Rear end wobble

[GrayS550]

When going around bends (40mph-60mph+) my car starts wobbling uncontrollably. It feels like the 2 back wheels move left and right as they please. When I step on it in a straight line it does it too. Almost as if the rear end is shaking its butt. The tires aren’t braking loose, and it’s not the normal floaty mustang IRS. It feels like the rear has a mind of its own. There in zero vibration when this occurs. I didn’t have this issue for 2 months after purchasing it back in July 2022. It randomly started when going around a bend on a highway.

Someone told me that if you lower your mustang, the axles shift either left or right.

Things I’ve tried:
- New Tires
- New rear wheel hubs
- Alignment

Has anyone experienced this? I want to track the car once summer starts but with this issue, it seems dangerous.

The picture below is an accurate description of what I’m experiencing. But still can’t find a solution.

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[NGOT8R]

Have a different shop check the balancing of the tires. It’s possible that the weights could have came off. Greasy fingers and/or failure to properly clean the wheels before applying them would be enough to do it.

 

[jcttraveler]

I did a quick search not on mustangs and came up with several links (most like the one below). The recent alignment should have found some of these, but some are not as obvious.

https://spirecar.com/troubleshooting/9-reasons-why-your-car-shakes-when-accelerating-and-how-to-fix/

 

[Trophy Hunter]

Sorry to hear of what you're running into and yes this can be challenging to track down. Moving left to right seems more of a connection or internal issue. Since you've ruled out the hubs and since you've already had a shop look at the allignment (external connections), then I unfortunately would suspect internal. Has anyone had the rear appart ? ....changing a gear set or anything ?

I would next look at your rear. There are clips that hold the half shafts in place at the "pumkin", it could be a simple as that, if it hasn't done any damage...... or a broken haft shaft, but I think that you would audibly hear that.
Personally, if you're comfortable with this, I would jack the back up, take off the the rear cove and see - or to a performance shop that is familiar with newer mustangs. The cost is relatively inexpensive to rule those things out and some others ..... but, as long as the allignment shop did a thorough job on checking things, then I would pull the rear cover.

Good luck and keep us posted ! !

 

[22MAVXLT]

Have you lowered your car recently and not use these https://www.steeda.com/steeda-s550-mustang-irs-subframe-alignment-kit-2015-all-555-4438.html? This will cause the sensation you are feeling as well.

 

[GrayS550]

Have you lowered your car recently and not use these https://www.steeda.com/steeda-s550-mustang-irs-subframe-alignment-kit-2015-all-555-4438.html? This will cause the sensation you are feeling as well.

Yes I’m lowered! I just bought these a couple days ago! They should be here soon. I’m hoping it fixes my issue

 

[22MAVXLT]

More than likely will. My co worker lowered his 2016 GT and didn't use these and it acted the very same way as you described. We couldn't figure it out. Took it to the guy who does my work and he knew exactly what it was the second he drove it. Put these in and never had the issue again. I did mine the same time as the lowering springs, so I never experienced what you are talking about.

 

[Roadsign]

When the rear wheel bearing assemblies were replaced was the most recently updated nut used?
There are several threads discussing the torque for the nut as well. May want to re-check the torque on the nut. What you are describing can be caused by loose rear hubs.

 

[WD Pro]

Have you lowered your car recently and not use these https://www.steeda.com/steeda-s550-mustang-irs-subframe-alignment-kit-2015-all-555-4438.html? This will cause the sensation you are feeling as well.

Yes I’m lowered! I just bought these a couple days ago! They should be here soon. I’m hoping it fixes my issue

They just hold the subframe in a central (and repeatable) position. So long as the subframe bolts are torqued correctly they will not be responsible for fixing a wobble.

I’m not rubbishing the product (I have them in my car), I’m just trying to manage your expectations that the product will magically fix you wobble on its own

WD

 

[ArrestmeRed]

How long after lowering the car did the wobble sensation start? I had a friend that had a similar issue after having lowering springs installed. Turns out the shop never torqued down the vertical links and lower control arms. I ended up nut and bolt checking the entire car just to find nothing was torqued to spec. This fixed his issue.

 

[K4fxd]

Mine felt like the rear was attached with rubberbands.

Steeda's IRS braces will fix most of it. The stop the hop kit will fix all of it. Unless you have bad hub bearings.

 

[GrayS550]

How long after lowering the car did the wobble sensation start? I had a friend that had a similar issue after having lowering springs installed. Turns out the shop never torqued down the vertical links and lower control arms. I ended up nut and bolt checking the entire car just to find nothing was torqued to spec. This fixed his issue.

I bought the car lowered. I drove it for 2 months and the car randomly started wobbling. The issue was the bolt that held the control arm to the swaybar was loose and it made it wobble. Dealer tightened it and it’s all fixed!

 

[GrayS550]

UPDATE: Solved! Bolt was loose where the control arm bolts to the swaybar. Tightened it and no more wobble

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