Diff-specific bunfight thread

[Astro_Al]

Ok then, since we seem to have a good few options for centre sections commonly available over here, but without lockers, what does The Panel feel about making a locker for a decently beefy diff that normally doesn't have one?

I thought about spooling it or just welding the thing up, but where's the fun in that?

Maybe a commonly available locker could be adapted to fit, say, a BMW diff? Or perhaps its easier to start from scratch?

Come on - lets hear it!

Cheers, Al

[bill van snorkle]

Ok then, since we seem to have a good few options for centre sections commonly available over here, but without lockers, what does The Panel feel about making a locker for a decently beefy diff that normally doesn't have one?

I thought about spooling it or just welding the thing up, but where's the fun in that?

Maybe a commonly available locker could be adapted to fit, say, a BMW diff? Or perhaps its easier to start from scratch?

Come on - lets hear it!

Cheers, Al

ARB manufacture a wide range of difflocks in various sizes, some of which may be modifyable for Beemer diffs. Trouble is, even around the corner from here at the factory where they make them, no one will let you in with a tape and vernier to measure anything. Even straight forward requests like fitting 1 1/2'' 35 spline dana 60 side gears to their Landy Salisbury Type airlockers was too much for their very computer reliant packaging system to cope with when I tried afew years back.

Bill.

PS. Never seen one but how would Audi Quattro diffs go ? I believe some of those had selectable lockers.

[Lewis]

Why not use the Dana diff as fitted to recent independant suspension Land Rovers such as Discovery 3 or Range Rover Sport, in the rear application these have e-lockers as standard

Lewis

[Astro_Al]

Bill - typical. If I post you a balaclava, bolt cutters and a glow-in-the-dark vernier, how much will it cost me to get you to do some 'noctural research'?

Lewis - I have no idea. Any idea how beefy they are? What would be the max torque, tyre size and vehicle weight they are recommended for (i.e. come in as standard)?

Cheers, Al.

[Lewis]

Up to 1000Nm of torque, through 27" tyres, Disco3 weighs 2700kg empty and is rated for a max train wieght of 6300kg which I assume is a conservative figure

[dirtydiesel]

Ok then, since we seem to have a good few options for centre sections commonly available over here, but without lockers, what does The Panel feel about making a locker for a decently beefy diff that normally doesn't have one?

I thought about spooling it or just welding the thing up, but where's the fun in that?

Cheers, Al

A sliding locking dog engagement on the long half shaft would be very easy to achieve if you were already having custom shafts made.

Real easy to machine if you use actual tube for the axle tubes, if i were to go about it i'd be copying the G setup as it's hellishly simple.

[Astro_Al]

Thanks for the numbers Lewis.

Is that engine output torque, or diff input torque? (I guess the latter, but just to be sure!)

Ok the tyres are TINY, but I'd less than double the radius (bad) and then compensate with the 2:1 portal reduction (good). So they could cancel each other out-ish.

Vehicle weight would be WAY down on those numbers. But if the torque is indeed diff input torque, I could be struggling on that. The last thing I'd want is to get custom shafts made to suit a chosen centre section and have it spitting teeth under the engine torque.

Dan - yes the shafts would have to be custom, so the opportunity is there to use a bit of imagination.

Got any Gs torn down for some photos? (Longshot ).

Al.

[dirtydiesel]

Thanks for the numbers Lewis.

Is that engine output torque, or diff input torque? (I guess the latter, but just to be sure!)

Dan - yes the shafts would have to be custom, so the opportunity is there to use a bit of imagination.

Got any Gs torn down for some photos? (Longshot ).

Al.

Lewis's numbers are at the crank!

It's your lucky day on the G's what do you want to see?

[Bush65]

... they (the shafts and cv's) are not as a result twice as strong (only around 30%)...

Not a good explanation or you suck at maths.

Now others inferred portals make the axle shafts and diff "twice as strong", which is strength x 2.

To convert to percentage you multiply the fraction by 100 so 2 x 100 = 200%.

Your 30% is obviously wrong, but I can't decide whether you meant 130% (ie. x 1.3), which still seems to be too low, or something else.

Would not an engine develop peak torque only when there is sufficient resistance,ie load to allow it to do so? one would hope that wheel spin would occur well before the engine was asked to develop maximum torque if the vehicle was in low range first gear. even in my own case with just a puny 2 1/4 litre petrol engine developing a paltry 115 lb ft of torque operating in low low crawler with an overall reduction of 278 :1, I could theoretically develop enough torque ( almost 32000 lb ft) to turn some of the strongest axles into shrapnel, but hopefully traction will always fail before the situation gets anywhere near that stage .

Bill.

Yes power and torque developed, both depend upon load.

In rock, you can get into situations where the tyre gets wedged into the rocks and traction is then greater than the weight on the wheel. But from my limited experience in mud I can't imagine any situation where you will have any traction better than half (or 50% ) the weight on the tyre (probably much less).

Regarding shock loads and strength of axle components.

IMHO, the worse situation for off road vehicles is the wheels spinning at high speed with a locked wheel off the ground. Then after moving a little the wheel that was in the air, suddenly comes down and impacts with the ground.

The rotational inertia of the spinning wheel contributes a lot to the shock load. And remember that larger diameter tyres have more inertia.

Regardless of portal boxes or not, the energy of the shock load is largely converted to strain energy in the drive train (and Simon, the portal box can not increase the energy - you need to think about the laws of physics and creation/conversion of energy).

The exercise in increasing the impact strength of axle components is one of detailing the components to maximise the amount of strain energy which can be absorbed, within the allowable stress of the materials.

To get back on topic. Because mog portals are 2 gear type, the diff has to rotate in the opposite direction. So it is important to remember that if you use a normal diff, from a non portal axle, it will have to be flipped (to reverse the rotational direction) and then, lubrication of the pinion bearings will have to be addressed.

[dirtydiesel]

Not a good explanation or you suck at maths.

Now others inferred portals make the axle shafts and diff "twice as strong", which is strength x 2.

To convert to percentage you multiply the fraction by 100 so 2 x 100 = 200%.

Your 30% is obviously wrong, but I can't decide whether you meant 130% (ie. x 1.3), which still seems to be too low, or something else.

I suck, both at maths and explaining stuff.

The 30% thing was expained to me by a grown up, and as such i don't claim to be able to back it up with numbers,

But i do have a growing pile of bit's my "choughs-and-snezel" shouldn't have been able to break if the 100% stronger thing were correct.

To get back on topic. Because mog portals are 2 gear type, the diff has to rotate in the opposite direction. So it is important to remember that if you use a normal diff, from a non portal axle, it will have to be flipped (to reverse the rotational direction) and then, lubrication of the pinion bearings will have to be addressed.

I am really not sure how much of a problem this really is. i know of quite a few compers that run salisbury upside down with no issues.

And at least in my case, the use that my car actually gets; 2 events a month(max) and zero road miles, i think it'd take an eternity for any problems to arise.

[dirtydiesel]

opps double post

[SOA 93]

A picture is worth a thousand words ........ http://performanceunlimited.com/illustrations/gears.html

http://performanceunlimited.com/illustrati...frontaxles.html

[bill van snorkle]

A picture is worth a thousand words ........ http://performanceunlimited.com/illustrations/gears.html

http://performanceunlimited.com/illustrati...frontaxles.html

I have a theory that the severe pressure angle of the crownwheel teeth on 9'' Ford diffs would give the the carrier bearing supports in the pinion housing a very hard time when driven on the coast side as in front diff application or in reverse in rear application. Most production 9'' pinion housings are made from cheap, nasty and brittle grey iron. I have seen some spectacular 9'' pinion housing failures that IMO could only be attributed to coast side thrust.Perhaps you John (Bush 65) could comment on this?

Bill.

[Astro_Al]

Dan - ta for the pm (I was travelling, so too late...).

Regarding G pics - any locker details, (locked / unlocked) general internals / sizes of pinion shaft / gears etc.

Ratios???

Bush65 - yeah I know about the flipping and pinion oiling - I'd be looking to include some oiling for the nose bearing.

Bill - I thin I'd be pushing my luck running on the coast side, unless it was a massively sturdy diff in the first place. I was leaning towards a reverse rotation gear set, but it kind of flies in the face of the cheapo options plan.

Interesting point about the side thrust - they are pretty weird looking gears!

Cheers, Al.

[bill van snorkle]

I rebuilt a hub reduction type differential from a 10 ton MAN bus today at work. Very compact and light for the type of vehicle it was fitted to. It had 9.25'' dia crownwheel and the housing would give a bit more ground clearance than a Salisbury, and was already set up for difflock.The carrier, bevel gears and cross shaft was a bit smaller than a Landy Salisbury.The crownwheel and pinion looked virtually unbreakable but unfortunately the ratio of

1.5:1 is a bit tall for portal application.

Bill

[Superpants]

There is quite a lot of useful information on lockers, including the e-locker at:

Eaton Diffs

Click on Manuals for more information!

[simonr]

I was thinking today about how one could make a simple locker - and came up with this.....

Imagine making a cylinder which fits into the space in the middle of the spider gears where the pins normally cross (in the case of a 4 pin diff). The outside of the cylinder is drilled to accept pins to hold the spider gears in place.

The axis of the cylinder is drilled and splined with the same spline as the end of the half shaft with a chamfer on the lip of the spline to guide the shaft in.

The mechanism of locking the diff is simply to slide the half-shaft in a bit further such that it connects to the side gear and the spider gears at the same time.

The sliding half shaft could be moved by a knob on one drive flange (for a real budget option) or electromagnetically.

OK, this would only be possible on the back - but the back is where you most need a locker.

It's low cost because you can re-use the original diff housing and spider gears (2 or 4 pin), just replace the pins and make the bit for the middle?

Waddya reckon?

Si

[bill van snorkle]

I was thinking today about how one could make a simple locker - and came up with this.....

Imagine making a cylinder which fits into the space in the middle of the spider gears where the pins normally cross (in the case of a 4 pin diff). The outside of the cylinder is drilled to accept pins to hold the spider gears in place.

The axis of the cylinder is drilled and splined with the same spline as the end of the half shaft with a chamfer on the lip of the spline to guide the shaft in.

The mechanism of locking the diff is simply to slide the half-shaft in a bit further such that it connects to the side gear and the spider gears at the same time.

The sliding half shaft could be moved by a knob on one drive flange (for a real budget option) or electromagnetically.

OK, this would only be possible on the back - but the back is where you most need a locker.

It's low cost because you can re-use the original diff housing and spider gears (2 or 4 pin), just replace the pins and make the bit for the middle?

Waddya reckon?

Si

I made a few Salisbury difflocks for 101 Landies that had a short length of splined shaft riding in the splined cross shaft that when locking the diff wouldbe slid over to engage with a side gear which had its halfshaft shortened by 1/2''. the other end of the short splined shaft was flanged onto which 3 hardened steel pins riding in holes drilled through the other side gear pushed this stub shaft into lock mode. 2 small return springs rode in holes drill drilled into the cross shaft and pushed against the flange to unlock this diff. This difflock was activated by a hollow pistoned pneumatic cylinder inside the axle tube concentic with the halfshaft . I feel it was the generous dimensions of the Salisbury that made this design feasible, and it may not work on a smaller diff.I still have a 24 splined one in the shed at my bush block. I may pull it down for a photo shoot one day .

bill.

[simonr]

Feasible then! Mine relies on the splines on the half shaft being long enough to allow it to slide such that it engages - which may mean making a new shaft (best avoided).

Si

[bill van snorkle]

Feasible then! Mine relies on the splines on the half shaft being long enough to allow it to slide such that it engages - which may mean making a new shaft (best avoided).

Si

If you have to make a new halfshaft, why not make it long enough to engage with the opposite sidegear and displace the halfshaft on that side by half an inch? That way you won't have to internally spline the cross shaft. Had them on some converted Transit diffs a few years ago.

Bill.

[Bush65]

Bill, didn't Jack McNamarra make a locker similar to this?

I've only seen them from the outside - screw in a bolt to lock the diff.

[dollythelw]

wouldnt the practicalities of engaging the sliding shaft (in terms of spline aligment) make the longshaft VanSnorkal-o-diff a non-starter?

[bill van snorkle]

John, The early McNamara difflock,which I had a a very large hand in designing whilst in their employ all those years ago, was activated by sliding under pressure from a coil spring one halfshaft, which was made about 1 1/4'' longer with longer splines, into engagement with matching internal splines the spider cross pin. By todays standards it was crude, but it was simple, and it was the first ''aftermarket'' selectable difflock available (circa 1978) for anything.

Jez, The other one I suggested in the above post, re Transit diffs works in a similar manner but does away with the cost of broaching a spline in the spider cross . So long as the axle assembly is straight and trueand wheel bearings snug, both types engage easily enough under spring pressure, but axle windup needs to be releived before they can be disengaged. In practice it was advised to lock the rear diff upon entering the offroad area, leave it locked for the duration and only unlock it once back on sealed roads where it is easier to jack up a rear wheel to releive windup and disengage the lock.

Bill