Can yall post some Pictures of rear crossmembers please!!!

[Hazieview]

I need to know the differences in the rearcrossmembers for the 73-87s.

On my truck the rear crossmember drops 2 inches below the frame. I'm having trouble with my fuel cell. It seems that there are a few different rear crossmembers I guess.

Can anyone help me out by maybe snapping a few pictures of their rear crossmember? I'm pretty desperate here!

thanks guys!

[Buick455]

Here is one of my 1987 3/4 ton 4x4 just before I removed the cross member last weekend. I am also going to install a fuel tank between the rails. I removed the cross member as the installer of the tilt bed torched some of the member so I will either repair it or make my own stronger member.

[motornut]

on the 88

[bigblock73]

my 73

[N2TRUX]

My 77 Cheyenne.

[Hazieview]

Bingo! See how some of these crossmembers are different? Like this one:


It has 4 holes in it and drops below the frame 2 inches.

WHAT YEAR DID THEY START PUTTING THE 4 HOLES IN THE CROSSMEMBER? Also why does it drop down below the frame instead of going straight across?

I need pictrues of the ones with the 4 holes in them that drope down about 2inches below the frame. Mine is an '87 and I know the '85 is the same way.

Anyone have any info or pics about this? Thanks!

[Buick455]

My 87 3/4 ton 4x4 does not have the holes (see photo in above post). My 86 1/2 ton 4x4 has the holes just like your photo above. The 1/2 ton also has notches in the frame and other cross member holes that the 3/4 ton does not have. Other than making it lighter and some what weeker I am not sure why some have holes and others do not.

[Hazieview]

Originally Posted by Buick455

Here is one of my 1987 3/4 ton 4x4 just before I removed the cross member last weekend. I am also going to install a fuel tank between the rails. I removed the cross member as the installer of the tilt bed torched some of the member so I will either repair it or make my own stronger member.

I'm glad you said that. I ordered a tank from performanceonline.com


Since I have the crossmember with holes in it that is dropped down 2 inches or so on in my 1/2 ton 2 wheel drive this tank will not work with my crossmember.

They said, "You do not have a stock crossmember! We have never seen a crossmember that is dropped down with 4 holes in it! The trucks only had solid crossmembers that went straight across flush with the bottom of the frame!"

I'm just trying to prove to them that that fuel cell will not work on ALL 73-87 trucks. I need pictures to show them that the dropped down crossmember with 4 holes in it is a factory crossmember.

Thanks for all you posts so far guys just want to let everyone know that you may have to modify your crossmember if you order one of their fuel cells!

Any more pictures would be great! Thanks!

(in order for the dropped down crossmember to work they need to move the brackets on the sides of the fuel cell up 2 inches.)

[MONTEZ]

I agree. Just take the stock one out and build one that will work for you. I plan to replace all of my factory cross braces with round tubing for a cleaner look. Similar to these on this chassis.

[Buick455]

The attached photos of my 86 4x4 1/2 ton Silver ado frame clearly has the drooped rear cross member with holes. The frame also has cutouts in it which narrow the frame top and bottom members which is why I am not using this frame to build my 3/4 tone truck. I am using the 3/4 ton frame from my 87 which still has the dropped member but with no holes and the frame does not have the notched sections.

I would just removed the dropped cross member and build your own (or have one built). I would not build it like the ones shown that are made from round tubbing as this is good for keeping the members apart but may not be as strong as the original in preventing twist of the frame rails. If you use tubing the ends need to transition to the top and bottom of the rails like a "v". This transitions the moment/stress induced from the twist of the rails into the tubing. The only way to adequately design the member is to reverse engineer what was used and make sure the new member is as strong.

[MONTEZ]

Originally Posted by Buick455

The attached photos of my 86 4x4 1/2 ton Silver ado frame clearly has the drooped rear cross member with holes. The frame also has cutouts in it which narrow the frame top and bottom members which is why I am not using this frame to build my 3/4 tone truck. I am using the 3/4 ton frame from my 87 which still has the dropped member but with no holes and the frame does not have the notched sections.

I would just removed the dropped cross member and build your own (or have one built). I would not build it like the ones shown that are made from round tubbing as this is good for keeping the members apart but may not be as strong as the original in preventing twist of the frame rails. If you use tubing the ends need to transition to the top and bottom of the rails like a "v". This transitions the moment/stress induced from the twist of the rails into the tubing. The only way to adequately design the member is to reverse engineer what was used and make sure the new member is as strong.

May be true , but from the looks of it, my moneys say that a stamped piece of .120 sheetmetal with holes in it would fold before a piece of 4140 tubing would. Plus I see lots of race chassis using tubing and inspectors pass them all the time.... Maybe needs to have better mounts than those in the pics, I agree on that, but I haven't built mine yet

[Buick455]

For simplicity sake we will assume the stock cross member does not have holes like that of my 87 3/4 ton. Comparing the stock cross member made from cold rolled steel with and Sy of 35 Ksi and a piece of 2" OD 1/8" wall tubing with an Sy of 75 Ksi the stock cross member is stronger in that it will resist bending in the vertical direction which is primarily how this member is stressed. Combine this with how the round tubing is joined to the members it is a substandard design compared to the original. This is assuming the tubing OD is 2" which is hard to tell from the photo. If the tubing is 2.5" OD with 1/8" wall and if the ends were attached to the frame with gussets (transitioned from the tubing OD to the frame height) this would be a superior design to the original.

[motornut]

went out this am took a couple pics closer ones lol, cause yesterday i crawled under and it looked/felt flat
and thats an 88 suburban tho not a pickup,is the burb the same part #?

[Moostifer]

[78 Chevyrado]

'78 3/4 ton

[Buick455]

It looks like the trucks in the 70's (1/2 ton and 3/4 ton) may have the same frame with straight rear solid cross member and the 80's 1/2 and 3/4 ton were dropped but the 1/2 ton had holes in the cross members and cut-outs in the frame rails where the 3/4 ton did not.

[chevyman95]

my 77

my 83

[chevyman95]

77 is a 1/2 ton short bed 2wd

83 is a 1/2 ton short bed 4x4