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| Torque for Diff Bolts https://www.ausmini.com/forums/viewtopic.php?f=2&t=89849 |
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| Author: | Bill B [ Thu Jul 02, 2015 11:31 am ] |
| Post subject: | Torque for Diff Bolts |
What torque settings should I use on the 6 bolts holding the crown wheel to diff cage? The first time I rebuilt a diff, I used the workshop setting of 60 lbs/ft and tore the heads off 2 of them. The bolts have no high-tensile markings and 60 was obviously too much. I THINK I used around 35-40 lbs/ft. Any suggestions? Thanks - Bill |
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| Author: | Curly [ Thu Jul 02, 2015 1:50 pm ] |
| Post subject: | Re: Torque for Diff Bolts |
I just did some up the other day and checked the workshop manual before hand. It said 60 lb/ft and I didn't have any issues with the bolts breaking. I'd be checking the accuracy of your torque wrench and the condition of the bolts. |
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| Author: | drmini in aust [ Thu Jul 02, 2015 1:53 pm ] |
| Post subject: | Re: Torque for Diff Bolts |
I think the book says 55 but I do the stock bolts to 50ft/lb, no more. They stretch (and yes, my torque wrench has been checked). Once I bought some 7/16" UNF grade 8s to replace them, they were plated. 40ft/lb stripped the threads and plating off.  If buying grade 8s at a bolt shop, go for the black ones. |
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| Author: | Bill B [ Thu Jul 02, 2015 6:33 pm ] |
| Post subject: | Re: Torque for Diff Bolts |
Thanks for your replies. "Curly": I can't guarantee my torque wrench, but the broken bolts were original and the car was bought new. These bolts are not high tensile - no markings other than manufacturers' GKN and NAP indicating "standard" tensile and most references quote about 35-40 lb/ft. for them. Drmini: I think I ended up using a lower torque setting without loss. I have been told that grade 5 & 8 fasteners should not be plated as the process causes 'oxygen embrittlement' to the surface layer. Bill |
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| Author: | bent65 [ Fri Jul 03, 2015 7:27 pm ] |
| Post subject: | Re: Torque for Diff Bolts |
Also give threads a good clean with brake cleaner and loctite the bolts in |
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| Author: | keithj [ Sun Jul 05, 2015 8:05 pm ] |
| Post subject: | Re: Torque for Diff Bolts |
bent65 wrote: Also give threads a good clean with brake cleaner and loctite the bolts in Can you get the correct bolts from Minispares or such - ATA7043? They are black high tensile bolts and, in the Minis I've worked on they were all torqued up to 60 ft lbs. Cheers |
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| Author: | 69k1100 [ Sun Jul 05, 2015 11:53 pm ] |
| Post subject: | Re: Torque for Diff Bolts |
https://www.boltdepot.com/fastener-info ... chart.aspx Have to be careful these days. I bought a linisher kit for the bench grinder once. Stripped All the 8.8 grade bolts (unc threads) seems Chinese manufacturers will chop and chance standards to catch people out. 8.8 metric bolts are roughly equivalent to grade 5 imperial. |
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| Author: | drmini in aust [ Mon Jul 06, 2015 7:44 am ] |
| Post subject: | Re: Torque for Diff Bolts |
keithj wrote: bent65 wrote: Also give threads a good clean with brake cleaner and loctite the bolts in Can you get the correct bolts from Minispares or such - ATA7043? They are black high tensile bolts and, in the Minis I've worked on they were all torqued up to 60 ft lbs. Cheers I'd bet they are no longer genuine GKN bolts and are sourced from the far east, like everything else these days. There again, when flying I worry about who supplied the bolts holding the Boeing's engines on.. 
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| Author: | bent65 [ Mon Jul 06, 2015 4:40 pm ] |
| Post subject: | Re: Torque for Diff Bolts |
Id agree Kev they probably cheese and will get ugly if they break/strip. Try to find a set of Genuine ones or a brand that offers tracebality like Unbrako? (they mark the heads) We put cut down cap screws in mates LSD in his race car. They were longer bolts, cut down, with the correct length of smooth shank to bear on the diff centre. That way the crownwheel isn't 'driving' by the threaded section. cheers Ben. PS. I was told you used to be able to get the Ti, 'lifed and disposed of' bolts from Aircraft until one day they started to get re-used into aircraft. Now they are apparently destroyed and melted down for conrods or front subframes? |
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| Author: | miniandmokeworld [ Mon Jul 06, 2015 4:45 pm ] |
| Post subject: | Re: Torque for Diff Bolts |
That must be the same Ti used in some Group N minis ...? AB |
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| Author: | bent65 [ Mon Jul 06, 2015 4:51 pm ] |
| Post subject: | Re: Torque for Diff Bolts |
No mate you got it all wrong. The Ti in the Gp N minis is recycled from Chinese Ti bolts that replaced the genuine Boeing ones! 
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| Author: | miniandmokeworld [ Mon Jul 06, 2015 5:16 pm ] |
| Post subject: | Re: Torque for Diff Bolts |
You've got all the contacts when it comes to Ti & Duralium hey Ben...? |
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| Author: | Bill B [ Mon Jul 06, 2015 8:40 pm ] |
| Post subject: | Re: Torque for Diff Bolts |
keithj wrote: bent65 wrote: Also give threads a good clean with brake cleaner and loctite the bolts in Can you get the correct bolts from Minispares or such - ATA7043? They are black high tensile bolts and, in the Minis I've worked on they were all torqued up to 60 ft lbs. Cheers The issue I wanted an answer to referred to the torque settings for original bolts used in standard diffs. The bolts that I sheared were originals being reused in a mini K diff I owned from new (and still run). All the diff bolts I have seen since, including the mkI S I am rebuilding, are all "standard"/original bolts i.e. marked GKN- NAP or just NAP. Thanks to "keithj" for his comments, but the standard bolts were NOT high tensile and would never take 60 lb/ft.. There are no markings to indicate they are either grade 5 or 8 so should not be tightened over about 35 lb/ft for a 3/8th inch fastener. 3/8th inch head studs are tightened to 42 lb/ft but they are high tensile. Thanks all for your input. Bill |
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| Author: | drmini in aust [ Mon Jul 06, 2015 10:36 pm ] |
| Post subject: | Re: Torque for Diff Bolts |
Bill, they are not 3/8, they are 7/16" UNF. So will stand a bit more. I find they can stretch at 55+ but 50 works OK. |
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| Author: | Bill B [ Tue Jul 07, 2015 7:16 pm ] |
| Post subject: | Re: Torque for Diff Bolts |
drmini, they are 3/8" UNF threads but the head takes a 5/8" A/F spanner; rather than 9/16" A/F which is the standard head size. |
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