What size are Brake Booster mounting nuts?

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The PIG Smith
Posts: 506
Joined: Sat Sep 03, 2011 10:54 pm
Location: Fort Wayne, Indiana

What size are Brake Booster mounting nuts?

Post by The PIG Smith »

I am replacing a Brake Booster on my J10.
Getting the old nuts off was not fun, both the nuts from the under the dash from the firewall adapter and from booster studs to the adapter.
Now, I am about to install the new dual diaphragm brake booster and the new unit comes with no fasteners.
My old flange nuts are messed up from me fighting to get it off.
The booster studs will not accept a standard hex nut, course or fine thread and a metric nut will not fit.

What size are these hex nuts and where can I purchase four?
Bryan Smith
Fort Wayne, Indiana
2017 Jeep Grand Cherokee Limited
- 75th Anniversary Edition - 1941 Trim Package - Recon Green --Daily Driver
1986 Jeep J20
- Super clean rig from the AZ/CA state line -- Current Project
1982 Jeep J10
- Has become a Long Term Project.
1981 Jeep J20
- Commercial flat bed - Lost in a Divorce --gone
1987 Jeep J20 Pioneer
- Former Rick Bielec aka Ricbee plow rig. Major rust!! --gone

IFSJA Member #1933 Joined November 30, 2001
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tgreese
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Joined: Fri Jun 08, 2012 6:31 am
Location: Medford MA USA

Re: What size are Brake Booster mounting nuts?

Post by tgreese »

You have a cheap tap and die set? Works good for testing thread sizes. Or you can use a cheap Harbor Freight caliper to measure the diameter of the hole or stud and get close. Or you can take the booster to your local Ace Hardware and try all the sizes they have. I would start with 5/16" and 8mm.
Tim Reese
Maine beekeeper's truck: '77 J10 LWB, 258/T15/D20/3.54 bone stock, low options (delete radio), PS/PDB, hubcaps.
Browless and proud: '82 J20 360/T18/NP208/3.73, Destination A/Ts, 7600 GVWR
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