Duffs 4 link issues

chris · Nov 27, 2008

I decieded to burn some vacation time this week and put the Duffs 4 link on just in time for a wheeling trip Dec 6th, It's a Bronco what could go wrong? %)

I'm having a issue with the alignment. If I mount the axle truss the way it's supposed to be then the pinion angle is WAY out of alignment. See picture one. Thought I had a picture with the driveshaft but guess not, this one will have to do.

Called Duff Tuesday and they said to rotate the truss assy further up on the axle. So I did and now have better pinion angle but the coil spring pads now tilt backard and I still need to go further forward as the upper links are still to short. See picture two.

I called Duffs yesterday in fustration but the tech guy was off, not back until next week. I don't have high hopes here of getting it done for the 6th. Something is way off.

Anyone else have any of these issues?

Running 5.5" lift and standard rear Bronco axle.

Did a little research and found a source that said the upper links shold be 70% of the length of the bottom links. The bottom links measure 38" and top links 40". ?????

Any thoughts?

I am thinking about making a upper link at the 70% measurement and placing it on the truck just to see what happens.

Broncobowsher · Nov 27, 2008

I look at the first and second pictures. I don't see the truss rotated on the housing, I see the whole truss and housing pushed back at the top to line up the pinion.

Can you put the truss and bars in the right place and rotate the housing withen the truss to get the right angle of the dangle?

As for the bar lengths, I wouldn't be messing with them so fast. There is a bit on internet lore that people follow that isn't always right. Second the length probably is closer to correct once you figure in the angle factor. Thoise top links are angled, not straight. Angling the links makes them do double duty, they also do lateral control. So the angling for lateral control makes the front to back effective measurement different then that of the length of the bar (look at it from the side and figure the front to back measurement).

Broncobowsher · Nov 27, 2008

Push the truss forward so these are not overhanging the back of the housing.

Madgyver · Nov 27, 2008

I think that the tech meant to cut your tack welds off the axle truss and rotate the 9" housing and tack it again.

All I see is that you're not finish with the install. Mock up everything with strong tack welds including coils and upper mounts and let your rig sit at ride height.
Finish it for your trip and then wheel it. Pinion angle should be off a few degrees to allow needle bearing rotation.

chris · Nov 27, 2008

Broncobowsher said:
Push the truss forward so these are not overhanging the back of the housing.

This was stage one of moving the axle bracket. Here is what it is supposed to look like and how you are supposed to mount it.

chris · Nov 27, 2008

Madgyver said:
I think that the tech meant to cut your tack welds off the axle truss and rotate the 9" housing and tack it again.

All I see is that you're not finish with the install. Mock up everything with strong tack welds including coils and upper mounts and let your rig sit at ride height.
Finish it for your trip and then wheel it. Pinion angle should be off a few degrees to allow needle bearing rotation.

Sorry, the second picture is not the right one. I did rotate it and it still looks like I should rotate it further but it will affect the coil spring pad being rotated as well. Here is a couple pictures showing the axle at ride hieght, stuffed and droop. Notice the driveshaft angle during the angle change. The straightest view is at full stuff.

I really don't want to mess this up so I'm not sure if I just want to wing it. There has got to be a good reason its this far off.

BTW, if your running the cage arms with the newer bracket you will have to cut the inside frame section for the Duff bracket to fit if your going to keep the stock wheel base.

Looks like another drive shaft is in my future as well, you can see how much it runs on the splines going up and down.

68ford · Nov 27, 2008

how much travel are you cycling it through in the pics where the drive shaft is plunging out? are you letting droop down a lot more that it will once its done? seems like it has a lot of drive shaft plunge for the amount of travel.

chris · Nov 27, 2008

68ford said:
how much travel are you cycling it through in the pics where the drive shaft is plunging out? are you letting droop down a lot more that it will once its done? seems like it has a lot of drive shaft plunge for the amount of travel.

It's 10 1/2" from droop to stuff.

68ford · Nov 27, 2008

stuff being limited by the upper links hitting the body? droop limited by drive shaft?
that really is a lot of plunge, if you not seeing suspension cycling at high speeds though, it probably isnt an issue.

chris · Nov 27, 2008

68ford said:
stuff being limited by the upper links hitting the body? droop limited by drive shaft?
that really is a lot of plunge, if you not seeing suspension cycling at high speeds though, it probably isnt an issue.

I don't have the springs on yet so not quite sure. I don't think it will go that far up when the coils get put in and it could go further down but I'm hitting the floor right now.

broncnaz · Nov 27, 2008

Keep in mind I dont know a lot about 4 link setups but I'm throwing this out there based upon the little that I do know.
Pinion angle should be set at actual ride height otherwise your just guessing But a educated guess would be to have the top of the axle tube 11- 11.5in. down from the bottom of the frame. As suggested I would mock everything up and measure it with some weight on it and maybe some extra weight in the tub if you normally carry stuff or your gas tank is empty. One other thing I dont see much adjustability in your hiems the way they are in your pics as once pinion angle is close I would think you could fine tune it by readjusting the hiems if you have any adjustment left. So you may want to readjust them to allow more adjustment both ways.
Eitherway even if you just weld the truss on where you think it should be you should still have some adjustment in the hiems to fine tune everything. I'm not sure how the coil spring mount angle plays into the mix but unless there is a specific angle it needs to be at (which I doubt) I wouldnt worry about it as much as you can adjust location of the top mount if need be.
Not sure if Duff uses a jig to weld these things up but if they dont that could be the reason it doesnt fit exactly.

chris · Nov 27, 2008

broncnaz said:
Keep in mind I dont know a lot about 4 link setups but I'm throwing this out there based upon the little that I do know.
Pinion angle should be set at actual ride height otherwise your just guessing But a educated guess would be to have the top of the axle tube 11- 11.5in. down from the bottom of the frame. As suggested I would mock everything up and measure it with some weight on it and maybe some extra weight in the tub if you normally carry stuff or your gas tank is empty. One other thing I dont see much adjustability in your hiems the way they are in your pics as once pinion angle is close I would think you could fine tune it by readjusting the hiems if you have any adjustment left. So you may want to readjust them to allow more adjustment both ways.
Eitherway even if you just weld the truss on where you think it should be you should still have some adjustment in the hiems to fine tune everything. I'm not sure how the coil spring mount angle plays into the mix but unless there is a specific angle it needs to be at (which I doubt) I wouldnt worry about it as much as you can adjust location of the top mount if need be.
Not sure if Duff uses a jig to weld these things up but if they dont that could be the reason it doesnt fit exactly.

Basicly it would work if the upper links were a few inches longer.

If you look at the picture below, that is about what ride height would be. If the truss was set back to the end of the housing where it should be then the spring pad would be level but the upper links would be pulled back and be to short. When it is in the intended location the housing gets rotated to far at the top.

MAD, can you tell me how long the upper links are in Tazz's bedroom, I know it's still not installed! Mine are 39 1/4" without the rods.

rjlougee · Nov 28, 2008

I've got some random thoughts here.

1. According to Duff's site, the lower links are supposed to be Right and Left threaded at each end "to allow for easy adjustability". I don't see that with your setup, it appears the top (as installed) is adjustable, but the back is a bushing setup. (it actually HAS to be this way to keep a bent link from rotating from torque input as the suspension cycles)

2. Bending the lower links and installing them as you have them is counterproductive. The way it is, your driveshaft/yoke will often hang up on obstacles. That would work well if you had a high pinion setup.

3. The 70% rule on uppers is bull. There are SO many variables, that's not a good rule to follow. The actual requirement is to have the upper/lower relationship allow the pinion to rotate as the axle moves and allow the pinion to continue to point toward the output of the T-case.

4. Would the uppers be the right length if you rotated the lowers upside-down and had the bend and mount below the centerline of the axle?

5. It would be good of Duffs to post at least one decent pic of the setup on a rig.

6. My rig (NOT a Duff's setup, mine) is set up so the lower links are mounted below the axle centerline and allow the vehicle to hit/climb up a link before contacting the driveshaft.

7. It also appears your axle is set an inch or two back from stock.
Joe

Madgyver · Nov 28, 2008

chris said:
MAD, can you tell me how long the upper links are in Taz's bedroom, I know it's still not installed! Mine are 39 1/4" without the rods.

Chris,
I measured the upper links without the hiems on them.
The end to end distance on the upper upper links are 36 1/4" or 3' 0-1/4".

This would be the accurate way to measure because the ball ends are threaded into the links and center to center may be different depending on how much you thread them in.
madgyver

chris · Nov 29, 2008

Madgyver said:
Chris,
I measured the upper links without the hiems on them.
The end to end distance on the upper upper links are 36 1/4" or 3' 0-1/4".

This would be the accurate way to measure because the ball ends are threaded into the links and center to center may be different depending on how much you thread them in.
madgyver

Just checked the same way you did. I have the exact same length.

chris · Nov 29, 2008

rjlougee said:
I've got some random thoughts here.

1. According to Duff's site, the lower links are supposed to be Right and Left threaded at each end "to allow for easy adjustability". I don't see that with your setup, it appears the top (as installed) is adjustable, but the back is a bushing setup. (it actually HAS to be this way to keep a bent link from rotating from torque input as the suspension cycles) THE LOWER LINK IS ADJUSTABLE IN THE FRONT.

2. Bending the lower links and installing them as you have them is counterproductive. The way it is, your driveshaft/yoke will often hang up on obstacles. That would work well if you had a high pinion setup. THE KIT COMES FROM DUFFS WITH THE BEND. I AGREE ABOUT THE DRIVESHAFT ISSUE, I BENT IT AND THE TORQUE ARM LAST TIME I WAS OUT.

3. The 70% rule on uppers is bull. There are SO many variables, that's not a good rule to follow. The actual requirement is to have the upper/lower relationship allow the pinion to rotate as the axle moves and allow the pinion to continue to point toward the output of the T-case. I AM TRYING HARD TO KEEP THE PINION AT THE RIGHT POINT. THATS WHY I STOPPED.

4. Would the uppers be the right length if you rotated the lowers upside-down and had the bend and mount below the centerline of the axle? IT WOULD AFFECT THE COIL PAD ANGLE.

5. It would be good of Duffs to post at least one decent pic of the setup on a rig. I'M CALLING THEM MONDAY AND WILL POINT TO THIS THREAD.

6. My rig (NOT a Duff's setup, mine) is set up so the lower links are mounted below the axle centerline and allow the vehicle to hit/climb up a link before contacting the driveshaft.

7. It also appears your axle is set an inch or two back from stock. MIGHT BE AN INCH OFF RIGHT NOW BUT NOT MUCH MORE THAN THAT.
Joe

Thanks Joe

chris · Nov 30, 2008

Posting some more pictures so the Duff guys can look at them Monday.

These are different from the pictures the other day. They also show the truss another 1/2" forward.

chris · Nov 30, 2008

couple more pictures

Broncobowsher · Nov 30, 2008

Suspension looks good in that shot, spring perches are level.

Now leave the truss alone and rotate the axle housing in the truss to fix that pinion angle.

Again, arms and truss are fine, leave alone.
Rotate the housing without changing the truss.
Note that the axle housing/truss interface will change.

rmfreeze · Nov 30, 2008

Broncobowsher said:
Now leave the truss alone and rotate the axle housing in the truss to fix that pinion angle.

Isn't that what he did in this pic? Hard to tell from the pic but looks like it.

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