Replaced half shafts need suspension checked?

[Evo_Rob]

Are you sure it's not just high speeds and feeling every bump in the road? What springs are you lowered on?

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[doodguy]

Are you sure it's not just high speeds and feeling every bump in the road? What springs are you lowered on?

Stock springs. Didn't have any issue prior to installing dss half shafts.

I'm not by any means blaming this on dss. I'm only saying I dint know what the heck I'm doing lol and wondering if I did something wrong during re install. Should I check a bolt tightness somewhere? I'm open to ideas.

 

[Evo_Rob]

You can. I'm baffled that you don't feel it until high speeds

 

[IvanCRF]

What does DSS say?

 

[doodguy]

What does DSS say?

Going to call them in the morning

 

[IvanCRF]

You can. I'm baffled that you don't feel it until high speeds

At high speed, he may be reaching a natural frequency of a halfshaft which causes dangerous vibration. He can stay away from this particular speed to avoid vibration or go even faster to get out of the vibration and hope he doesn't find another natural frequency. The halfshaft should be designed to vibrate outside of the range of the car's possibilities by calculating the object's mass and the material's spring constant.

 

[doodguy]

At high speed, he may be reaching a natural frequency of a halfshaft which causes dangerous vibration. He can stay away from this particular speed to avoid vibration or go even faster to get out of the vibration and hope he doesn't find another natural frequency.

Can you elaborate on this? Why would I not feel this with the stock half shafts? I wouldn't say the car gets out of control, but almost feels like driving through high wind.

I went to get my first run in at the track last week and stock snapped in two. Until then had zero issues with driveability. Got home, installed the DSS half shafts, and babied the car around town, as I got confident everything felt solid I punched it at one point to 130 on the highway, and it just felt a little squirrely. I tried it a few times here and there same result. I tried not punching it, but just getting up to 110 or so, and felt ok.

For what its worth there are 4 major bolts I removed to completely pull the piece off that the rotor attaches to. I then swapped the half shaft and put those 4 bolts back on attaching everything back together and ensuring the spindle nut was torqued to 125 ft. lbs. I didn't know the torque specs of the other bolts but I tightened them like they were when I took them off.

 

[IvanCRF]

Can you elaborate on this? Why would I not feel this with the stock half shafts? I wouldn't say the car gets out of control, but almost feels like driving through high wind.

I went to get my first run in at the track last week and stock snapped in two. Until then had zero issues with driveability. Got home, installed the DSS half shafts, and babied the car around town, as I got confident everything felt solid I punched it at one point to 130 on the highway, and it just felt a little squirrely. I tried it a few times here and there same result. I tried not punching it, but just getting up to 110 or so, and felt ok.

For what its worth there are 4 major bolts I removed to completely pull the piece off that the rotor attaches to. I then swapped the half shaft and put those 4 bolts back on attaching everything back together and ensuring the spindle nut was torqued to 125 ft. lbs. I didn't know the torque specs of the other bolts but I tightened them like they were when I took them off.

Designing parts so that they do not vibrate is tricky. All objects will vibrate at different velocities. I recall reading another forum member having trouble with his DSS driveshaft because of its vibration. The Ford engineers likely designed the stock driveshaft and halfshafts so that they would not vibrate in the car's possible realm. I'm not saying this is your problem, but it is a possibility.

 

[Dramad1]

I too have noticed a similar feeling with my car after putting new rear tires on. My buddy says it's all in my head. I'm like no, Def something going on here and it wasn't like that before.
I notice similar, wiggle in the rear at high speeds as well as when taking corners aggressively, so much so it kinda scares me.
My first thought was the tires, but they are the same size as stock and are brand new. I figured they needed to break in a bit more. Kinda seems like the rear is tracking left and right. My buddy says it's probably the grooves on the road and the tires are new, I drive the same roads every day and it was never like the way it feels now.
I have had the rear up on Jack stands countless times. Is it possible the irs settled wrong when letting the car down? Could it be the bushing on the trailing arm?
Following along.... I want the car back to the way it felt befoe

 

[IvanCRF]

I too have noticed a similar feeling with my car after putting new rear tires on. My buddy says it's all in my head. I'm like no, Def something going on here and it wasn't like that before.
I notice similar, wiggle in the rear at high speeds as well as when taking corners aggressively, so much so it kinda scares me.
My first thought was the tires, but they are the same size as stock and are brand new. I figured they needed to break in a bit more. Kinda seems like the rear is tracking left and right. My buddy says it's probably the grooves on the road and the tires are new, I drive the same roads every day and it was never like the way it feels now.
I have had the rear up on Jack stands countless times. Is it possible the irs settled wrong when letting the car down? Could it be the bushing on the trailing arm?
Following along.... I want the car back to the way it felt befoe

I'd start with the simple stuff first and verify lugs are properly tightened, none of the weights are missing, the wheels are properly balanced.

Back to the DSS halfshafts, I hope it is something simple or just an anomaly from manufacturing. I haven't read too many exceptions for them so I hope it works out.

 

[doodguy]

I just talked to DSS, and they said the driver and passenger axles are different sizes. THey said the drivers side should be 20 and 3/4 inches (The thick black bar part) so I will hop under car tonight and measure. If I have them backwards (sucks) I will pull out swap and keep you all updated. If that's the issue, and fixes it some of you might be in same boat.

 

[doodguy]

Just looked under car; the length of the bar on both sides is 17 inches, I did notice the passenger side bar has these divots in it where the drivers side did not.

Checked American Muscle, and saw them listing pictures of the passenger side with these divots while the drivers side did not, so it looks like the half shafts are on the proper side.

I'm tired, but going to pull the tires tomorrow night double check the bolt tightness. I know the center axle nut at the center of the rotor should be torqued to 125 FT. lbs. Can anyone tell me what the other 4 bolts should be torqued to? These are the bolts that hold the whole rotor assembly to the car. There are two top left, one lower left, and one lower right; not sure what you call this assembly.

If the bolts are all torqued properly, what else could I check?

I measured the distance from the tire to the wheel well on both sides, and it is very close. Maybe a mm or two off, but that could just be not measuring exactly same spot or something.

 

[IvanCRF]

Step 14 and on has the torque specs:

http://fordperformanceracingparts.com/download/instructionsheets/FordInstShtM-4130-M.pdf

 

[Evo_Rob]

Just looked under car; the length of the bar on both sides is 17 inches, I did notice the passenger side bar has these divots in it where the drivers side did not.

Checked American Muscle, and saw them listing pictures of the passenger side with these divots while the drivers side did not, so it looks like the half shafts are on the proper side.

I'm tired, but going to pull the tires tomorrow night double check the bolt tightness. I know the center axle nut at the center of the rotor should be torqued to 125 FT. lbs. Can anyone tell me what the other 4 bolts should be torqued to? These are the bolts that hold the whole rotor assembly to the car. There are two top left, one lower left, and one lower right; not sure what you call this assembly.

If the bolts are all torqued properly, what else could I check?

I measured the distance from the tire to the wheel well on both sides, and it is very close. Maybe a mm or two off, but that could just be not measuring exactly same spot or something.

17" is the length from the rubber boot to boot? Or from the joint to the other joint? Something is missing, I think

 

[doodguy]

17" is the length from the rubber boot to boot? Or from the joint to the other joint? Something is missing, I think

17 is the length from boot to boot. In other words on each end of the bar is a boot which buts up to a metal cylinder. This cylinder attaches to the other bar that goes through the rotor.

17 inches is the measurement cylinder to cylinder.

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