Quaife LSD

[andyblackman777]

Interestingly in my overthinking of the crown wheel bolts I realised that if your backlash needs adjustment you would have to remove these to remove the bearing to get to the shim!

Therefore I intend to assemble the thing with the old bolts, check the preload, and then the backlash with the shafts installed but casings not sealed. Then when I'm happy, probably after a shim replacement, I'll replace the bolts and do the final assembly

 

[NG5]

The requirement for new bolts on the crown wheel has very little to do with strength, they are massively over designed. The bolts act in shear and each bolt correctly torqued even if it was only grade 8.8 has a shear capacity of 45kn that's approx 4.5tn, and there are 10 of them so over 45tn. Not sure of the actual grade of bolt but they are actually higher grade than that so even higher shear strength and they don't suffer significant fatigue in the way that flywheel bolts do. If you can break those with even the stickiest tyres it would be astonishing.

The real reason is locking compound, if the bolts come loose then all sorts can happen. All new crown (and flywheel) bolts from Renault (and they warranted the gearbox for Lotus), come with locking compound already applied to the bolts. This has been Renaults practice going all the way back to the Renault 4 where the basic Renault transaxle design originated (this was developed further into the R16 and since then all later transaxles are basically the same as the Renault 16 but scaled up to be bigger and stronger) even most of the diagrams in the Lotus Esprit manual are identical to the ones in the 1960's Renault 16 manual. Rather than tell their mechanics to clean all traces of locking compound from the bolts and then apply a set amount of a specific locking compound, which is slow and labour intensive, it's been far easier and cheaper for the customer, to say bin the old ones and use new ones that are already prepared. The same thing happens on most modern cars with brake caliper bolts.

So nowhere in the workshop manuals, Lotus or Renault, does it tell you to use locking compound or what grade to use because the correct bolts already have it. When rebuilding the smaller Renault transaxles (and Renault flywheels) I've always used Loctite 243 without issues, but I've never rebuilt an Esprit box, and hope I never have to!

What locking compound do others use?

Typical new Renault crown wheel bolts

Edited May 11, 2023 by NG5
typo

[andyblackman777]

Ng5 

Thanks for your very informative reply. Makes sense. This answers a question I had. In the list of consumables required in the service notes it mentions loctite 270 for shafts nuts and crown wheel bolts. However in the re assembly notes it just says use new bolts and oil the threads 
Surely you can’t apply thread lock and oil the threads. Would that not effect the thread lock properties? 🤔. 
 

[NG5]

17 minutes ago, andyblackman777 said:

and oil the threads 

?

Where did you read that. 5 just says use new self locking bolts in the manual I have..... (FG

 

Earlier it does say immerse all parts in oil before reassembly, but I think that is meant to be about the wear parts, gears and bearings not threads.

Quickly looking at the Renault and Lotus manuals for the earlier transaxles (365, 395 etc) it just says dip the sun wheels in oil 1st. On the UN5 in addition it does say oil all parts before reassembly but I wouldn't read that as oiling threads

[NG5]

1 hour ago, andyblackman777 said:

it mentions loctite 270 for shafts nuts and crown wheel bolts

So it does, missed that ... 

Interesting because you should heat 270 to 300C prior to disassembly because it's so strong, The standard bolts don't need heating as far as I'm aware.

Perhaps they need very high strength because reused bolts are oiled 🤣

[andyblackman777]

When removed my bolts had no sign off any compound on the treads ???

I'll loctite the new ones in

[sailorbob]

The OE crown wheel bolts are listed as single use because they are AA type self locking place bolts.

[andyblackman777]

aha,

Looks like a re use is ok if they are thread locked then

 

Found a place that sells them, all imperial sizes though. 

Place bolts (or Type AA Hex Lock Bolts) have a special head design that provide a "locking" action between the head of the bolt and the material being clamped. The combination of the recess under the head of the slots in the top of the head cause the head to flex as it is tightened. This creates a spring action in the head that provides additional elastic elongation that is not provided by standard hex head cap screws. This spring action provides increased resistance to loosening in high vibration applications.

[NG5]

So Renault went with belt and braces then. The originals appear to be AA type self locking place bolts with locking compound patch.

[NG5]

Interesting, thanks @sailorbob , not looked at the properties of place bolts before. Found this site https://wilsongarner.com/what-are-place-bolts-used-for/ which is very informative. In particular it states

"because it not only produces up to seven times more vibration resistance than conventional hex head cap screws, but it also makes the bolts reusable — giving you the ability to loosen and re-tighten them without any loss of locking." (my bold)

Also this https://wilsongarner.com/what-is-a-self-locking-bolt-and-how-does-it-work/ which covers a few more things including place bolts with locking patches.

Edited May 12, 2023 by NG5
2nd link added

[andyblackman777]

You always find this out when you've just spent a bomb on new bolts!!

Now I'm left with the dilemma of reusing the old correct bolts  or fitting the new arp 'Dodge Cummings flywheel bolts' hmm

[sailorbob]

Just because one manufacturer of self locking place bolts says theirs are re-usable does not mean you can apply that characteristic to all of them. It could be an expensive assumption to make considering where they are used. Edited May 12, 2023 by sailorbob

[NG5]

I seem to have confused matters rather than clarifying. Sorry

[sailorbob]

No need for apologies, discourse is good and often useful plus I'm risk averse when it comes to the hard to replace parts on our cars.

[andyblackman777]

Jim,

Not at all. Its all good information, the more options the better the decision. It's interesting how Lotus recommend new bolts yet that particular bolt manufacturer states they are ideal for re use. It might simply be that Lotus recommended replacement so they were not 'liable' if they were to fail. They were not that expensive when available and could easily be damaged when removing etc.

Ps its driving me nuts 😂

 

[sailorbob]

From some rummaging around on the Wilson Garner website it is their type BH place bolts that have the 7 times more vibration resistance when compared to a cap screw. They give the type AA as having just over 2 1/2 times and the type B as having 4 times; see https://wilsongarner.com/wp-content/uploads/2021/04/Place-Bolt-Vibration-Chart-300x149.png

Maybe their comment about re-use may only apply to the type BH?

The type B and BH look to be an upgrade over the OE bolts depending on what they would need torquing up to and if the differential carrier can take any increase.

[andyblackman777]

Maybe I’ll torque them up and then weld them to the CW !!!! 

[NG5]

24 minutes ago, andyblackman777 said:

weld them to the CW

That will reduce their strength nicely 🤣

Which ever bolts you use if you go back to your idea of using loctite 270 then they are highly unlikely going to come loose.

Removal at some time in the future by heating is no big deal. I've just had to change the flywheel bolts on a Jabiru 3300 engine with restricted access that had been held in with loctite 620 which needs similar heating to 300C, easy done with a pencil torch. But if you sell, make sure the next owner knows!

[andyblackman777]

This is driving me nuts!!

I decided to use new bolts made by ARP in California. on receipt of the bolts I noticed that the shank is 12mm along with the thread, they are also 5mm shorter. The originals have a smaller shank than the m12 thread.

The bolts have a small "fillet' where the shank joins the head. Most bolts are like this. The fact that they are m12 means that the fillet wedges in the Crown wheel hole before the head makes contact. This weakens the bolt eventually maybe leading to failure. After speaking with ARP they say that the crown wheel hole must be chamfered to provide clearance. Or a washer With a chamfer fitted further reducing the bolt length.

So ARP bolts, wrong length, no self locking and wrong application.......

So Im gonna re use the old bolts! 

[Jacques]

Seems like a sound idea! That's what I did anyway.

Kind regards,

Jacques