Ring Gear Bolts

[tuko]

Today I loosely fitted the truetrac's in the diff's and ran into a few problems that have raised a few questions. The Ring gear bolts or should I call them Poo Bolts, the first two that I used to secure the ring gear to the new diff, they snapped like twigs.

Those bolts that I did find to hold on for the time being, the threads no longer came out the gear side as far as they did without the ring spacer that I have for the 4.70 gears. Plus I wasn't using the locking tabs.

Is this acceptable or should I be looking at longer bolts equal to the ring spacers?

The bolt heads are 15mm and the threads appear to be metric and are course. Would it be possible to replace them with 8.8 grade bolts from a local supply depot? Using 270 loctite, would I then need the locking tabs for the bolt heads or is loctite enough?

Todd.

[Hybrid_From_Hell]

FTC5150

12.9 Ton LR CWP Flange head bolts

Nige

[tuko]

Thanks for the part number, Nige.

Do you know the length of that bolt? I'm wondering if it will protrude through the ring gear or sit flush? But then again, I have no idea if that makes a world of difference or not as the bolts will be secured with loctite 270.

Todd.

[Retroanaconda]

FTC5150

12.9 Ton LR CWP Flange head bolts

Nige

Hope I'm not teaching to suck eggs here Nige, but just wanted to classify that the 12.9 property class (ie. bolt rating) doesn't mean 12.9 tons of strength.

The first number is the ultimate tensile strength in MPa, divided by 100. So in this case 12000 MPa.

The second number is the ratio between the above and the tensile yield strength, multiplied by 10. In this case it would be 0.9 (giving a tensile yield strength of 0.9 x 12000 = 10800 MPa).

To work out the load carried by the bolt, you'd need to take the cross-sectional area of it and apply the tensile strength to that. So a 12.9 rated bolt 12mm in diameter would have a yield strength of 1220400 newtons, or about 125 metric tons.

I think anyhow, if anyone can correct me then please do

[Hybrid_From_Hell]

EXCLUDING head and flange bolt length is 24mm

Overall inc head / flange about 36m

Nige

[Daan]

Aren't these bsf bolts? In which case you are in a bit of a situation; I never managed to find high tension ones for my KAM ringgears. The only ones available are capheads, but they foul the casing.

Daan

[western]

Aren't these bsf bolts? In which case you are in a bit of a situation; I never managed to find high tension ones for my KAM ringgears. The only ones available are capheads, but they foul the casing.

Daan

FTC5150 according to Brit-car are 3/8 UNF thread http://www.brit-car.co.uk/product.php?xProd=99796 & confirms with Microcat too.

[tuko]

I find it a bit misleading on the internet to see what the bolt looks like, ie:

This is from Brit-car, note the length of the bolt:

Then there is this image from Deven4x4 for the same part number:

The above bolt has to be the one that Nige is referring to, that bolt or image from Brit-car doesn't even resemble the bolts I removed today.

Todd.

[Retroanaconda]

Er....ignore my calculation above. Just re-read it and I was a few factors out on the ultimate yield strength calculation!

So please ignore my numbers, I think the method is correct though

Edit: I think it actually works out to 13.8 metric tons of force.

[Mr Ian]

As Daan said are these 3/8 bsf? or do you have an aftermarket R&P with 3/8 unf thread, the stock BSF LR BOLTS are very low grade, they need to be at least SAE grade 8, (equal to 10.9 metric). But again as noted by Daan these are generally only available in cap hd, if you can get 'low profile' cap head these will clear the case. Just for info the pic shows a set screw ie threaded up to the head, a bolt,which is the correct fastener, has section of plain shank. Regards Ian Ashcroft

[tuko]

Thanks Daan & Ian for the replies. I'm installing the truetrac's in standard series 3 diff's. The bolts to help to identify them they have "WILEY" written across the top and at the bottom is the letter T. The diff's don't appear to have been altered at any time so I have to assume that they are the original 3/8 BSF bolts as already stated.

Ian, I just bought the spacer rings from Dave this week, he never mentioned anything about needing longer bolts or replacements so you guys have to accept that this is a new adventure that I have no experience with. But I am learning quickly.

Any suggestions where I can buy these bolts? I found this: http://www.teng.co.uk/h101s0160118-3-or-8-x-1.1-or-2-inches-bsf-high-tensile-b0lt-s-or-c-bs1083-grade-r_60946_pd.asp

No idea if Grade "R" is a sufficient grade for bolts in this environment, I'll have to google to find out.

Cheers,

Todd.

[Daan]

I got my bolts from this lot:

http://www.namrick.co.uk/

They are good quality but I dont think they are any better than 8.8. The length I used, I think was 1.25 inch, but please double check this.

The problem I found is that proper high tension in this treadform is unobtanium. As I mentioned, capheads do exist, but dont fit. In the end, I loctited the diff, spacer and ringgear together and it has been reliable ever since using the strongest loctite known to man (cant remember the number). after loctiting, the bolts dont serve any purpose and, in theory, could be left out. If you ever need to replace a ringgear, it involves making a campfire to split them again.

Desperate times, desperate measures...

Daan

[Mr Ian]

Hi the mark on the head indicates SAE Grade 8, see attached. Ian

www.boltdepot.com/fastener-information/materials-and-grades/bolt-grade-chart.aspx

[western]

Hi the mark on the head indicates SAE Grade 8, see attached. Ian

www.boltdepot.com/fastener-information/materials-and-grades/bolt-grade-chart.aspx

clicky link to above

[Daan]

As that link shows, yes it explains grade 8, but no, not available in BSF. To answer your original question tuko, I think, looking from the picture, that you are ok on the length as is. I also used schnorr washers under the boltheads, since there was enough length, but it isn't strictly needed I reckon. Lock tab washers was something else I tried, but they dont work with a pegged diff.

Hmm, memories of desperate times.

Daan

[tuko]

As that link shows, yes it explains grade 8, but no, not available in BSF. To answer your original question tuko, I think, looking from the picture, that you are ok on the length as is. I also used schnorr washers under the boltheads, since there was enough length, but it isn't strictly needed I reckon. Lock tab washers was something else I tried, but they dont work with a pegged diff.

Hmm, memories of desperate times.

Daan

Daan,

Thank you for answering those questions, now I have a better idea for what bolts to order tomorrow. It doesn't look like that I'll be using any washer under the bolt heads because of the bolt length's, but I will loctite the h€ll out of them.

Todd.

[Phil Hancock]

The bolts to help to identify them they have "WILEY" written across the top and at the bottom is the letter T. The diff's don't appear to have been altered at any time so I have to assume that they are the original 3/8 BSF bolts as already stated.

Cheers,

Todd.

They can be 3/8"UNF as original, IIRC the change from BSF was about the time the diffs lost the bolted on seal holder for the pinion oil seal, the T on the bolt head denotes grade T tensile which is a high strength, R is not very high strength.

[tuko]

They can be 3/8"UNF as original, IIRC the change from BSF was about the time the diffs lost the bolted on seal holder for the pinion oil seal, the T on the bolt head denotes grade T tensile which is a high strength, R is not very high strength.

Phil,

That I can confirm that they are not. I dug out a RRC 10 spline diff yesterday to compare the bolts and they were 3/8 UNF. The ring gear had clearly stamped in it "UNF". Rechecking my two diff's and ring gears, they have no stamping anywheres to identify the thread patterns, just makings for the matching pinion gear.

Oh, thanks for the info on the letter "T".

Todd.

[tuko]

Bolts are ordered from the same place as Daan.

But in the mean time while talking to another Land Rover owner last night he suggested a crazy idea. So I thought that I would ask it here to see what the reaction would be.... He suggested to drill out the BSF threads in the ring gear and re tap it to UNF. Is this plausible or just a waste of time?

Todd.

[Mr Ian]

Hi I don't think you could re-tap the crown wheel, it should be HRC60 or HV724, your drill/tap will not even touch it.

Reagrds Ian Ashcroft

[bishbosh]

Hope I'm not teaching to suck eggs here Nige, but just wanted to classify that the 12.9 property class (ie. bolt rating) doesn't mean 12.9 tons of strength.

The first number is the ultimate tensile strength in MPa, divided by 100. So in this case 12000 MPa.

The second number is the ratio between the above and the tensile yield strength, multiplied by 10. In this case it would be 0.9 (giving a tensile yield strength of 0.9 x 12000 = 10800 MPa).

To work out the load carried by the bolt, you'd need to take the cross-sectional area of it and apply the tensile strength to that. So a 12.9 rated bolt 12mm in diameter would have a yield strength of 1220400 newtons, or about 125 metric tons.

I think anyhow, if anyone can correct me then please do

Logic is OK, but some fat fingers when you crunched the numbers! (As you have subsequently noticed!!)

For a 12.9 bolt, UTS = 1,200 MPa, not 12,000MPa, therefore the yeild stress = 0.9 x 1,200 = 1,080MPa (MPa = N/mm²)

The only real error is that to calculate the tensile capacity of a bolt you must use the threaded cross sectional area, not the shank. So for an M12 bolt, you can't use 12² x PI /4 as the threads reduce the diameter of material available. For a rule of thumb, the threaded area is about 80% of the shank area, but for propper calcs you need to look it up in a book.

So your calc becomes 0.8 x 12² x PI /4 x 1,080N/mm² = 97.7kN. (or about 10 metric tonnes)

Putting my pedant hat on - "metric tons" is an oxymoron - "tons" are imperial, "tonnes" are mteric

Hope this helps.

[bishbosh]

As that link shows, yes it explains grade 8, but no, not available in BSF. To answer your original question tuko, I think, looking from the picture, that you are ok on the length as is. I also used schnorr washers under the boltheads, since there was enough length, but it isn't strictly needed I reckon. Lock tab washers was something else I tried, but they dont work with a pegged diff.

Hmm, memories of desperate times.

Daan

The length of thread engagement will be a function of the material it is screwed into - if it was a nut of the same grade as the bolt, you get the full strength of the bolt if you have the threads of the nut fully engaged - usually you would want one complete thread protruding from the nut to ensure full engagement has been achieved.

With a crown wheel, the material is different to the bolt material - Ian has mentioned a spec but that means nothing to a dull Civil Engineer like me - trust the mechies to complicate things!!!

If the crown wheel material is stronger then you just need the equivelent nut's thickness of engagement. If it is weaker, you will need more....

[Retroanaconda]

Logic is OK, but some fat fingers when you crunched the numbers! (As you have subsequently noticed!!)

For a 12.9 bolt, UTS = 1,200 MPa, not 12,000MPa, therefore the yeild stress = 0.9 x 1,200 = 1,080MPa (MPa = N/mm²)

The only real error is that to calculate the tensile capacity of a bolt you must use the threaded cross sectional area, not the shank. So for an M12 bolt, you can't use 12² x PI /4 as the threads reduce the diameter of material available. For a rule of thumb, the threaded area is about 80% of the shank area, but for propper calcs you need to look it up in a book.

So your calc becomes 0.8 x 12² x PI /4 x 1,080N/mm² = 97.7kN. (or about 10 metric tonnes)

Putting my pedant hat on - "metric tons" is an oxymoron - "tons" are imperial, "tonnes" are mteric

Hope this helps.

Thanks, that's a good explanation. I did the first lot in my head which is why I got the numbers off!

Neglected to account for the threaded diameter too, will bear than in mind. Cheers

[Mr Ian]

Hi Bishbosh what I really meant to say was the crown wheels are 'bl***y' hard in fact a lot harder than your average drill/tap. My pet hate !!!!!! people who don't know ton from tonne. Regards Ian Ashcroft

[Phil Hancock]

Phil,

That I can confirm that they are not. I dug out a RRC 10 spline diff yesterday to compare the bolts and they were 3/8 UNF. The ring gear had clearly stamped in it "UNF". Rechecking my two diff's and ring gears, they have no stamping anywheres to identify the thread patterns, just makings for the matching pinion gear.

Oh, thanks for the info on the letter "T".

Todd.

In that case they are grade T BSF bolts. All this number stuff for bolt grades is a metric thing, imperial uses letters.

http://www.ac2litre.com/fasteners6.html