Torqueing up the crown wheel bolts today and SNAP !
Book says 60 lb , thought that's a lot ,
didn't feel right .
any one else had this happen ?
can you use spring washers and locktight instead of the lock tabs ?
or a flat washer and locktight ?
Thoughts ?

Mark

I wouldn't not use the lock tabs, if a bolt came out, I'd hate to think what it would do. I know what happens when a conrod goes into the gears, not nice.

I limit stock bolts to 50. I have had these stretch at 55.
I used grade 8 bolts once on a Quaife diff, which were plated. The threads peeled off at 55 ft lb. So I bought black grade 8 instead, and they worked fine at 60.
I used with Loctite 262 instead of the locktabs.

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DrMini- 1970 wasaMatic 1360, Mk1S crank, 86.6HP (ATW) =~125 @ crank, 45 Dellorto (38 chokes), RE282 sprint cam, 1.5 rockers, 11.0:1 C/R.

Looks like I will get new bolts , locktabs , Loctite and 50 ft / lb

Deja vu!
I listed this exact question here some time ago with inconclusive answers.
I had the same result when taking original bolts past about 50 - went soft then sheered. Everyone quoted the manual at 60 lbs/ft but that was not going to work.
The standard bolts don't have any grade markings so I now assume they are same size as head stud/bolts and take them to about 40-42 lbs/ft. They aren't for a race engine, nothing has ever 'let go' over many years.
I also use locktite and locktabs.
The original bolts have an unthreaded section that I assume helps to centre the crown wheel.

I read this thread before pulling the gearbox/diff apart. Old crown wheel bolts were 60lbs/ft when checked. I bought some new bolts from mspares and they started stretching at 50lbs/ft. I have since bought some arp bolts. Do I use locktite and the lock tabs (which don't really fit a 12 point bolt) ? or Locktite and no lock tabs ? Would locktite 242 or 243 be suitable ? or a more permanent 262/263 (as Dr used) ?? Sorry for all the questions. Diff is a Quaife.

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1970 Mk2 Cooper S under restoration

no lock tabs, 262

I've only ever used stock bolts - they have "GKN" on the heads

What's a suitable part number for ARP?

edit: though it's possible I used ARP assembly lube instead, it's been a long time.. it's out of the car and I need to change the ratio anyway, I'm gonna go take it apart

edit2: I think I used 262 on the threads and a bit of assembly lube under the heads - but ARP have supplied you with assembly lube, use that. I don't know what I torqued the bolts up to, probably 60lbft - my bendy bar torque wrench only goes forwards, it clicked off when I set it to 70lbs and tried to tighten it a bit

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did I tell you that I won a trophy?

I assume you measured the torque by removing them with a torque wrench. In that case the reading will be higher than the torque that they were done up to.

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1986 Mayfair (998 auto), 1974 S, 1974 Van, 1972 PMG Van

Too many minis

Actually, no. I adjusted the torque wrench to 60lbs/ft and foolishly tried to tighten. It clicked and none sheared.

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1970 Mk2 Cooper S under restoration

I couldn't get the stock bolts, only the ones from mspares, black and no writing on heads. ARP bolts are #206-2802. Pic shows "GKN" std bolt, stretched mspares bolt and ARP.
ARP has a shorter shank area, and a tat longer - same apparently (I'm told) as what KAD & swiftune offer.

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1970 Mk2 Cooper S under restoration

I also had this problem with my recent 850 gearbox rebuild, and had to get replacement "original" bolts from a nearby mini parts outlet and not do them up so tightly. In my case, I found my expensive Warren and Brown torque wrench was 10% in error when I checked it with a digital gauge. I don't know why, but I am not happy given that I thought I was buying the best. The wrench doesn't appear to be damaged and it has had little use.

Before purchasing a digital torque gauge , I tested my W&B torque wrench by clamping the square drive in a vise and then hanging a 20L drum of water off the handle. It is then an easy matter to calculate the actual torque applied (20 kg x the leverage arm length) and compare against the torque wrench setting. An interesting check to make and may alert you to something not right with the wrench. Rather surprisingly, my old Sidchrome torque wrench with the leaft spring indicator that snaps over a pin (some 50 years old) was spot on.

However, I've sometimes wondered why many of the important nuts and bolts have to be done up so tightly - gearbox input gear, 3rd motion shaft pinion nut, drive shaft yoke nuts, CV joint nuts, etc and I think the reason must be that to increase friction forces at the mating shear faces so that there is no rocking on the splines in these parts. In the case of the crownwheel to cage there is rather large diameter friction surface and so a spline isn't necessary. Perhaps all these splines don't actually do anything unless the fasteners become loose and then serve to transmit torque as a backup - although I note on the drawing for a grearbox pinion that these are supposed to be a selective tap fit on to the 3rd motion shaft (a condition which I don't remember reading in the workshop manual).

That will do the same too although probably to less extent.



Is that W&B a deflecting beam like it sounds like the Sidchrome is? (an interesting point is actually that Sidchrome ones were made by both Warren & Brown and Ritch, yours probably being a Ritch)

The main benefit of them is actually consistency not accuracy although they should be close enough

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1986 Mayfair (998 auto), 1974 S, 1974 Van, 1972 PMG Van

Too many minis

Looks like they suggest re-calibrating every 12mths, so i think all of us are probably just winging it +/- 10%. Not using it doesn’t mean it keeps perfect calibration. Springs change with changes in temp, and apparently you should wind off the torque before storage.

I used my old bolts for diff , i dont trust any of the new stuff unless its arp.

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1966 Mini Deluxe - “Gabby” 34 years under restoration and counting...
1970 MGBGT
1959 MGA

mine is a W&B - my employer has an office in Brisbane, I spent the first half of last year up there and had taken my mini and tools including torque wrench with me. The business next door does measuring tool calibrations - they didn't charge me to test it

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did I tell you that I won a trophy?

I suspect eightfifty's W&B may be one of their spring type import ones of unknown COO. Deflecting beam torque wrenches very rarely need calibration (can be 50+ years old and fine) which is what W&B ones are known for.

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1986 Mayfair (998 auto), 1974 S, 1974 Van, 1972 PMG Van

Too many minis