Suspension lean/sag

[project71]

My 71 Bronco has a 2 1/2" James Duff suspension lift that was professionally installed before I purchased it. It has two 70/30 shocks installed at each corner and 9 leaf rear springs. When sitting on my level shop floor, there is a very visible lean towards the drivers rear. Measuring at various spots show that the drivers rear is about 1 1/2" lower then the passenger rear, and the driver front is about 1 3/4" lower then passenger front. Also the entire rear is considerably lower then the front with about a 3" difference. I don't think it has seen any abusive off-roading before my purchase of it with no signs of damage or loose components. Any ideas as to cause or possible solution?

 

[miesk5]

Yo project 71,
May need to inspect rear leaf bushings, body mounts & C bushings
Following by Ford for an unknown model and year, but has a few tips:

1. Place the vehicle on a flat, smooth surface.

1. Inspect vehicle for any heavy add-ons that may cause excessive weight on any corner of the vehicle.
   • In cases where the excess weight is a snow plow, a rear tailgate lift, etc., the vehicle must be diagnosed with the equipment in place.
   • Measure corner weights if necessary.
   • Vehicle should be empty, fuel tanks full, no cargo such as tools, equipment or debris in the pickup box or rear body section.
   • Vehicle must be sitting on the wheels and tires and not a hoist, jack or jack stands.

1. Check all wheels and tires:
   • Wheels must be same size and design, right and left side on each axle.
   • Wheels size and design, tire size and tire design should be as indicated on the Vehicle Certification Label.
   • Check air pressure of all tires; inflate to specifications indicated on the Vehicle Certification Label.

1. Check front and rear suspension. Make sure the same spring is on the left/right front and left/right rear. The front springs have I.D. tags indicating the part number. The rear springs have the part number stamped on the bottom just behind the U-bolt attachment.

1. Jounce the vehicle's front and rear suspension to normalize the vehicle static ride height.

1. Measure the height of the right and left fender lip openings for both front (dimension A) and rear (dimension B).

1. Calculate the side-to-side differences for each dimension. If these differences are greater than 16mm (5/8 inch) between left or right front and/or 19mm (3/4 inch) between left and right rear, adjustment can be performed following thus procedure:
2. A side-to-side lean at the rear of the vehicle can be adjusted by approximately 10mm (3/8 inch) by installing a shim between the rear spring (5560) and rear axle on the low side of the vehicle. A "low at the rear" vehicle can be raised approximately 10mm (3/8 inch) by installation of one shim on each side. Use the following procedure to install the shim.
   
   1. Raise the vehicle frame until the weight is off the rear springs but with the tires still touching the floor.
   2. Loosen the spring U-bolts to allow the rear axle to separate from the spring approximately 13mm (1/2 inch).
   3. Position the shim between the spring and the spring seat and with the tie bolt head through the hole in the shim. On 4x4 vehicles, position the shim between the rear spring and axle spacer. Tape may be used to hold the shim in position.
   4. Make sure the spring leaves are properly aligned and the spring U-bolts contact the edges of the spring assembly or axle seat.
   5. Tighten the spring U-bolt sufficiently. The spring bolt end should extend through shim into axle seat hole.

 

[Tiha]

After inspecting all of that stuff sitting on the level ground like suggested we always jack it up by the bumper until both rear tires are off the ground and inspect again.
Basically it moves all of the bushings, shackles to the other end of their travel allowing a different view point.

If you still don't see anything loose it is just bad springs. Not knocking James Duff, but they are built to be cost competitive and ride nice, so often the parts are not as heavy duty as OEM and need replaced more frequently.

I have a 1 ton diesel with 4' lift. It eats front springs. Maybe most people wouldn't care or notice but I can tell the way it rides and drives and that is all that is important. So I put a new set of springs on about every 4-5 years.

 

[69Lover]

Project71, this is a known issue with the vintage Bronco. While I don't know the reasoning or corrective action I have a 69 with the same issue. I am up in the Dearborn Michigan area and have access to several excellent Ford engineers, problem is that they were not alive when our trucks were built. I am in process of an complete rebuild off frame restoration. I am replacing all of the bushings, shocks, radius arms, front end steering components. I have 1 ton springs in the rear and will be running dual Bilstein B5125, I have a 3" lift in the springs up front and will run a dual Bilstein B5100. I will know if any of this corrected this issue in about a month. That is when I will get the frame back from powder coat.

 

[69Lover]

Yo project 71,
May need to inspect rear leaf bushings, body mounts & C bushings
Following by Ford for an unknown model and year, but has a few tips:

1. Place the vehicle on a flat, smooth surface.

1. Inspect vehicle for any heavy add-ons that may cause excessive weight on any corner of the vehicle.
   • In cases where the excess weight is a snow plow, a rear tailgate lift, etc., the vehicle must be diagnosed with the equipment in place.
   • Measure corner weights if necessary.
   • Vehicle should be empty, fuel tanks full, no cargo such as tools, equipment or debris in the pickup box or rear body section.
   • Vehicle must be sitting on the wheels and tires and not a hoist, jack or jack stands.

1. Check all wheels and tires:
   • Wheels must be same size and design, right and left side on each axle.
   • Wheels size and design, tire size and tire design should be as indicated on the Vehicle Certification Label.
   • Check air pressure of all tires; inflate to specifications indicated on the Vehicle Certification Label.

1. Check front and rear suspension. Make sure the same spring is on the left/right front and left/right rear. The front springs have I.D. tags indicating the part number. The rear springs have the part number stamped on the bottom just behind the U-bolt attachment.

1. Jounce the vehicle's front and rear suspension to normalize the vehicle static ride height.

1. Measure the height of the right and left fender lip openings for both front (dimension A) and rear (dimension B).

1. Calculate the side-to-side differences for each dimension. If these differences are greater than 16mm (5/8 inch) between left or right front and/or 19mm (3/4 inch) between left and right rear, adjustment can be performed following thus procedure:
2. A side-to-side lean at the rear of the vehicle can be adjusted by approximately 10mm (3/8 inch) by installing a shim between the rear spring (5560) and rear axle on the low side of the vehicle. A "low at the rear" vehicle can be raised approximately 10mm (3/8 inch) by installation of one shim on each side. Use the following procedure to install the shim.
   1. Raise the vehicle frame until the weight is off the rear springs but with the tires still touching the floor.
   2. Loosen the spring U-bolts to allow the rear axle to separate from the spring approximately 13mm (1/2 inch).
   3. Position the shim between the spring and the spring seat and with the tie bolt head through the hole in the shim. On 4x4 vehicles, position the shim between the rear spring and axle spacer. Tape may be used to hold the shim in position.
   4. Make sure the spring leaves are properly aligned and the spring U-bolts contact the edges of the spring assembly or axle seat.
   5. Tighten the spring U-bolt sufficiently. The spring bolt end should extend through shim into axle seat hole.

Thank you Swabby! Former Deep Sea Diver

 

[chrlsful]

's not ur problem. It's theirs. IF U went in w/o this problem - they caused it. Gentilly, calmly report what you see and say "could something you guys did cause this?" U must do this quickly tho. Usually on the way out the store...but NOT too late now. Keep in touch, more info to get/give...

 

[jsdet]

Hello I have had this problem before and it drove me nuts until I figured it out .
Its really simple . If your bronco still uses the C bushings in the front thats where the problem is . There is more to tightening the 4 bolts than just drawing them down . first you have to **** up both sides of the bushings wit some grease . Then start all the bolts and slowly draw them down evenly until tight . If you dont it puts the front axle in a bind and gives you your problem . I know this sounds stupid but its not . I proved this by removing the whole front axle radius arms and all with the tires mounted and let the radius arms rest on the floor . One radius arm was 6 inches off the floor while the other touched the floor. I loosened the radius arm C bushings and re torqued them until both arms touched the floor evenly and reinstalled the axle assembly. The bronco leveled out perfect . I had tried everything to try and fix this . I even scaled it out on digital race car scales and it showed where the problem was and it dawned on me how to fix it . If you use stock rubber C bushings this cant happen because they are soft but use the hard ones and it can . Most of the time you luck out and this dont happen or at least its so slight you dont notice .
I know this sounds like BS but I have done this three times and it works . Hope this helps .

 

[chrlsful]

thats Y those in the know instal w/the "full droop" in effect @ assembly time. Some kids (U need the white haired denture crowd) or non bronk guys got aholda it...

 

[69Lover]

Weird, cause this was an issue when I bought the truck in the 80's and was stock then. I agree that this will help realign the front, but until I went with the one ton springs in back the driver's side drooped.

 

[blksn8k]

Thanks jsdet. My '75 has sat 3/4" higher on the pass side front since I bought it in 2003. Someone installed what looks like a Rough Country lift kit before I got it and it has poly C-bushings on the front axle. Your explanation makes perfect sense and I'll bet that's exactly what my problem is too because, like you, I've tried just about everything else that seemed to make any sense. Thanks again!

 

[chrlsful]

Have not watched but Duffy's son usually duz a good job:

not seen this either but, again, bet its done in the "droop" style (he's just learnin hada Scout instead so not sure):