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Changing from low to high ratios while on the move


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Planning to up the LT230 gearing from 1.667 to 1.41 on my 1987 110 NA 2.5 diesel - currently in bits. One concern is losing hill start capability at higher loadings, and thinking about how the low ratio could be used to help out in this case. So the simple question is, how easy is it to change from low to high ratio while moving? I don't want to end up with a compromised vehicle.

The best written information I've been able to find on this is from the  Army Equipment Support Operation Information manual, Chapter 3 (can't locate where I found this document now!):

5.1.4 Changes from low "L" to high "H" can easily be made without stopping the vehicle as follows:

   5.1.4.1  Depress the clutch pedal and release the accelerator pedal as for normal gear change

   5.1.4.2  Release the clutch pedal for three seconds then depress the clutch again and move the transfer lever firmly into the high "H" position

   5.1.4.3  Move the main gear lever to second gear and release the clutch pedal while depressing the accelerator to take up the drive smoothly

   5.1.4.4  As the vehicle accelerates, change gear in the main gearbox in the normal way

   Note ...

           This operation can be carried out smoothly and quickly after a little practice

I think what is being described here is a garbled account of how to double declutch? And I assume the supposed starting point of the sequence described is low ratio second gear?

My specific interest is in how this works out in practice. Can the ratio change actually be carried out smoothly and quickly or is it a bit of a dogs breakfast?

Anybody out there who actually uses this? 

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Yes can be done, IIRC with a 1.4 low third is roughly equivalent to high first, I generally work up to third low, depress the clutch knock the transfer box into neutral, put the main box to first, lift the clutch, depress the clutch and pull back into high.  in a garbled double de clutch as you suggest. using two hands makes things a little easier I find.

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I tried it and found it better (but not easier) to shift the LT230 in Neutral first.

LT230 in LO

LT77 or R380 in third

clutch

LT230 Neutral

clutch

LT230 in HI

LT77 or R380 in first

clutch release ... done ...

 

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I'd be surprised if you needed to do this as I thought 1st was quite low anyway, and 1.4 isn't exactly super-high geared (it's what most Defenders came with as stock).

Alternatively for heavy loads on hills etc. just stay in low box given you can get up to at least 30-40mph in low 5th.

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As above, you'll rarely need to use low, unless starting on a hill or on soft ground with a heavy trailer.

In practice you can get up to 30mph/5th low and then change to 2nd or 3rd high without a problem. Just takes some getting used to, preferably at lower speeds and without a load. I usually shifted (past tense, it's been some time since I drove a Defender in anger, very happy my P38 will now also shift from low to high on the move) the main gearbox first, keep the clutch disengaged, transfer to neutral, release clutch, declutch again, transfer to high and then release clutch to take up drive. In effect double clutching the transfer case, as it's not synchronised.

Filip 

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Thanks guys for the collective wisdom. I'm probably worrying unnecessarily about the potential downsides of upping the LT230 gearing to 1.4 on my 110, but remember I only have 39BHP at 1,800 RPM - hence the concerns.

So if I need hill start capability at heavy load, I can be pretty certain I'll be able to use the low ratios and not be burning up the clutch unnecessarily.

Thanks all

Phill

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In reality you’ll be busy faffing swapping the low to high and engaging the gears the  lose momentum and after a few attempts, your temper😂

 

By the time you’ve cracked it, you’ll probably run out of hill 😁

  • Haha 1
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6 hours ago, Badger110 said:

you’ll be busy faffing swapping the low to high and engaging the gears the  lose momentum

Yeah I know. I've driven vehicles before now with crash gearbox on all 4 gears, that's not really a problem. Loss of momentum is certainly the thing, and I guess that all comes down to skill and judgement.

41 minutes ago, Mo Murphy said:

21/2 NA diesel is not really the best engine

Yeah I know, but it's what I've got and with only 3,500 miles on the clock it's going to be what I'm working with for the next little while. I'm not really expecting unduly heavy loads ever, but there are fundamental laws of nature that will catch a person out at some point.

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Give it a try 😉

All concerns have been mentioned, so I guess you won't be surprised by anything. If it's going to be ok, it was worth it.

If not, there will only the LT230 have to be changed. That's not too much work.

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I do this fairly often too, as theres a famous light in my town at the apex of a hairpin turn on a steep hill. So if I have to go from dead stop I do the following:

Start in 2nd LO

Get going a bit running thru the gears in LO until 4th or 5th

Clutch>shift main box to N

Clutch>shift transfer case to N

Rev match>clutch>shift transfer case to H

Rev match>Clutch shift main box to 2nd or 3rd.

 

May seem like alot but Im basically always rev matching on downshifts in normal driving just to be as smooth as possible on the entire driveline with my 12J engine so its second nature. 

 

Plus going from LO to HI with a passenger looks pretty cool if you have a passenger hahaha

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