Crawler Gears

[Mr Noisy]

Grrr now I'm doubting myself thinking I got my maths wrong.

It's going back a month or so but I distinctly remember thinking "oh" for some reason and then needing a chance of tack, to look for a 1.2 instead!

[Mr Noisy]

Yeah just looked on Ashcroft site, 1.0-4.75 is slightly higher than 1.4-3.54 whereas 1.2-4.1 is near as damnit same

That must be it

Plus

Gives me headroom for larger tyres by easily changing diff ratios I guess

[LowRanger]

What do you mean by "more robust than an underdrive" ? I wasn't aware of any weakness with the Ashcroft underdrive, and I would have thought them to be very much longer lived than any 4.7 ish Rover type diff.

I agree with Bill.I have had my Underdrive for a few years now and every time I go out it gets used.It gets used climbing large rock ledges that are the normal here in the Great Dividing Range on the East Coast of Australia,and the vehicle runs 36" tyres and certainly puts a lot of strain on the whole drive train,but I have chosen parts carefully and have found the Underdrive to be perfectly capable of handling whatever I dish out to the vehicle.So much so,that I bought a second one and fitted it to my 130HCPU Tourer,that also runs on 35's,for those times when you're out touring and you're looking for that lower gear

4.7 Rover gear sets would be a far weaker prospect in my opinion,but each unto their own.They may be ok if you just play in mud puddles,but they don't like shock loading.

[Bowie69]

Ashcroft 4.7s are a completely different kettle of fish....

[bill van snorkle]

Ashcroft 4.7s are a completely different kettle of fish....

Yes they are, but there is only so much that can be done with the Spiral Bevel design, especially in the lower ratio options.

[LowRanger]

Ashcroft 4.7s are a completely different kettle of fish....

Now I wonder if we ask Ashcrofts which they have broken more often,which one will they say?

[Mr Noisy]

Seeing as all the pinions are the same, I guess the more teeth on the crown the weaker it will be, hands down.

[Anderzander]

Or we petition Ashcroft to make another batch of crawler gears - to obviate the issue entirely.

Please !!!

[bill van snorkle]

Or we petition Ashcroft to make another batch of crawler gears - to obviate the issue entirely.

Please !!!

I believe the successors to Maxidrive still make reduction gear sets for group purchases, and a lr4x4.com group purchase would save a bit on freight costs to the UK too I would think.

[simonr]

If you can obtain some of the details about the crawler gears, I know a very good and surprisingly good value gear cutting company. They make some of the bits for Delta-Tek as well as some very big names.

Might be worth having a chat as it's right up their street.

Ping me a PM if you want the details.

Si

[Anderzander]

I'd love to Si - but I don't have the details... beyond:

The 30% gears are apparently tooth count as follows:

Input/Intermediate/Low-Int/Low

26/41/20/55

The low gear for the 30% set in overall diameter is 181 mm.

Picture of the kit a few down here :

http://www.pirate4x4.com/forum/land-rover/213796-maxi-drive-crawler-gear-installed.html

[Anderzander]

Bit more detail here : http://www.landroverclub.net/Club/HTML/Ashcroft_Underdrive.htm

[Lewis]

Double post

[Lewis]

If some kind of group buy or batch goes ahead I'd be interested in a set too

[Anderzander]

I've dropped them a line to ask about a group buy and also what difference sending them your intermediate gear to be modified makes.

I'll post up the reply.

[uninformed]

dont forget that the MD crawler gears are available in either 30% or 49% lower low range.

[Mr Noisy]

Bummer reading this thread after just putting much time and effort into rebuilding a 28 tooth LT230

[Les Brock]

Ashcroft underdrive also only fits a 26 tooth box ....dont ask me how I know lol

[Snagger]

What do you mean by "more robust than an underdrive" ? I wasn't aware of any weakness with the Ashcroft underdrive, and I would have thought them to be very much longer lived than any 4.7 ish Rover type diff.

Salisbury rear or p38 Rover 4-pin diffs with KAM or Ashcroft gears would be damned tough, especially if you pegged them, and have less to go wrong than an underdrive or overdrive - less splines, bearings, shaft and gears in the overall system mean that the transmission has to be more robust. I have no doubts about the underdrive, but its only advantage to the above would be its flexibility in being selectable rather than fixed.

[Mr Noisy]

Ashcroft underdrive also only fits a 26 tooth box ....dont ask me how I know lol

Indeed

Alas, if I got to needing/wanting one I would simply prepare another LT230 for the task, they are damned cheap to get hold of.

As someone who does predominantly operate at the higher end of the low ratios I would much prefer underdrive to low range gearset.

[bill van snorkle]

Salisbury rear or p38 Rover 4-pin diffs with KAM or Ashcroft gears would be damned tough, especially if you pegged them, and have less to go wrong than an underdrive or overdrive - less splines, bearings, shaft and gears in the overall system mean that the transmission has to be more robust. I have no doubts about the underdrive, but its only advantage to the above would be its flexibility in being selectable rather than fixed.

I've observed over the decades that I have been involved in 4WDrives, that components considered to be strong and reliable in the UK are marginal at best and very fragile at worse on the generally drier, harder, steeper and less refined offroad tracks/trails in our more mountainous regions here. Salisbury diffs are fine even in the lower ratio variants, but you also have to change the front CWP. History, and often bitter experience has shown that the Rover spiral bevel CWP's are just too fragile for serious offroading on decent tyres once the ratio is dropped much below 4.1 :1. P38 diffs with their more closely spaced pinion bearings are not a particularly good example when it comes to building a "damned tough" differential.

I agree with Wayne (Low Ranger), that just like difflocks, and a balanced, flexible suspension system for truly serious offroading , once one experiences the benefits and versatility of a proper underdrive, which basically gives a 4speed transfercase, there really is no going back to the standard arrangement. 30% reduction gears give around 60 :1 low range vs around 120-130 :1 for the Ashcroft unit. In certain instances a 4.3:1 permanent low range ratio is too low for intermediate difficulty terrain where high range won't pull, and the straight cut gears are quite noisy and possibly not quite as robust and long wearing as the original helical gears.

[LowRanger]

I've observed over the decades that I have been involved in 4WDrives, that components considered to be strong and reliable in the UK are marginal at best and very fragile at worse on the generally drier, harder, steeper and less refined offroad tracks/trails in our more mountainous regions here. Salisbury diffs are fine even in the lower ratio variants, but you also have to change the front CWP. History, and often bitter experience has shown that the Rover spiral bevel CWP's are just too fragile for serious offroading on decent tyres once the ratio is dropped much below 4.1 :1. P38 diffs with their more closely spaced pinion bearings are not a particularly good example when it comes to building a "damned tough" differential.

I agree with Wayne (Low Ranger), that just like difflocks, and a balanced, flexible suspension system for truly serious offroading , once one experiences the benefits and versatility of a proper underdrive, which basically gives a 4speed transfercase, there really is no going back to the standard arrangement. 30% reduction gears give around 60 :1 low range vs around 120-130 :1 for the Ashcroft unit. In certain instances a 4.3:1 permanent low range ratio is too low for intermediate difficulty terrain where high range won't pull, and the straight cut gears are quite noisy and possibly not quite as robust and long wearing as the original helical gears.

As Bill has stated,it is the versatility of an Underdrive unit,be it Ashcroft or something like Bill has manufactured previously,that makes it so much better.You get to maintain the standard ratios and have various selectable ratios as the situation arises.Maybe this isn't so important when setting up a vehicle for British conditions or when just looking for a Challenge event vehicle,but these extra gears come into their own when climbing metre plus rock steps and boulders up a steep incline.This is the type of terrain that the serious guys in this part of the world like to drive,and having driven with guys with lower transfer ratios and then tackling the same terrain with the Underdrive,I like the ability to select the gear ration for the moment,and not just having to make do,and only running a 200Tdi that makes no power and running relatively big rubber,the added extra low ratios allow the truck to work a lot easier and reduce wear and tear on the vehicle.No need to stick the boot in to get it to climb,just let the gearing and the suspension do the work it was designed to do.And when you are descending very steep tracks with large steps etc,the ultra low ratios make it a much more pleasant thing to do,when you don't have to worry about holding the vehicle back on the brakes and risk locking wheels and sliding out of control.And the Underdrive has the added advantage that it is a fairly straight bolt in application,as long as you have a 26tooth transfer,certainly a lot easier than fitting a gear set to the transfer and also easier fitting a second transfer or adapting an Atlas etc.

None of the ways to reduce the gearing is cheap to do,but people should just do what suits their particular application for their vehicle,but for those considering the lower tranfer ratios for a road driven vehicle,be advised that they howl like a banshee,where you wouldn't know the Underdrive is there,if you didn't see the operating lever.

[Les Brock]

I loved the underdrive on the Trayback for challenge events , so I just had to have another, luckily I had Will Warne's one off him.

IIRC dont also have the torque multiplying effect on your drive gear as well

[bill van snorkle]

I loved the underdrive on the Trayback for challenge events , so I just had to have another, luckily I had Will Warne's one off him.

IIRC dont also have the torque multiplying effect on your drive gear as well

So what is the latest on the Warnemobile ? Did it ever get completed ? Or is it just Warne out?

[FridgeFreezer]

Bill - I suspect that, as you say, dry hard rocky grippy terrain puts a lot more strain on things than the "european" style muddy / loose / wet surfaces. Certainly in the UK there's nowhere you can do what many would call proper rock crawling. There are a few sites, such as Seven Sisters, that have rock runs, but they're relatively limited and rarely perfectly dry & grippy compared to slick rock or the sort of terrain you get in Aus & the US.