GMT800 People - Opinions wanted on upgrades/mods

[ExplorerTom]

I don’t think you want the gas tank skid to be a structural member. You just want it to spread out the impact point of any debris or help spread the weight.

My Explorer/Expedition gas tank skid plates are integral to the gas tanks. The skid is somehow attached to the plastic tank and then the tank/skid is hung by the straps that hold up the tank. I’ve pivoted the Explorer while hung up on a rock.

 

[rayra]

That's exactly the issue, a high-center situation with the long wheelbase of these vehicles. As it's built, you ride on the frame rails and hope nothing sticks up to far to rub on the tank. THere's not even 1/2" of room between the tank bottom and the frame rail bottom. So no room to space a plate away from teh tank without that plate then becoming the low-hanging load-bearing element. So you either have to build a vehicle-weight-bearing support structure for a tank plate, or you avoid it all and just slip a metal shield in right against the bottom of the tank.
The tank does have a stamped sheetmetal shield on its inboard side, facing the driveshaft, in case that comes loose, I guess. I've been looking things over intermittingly, trying to figure how to add some support framing for a large plate, without creating more potential harm than good.
But I think it's going to come down to a flat plate with some bends in it to align with the tank mount strap locations and with the front edge of the plate bolted to the crossmember right in front of the tank. Or at least bent / turned up to ride above that. IIRC that crossmember is a floating element for the torsion keys. It moves on rubber mounts, can't really bolt anything to both it and something rigid, it'll just get torn apart.
I'm going to so some 'Cardboard Aided Design' and figure where the bends need to be and then find a shop with a bending break that can bend up the plate. That or figure out some mounting hoops that the saddle straps can be fed thru, such that the tank plate is just a long flat sheet on its bottom aspect. No 'traps' or obstructions.

 

[rho]

I'll be posting up some ideas for gas-tank options when I start working on them for our truck... The best idea I have currently for our pickup is to do a skid bar or two under the tank that run down the length of it and supported from both framerails. This cold help give some muffler protection as well. I'm not sure if the chassis differences between the burbs and the pickups would be enough to preclude something similar for your truck, but we've definitely scraped our gas tank and our wheelbase is a lot shorter than yours.

 

[rayra]

problem there is driveshaft clearance under suspension compression. Too, the back portion of the tank is rearward of the upturn in the frame rail, in front of the rear axle and there's really nothign back there to support a plate. You have to add a lot of supporting framework to reinforce the rear part of any plate. Next time I hit the scrapyard I'm grabbing another pair of tank straps. I think it might be possible to hand a second pair on the factory mounts. There's a T-slot on one end and the bolted end on the other. Might be possible to double up the straps and hold a plate up against the tank. Not sure until I actually try it.

 

[CrazyDrei]

This might be a stupid question but why does everyone want a skid plate or extra protection for their fuel tank? I am not looking for a rhetorical answer to the question of what a skid plate does, I am fully aware that it is strategically designed to do. But why does anyone in a GMT800 truck need actually need one?

Have you personally punctured a hole in your tank and were stranded on a trail?
Do you go rock crawling on trails that you have no business going on with 33" tires, 8" ground clearance and 130" wheelbase?
Do you need that extra protection in case you accidentally back up over a parking lot bump?
Do you purposefully want to cut off all airflow under the truck and overheat it?
Do you think that after market parts designers are better engineers that GM?

Just curious, I ran 20,000+ miles of easy to difficult trails in the southwest for three years pretty much non stop. Have done the big 3 in Death Valley in one day in 2wd. When I saw sharp pointy rocks I went around them, kicked up plenty 2"-6" rocks that bounced right off my fuel tank. I removed all skid plates to save that extra weight. My gas tank is all scratched up but not gouged up. The plastic tank is much stronger than any of the metal tanks I ever used off-road.

The fuel tank is well protected by the frame rails and cross members. You will rip your bumpers and side steps off before anything comes close to the fuel tank.

So why are so many people so pressed on the skid plate for the fuel tank?

 

[XJLI]

Agreed. I've seen plenty of HPDE fuel tanks dragged over rocks with the full weight of a XJ pressing down on it (and I've knocked mine around a few times) and they don't even get gouges in them. In these trucks you need a front diff skid, transfer case skid, and the rock rails... in that order. The factory aluminum skids are adequate.

 

[rho]

This might be a stupid question but why does everyone want a skid plate or extra protection for their fuel tank? I am not looking for a rhetorical answer to the question of what a skid plate does, I am fully aware that it is strategically designed to do. But why does anyone in a GMT800 truck need actually need one?

So why are so many people so pressed on the skid plate for the fuel tank?

We've drug ours on rocks and dirt already. The tank itself is fine, I'm more worried about stuff snagging on the tank and damaging the straps or brush reaching up and snagging hoses around the evap. Its less of an issue on most trails but we've drug ours on a lot of stuff at our property in the mountains pretty frequently... slide bars are gonna work for us, not sure about others.

My JKU has a full tank skid and I've parked that sucker on rocks a LOT, but I also go crawling in the jeep (we don't in the truck) so its a bit of a different ballgame.

Agreed. I've seen plenty of HPDE fuel tanks dragged over rocks with the full weight of a XJ pressing down on it (and I've knocked mine around a few times) and they don't even get gouges in them. In these trucks you need a front diff skid, transfer case skid, and the rock rails... in that order. The factory aluminum skids are adequate.

I think location comes down to the big thing, my prior XJ's would drag but it would only be going up/down something as the tank was in the rear, when its in the middle of the body its a little different as its pretty easy to high center truck on the tank.

I dunno if we're going to do a tank skid on ours yet, our truck needs front skids, and an engine/trans skid first.

 

[stomperxj]

Suburban roof isn't flat. It's crowned in both ways much like the Tahoe. In fact I'd wager that it's total rise in the middle is the same as the Tahoe. We sold our GMT800 Tahoe last Halloween, elsewise I'd do a side by side comparison

It is crowned but when you place a neoprene spacer under the bracket it shouldnt be too bad. Its a very small amount over the distance between the pairs of bolts. If its too severe when I make them Ill modify them with as large a footprint as I can. I have a brake that will do 1/4", welders and plasma cutter at home and access to a water jet and laser at a buddies shop. My plan is to set the brackets and weld as much of the rails and bars in place so I dont have fitment issues. Im still up in the air on whether to just do rails and crossbars with a removable basket or just do a permanent basket.

I really like those angle rails you made.

For the record I didnt mean from side to side. Just each bracket that has two rivnuts. Or at the very least make the feet bigger

See below the Tahoe roof how it changes elevation between the rivnuts vs the Suburban which is relatively flat (longitudinally) in the same area. This is why my brackets are shaped they way they are with separate feet.

Tahoe:



Suburban:

 

[rayra]

yes, they share the same front doors, sunroof etc. roofline to the trailing edge of the front doors. But I'll say again the Sub has the the same rise / crown, it's just over a ~23" longer roof section. It isn't flat. I can go find a straight board and lay it on the luggage rails if you want. I've already had to deal with that crown when mounting the first two iterations of my roof deck.

Anyway, doesn't matter. You could draw your plates so each set front to back is shaped and bent to accommodate the different angles and have a wider foot, if you wanted to. But do it however you want. I'm just saying bigger 'feet' would be better. Akin to the plastic shoes that are under the aerodynamic outer shells.


eta. The Sub appears flat-er, but it's not flat by any means. If you want to make some rack feet you'll probably need to scan a Sub, or set your feet on one and make adjustments in the design.
The pan photo didn't work out and couldn't get back far enough at a decent elevation for a single frame to show it all. Nor did I cut the board to a matchign length so it would balance equally, so the rear gap is slightly exaggerated. But it's about 5/8" at either end over the 7' length of the luggage rails.

 

[stomperxj]

yes, they share the same front doors, sunroof etc. roofline to the trailing edge of the front doors. But I'll say again the Sub has the the same rise / crown, it's just over a ~23" longer roof section. It isn't flat. I can go find a straight board and lay it on the luggage rails if you want. I've already had to deal with that crown when mounting the first two iterations of my roof deck.

Anyway, doesn't matter. You could draw your plates so each set front to back is shaped and bent to accommodate the different angles and have a wider foot, if you wanted to. But do it however you want. I'm just saying bigger 'feet' would be better. Akin to the plastic shoes that are under the aerodynamic outer shells.

It's hard to read tone via text. I'm not disagreeing with you about the roof crown front to back or side to side. I'm not saying the whole suburban roof is dead flat. My neighbor has two suburbans and I've looked at both roofs a lot during this design process. All I am saying is the roof is shaped differently under the forward most bracket between the two roofs. You can see this by looking at the leading edge of the rear door as well.

 

[rayra]

sorry, it isnt flat there, either. I've added the board pics to the previous post.

when I get around to pulling that foot to run some roof light wiring thru it, I'll put a straightedge on that part or on the foot and show you. It's close, but it isn't flat. The Tahoe roof does dive down more there, where the design departs from the common parts. But the Sub ain't flat.

 

[stomperxj]

sorry, it isnt flat there, either.

All I am saying is the roof is shaped differently under the forward most bracket

when I get around to pulling that foot to run some roof light wiring thru it, I'll put a straightedge on that part or on the foot and show you. It's close, but it isn't flat. The Tahoe roof does dive down more there, where the design departs from the common parts. But the Sub ain't flat.

Sounds good. Looking forward to pics.

 

[Mericas_Meuth]

I agree with you stomper, I think anything is an improvement over the OEM rack... And like you mentioned I wouldn't ever be strapping 300lbs to my roof for any trip anyways. That hard curve on the roof line is what has kept me from tackling the design thus far.

The mounts look great to me... Do you plan on selling them? Or maybe sharing/selling the CAD file if you have one?

Sent from my Pixel 3 XL using Tapatalk

 

[stomperxj]

I agree with you stomper, I think anything is an improvement over the OEM rack... And like you mentioned I wouldn't ever be strapping 300lbs to my roof for any trip anyways. That hard curve on the roof line is what has kept me from tackling the design thus far.

The mounts look great to me... Do you plan on selling them? Or maybe sharing/selling the CAD file if you have one?

Thanks @Mericas_Meuth As soon as I can get these mounted permanently and get a rack on them and do a bit of testing I'll be either releasing CAD data or kits for sale depending on the demand for each.

 

[lilkia]

Rayra I dont think hes saying its completely flat on the burb, just flatter than the tahoe. The tahoe has a more drastic curve in between the front two bolts that the sub doesnt. On a burb its flat enough you could get away with a solid foot plate with a neoprene gasket under it. I also didnt mean full length feet. Just roughly the same size as the plastic ones to spread the load over say 10-15 square inches per foot/bracket versus 2 square inches.