Shims and Brake Wobble Downhill?

[CharlesUSMC]

Hello the first I'd like to say thank you for taking the time to read this.

About two years ago I took my 2005 Ford Expedition to the mechanic for a rear differential repair. Even though it was under a third party warranty the mechanic billed me $400. This was a Ford dealership.

The mechanic told me that it needed shims as well. But after being nickeled and dimed over what I thought was under warranty I decided to take my car home anyway.

I'd like to try to repair this issue myself. My rudimentary understanding is that shims would go around an axle preventing the wheels from wobbling. Basically filling in the Gap that may have formed due to the differential replacement or some other wear and tear.

Can someone please explain to me what this forward and backwards wobbling is when I brake going downhill and how I should go about repairing it. I am reasonably good with mechanics but do not quite understand what I'd be getting myself into on this one. I have pulled Transmissions off of cars and replaced clutch plates, bearings, alternators, belts, brakes, oil, sensors, but have never been familiarized with drivetrain axles and suspension. Thank you for taking the time to read and hope someone can give me advice on how to do this work myself.

 

[Vancouver Bob]

What year Expy? And what was the differential repair that was needed?

When I hear shims and differential my mind goes straight to the shims that are inside the differential. They are used in a couple of ways... to help set the pinion gear in relation to the ring gear to get the correct gear mesh, backlash. They are also used to "preload" the differential.

I think you need to find out where the wobble is coming from. Can you feel unusual movement of your axles? Because it could be brakes.

 

[CharlesUSMC]

It's a 2005. I've never felt anything quite like it before. It only happens when going downhill. The wobble correlates with how fast the wheels are turning over. The wobble is definitely forward and backwards. If you're sitting in front of your computer right now and you just kind of Nod your head forward and backwards forwards and backwards you'll feel what I mean.

 

[CharlesUSMC]

The repairs that were done on the rear differential were due to a shuttering sound that was coming from the rear differential when I gave it gas. Specifically when turning the wheels to the right or left and accelerating from a stop. The dealership had to take apart the rear differential and order a bunch of parts to rebuild it.

 

[Vancouver Bob]

It's a 2005. I've never felt anything quite like it before. It only happens when going downhill. The wobble correlates with how fast the wheels are turning over. The wobble is definitely forward and backwards. If you're sitting in front of your computer right now and you just kind of Nod your head forward and backwards forwards and backwards you'll feel what I mean.

Only happens going down hill while you're applying brakes?

 

[Vancouver Bob]

The head nod or forward/back wobble would make sense if brakes or something else is dragging at certain rotation.

 

[CharlesUSMC]

I don't think it's the brakes it feels something like axles. Which makes sense because the mechanic said I needed shims and if the axles are wobble and then it might be because I need shims.

 

[Vancouver Bob]

The rear knuckles and suspension components are what hold your spindles/wheel/tire in position. The half shafts just provide the power so they wouldn't cause any wobble. But maybe something is binding inside the differential that's causing resistance to rotation? Although not sure how going downhill would cause that to happen. Perhaps you can try to isolate the issue a bit more.