Drive train mount bracket bolt size?

[mongoswede]

What is the size of the bolt and threads that bolt the two brackets to the transfer case....the two brackets that bolt to the chassis mounts. I pulled on of the nuts today and took it to the hardware store and could not find a match. bigger then a 10mm, smaller than a 12 mm. 7/16" was a good fit but the 14 count thread was too course and the 20 count was also not correct.

[TJR]

If the 7/16 was the right Dia, they are probably, 7/16-18 BSF

http://homepages.tesco.net/~A10bsa/bsfgo.htm

http://www.hells-confetti.com/Technical%20data/Engineering/BSF%20threads.htm

brb..... Yep.. Just checked mine w/ a thread gage 18 TPI...

Try yourself. I also placed a std 5/16-18 UNC bolt into the nut and it should mesh w/ the threads...
..Talbot

[mongoswede]

If the 7/16 was the right Dia, they are probably, 7/16-18 BSF

http://homepages.tesco.net/~A10bsa/bsfgo.htm

http://www.hells-confetti.com/Technical%20data/Engineering/BSF%20threads.htm

brb..... Yep.. Just checked mine w/ a thread gage 18 TPI...

Try yourself. I also placed a std 5/16-18 UNC bolt into the nut and it should mesh w/ the threads...
..Talbot

thanks....now I know what to look for at least....or I'll see if I have some in my parts pile. I am not sure what I did with them when I pulled the drivetrain out a year ago.

[JackIIA]

I've seen 'threads' here through the years (sorry for the pun) which ignore some of the nuances of the fixings/hardware etc used on our trucks. I am under the impression that you can't use nuts and bolts that will thread into existing parts of LRs just because they fit. That means special ordering BSF, UNF, to make things match up. Unless of course it's a stand alone bolt/nut arrangement. And the reason for that is the pitch of the thread is different so regardless of matching TPI, you don't get the contact you need to truly hold things together.

I've seen different charts cataloging bolt variations, but my eyes start to gloss over. If that is not the case and there is a simple rule of thumb I'd love to know. This is one area I'm more than happy not to be a purist about.

Also, apart from our rover parts suppliers, I'm guessing it's basically impossible to buy BSF, UNF locally here in the states, e.g., you can't go to a hardware store for this solution....at least I haven't been able to or don't know what American equivalent to ask for.

[greenmeanie]

IIRC the threads in the housing are imperial so it may be BSF TPI on the male end of the stud for the nut but the female end is imperial. You can make sure by simply chasing it with an imperial tap. Then you can just buy the imperial studs and nuts from the hardware store. It is not for the purists but it means you can forget the cost & complications of obtaining BSF hardware.

[JackIIA]

Good to know Gregor.

[TJR]

IIRC the threads in the housing are imperial so it may be BSF TPI on the male end of the stud for the nut but the female end is imperial. You can make sure by simply chasing it with an imperial tap. Then you can just buy the imperial studs and nuts from the hardware store. It is not for the purists but it means you can forget the cost & complications of obtaining BSF hardware.

SAE 7/16 -14 UNC and SAE 7/16 -20 are 60 degree threads.

BSW 7/16-14 and BSF 7/16-18 are 55degree threads..

http://www.boltscience.com/pages/screw4.htm

http://www.britishfasteners.com/threads/bsw.html

http://www.lrfaq.org/Series/Other.threads.html

So will a 7/16-14 UNC stud engage the BSW 7/16-14 tapped hole(assumining it is) in the T/C ? Probably since it's aluminum, but its not going to load the thread faces as intended.

all that being said I may have an extra set of the OEM T/C mount nuts?

..Talbot

[greenmeanie]

Talbot,
That would be of great consideration if this were aerospace or a highly loaded application such as head bolts. Note that I said to chase it with a tap which results in your desired 60° thread. I can guarrantee through 10s of thousands of miles of use that it is of damn all consequence on a LR transfer case.

[TJR]

Talbot,
That would be of great consideration if this were aerospace or a highly loaded application such as head bolts. Note that I said to chase it with a tap which results in your desired 60° thread. I can guarrantee through 10s of thousands of miles of use that it is of damn all consequence on a LR transfer case.

Yep..Just pointing out the sublte differences that they are not 100% the same.. Running a tap should finish cut the square root bottom and thread flank differences however small they are. Since there are four studs per side.. add some loctite and it will probably hold well.

Or buy the required nuts ....

http://www.roversnorth.com/store/p-7516-nut-716-bsf.aspx

and use the orignal studs.

The OE stud is coarse thread case side, Fine thread bracket side. You get the holding power of the coarse thread in a soft material and the clamping power of a fine thread on the bracket side. Well. stripping my TC studs and mounts, 50% of the of the studs stayed together on the BSF side from rust, and the therefore the whole stud and nut combo unscrewed from the T/C. Nice.. ..

[mongoswede]

2 of the studs came out with the nuts when I took it apart originally. Interestingly when I looked at one of my parts cases it also had the same two studs missing (Left hand side). So either they used two studs and two bolts on that side...or for some reason the nuts on that side commonly come out with the studs. I need to get a stud remover tool and then I can take them off the parts transmission. Right now the bracket is on there with just two nuts and two studs.

[TJR]

Here are some pics of my S3 Trans & TC during it's cleaning phase last year. Not much has changed to it since :-(
You can see the supports on and off the TC.

Seems like I has a similar stud/nut d'assy issue as yours... Left side...