Frame bends...under hard braking!?
Thread Starter
|
Senior User
Joined: Jun 2006
Posts: 292
Likes: 0
From: Phoenix, AZ
Frame bends...under hard braking!?
Drama with my '82 Bronco
Yeah...I couldn't believe it. I have an issue with a pull while braking. After replacing pretty much all of the hydraulics ie: calipers, hoses, wheel cylinders...I still have a brake pull. But...the wheel doesn't move when the pull happens.
So I decided to strap a video camera to the bottom of my rig to see what's going on. I thought it may have been a radius arm bushing acting up, but those are a newer poly set.
Its the frame flexing!
Every time I hit the brakes hard I could see the frame flexing in where the radius arm bracket attaches allowing the left "I" beam to move backwards and pull the truck to the left. This bronco is a rust free desert rig with no frame cracks.
Anybody seen this before? I've tried everything to fix this issue with new bushings, pretty much all new brake system and alignments...I never thought it would be a frame issue! Any suggestions?
Yeah...I couldn't believe it. I have an issue with a pull while braking. After replacing pretty much all of the hydraulics ie: calipers, hoses, wheel cylinders...I still have a brake pull. But...the wheel doesn't move when the pull happens.
So I decided to strap a video camera to the bottom of my rig to see what's going on. I thought it may have been a radius arm bushing acting up, but those are a newer poly set.
Its the frame flexing!
Every time I hit the brakes hard I could see the frame flexing in where the radius arm bracket attaches allowing the left "I" beam to move backwards and pull the truck to the left. This bronco is a rust free desert rig with no frame cracks.
Anybody seen this before? I've tried everything to fix this issue with new bushings, pretty much all new brake system and alignments...I never thought it would be a frame issue! Any suggestions?
Moderator
Joined: Jan 2001
Posts: 56,983
Likes: 2,736
From: Virginia
Have any drivetrain swaps been done on this vehicle? If so, were the upper crossmembers put back in place where the tranny crossmember is located?
This is not a common problem, so something is wrong somewhere. I would check for loose frame rivets on the crossmembers also. From your post, I am assuming the frame is "caving in" at the top or twisting?
This is not a common problem, so something is wrong somewhere. I would check for loose frame rivets on the crossmembers also. From your post, I am assuming the frame is "caving in" at the top or twisting?
More Turbo
Joined: Oct 2009
Posts: 731
Likes: 6
From: Jonesborough, TN
Me, too. I agree with Franklin2. This is very odd. Are the diagonals on the trans crossmember present? When I replaced the clutch on my truck a few years ago, a guy at the MWR Auto Shop suggested I just leave them out, saying most folks don't put them back in. I did replace them, though. In retrospect, it was a good decision, because their abscencec could allow the frame to flex in that area. Also, as Franklin2 mentioned, loose rivets might also allow crossmembers to loosen and allow flex, but that would sure be unlikely. Good luck getting this thing fixed.
Thread Starter
|
Senior User
Joined: Jun 2006
Posts: 292
Likes: 0
From: Phoenix, AZ
All original drivetrain. It bows in at the bottom of the frame rail where the radius arm mount is. Its making it kind of twist from the bottom. Ill have to throw it up on a rack at work and check the fastners in that area. I had loose rivets in the steering box area on an '85 I had.
Laughing Gas
Joined: Nov 2011
Posts: 1,033
Likes: 11
From: Wausau, WI
So I decided to strap a video camera to the bottom of my rig to see what's going on. I thought it may have been a radius arm bushing acting up, but those are a newer poly set.
Its the frame flexing!
Every time I hit the brakes hard I could see the frame flexing in where the radius arm bracket attaches allowing the left "I" beam to move backwards and pull the truck to the left. This bronco is a rust free desert rig with no frame cracks.
If you have video of this, can you post it on youtube or something so we can all see it?
Fleet Mechanic
Joined: Jul 2011
Posts: 1,916
Likes: 4
I guess it's safe to say you can lock up all four wheels? 
This is definitely a strange issue!
The radius arm itself isn't bent, or the rivets holding the radius arm bracket to the frame aren't loose, are they? If the rivets holding the radius arm bracket have come loose, grind off the heads, drive 'em out, and stick in no less than quality grade 8 bolts and nuts. Do them one at a time and the radius arm bracket won't even have to move.
This is definitely a strange issue!
The radius arm itself isn't bent, or the rivets holding the radius arm bracket to the frame aren't loose, are they? If the rivets holding the radius arm bracket have come loose, grind off the heads, drive 'em out, and stick in no less than quality grade 8 bolts and nuts. Do them one at a time and the radius arm bracket won't even have to move.
Trending Topics
Elder User
Joined: May 2012
Posts: 978
Likes: 1
From: Covington VA
FTE Stories
Ford Trucks for Ford Truck Enthusiasts
2027 Ford Super Duty Buyer's Guide (Every Model, Engine, & Package)
Brett Foote
Top 10 Ford Truck Tragedies
Joe Kucinski
AEV FXL Super Duty - the Super Duty Raptor Ford Doesn't Make
Brett Foote
Lobo Vs Lobo: Proof the F-150 Lobo Should Be Even Lower!
Michael S. Palmer
Ford's 2001 Explorer Sportsman Concept Looks For a New Home
Verdad Gallardo
10 Best Ford Truck Engines We Miss the Most!
Joe Kucinski
2026 Shelby F-150 Off-Road: Better Than a Raptor R?
Brett Foote
2027 Super Duty Carhartt Package First Look: 12 Things You NEED to Know!
Michael S. Palmer
10 Most Surprising 2026 Ford Truck Features!
Joe Kucinski
Moderator
Joined: Jan 2001
Posts: 56,983
Likes: 2,736
From: Virginia
Like I said this is not a common problem, so something has to be wrong. I would also eyeball the radius arm bracket for being plumb compared to the other side. I believe from memory the radius arm should be pretty much underneath the frame correct? What if the radius arm bracket was slightly bent and that put the radius arm mounting out beyond the bottom of the frame. That would give it some leverage to put pressure on the frame.
The frame is very strong against forces straight up and down. It's not very strong as far as resisting twisting, and that's the reason for the crossmembers being tied to the top and bottom of the frame.
If you notice, the rear springs are mounted on the outside of the frame using brackets. That would normally be a no-no, but they also have crossmembers in the same area to hold the frame straight up and down. If they weren't there, the outside mounted spring perches would want to cave the frame in at the top when weight was put in the truck.
I can't remember if there are crossmembers in the radius arm bracket area or not.
The frame is very strong against forces straight up and down. It's not very strong as far as resisting twisting, and that's the reason for the crossmembers being tied to the top and bottom of the frame.
If you notice, the rear springs are mounted on the outside of the frame using brackets. That would normally be a no-no, but they also have crossmembers in the same area to hold the frame straight up and down. If they weren't there, the outside mounted spring perches would want to cave the frame in at the top when weight was put in the truck.
I can't remember if there are crossmembers in the radius arm bracket area or not.
Thread Starter
|
Senior User
Joined: Jun 2006
Posts: 292
Likes: 0
From: Phoenix, AZ
Well got it up on a rack at work today and went at it with a pry bar checking out rivets and cross members, everything checked out. So I decided to do an alignment...myself! I'm a parts counterman at a dealer, but used to be a tech. I had never done alignments myself since I was a electrical guy, I always traded electrical jobs for alignments. So I had a buddy in the shop show me how to set the machine up and did the alignment myself.
Just about everything was out of whack. Now the thing goes down the road really good, with no brake pull! It took me quite a while to get everything adjusted perfect. Handles way better too! I can see why a flat rate tech wouldnt want to spend too much time lining up one of these things.
Thanks for the help/suggestions...I really appreciate it. I never thought an alignment issue would cause something like this.
Just about everything was out of whack. Now the thing goes down the road really good, with no brake pull! It took me quite a while to get everything adjusted perfect. Handles way better too! I can see why a flat rate tech wouldnt want to spend too much time lining up one of these things.
Thanks for the help/suggestions...I really appreciate it. I never thought an alignment issue would cause something like this.
