Bison Bumper Fitment

[AXE]

I just noticed my rear Bison bumper doesn't fit squarely on passengers side. You can see in these photos that the drivers side appears normal at about 7/8 inch gap between lower corner of bumper and quarter panel. While the passenger side was almost up against the quarter panel. The top portion of bumper is not as bad.

The mounts underneath are pretty solid with a direct mount into frame in the middle and the outer corners has a heavy brace from corner to frame.

I think the damn bumper is out of square. Not sure if there is much of a fix other than a new bumper replacement. I did put a tow strap and come along on it and pulled it rearward some. It's better but it's still not quite right.

Take a look at your Bison bumpers and let me know if you see any variability in fitment for them.

 

[sardarjee]

I just noticed my rear Bison bumper doesn't fit squarely on passengers side. You can see in these photos that the drivers side appears normal at about 7/8 inch gap between lower corner of bumper and quarter panel. While the passenger side was almost up against the quarter panel. The top portion of bumper is not as bad.

The mounts underneath are pretty solid with a direct mount into frame in the middle and the outer corners has a heavy brace from corner to frame.

I think the damn bumper is out of square. Not sure if there is much of a fix other than a new bumper replacement. I did put a tow strap and come along on it and pulled it rearward some. It's better but it's still not quite right.

Take a look at your Bison bumpers and let me know if you see any variability in fitment for them.

Looks like it is under load or misaligned. I am sure it is under warranty so why not dealer to fix it before they say you broke it

 

[HighTechPauper]

That is pretty bad, it would be straight back to the dealer for me on that one!

 

[securityguy]

I'm sure the dealer will adjust the drivers side to look the same as the passengers side

 

[AXE]

I can tell you one thing, that bumper is stout as hell. I busted a bolt in the come along hook and only got it to move about 1/4 inch. Gonna pull all that shitty plastic off the bumper and put some heat on it with a torch and get it back in its proper place.

Then I might fab up some filler pieces and weld them in place of that shit plastic. I was about to install my rear bumper lights and they have shitty mounts behind that shitty plastic too. Maybe AEV can use some pointers, so I'll have to show them how.

It would take 4 trips to the dealer and 8 days of downtime to get GM to address it. I grew up farming, development/construction, and in the oil field. If you waited for someone to fix your shit you'd be broke and hungry.

 

[8ball_99]

I would be more concerned that you were able to move it with just a come along. I would think something is loose somewhere. No way it should move that easy. What happens when you hook a snatch strap to one of the shackles?, lol

 

[AXE]

I would be more concerned that you were able to move it with just a come along. I would think something is loose somewhere. No way it should move that easy. What happens when you hook a snatch strap to one of the shackles?, lol

I hooked up a chain and rolled forward and it wouldn't move then. Stopped that low torque Duramax motor in its tracks. I was anchored into a steel post embedded in concrete. I can guarantee it's the stiffest picece of iron on this rig, sans frame.

This is what it should look like when not under significant load. That fuckin 20K strap was crying uncle too.

Decided I had to go back to some controllled chaos. Gonna have to add some heat or a Ram with a Cummins.

 

[ZR2BIZON]

I'm no mathematician but If my calculations are correct. . . .

you could technically tie that end of the bumper to a Hummer EV give it enough slack to be able to hit 90 mph before tension and boom another 1/4" with out you having to heat anything up.

 

[AXE]

I'm no mathematician but If my calculations are correct. . . .

you could technically tie that end of the bumper to a Hummer EV give it enough slack to be able to hit 90 mph before tension and boom another 1/4" with out you having to heat anything up.

Might try that. I couldn't believe how hard it was to move. Gonna take another look at it when I'm installing my lights. Might pull the brace and see if I can move it a tad more, then modify the brace. To fit better.

 

[ZR2BIZON]

You would think it would have been caught at the plant

 

[AXE]

You would think it would have been caught at the plant

Not sure if the mounting brackets are off or if the bumper metal warped during manufacturing. You see that with lighter metals, but not usually this heavy. And there's a lot of support metal under the bumper facade too.

The brackets look pretty even on both sides and the bumper seem fine across the rear. Mounts directly to the receiver hitch attached to the frame. Corner brackets go from corner of bumper back to a stock hole in the frame. If I loosened all the mounts, I may be able to adjust it enough to get it square.

It just seems like that corner was a little far forward and maybe canted upwards a few mm. It's only off about 3-4 mm now. Hard to measure exactly cause everything is rouded or curved.

Not sure if bumpers are built in Michigan or not, but that's where the light brackets I ordered came from. I assume everything is installed at the assembly plant.

 

[securityguy]

Not sure if the mounting brackets are off or if the bumper metal warped during manufacturing. You see that with lighter metals, but not usually this heavy. And there's a lot of support metal under the bumper facade too.

The brackets look pretty even on both sides and the bumper seem fine across the rear. Mounts directly to the receiver hitch attached to the frame. Corner brackets go from corner of bumper back to a stock hole in the frame. If I loosened all the mounts, I may be able to adjust it enough to get it square.

It just seems like that corner was a little far forward and maybe canted upwards a few mm. It's only off about 3-4 mm now. Hard to measure exactly cause everything is rouded or curved.

Not sure if bumpers are built in Michigan or not, but that's where the light brackets I ordered came from. I assume everything is installed at the assembly plant.

I would just trade it in for another one.....

 

[44sixpack]

Mine fits perfect. I'd let the dealer look at it before I made it my problem.

 

[AXE]

I would just trade it in for another one.....

Funny you should say that because I was thinking last week I might just run this one to ND and leave it there for work and get different one for here. Trade off the 1500.

 

[AXE]

Mine fits perfect. I'd let the dealer look at it before I made it my problem.

I've already fixed 75% of it, why would I let them take all the glory!

 

[ZR2BIZON]

It's a head scratcher why it's off that much. You would think a bracket would be bent.

 

[AXE]

It's a head scratcher why it's off that much. You would think a bracket would be bent.

Yeah, it certainly doesn't look like poor mounting. I haven't quite figured it out. I'm going to swing by a couple nearby dealers and look at the ones they have in stock. Maybe it'll be easier to determine after I compare.

The only reason I noticed it was I got into some mud and when I was washing it I noticed some pebbles trapped between bumper and quarter panel. I thought damn that looks tight. Looked at the other side and it had much bigger gap.

 

[AXE]

Well I got a good look at a couple other AEV bumpers on two other 2500HD Bison rigs. The fact of the matter is crooked bumpers are not a design, manufacturing, or install flaw, apparently it is a feature to enhnace the rugged appearance of the Bison package. They are all crooked as hell and mine looks pretty good compared to one of them, especially after I straightened it.

It's 100% avoidable, but would depend upon making some design changes to the corner braces and having enough people on the line during install to keep them square. The corner brackets need to have some flexibility in length and mounting interface in order to account for inherent variability in frame and bumper. If you torque them down the way they are, you'll get a crooked bumper most of the time. They must do the drivers side first then the passenger as it's always the most crooked on passenger side.

In fact they've incorporated the crooked bumper feature on standard HDs as well. I looked at many of them and the passenger side is almost always not square. It's just not as exaggerated due to the different mount braces.

None of the 1500s had crooked bumpers.

Here are some pictures I took at the dealer. This black one is built same as mine. Bumpers are really bad, crooked front and back. I told them it should go to the body shop before its sold. The dealer GM has a white one there, it should be fixed as well.

GM/AEV give me a call, I've been a consultant building complicated infrastructure for 33 years. I'm can help and my shit isn't crooked.

 

[ZR2BIZON]

Well that's really shitty. Too bad we have to keep issues from these trucks to ourselves because freedom of speech is not allowed.

 

[AXE]

I spent a little more time on getting my bumper to sit more squarely. I almost got it squared, but it's still of about 1-1.5mm too far forward with just a hint of upward cant. I don't think most people would notice at a casual glance. Much better than how it started.

I looseend the brace bolts at the frame and bumper, as well as the torx head bolts that connect outer bumper to the subframe of the bumper.

I believe the corner brace is 6-8 mm short on OAL. I took the brace off and added two washers to the frame mount and two to the bumper. Then tightened the fasteners back up. This got me nearly perfect measurements when still in tension, but it did pull back a little when I pulled the strap off. The bolts aren't long enough for me to add more washers, it would be better to cut the pipe in the middle and add the length there.

I called AEV and they had no idea what I was talking about, so I sent them some pictures and they said they would have an engineer review. They also weren't able to tell me what the Bison Wheel offset was, but are gonna get me that info too.