How to mount factory Front Air Deflector on 1980 Square Body

[Wrench At Home]

I almost can't believe it myself, but I managed to find a genuine front air deflector / air dam for my 1980 Square Body GMC, part number GM 14014391, with minimal shelf wear. These things are supposedly very rare nowadays, especially new ones.

I'm from the Netherlands (Europe) and found the part in an online shop from Sweden that had two of them in stock. They didn't have any images or product description posted, only a product title and the GM part number.. so it was a bit of a gamble, but it turned out to be the correct part and I couldn't be happier with it.

Does anyone here know how to mount the outside holes to the truck, or does anyone have pictures of this type of deflector mounted on his/her truck? The two holes in the middle line up perfectly with the frame, but the outside holes have a weird shape that makes me think that there has to be some kind of special bracket to attach them..

Pics:

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More pics: https://imgur.com/a/nu0poV8

I will make and post a video about mounting the deflector to the truck on my YouTube channel soon!

 

[Dave M]

Firstly, welcome aboard. Not familiar wiith these, but I did find this, hope it helps.

http://www.gmpartswiki.com/getpage?pageid=57780

 

[Wrench At Home]

Firstly, welcome aboard. Not familiar wiith these, but I did find this, hope it helps.

Thank you!

Yes I have seen that diagram, but it's not very clear on the actual mounting of the deflector.. looks like it's only bolted to the frame through the two center holes, but why then would there be any (weirdly shaped) holes at all on the outsides of the deflector?

Seems to me the sides would bend backwards while driving if not connected to anything, as the deflector is made from some kind of plastic and is quite flexy.

 

[75gmck25]

I may be wrong, but I didn’t think they started using those deflectors until 1981 after they restyled the front end. It doesn’t mean you can’t make it fit, but it does mean your truck may not have all the support brackets.

Also look through all the repair manuals they have posted on this site. Most of the manuals have minimal information on body repairs, but for my ‘75 I found a body spec manual that had more detail.

 

[Wrench At Home]

I may be wrong, but I didn’t think they started using those deflectors until 1981 after they restyled the front end. It doesn’t mean you can’t make it fit, but it does mean your truck may not have all the support brackets.

Apparently part number 14014391 fits trucks from 1973-1980.. These are positioned a bit further back than the later models, approximately underneath the radiator mounted to the frame rails, instead of directly beneath the front bumper.

 

[bucket]

Yes, there was a lower deflector used on some 1980 model trucks. I've only seen them on 4x4 1/2 tons. I haven't seen one in years, but I may still have a picture saved somewhere of how they mount.

 

[Bextreme04]

Just a guess here, but the way those holes look... i'm guessing that the deflector itself gets a slide on nut plate and then a bolt would go through a hole in the inner fender or bumper side mounting bracket(its hard to visualize where this actually sits) and screw into that nut insert.

 

[Wrench At Home]

Yes, there was a lower deflector used on some 1980 model trucks. I've only seen them on 4x4 1/2 tons. I haven't seen one in years, but I may still have a picture saved somewhere of how they mount.

That would be great, thank you!

Just a guess here, but the way those holes look... i'm guessing that the deflector itself gets a slide on nut plate and then a bolt would go through a hole in the inner fender or bumper side mounting bracket(its hard to visualize where this actually sits) and screw into that nut insert.

Yeah that's what I'm thinking too.. there is nothing in that spot on the truck itself, so I'll probably have to make a bracket of some sorts for this..

 

[Wrench At Home]

I had a look last night and did some pre-fitment of the deflector. The side holes seem to line up pretty well with bolts holding the wheel well/fender liner.
I tried mounting it that way; center holes mounted to the frame rails with M10 nuts and bolts (will replace with stainless hardware and include a big washer on the bottom and a spring washer up top at final installation), and the side holes mounted to the fender wells with the nearest bolts. I used a large washer here, that can fit nicely in the slot cutout in the deflector (altough I'm not sure that it should..).

First of all, it looks awesome. It's subtle, but when looking from a down low angle or from a distance it really makes the truck look like its sitting a lot lower.
I can see the deflector is under a bit of stress and curving a little bit.. not sure I like that. I have the feeling the sides are being pulled back too far causing the deflector to bend..

It still needs a good cleaning, but before I do a final install I wan't to mess around with it a bit more, see if I can't get it to sit more straight, maybe I should fab up some kind of braces/brackets after all. Also, most of the screw holes on the deflector are more like wide channels, so there's some room for adjustment.

I'll keep this topic updated when I make progress!

Pics:

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More pics: https://imgur.com/a/CMXNOIB

 

[RoryH19]

Does anyone know if GM ever made these with tow hook provisions like the 81-87 trucks?
Thinking about putting one on my 78 k10.

 

[Bextreme04]

Does anyone know if GM ever made these with tow hook provisions like the 81-87 trucks?
Thinking about putting one on my 78 k10.

The deflector is farther back on the 73-80, so it doesn't interfere with where the tow hooks would mount.

 

[bucket]

My guess is there's supposed to be a mounting tab at the fender liner bolt, that the deflector clips to. A solid mount like that may rip out the bolts since the cab will move around somewhat independent of the frame.

 

[Turbo4whl]

Looking at the diagram Dave posted, see u-nut number 15? Maybe that nut needs to be removed and re-installed on the deflector. Then that lower radiator support bolt holds it all together.

That would also explain why another piece of hardware is not shown for the deflector outer hole.

 

[Goldie Driver]

Getting dark, but here are some pics from Goldie - 1980 K1500 Suburban.

Random shots - I can get more specific ones if desired.

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[Wrench At Home]

Looking at the diagram Dave posted, see u-nut number 15? Maybe that nut needs to be removed and re-installed on the deflector. Then that lower radiator support bolt holds it all together. That would also explain why another piece of hardware is not shown for the deflector outer hole.

Thanks! Looks like u-nut number 15 and bolt number 17 are lining up with the frame rails to hold the two center mounts of the deflector (16). I don't have them, but I replaced them with stainless steel M10 nuts, bolts and washers.

Getting dark, but here are some pics from Goldie - 1980 K1500 Suburban. Random shots - I can get more specific ones if desired.

Thanks for the photos Britt! That's really helpful. It looks like your deflector is a little bit different than mine, but on yours it's clear that there should be a small tab sticking out thats connecting the deflector to the bolt in the wheel well. I think I will try to recreate that look with some kind of metal strip instead of mounting the deflector directly to that bolt..