Distance between frame rail & rear sport bumper on a factory build?

[71CHEVYSHORTBED402]

I can't imagine year matters, but I'm working on a 71 C10. Long story short I have to modify brackets because there's no such thing as available brackets for a SWB, 2WD with leaf springs. It's a posing as a

So I'm asking for the distance from the back of the frame rails to whatever portion of a sport-bumper you can describe for factory brackets and frame.

Thank you

[FirstOwner69]

I am not knowledgeable about 4X4 and 2WD frame differences, but is there any chance the rear brackets for a shortbed with leaf springs be the same for both? If so, Classic Industries has them.
https://www.classicindustries.com/pr...s/cx1655.html#

[71CHEVYSHORTBED402]

Originally Posted by FirstOwner69

I am not knowledgeable about 4X4 and 2WD frame differences, but is there any chance the rear brackets for a shortbed with leaf springs be the same for both? If so, Classic Industries has them.
https://www.classicindustries.com/pr...s/cx1655.html#

Thanks Jim, but it depends who you ask, an owner or a vendor. More seriously they don't work. The closest set of brackets for my application are often called "coil spring" brackets. They have a 5" bolt pattern, my frame rails are 5.3". The 4x4 brackets have something like a 7" bolt pattern, I don't remember.

The outer brackets are the same on "4x4" and "coil spring" brackets. Go figure my outer brackets would have to be different as well, because the rear hole in my frame rails are further back than most frames.

Looking at my "coil spring" brackets and info. Randy500 once provided, I believe a rear chrome bumper extends approx. 8.1" from the frame rail to where the bumper mounts. Edit: Probably closer to 8.3" measured from the top side of the inner bracket, due to the pitch of the brackets.

Two pictures, one is my frame the other is what I believe is more common, compliments Randy. He says his measures "closest is 1.7/16". They built this stuff in 10s, it's likely 1.4" but close enough.

[FirstOwner69]

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http://sokyclassics.com/product.php?skcid=1001329

[71CHEVYSHORTBED402]

Originally Posted by FirstOwner69

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http://sokyclassics.com/product.php?skcid=1001329

Nope.........Somewhere along the line folks swear those "4x4" brackets work on a 2wd SB with leafs. I have an original set and had a replacement set too, they're not close. You could modify them, but it's more involved than "coil spring" brackets

[Richard]

Should you be focused on the rear bed mount point to the bumper instead of the frame since your frame seems to be different?

[71CHEVYSHORTBED402]

Originally Posted by Richard

Should you be focused on the rear bed mount point to the bumper instead of the frame since your frame seems to be different?

Either one will work, though an unaltered frame is fixed where a bed has some play. For what it's worth the cab on my C10 to the top front bed panel is 1", and the rear of the frame rail to the rear of the bed floor is 3.9". My C20 measures about 1/2" short of that total 4.9", but the bed is crooked, and more than that the cab mounts are shot. I suspect that 4.9" number is common with new cab mounts.

[weim55]

Curious: have you ever been able to look up your brackets in an original GM parts book and then compare part numbers for various applications including your own? If so, does your application take a dedicated part number that does not cross with any other set up?

Steve weim55 Colorado

[71CHEVYSHORTBED402]

Originally Posted by weim55

Curious: have you ever been able to look up your brackets in an original GM parts book and then compare part numbers for various applications including your own? If so, does your application take a dedicated part number that does not cross with any other set up?

Steve weim55 Colorado

Yep. Matter of fact more than a few vendors are referencing the wrong part number for common outer brackets, because the number they're using is literally for the outer brackets on this application Shame it's the wrong bracket, vendors get a few things wrong, it’s been 50 years.

I've researched this out have come up empty on parts. There are just not a lot of SWB 2WD with leaf springs. I've only seen pics of 1-2 similar frames. The rails are correct because there is no where else to punch holes for brackets.

I just finished two options for modifying the "coil spring" type bracket, just haven’t picked one yet.

[HO455]

Have you considered that your truck may have had an aftermarket dealership bumper installed when new. It wouldn't be that unusual if a dealership ordered all their trucks as bumper deletes with no holes drilled, so their dealership bumpers mounted better.

[71CHEVYSHORTBED402]

Originally Posted by HO455

Have you considered that your truck may have had an aftermarket dealership bumper installed when new. It wouldn't be that unusual if a dealership ordered all their trucks as bumper deletes with no holes drilled, so their dealership bumpers mounted better.

My truck had big ()*& step bumper from factory. Wish I still had it, I sold it for $40 30 years ago.......This goes way back, I pulled what people call "4x4" brackets off I think it was a Blazer. So I hired some guys to remove the old bumper and set me up with the new sport bumper I managed to bend up installing it.

Those 4x4 brackets don't work by a mile, I've seen replacements too. They punched an open hole where a hole already was, and the brackets laid on top a hanger rivet. Plus it was about 1/2" too far back. Looked like crap man...... I suppose you can modify "4x4" brackets to work, but "coil spring" brackets are much closer. I know at least one guy who made 4x4 brackets work by punching a new hole in the frame rails.

Nice thing is the outer brackets I pulled off that truck years ago are super, replacements aren't as nice. I'll get them to work, but I'm no welder, and there's no room for error. That's .8" from the rear hole to the swell in the frame rail, the other side is just 6.5. There's enough surface to clear a standard washer for a 1/2" bolt though, plus another .1" or so.

Here's a picture of my frame. Where else would you punch a hole for bumper brackets? 99/1 this is factory.

[Richard]

I know you have been looking for bumper brackets for some time. One thing that confuses me when you say the shorty 4x4 brackets are way off. On the short 4x4 the hole in the front of the bracket bolts to a hole at the top and in-between the rear hanger bracket. I see the same hole at your rear hanger. Short inner bracket has a half moon cutout to clear the rivet that attaches the hanger bracket. Can you take a measurement from the hole at the hanger to the rear bed mounting point? I will measure my short 4x4 on Wednesday when I go to the paint shop. If they are not the same it would mean your rear springs and hanger locations are unique to your truck as well. The wheel opening location your bed has to be in the same location as all the 67-72 shortbeds.

[randy500]

Its been a while but isnt Hole “B” is in the same location on all trucks? I believe it is.
The relationship of the your rear bumper bracket hole to the last bed mount hole looks the same as all 2wd, mount the regular brackets there and drill a new front hole or extend the bracket.
I just made a k20 into a short bed and used 2wd brackets at the back hole and drilled a new front hole, i clearanced the bracket for the interfering rivet head. Assembled the body and the bumper fit well. (3/8” or so from the bed)

[Richard]

Originally Posted by 71CHEVYSHORTBED402

Either one will work, though an unaltered frame is fixed where a bed has some play. For what it's worth the cab on my C10 to the top front bed panel is 1", and the rear of the frame rail to the rear of the bed floor is 3.9". My C20 measures about 1/2" short of that total 4.9", but the bed is crooked, and more than that the cab mounts are shot. I suspect that 4.9" number is common with new cab mounts.

Not understanding "either one will work" When your rear hole is closer to the end of the frame than others? The bed mount point will not change from truck to truck. It seems more important than any holes in the frame.

[HO455]

Look familiar?

https://seattle.craigslist.org/est/p...112786517.html

[71CHEVYSHORTBED402]

Originally Posted by HO455

Look familiar?

https://seattle.craigslist.org/est/p...112786517.html

Ha, sure does. Even the brackets look familiar somehow. Looks like they allow for a 5"-5.3" or so bolt pattern.

Originally Posted by randy500

Its been a while but isnt Hole “B” is in the same location on all trucks? I believe it is.
The relationship of the your rear bumper bracket hole to the last bed mount hole looks the same as all 2wd, mount the regular brackets there and drill a new front hole or extend the bracket.
I just made a k20 into a short bed and used 2wd brackets at the back hole and drilled a new front hole, i clearanced the bracket for the interfering rivet head. Assembled the body and the bumper fit well. (3/8” or so from the bed)

It's not the same on 2WD SWB with leaf springs. Thanks to you in another thread, the hole in most frames is probably 1.4" from the end of the frame rail. Mine is just .8". 1.4" would put the hole immediately behind the swell in the frame for the rear hanger, so it requires different inner and outer brackets.

There just aren't many 2WD SWB with leaf springs.

Originally Posted by Richard

Not understanding "either one will work" When your rear hole is closer to the end of the frame than others? The bed mount point will not change from truck to truck. It seems more important than any holes in the frame.

The bed doesn't work so much for modifying these brackets. A bed has some slop because the holes in the frame are slotted, where-as the holes for the bumper aren't, so there can't be more than a 16"ish of play. That said, a measure from the bed would be a guide.

Measuring from the frame with the bumper on might be difficult. The 8.1" from the frame rail to the bumper surface I mentioned earlier is probably closer to 8.3" measured from the top side of the inner bracket. Reason it's different is due to a pitch in the brackets.

I believe I have this one figured out, though I welcome a measuring stick for confirmation. I'll be more concerned how it looks with the bed when I install for permanent.

Using the front holes in the existing frame rail and "coil spring" brackets my bumper should be .3" further back than normal. I'm probably burring slots in the brackets where I can. Might give back .1" or so.

Originally Posted by Richard

I know you have been looking for bumper brackets for some time. One thing that confuses me when you say the shorty 4x4 brackets are way off. On the short 4x4 the hole in the front of the bracket bolts to a hole at the top and in-between the rear hanger bracket. I see the same hole at your rear hanger. Short inner bracket has a half moon cutout to clear the rivet that attaches the hanger bracket. Can you take a measurement from the hole at the hanger to the rear bed mounting point? I will measure my short 4x4 on Wednesday when I go to the paint shop. If they are not the same it would mean your rear springs and hanger locations are unique to your truck as well. The wheel opening location your bed has to be in the same location as all the 67-72 shortbeds.

The hole above the hanger you're looking at probably looks the same on all leaf spring trucks. Difference being the bolt pattern. My bolt pattern is 5.3. Interested in your report, especially the rear hole. Since they're both SWB, I agree, seems the hangers would be the same, which should put the rear hole .8" forward the back of your frame rail.

[71CHEVYSHORTBED402]

For any poor sap who needs brackets for 2wd, swb with leaf springs using "coil spring" type brackets.

Inner bracket:
I'm using the front hole in the inner bracket to the front hole in the frame as intended. Deal is I'm 95/100 most frame rails have a rear bumper hole at 1.4" forward the back of the rail. In my frame it's .8". So that would put me .6" too far back, but I gain .3" because my bolt pattern is .3" longer than what the brackets are intended for. So a net of .3" too far back with no slots.

I'm slotting the front hole of the inner bracket for the .3" difference in bolt pattern plus another .2" for play. With those slots to the rear I should be able to take up .2" leaving .1" too far back. I may bore the slots further, but I have to see the new hole in the outer bracket first.

The top front corner on the tall portion on the inner bracket has to be cut to clear a hanger rivet. A 1/2" would probably do it, I'm take off .8" or so, it doesn't matter. The good news is the half-moon designed to clear a bed bolt is in a better location than what the brackets were intended for

Outer bracket:
The outer bracket is a trick because there's a limit on surface area. How much I don't know yet, but it's more than enough to clear a standard flat washer. The existing hole has to be welded, and the new hole goes through about half of it. I'm having the hole punched 9/16" approx .15" further back than the .3" bolt pattern difference, plus a .1" slot to the rear. If I need to bore the hole forward okay, but that would defeat the plan to push the bumper forward by .2".

The front of the outer bracket will be cut in a pie shape because the brackets are on a pitch, should be better than new If I remember right the assembly manual shows no washers for the brackets. I'm using washers, and may use lock washers because of the slots.

First picture is a 67 SWB, 2WD with a factory (or dealer) sport bumper. If I remember right the 67 brackets had a different part number than 68-72, but the brackets would have to be close or the same because it's the same frame & bumper.

The rear hole in the second picture is more common, same with the 3rd pic. one of you might remember

[Richard]

I forgot to post these for you.