I removed the military trailer connector from the bumper - and saw that there were two 3-pin plastic connectors wired into the back of the connector - that look like this:



In the second photo - a black jumper wire is loosely attached to the left end brown wire - this provides power for the license plate light.


Might anyone who has done this - be able to tell me what each wire is supposed to provide power to (or the ground)...it would save me a bunch of time.

I plan on splicing in a standard 4-wire trailer wiring harness - that will plug into the new 7-pin trailer connector.

Thanks again...!

 

[m1010plowboy]

Trailer wiring.

The new civi trucks I have been around all have the Pollak style connectors so it looks like it's exactly what you're doing.

http://www.pollakaftermarket.com/

http://wiringdiagram.ncracres.com/pollak-7-way-trailer-connector-wiring-diagram/




Once we went flat 7-way on 14 trucks that hooked up to 6 different trailers our major trailer lighting problems went away. Co-workers ran Fords and Dodges, I ran Chev and we could swap trailers with each other with few problems. We added a 'brake controller' to the M1010, used the 3 wires that power A) left signal/brake B) Right signal/brake C) Running(park) lights.

The ground wire on the lights on some trailers went directly to the trailer frame so tying into the ground system on the towing vehicle was always a priority.

The wire colors may not match with older trucks so it's more important to get the wires in the correct locations. This is fun stuff once it all works.

 

[Andercomm]

Yes...I decided to switch my CUCV-2 over to the Pollack 7-pin socket to make things easier between my military and civilian SUV's.

I must presume my M101A3 only needs the 3 power wires and the 1 ground wire as you used.

 

[m1010plowboy]

Yes...I decided to switch my CUCV-2 over to the Pollack 7-pin socket to make things easier between my military and civilian SUV's.

I must presume my M101A3 only needs the 3 power wires and the 1 ground wire as you used.

With the 3 hot wires you'll have signal, brake and park/running lights. The light assemblies I've seen were grounded to the trailer frame through the bolts. Our trail tech had a ground stud welded up near the tongue and a black/ground wire running back to the plug.

Does that M101A3 have black out lights on it? ......If so you may have an extra wire on the light box to sort out.

 

[Andercomm]

Need Help with New CUCV-2 Vehicle End Trailer Connector

In further research I found this post from January 2010 from 'lavarok' who provided the big key to help me out on this project.

For civilian trailer connectors, I just use the blue trailer splice connectors. There are two wiring harnesses that connect to the military trailer plug. On the vehicle side harness, behind the bumper is where I connect. One harness has the black, yellow, and brown/white. The other has green, brown, and green/white.

Connect:
green to green
brown to brown
yellow to yellow
white to black ( ground )

Since other newbies (like me) always follow behind with the same questions when they are trying to do things...I want to post my what I did too and maybe save them some time!

It seems the single GM civilian 4-pole plug is not present in military conversion CUCV builds. As 'lavarok' observed (above) - there are two 3-pole light connectors that then plug into the rear of the NATO power plug connector mounted in the rear bumper.

To build on 'lavarok's post on the coloring of wires in the two 3-pole light connectors - I got some test leads and a spare trailer light assembly and tested all of these wires out and observed the following:

Black (12G) = GROUND
Brown = TAIL LIGHTS (I also had a black wire running spliced in here that provided always 'on' power for the bumper mounted license plate light)
Yellow = LEFT TURN SIGNAL/BRAKE LIGHT
Green = RIGHT TURN SIGNAL/BRAKE LIGHTS

BROWN/WHITE = NOT USED IN MY APPLICATION FOR M101A3 TRAILER
GREEN/WHITE = NOT USED IN MY APPLICATION FOR M101A3 TRAILER

* Small Note: I have read that many of the commercial replacement 7-pole RV trailer light connectors disable the ground wire inside the new 4-pole end connector where you are likely to splice together the old and new wires. They apparently want you to run the new White colored Ground Wire to a new install location (outside of the plug wiring) to likely ensure that you have a good Ground and probably alleviate many of the poor circuit connection issues people experience.

I went the easy route and spliced (soldered/shrink-wrapped) my factory Thick Black Ground wire directly to the new White colored Ground Wire replacement 7-pole RV trailer light connector...so my 4-pole connector only has the 3 wires. It all seemed to work.