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Can anyone see a problem with the following recommodation by Dave at Ashcrofts it seems to be the answer to my problem ??

With 42 " Tyres Unimog axles & a 3 speed auto basically i need an overall gearing increase of 20% in high & low .

High is not a problem but low cannot be changed aparantly!

So Dave has sujested a Under Drive & run in high range with it engaged as it gives approx the right gearing that i wanted in low range :)

Plus obviously i gain a super low etc.

Any worries ??????????

Thanks F***ker

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Pete had mine fitted for 2-3 years used for events and daily driving,

best ££ spent on the L/R

gives wheel speed exactly the same as the winches pulling so aides momentum

very strong unit compact and easily fitted.

best of all worlds as you keep normal high/Low ranges but add another 2 sets of ratios when engaged.

finally deceents are a breeze rather than a roller coaster ride(unless that is what you want)

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20% bigger tyres?

having 35"s and a tdi mine is underpowered at times when low 1st is too low and low 2nd too high. therefore high range and underdrive engaged and then 1st is a perfect split on my std setup (LT77, LT230) and works well for hill climbs.

guess it depends what the difference is between your high and low range and whether high+underdrive works out 20% higher than normal low.

i have got it wrong though (many a time) and low + underdrive is far too much torque on std LR diffs! mog will be significantly better but thats alot of torque multiplication esp with 42s

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an alternative may be to run a 4 speed box but a three speed 1:1 transfer box- you get 7 separate gears which when used with mog axles and 40"s gives a first equal to somewhere between u/drive 1st and 2nd on a 90, and a high 4th gear just longer than third in a standard three speed rangie (if that makes sense). i have a yank 4 speed auto, a 1:1 t/box, mog axles and 38.5" boots and the gear ratio's are going to be perfect i hope (the calculations certainly suggest that they are going to be useful anyway!)

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Pete, I used to do this to get a 30% reduction on low by using high range and putting the underdrive in. I only used it for short times (some nasty hill climbs) and had no problems. Strength won't be the issue but it might get a bit warm as there's not a huge amount of oil in the underdrive and it'll be used hard. However, if that gave problems I don't think it'd be a massive problems to fit an external oil reservoir.

It'll solve your low range problems but not the high range ones. Oh, and pop it in low / low and the control down hills is unreal.

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or run an atlas 4 speed T case............?
UMMMMMMMMMM !!!!

Looked at that but decided that we be the next truck with all Yank bits this seems the easiest option at the moment <_<

Ill stick with the 3 speed fridge as its rated to 1200hp as it is .The underdrive is really a easy out solution on this truck :D

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so is the atlas, its a bolt on from memory to a TF727 like yours (if theres an adaptor kit needed its gonna be less than $400),it would give you twin stick and 4 ratios.................?

tasty, nutritious and mind numbingly bling... :)

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and faintly expensive too- i think it was quoted at about $1400 + delivery for a nice atlas case.

they would help with clearance around yank gearboxes though, which is a bit of a god send compared to the clearance from an LT230!

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wash your mouth out Mark!!!

:lol:

I contacted Advantaced Adaptor last year & the seemed to know nothing about a box to fit a 3 speed :angry:

Any part No etc

Thanks

Bit late for this project as the underdrive turned up today :blink:

But would be good for reference ;)

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