Underdrive

[dollythelw]

I'm trying to assess the financial feasability of making a batch of underdrives for Landies

I would leave your normal gearing but when operated would give between 17 and 30% reduction to all gear selections, effectively turning an LT77 or R380 into a 20 speed :-)

anyone interested? and whats a fair price? its looking like being around a grand and a bit

Cheers

Jez

[MogLite]

Haven't Ashcroft just re-released their crawler box.

That will give you some competition

[dollythelw]

Ahh Ashcrofts' bought it back out, Didnt see that Andy - cheers

- £1500 + vat hurts a bit though, I'll price it up and see what I can do anyway. Im still not convinced about using planetary gears with torque multiplication in a package like that but its a neat solution, I was thinking more along the lines of a splitter box infront of the main gearbox which would leave the pto open for winch use...

hmm

[JST]

a futher splitter box would also complicate fitting etc possibly needing remote linkage for g + T box etc. i for one would consider the PTO blot on, easy to remove option over a splitter box.

but agreed a splitter box keeps the PTO option open for a winch or . over drive!

[LR90]

Another pricy option but worth a look

Stak Box

[FridgeFreezer]

Something tells me you wouldn't want to drop one of THOSE on your foot...

[simonr]

There is no particular reason why, if you are building one, that you cannot incorporate a PTO drive on the back.

OK the shafts would have to be a different length and tere might be issues with clearance - but it would be worth a shot.

For what it's worth, I agree with avoiding a planetary arrangement - neat though it is - but mostly for cost reasons. The concentric in & out shafts lend themselves quite well to a simple gearbox with a similar selector dog clutch to PTO's which connects the inner and outer shafts together or connects the inner shaft to one of the gears. The gears themselves seem to be about the most expensive bit to manufacture / buy - but an arrangement like this could utilise gears out of a gear/transfer box reducing the expense to the inner spline/drive shafts and a suitable casing.

Si

[will_warne]

Si, AFAIK Ashcrofts buy in the planetary gears in their underdrive. IIRC it comes from a P38 transfer box. I may well be wrong but I have a feeling thats what I was told.

[rick]

I think you're right Will. I also heard the gearset was from a Rangie Borg Warner t/case ?

I know Bill/Daddylonglegs on Outerlimits has made a crawler box using the low range reduction from an original 70's/early eighties Jeep Quadratrac t/case that bolted on the PTO output just like the Ashcroft Underdrive.

The advantage here, other than a cheap gearset from a wrecker, was that the planetary setup locked up in low range, and so didn't generate as much heat as the Ashcroft underdrive. A disadvantage was that Bill cut down the Jeep t/case, and the diameter of the planetary section necessitated a smaller (Series ??) hand brake in place of the LT230 one.