[tanshi]

I asked this on facebook and got a few good responses but thought id throw it up on here.

im hoping this just doesn't turn into a drop shackles vs no drop shackels conversation.

the gist is this im building a crawler/ aust4 racer.

Im running a h27a v6, looking at 4 speed Vitara auto, or similar, lt230 transfer case. and 60 series diffs.
the motor with 130 odd kw and 160NM odd has a bit of power, but its not exactly a 500nm v8.

the first gear on the auto is 2.8:1, low range in the LT is 3.32:1 and the lowest diffs I can get are 5.29s.

this will give me a crawl ratio of about 49:1. on 37s or indeed 40s will this be enough gearing. Personally id like to see 70:1 +

some people have said yes, and some have said no.

my other option is to either put maxi drive reduction in the LT case or run a dual case of some sort to get me some more crawl.

[Gwagensteve]

I'd like to see more than 49:1 too, but I don't think its going to be as bad as you think. With converter ratio (2.4:1 from memory) your effective ratio is 112:1 when the trans is loaded and you're under stall speed of circa 2500rpm

If your numerical gearing is too short this effect basically disappears. With my 99:1 numerical I can't load the converter up enough to make the gearing elastic under load.

[Gwagensteve]

Oh, and drop shackles.

[tanshi]

I could in theory run a Vitara/xl7 transfer as a dual case to give me that extra gearing.

just not super sure how the case would deal with that punishment

[Gwagensteve]

The lt230 case will take it.

[tanshi]

I know the lt will. but not sure the zook case will.

eventually im planning on doubling the power and torque from the motor.

racing it is gonna be a lot about reliability.

I could run reduction gearing in the LT I suppose but at nearly 2k for gears id be better off buying an atlas

[Gwagensteve]

Build it at 49:1 and see how you go. I reckon it will be better than you think.

[dank]

tanshi wrote:

eventually im planning on doubling the power and torque from the motor.

racing it is gonna be a lot about reliability.

Those two lines contradict themselves. Anyone I can think of that has gone down this path ends in pain.

[SierraDan]

The green car runs 53:1 with a 3.8 and climbs well.
A little more gearing might be desireable on the odd occasion to get more feel in the technical stuff.

[tanshi]

haha yeah I know dan. that's why im wanting to build it right first.

then I can decide once if driven it if it needs more.

[christover1]

I find the huge gap between 1st and 2nd on my Vitara auto to be a pain.
It screams in 1st, and almost dies when it pops into 2nd.
Rest of ratios seem good.
No idea if that is an issue for you with much more motor.
You may never need 1st.

[tanshi]

Im looking at options for a reduction box. I should be able to have a stupidly low low range. of about 100:1 with the converter on top of that.

but still have the 50:1 in the normal ranges with it disengaged.

[Gwagensteve]

You might want to send Bill Larman a message on FB. I think he has made a reduction box that goes on the back of the lt230 that uses a quadratrac planetary.

[tanshi]

thanks steve. might just do that.

ive found some examples of what I want to do, just need to find the right planetary

[MrRocky]

I was running 4.1 diffs with 6.5 gears and 32"s, i still found i was wanting to go about half as fast as that in 1st low in quite a few bits of technical driving but its always a compramise on a multi terrain type vehicle unless u throw more money than i had at it haha

[pezz]

Could a atlas 4 speed transfer be the answer

[tanshi]

atlas 4 speed is basically a two speed box with an underdrive strapped onto it.

that is pretty much what ill be building If I go with a reduction box

[Gwagensteve]

Mr Rocky, was that with a manual?
Autos can go a LONG way to "smudging" gearing deficiencies over, up until the point stall speed is reached.
I've driven a car with 35's, 3.9 diffs and 4.1 case and it crawled flawlessly, even though on paper the gearing was terrible That's 40.6:1 X1.8 converter.
Felt a bit quick once the converter was stalled up, but it was nowhere near as bad as you'd think.

Hence the reason I'm thinking with the deeper 1st and bigger converter ratio of the AW/4, and miles more HP than an anaemic G16A, 49:1 might be workable. Depends a bit on the overall weight of the car though. Another possibility might be a looser converter. A higher stall speed will allow more revs for the engine to build torque before it stalls up so it would aid drivability off road as well as improving acceleration.

All up though, I think the biggest enemy of the build isn't going to 49:1, it's going to be the weight of the finished car and the torque delivery of the H27.

Steve.

[tanshi]

any idea what a jimny TC has in the way of torque multiplication ratio?

[Jezza86]

before or after it fails?

[tanshi]

I have a sierra with a jimny auto in it, has been working fine for really hard wheeling for 3 years now

[Gwagensteve]

I think they are about the same as a AW-4.

Steve.

[MrRocky]

Yeah that was manual steve, i do feel an auto would be the box of choice for the type of driving i do but 100km phr on the twisty gravel to get there means a manual has its place there so its a compramise i spose

[Gwagensteve]

Gregc is up to about 7 or 8 years of wheeling on his Jimny auto and it's fine. ran 4.1 case and 5.12's for a while, now 6.5:1 case. Runs a gauge and loads of cooling.

Has a spare auto but it's never looked like it's going to give any trouble.

Steve.

[vet 180]

Hmmm in your engine thread I thought the h27 would be a good idea, but now hearing about the "duel" capabilities of the engine I am starting the think the vq40de and 5 speed auto gearbox would be a better option.

The automatic trans ratios look like this:

3.842
2.353
1.529
1.000
0.839

Unfortunately the transfer case is only 2.652 in low range so 54:1 in first gear, but the low end torque of this engine is great. It will also have a higher top speed in low range, but lower top speed in high range. Thats just with a full half cut slapped in engine box transfer.

It will have a lower crawl gear than with the vitara box with its 3.3 transfer and 2.8 low gear and also have more top end for the "racing work" and a better spread through the gears. The engine makes a very reliable 266hp, is very light (would be heavier than the H27 though) and is much better option if you want to "modify" you h27 later. In the end it will save you money as modding the vq40de will be cheaper and more reliable (in reference to you wanting to double the power and torque of the engine).

Otherwise reduction box will be a good option

[sideways]

tanshi wrote:

any idea what a jimny TC has in the way of torque multiplication ratio?

"More than 1.7" according to the manual.

[riley]

Darren , the hot lap you did at jenowan with hillbilly .....you never got out of low range, and that's 5;1, and with 160 hp we struggled to hold top gear, we are refitting the old bunzuki with a 5ltr for aust4 next yr, and we will be running the lt230. But with only 37's...you have a hard decision to make.and for the record ,seeing as it was never posted on here, the hillbilly suzukilj80 won overall in the aust4 series, not bad for its first year of competing