Differential Bolts

[MAV]

I'm replacing my 3.73 rear gear with a 4.56 unit I built, and while the diff is out of the car, I want to do some upgrades. I'm planning to drill the threads out of the front diff bushings and use 9/16-18 4 1/2" grade 8 bolts for a bolt-through connection. I want to do the same on the rear bolts, but I can't find any information that indicates bushings are 9/16" inside. Can someone that's been in there before verify that the inside diameter of the rear differential bushings are the same size as the fronts?

Also, for a through-mount bolt in the rear diff mounts, would this also be a 4 1/2" length as the front is? I'm using the stock bushings (no lockout kits).

Thanks!

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[NGOT8R]

Steeda makes a through bolt kit. I have one on my 2019 Bullitt. No drilling required.

 

[MAV]

Yep, that's a nice kit (it better be for >$100!), but I'm running stock bushings with no inserts or lockouts. I don't mind drilling out the front bushings since I'm going to have the diff out of the car anyway, and I'm going to use a 9/16"-18 through bolt as described in this post: https://www.mustang6g.com/forums/th...ts-issues-resolutions-pics.74891/post-1706905

I could use the rear part of the Steeda kit, but I would need shorter bolts, and I doubt they would sell just the inserts by themselves. So, since I can easily drill the ears of the diff cover while it's out of the car, I can either make it a through bolt mounting like the front, or at the very least drill it and tap it for a larger bolt. That's why I need the inside dimensions of the rear diff bushing.

Anyone got an old one laying around they could measure?

 

[WD Pro]

I think you would find just the bushing inserts (new) reasonably easy.

One of the Steeda kits comes with both red and black bushes meaning spares will be out there, I have a spare black set (but in the U.K. …).

With regards to the size of the hole I might be able to help - I have some bolt sleeves in the garage and I’m pretty sure they are 16mm OD

WD

 

[MAV]

Thanks for that info! If the bolt hole in the bushing is 16mm, that leaves me wondering why I couldn't just drill and tap the diff cover mounting holes for a 16mm bolt same length as stock. That would be as strong if not stronger than a 9/16 through bolt, and I wouldn't have to worry about the sleeves.

 

[MAV]

I found another thread that reported the inside diameter of the stock bushing is 17.3mm. I believe I'm going to simply drill and tap the ears of the diff to fit an M16-20 bolt. If anyone has one laying around, would you mind measuring the length of the factory rear diff bolt (under head to tip) and let me know what that is? From what I've gathered, I believe it's going to be either a 90mm or 100mm bolt, but I'm not exactly sure.

Thanks!

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