12 replies to this topic

[colinu]

What torque setting should be use when fitting the clutch case (aka transfer casing) back on to the side of the block+gearbox? The torque table on the forum has me a little confused. Should they be:

• 6 lbft for the 5/16" UNC (those that go into the alloy gearbox case)
• 18 lbft for the 5/16" UNF (those that go into the block

What's confusing me?... just a little surprised that there's such a difference in the clamping force across a single assembly (and if me getting it wrong has been the cause of a very minor oil trickle from the rear side of the transfer case).

 

Note: I'm using bolts (machine screws) for all - most parts lists imply some should be studs and nuts. Does that make a difference?

 

 

   Cheers,

   Colin.

[Swift_General]

The studs themselves where they screw into the box to 6lbft (UNC thread). But the nuts that clamp the casing that go on the studs (UNF) to 18lbft (and the bolts also). In reality I just nip the studs up when screwing them in rather than torquing them, it just helps to keep the studs in place when you undo the nuts. So all fastenders will be clamped to 18lbft ultimately. I would be wary of torquing up a machine screw straight into the alloy casting to 18lbft as you would risk stripping it.

Edited by Swift_General, 26 January 2019 - 06:56 PM.

[colinu]

Thanks for the reply. Yes setting a UNC bolt to 18 lbft in the gearbox alloy was my worry too... stripped threads!  I found one stripped already so it's time to helicoil it. Guess I should really buy the MSSK062 stud and bolt kit and do it properly!

[nicklouse]

well yes different materials and thread pitches require different torque settings to give the same clamping force.

 

now also consider that the early ones used studs and nuts and the later used bolts.

 

what you got?

[Swift_General]

I've helicoiled quite a few of those threads sucesfully. Ironically you end up with a more durable thread than original, as the weak spot will always be the steel to alloy, rather than the steel to steel, and if course with a helicoil you're making the steel to alloy interface bigger.

[colinu]

Nick... bolts is what was in it when I bought the Mini 10 years ago (and I used bolts again when rebuilt 5-ish years ago). I should really do it correctly and fit the UNC/UNF studs.

 

Swift... I've been soooo thinking I should just helical the lot for that very reason :)

[nicklouse]

Nick... bolts is what was in it when I bought the Mini 10 years ago (and I used bolts again when rebuilt 5-ish years ago). I should really do it correctly and fit the UNC/UNF studs.

 

Swift... I've been soooo thinking I should just helical the lot for that very reason :)

nope. if you had bolt (A+) it is correct only the A had the studs and many change to bolts.

[colinu]

Nick... it's a hodgepodge of years... block is pre A+ (late 60's?), box is late 80's or 90's (DAM5626), transfer case is '87 (DAM5785).  So if using UNC bolts instead of UNC/UNF studs, then what lbft would you use for those mounting into the alloy of the gearbox?

[nicklouse]

Nick... it's a hodgepodge of years... block is pre A+ (late 60's?), box is late 80's or 90's (DAM5626), transfer case is '87 (DAM5785).  So if using UNC bolts instead of UNC/UNF studs, then what lbft would you use for those mounting into the alloy of the gearbox?

just use the bolts. with thread lock and torque to spec.

[colinu]

spec being 6 lbft?

[Spider]

According to Rover, all bolts here, both the UNF and UNC, are torqued to 25 Nm.

[GraemeC]

25Nm / 18lbft

If the threads are in good condition and you have the right length bolts to give correct engagement length then the the UNC ones will be fine. When bolts were used they were the type with the reduced A/F heads which give a more even and better clamp - no need for locktabs or washers.

UNC - DAM7756 & DAM7759
UNF - DAM7753 & DAM7758

Edited by GraemeC, 27 January 2019 - 06:27 AM.

[colinu]

Threads may not be in the best of condition (one already helicoiled, and I had to do another yesterday).  Based on that I don't feel too confident that the others will hold up to bolts at 18lbft... so will be using studs at 6lbft on the UNC side and 18lbft for the UNF nuts.

Thanks for the discussion :)