[troopy]

Hi everyone I have pretty much finished collecting parts for building a new comp rig based on a lj80 hardtop but I am trying to decide to stay with the 4 speed auto that came with the g16b or convert it to a sierra 5 speed. The main reason for the new build is to get rid of as much weight as possible and a better centre of gravity.
I plan to run a sierra transfer with 6.5 gears and 60 series diffs with 4.11 ratio but with the manual will there be enough gearing for 40 inch tyres?
I like the flexability of the auto in my current crawler but is it worth the hassels of getting the auto to work in the lj and the extra weight and I'm keen to hear if anyone has any tips on how to keep this thing light.

[alien]

surely the weight added from the auto would be outweighed by the smoothness of the way it drives though?

That and the weight is well low down as well, so its not reallllly going to affect your COG.... 40" tyres would take a fair bit of weight to bag out properly as well, i would have thought building to the load of the tyre's sidewall would be a better option to get the most out of both the tyres and your suspension? (unsprung vs sprung weight).

either way - this thread now needs pics =)

[troopy]

Pics will come shortly but at this stage it is just a collection of parts and and the sad little lj. Building to load the tyres isn't such a concern as if I need more weight then I will just add it to the tyres and run ultra low pressures, it seems almost all the competitive crawlers are getting lighter with lower cog's

[RIKSTR]

Stick with the auto

[MrRocky]

http://www.westcoastcrawlers.com.au/php ... 4&start=75

[Gwagensteve]

Auto.

I'd argue it's almost less hassle because it's already attached to the G16B.

The extra weight is in the best spot too - within the wheelbase and as low as it go whilst still being sprung.

Steve

[LAY80N]

Gwagensteve wrote:

Auto.

I'd argue it's almost less hassle because it's already attached to the G16B.

The extra weight is in the best spot too - within the wheelbase and as low as it go whilst still being sprung.

Steve

+1 - stick with the auto.

Layto....

[Fatzook]

Another vote for auto. As a comp rig it will be far better to drive with the auto. And I reckon the sierra 5sp isn't really up to the task of a G16B long term.

JMO
Peter

[troopy]

Thanks MrRocky I have been watching bazooked build with interest but would the reduction of duals really be needed with 6.5 gears and an auto? My current zook has about 4.2:1 reduction in double low which seems to work well with the v6 and auto. The goal is to keep the zook under 1200kg which is around 500kg less than the sierra truggy.

[Gwagensteve]

I have no experience with the exact setup you are describing, but I have played with some numbers based on cars I do have experience with.

Michael's trolley tug runs 35.5" tyre with an trimatic auto, 6.5 gears and 3.7 diffs.

My standard offroad calcs come out like this:

Crawl ratio 64.39:1
speed@idle in 1st gear 1.98 km/h
speed @peak torque in 1st gear 9.24 km/h

Your setup based on an AW-4, 6.5's, 6.5 gears and 4.1 diffs, I get this:

Crawl ratio 78.62:1
speed@idle in 1st gear 1.83 km/h
speed @peak torque in 1st gear 8.53 km/h

The trolley tug runs a baleno motor - so near enough the same, and the trimatic has a tall converter ratio compared to the AW-4 ( 1.8:1 to 2.4:1)

It crawls fine and always seems to be able to generate wheelspeed when required.

However, your setup will be heavier and have more traction. PErsonally, I think a little bit more gearing would be ideal

Here's the data with 4.88's in the diffs:

Crawl ratio 93.57:1
speed@idle in 1st gear 1.54 km/h
speed @peak torque in 1st gear 7.16 km/h

I think that would be better.

Just my 2C.

Steve.


However,

[troopy]

Thanks Steve that's some very helpful info and after reading it I will stick with the single sierra case with the 6.5s and if it isn't low enough then a diff ratio change should be all I need.

[canberramav]

I can tell you that you wont be able to run the 40's with the 4.1 diffs and Sierra transfer.

Easiest example i can give you is my mates zook.
Baleno 1.6, 3 speed Auto with 6.5 transfer and 4.88 diffs. This runs 37 Trepadors.
His gearing is pretty much spot on. Slighty lower gearing would be good but very im talking VERY slight.

For you to run the 40's i would guess 5.29 diffs would be needed or duals.

This is for a mostly rock crawling setup.

I have duals in my zook. 6.5's in the Sierra box with 4.88 and 5 speed(Vit). I could easily run 40's if i wanted to.

My old zook ran 1.3 GTI with 5 speed Sierra box and 6.5 transfer gears. 5.29 diff centres. I ran 38's with this setup pretty comfortably.

Hope this helps

[troopy]

Thanks very much real world experience is exactly what I wanted to hear as I have only had experience with 6.5s and large tyres behind sierra 5 speeds.I hope to run around a 105inch wheel base but that can be extended a little if needed to fit in duals and still have a decent length rear drive shaft.
Now the big question is then if I go with duals with the sierra case at the rear will it hold up to the extra loads from doubling the torque from the 1.6?

[93zook]

have a read through some of the us sites, some of them still use a 1.6 with a doubler and sierra case

[canberramav]

I just blew up my Sierra transfer case.

Im pretty sure its been in the zook for years though so it was prob about time.

[93zook]

how much can a sierra case tack? how did you blow yours?

[troopy]

Hopefully they can take more than what a turbo g16b puts out

[Fatzook]

troopy wrote:

Hopefully they can take more than what a turbo g16b puts out

That depends greatly on how you drive it.

[troopy]

The ultimate goal is to build it for tufftruck so it will be in for a hard life and I'm not afraid to use the throttle when it is needed but I do have some mechanical sympathy.

[Fatzook]

Well keping it light will go a long way towards keeping the gears in the transfer case

[canberramav]

I did a front dig on a very slippery surface and then when i engaged all 4 wheels again it went boom.

I did have some gear whine before hand so it was prob just its time.

Ill hopefully be able to tell you how its all goes behind a turbo 1.6 in the next few months.