rear frame crossmember/panhard attachment - The 1947 - Present Chevrolet & GMC Truck Message Board Network

Crazy Rusty · 03-07-2016, 03:05 PM

I noticed while I started my frame prep that the frame crossmember that has the panhard bar connection point on it is about 1 1/2" offset from where it attaches side to side (shorter on the pass side I think) (red lines). While the rear measurements are exactly the same (blue lines)

This seems to be from the factory as while the frame is slightly out of square (1/4 - 1/2"), the crossmembers are all still factory riveted. Does anyone know why this was done? At first I thought the frame was way off or something was bent but measuring from rivet to rivet shows a definite change.

Rust-O-Matic · 03-07-2016, 03:17 PM

Unfortunately I don't have an answer to your specific question, but I can tell you it's not just your frame. My frame looks exactly the same as yours, and every frame for these trucks I have ever seen has the same skewed crossmember.

scoot_mcgrute · 03-07-2016, 03:51 PM

I've noticed that they are all that way. I think it might be angled for the panhard bar to be able to move up without hitting the cross member. My dad thinks it's angled for the tire carrier. Messes with my head every time I see it!

**The Rocknrod** · 03-07-2016, 03:54 PM

As I understand it, it's angled for ladder type rigidity.

chevy_mike · 03-07-2016, 04:14 PM

GM angled this crossmember to prevent the frame from "racking" like a ladder frame would naturally want to do. This is an engineering design.

Rust-O-Matic · 03-07-2016, 04:50 PM

I don't mean to question anyone's intelligence or start an argument, but the slight angle of that skewed crossmember does not look sufficient to have any real effect on the frame's potential for racking. Seems more like it's meant for clearance, or something along those lines.

I'm admittedly not an engineer, but I am an engineering technician, and have spent every day of the last 9 years drawing structural plans for the same firm. Diagonal bracing meant to resist racking in a rectangular frame is typically positioned at no less than 45 degrees.

**Captainfab** · 03-08-2016, 12:44 AM

In my opinion the crossmember is angled for clearance with the panhard bar should it come up that far.

03-07-2016, 03:05 PM	#1
Crazy Rusty Registered User Join Date: Jul 2011 Location: Tacoma, WA Posts: 176	rear frame crossmember/panhard attachment I noticed while I started my frame prep that the frame crossmember that has the panhard bar connection point on it is about 1 1/2" offset from where it attaches side to side (shorter on the pass side I think) (red lines). While the rear measurements are exactly the same (blue lines) This seems to be from the factory as while the frame is slightly out of square (1/4 - 1/2"), the crossmembers are all still factory riveted. Does anyone know why this was done? At first I thought the frame was way off or something was bent but measuring from rivet to rivet shows a definite change. Attached Images __________________ 1965 C10 Longbed Stepside 1969 Chevelle Malibu 1962 C20 Fleetside - Build Thread (Sold before I could finish)

03-07-2016, 03:17 PM	#2
Rust-O-Matic Registered User Join Date: Apr 2015 Location: Gallatin, MO Posts: 295	Re: rear frame crossmember/panhard attachment Unfortunately I don't have an answer to your specific question, but I can tell you it's not just your frame. My frame looks exactly the same as yours, and every frame for these trucks I have ever seen has the same skewed crossmember.

03-07-2016, 03:51 PM	#3
scoot_mcgrute Registered User Join Date: Apr 2004 Location: Tigard, Or Posts: 503	Re: rear frame crossmember/panhard attachment I've noticed that they are all that way. I think it might be angled for the panhard bar to be able to move up without hitting the cross member. My dad thinks it's angled for the tire carrier. Messes with my head every time I see it! __________________ 1966 Army Truck http://67-72chevytrucks.com/vboard/s...d.php?t=691778

03-07-2016, 03:54 PM	#4
The Rocknrod Moderator Join Date: Aug 2011 Location: China Spring, TX Posts: 7,280	Re: rear frame crossmember/panhard attachment As I understand it, it's angled for ladder type rigidity. __________________ Master Chief, US Navy, Retired 1964 C10 Step-side Short Bed - In Progress 2009 2500HD Duramax LTZ 1948 GMC Panel 1956 Big Window Stepside 1953 5 Window Chevy Stepside 1932 Coupe New Seat Foam for Bench Seats?

03-07-2016, 04:14 PM	#5
chevy_mike Never Ending Projects Join Date: Jul 2006 Location: San Diego, CA Posts: 3,836	Re: rear frame crossmember/panhard attachment GM angled this crossmember to prevent the frame from "racking" like a ladder frame would naturally want to do. This is an engineering design. __________________ . 1965 C10 Panel, Tiki Express http://www.67-72chevytrucks.com/vboa...d.php?t=506580 SOLD 1968 Chevy C10, Long, Fleetside, Hot Rod Hauler http://67-72chevytrucks.com/vboard/s...d.php?t=313233 SOLD 1965 Chevy C10, Long, Fleetside, Hot Rod C10 http://67-72chevytrucks.com/vboard/s...d.php?t=415702 SOLD We were given two ears and one mouth for a reason... listen twice as much and speak half as often...

03-07-2016, 04:50 PM	#6
Rust-O-Matic Registered User Join Date: Apr 2015 Location: Gallatin, MO Posts: 295	Re: rear frame crossmember/panhard attachment I don't mean to question anyone's intelligence or start an argument, but the slight angle of that skewed crossmember does not look sufficient to have any real effect on the frame's potential for racking. Seems more like it's meant for clearance, or something along those lines. I'm admittedly not an engineer, but I am an engineering technician, and have spent every day of the last 9 years drawing structural plans for the same firm. Diagonal bracing meant to resist racking in a rectangular frame is typically positioned at no less than 45 degrees.

03-08-2016, 12:44 AM	#7
Captainfab 60-66 Nut Join Date: Mar 2007 Location: Coeur d'Alene, Idaho Posts: 23,251	Re: rear frame crossmember/panhard attachment In my opinion the crossmember is angled for clearance with the panhard bar should it come up that far. __________________ Power Steering Box Adapter Plates For Sale HERE Power Brake Booster Adapter Brackets For Sale '63-'66 HERE and '67-'72 HERE and '60-'62 HERE and "60-'62 with clutch HERE Rear Disc Brake Brackets For Sale. Impala SS calipers HERE Camaro Calipers HERE D52 Calipers HERE 6 Lug HERE Hydroboost Mounting Plates HERE

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