So I ordered a new nut and bolt for the front differential mount for my car just to have in case mine are badly corroded.

I got them in the mail the other day and after returning the 17mm flex head wrench and picked up a flex socket set from lowes ($15 for 7 sockets) I check to see if the bolt is 15mm... Nope too big and too small for 17mm... WTF, a 16mm bolt????

Thats part 1 of this confusion

Part 2 is when I try to thread it onto the bolt so to not lose it. It threads 1mm and stop. I flip it over and it wont even thread onto the bolt.

I pull it off and look at it, I swear the bolt hole looks oval'd.

(pic coming in a few seconds)

Am I going crazy? I am going to remove this mount first before anything just to make sure the nut is a-ok. $2 for a nut and its useless.... First time for everything. I might even have to go to Lowes for a darn nut and maybe a 16mm flex.

Possibly a distorted thread Locknut, also called an eliptical offset nut, I think.

MM

__________________
05 Passat TDI Wagon, 155k miles
05 Tacoma, 135k miles
96 F-250 7.3, 225k miles
85 MB 300TD, 275k miles
52 Dodge M37, 4BTA powered
52 Dodge PW, 23k miles
40 Ford Tudor Sedan (parts everywhere)

That's odd. It didn't mention that in the FSM. If so then the nut would be one time use then and possibly the bolt.

Interesting. Never heard of such a thing. It looks oval in the photo.

__________________
1977 300d 70k--sold 08
1985 300TD 185k+
1984 307d 126k--sold 8/03
1985 409d 65k--sold 06
1984 300SD 315k--daughter's car
1979 300SD 122k--sold 2/11
1999 Fuso FG Expedition Camper
1993 GMC Sierra 6.5 TD 4x4
1982 Bluebird Wanderlodge CAT 3208--Sold 2/13

It is a prevailing torque nut and it is supposed to be that way. They are reusable at least once, if they do loosen up, just hit the cone portion with a hammer to flatten it out a bit.

For completeness,most bolt sizes are measured by thread diameter not head diameter. ( British Whitworth being a exception ) .

^What he said.

We use them all the time at work.

Distorted thread locknut - Wikipedia, the free encyclopedia

That piece says they are reusable.

__________________
1977 300d 70k--sold 08
1985 300TD 185k+
1984 307d 126k--sold 8/03
1985 409d 65k--sold 06
1984 300SD 315k--daughter's car
1979 300SD 122k--sold 2/11
1999 Fuso FG Expedition Camper
1993 GMC Sierra 6.5 TD 4x4
1982 Bluebird Wanderlodge CAT 3208--Sold 2/13

Interesting, I had no idea, the fsm did mention locknut but I expected a nylock. I guess because of vibrations it is this type.

Those are used on the flex discs as well.

__________________
-diesel is not just a fuel, its a way of life-
'15 GLK250 Bluetec 118k - mine - (OC-123,800)
'17 Metris(VITO!) - 37k - wifes (OC-41k)
'09 Sprinter 3500 Winnebago View - 62k (OC - 67k)
'13 ML350 Bluetec - 95k - dad's (OC-98k)
'01 SL500 - 103k(km) - dad's (OC-110,000km)
'16 E400 4matic Sedan - 148k - Brothers (OC-155k)

Really? I just removed those nuts and they looked normal.

They have been on all the flex discs I have installed or removed.....hence the need to use a wrench to the very end, they will not just "spin off" once lose or spin on either past the first few threads when installing....

__________________
-diesel is not just a fuel, its a way of life-
'15 GLK250 Bluetec 118k - mine - (OC-123,800)
'17 Metris(VITO!) - 37k - wifes (OC-41k)
'09 Sprinter 3500 Winnebago View - 62k (OC - 67k)
'13 ML350 Bluetec - 95k - dad's (OC-98k)
'01 SL500 - 103k(km) - dad's (OC-110,000km)
'16 E400 4matic Sedan - 148k - Brothers (OC-155k)

I've noticed one brand of flex discs comes with nylocks.

What had me confuse from the start is in this thread

http://www.peachparts.com/shopforum/diesel-discussion/186008-got-w124-300d-diff-mount-repaired.html

777Funk says its a 17mm but this new nut is 16mm... I bought a 16mm and 17mm wrench to bend to easily hold it in place while I remove the bolt. So I guess I shall see....

that is once i get past the drive shaft not wanting to budge