[wolfyy395]

I just bought my zook on boxing day, it's a Sierra 90 JX widetrack G13A running 31" Summit Mud Hog's.

Yesterday i replaced the following;
Bearings,
Spark plugs,
New oil & fuel filter,
Engine, diff(s), gearbox & transfer case oil
Lubed the crankshaft nipples
Idler pulley
Fan belt

I drove up to lancelin today, thrashed around the dunes for a while & headed home.

I had 3/4 tank before heading up & was pretty much empty once i got there, i put $30 (21L)
on way home had to stop off at guilderton and put another $20 (12L) in, got home and it was empty again..

total journey was 320km's

surely it shouldn't be using over 50L of fuel for 320k's ???...

Any suggestions on what to do to increase milage?

Another thing, now i know zooks aren't the fastest things in the world, but i could literally not get it into fifth gear.
I was foot to the floor in 4th pretty much all the way there and back, it's literally impossible to get it over 3500RPM, getting into fifth gear dropped to about 2600RPM
and would not raise at all, i'm not sure whether or not its a gearing issue, tyre size or just that all zooks are like this?

[sideways]

31s with no gearing will do that. I don't think any 1980s 4wd would still have a useful 5th high after going up 5" in tyre size. If you're going off the odometer reading then your big tyres will be throwing that off by about 18%, so you'l have actually gone 18% further than it says.

If you're having trouble making power higher up;

If it's running the original exhaust get it replaced, it'l be well buggered by now.
Check your vacuum secondary is working properly. The vac sec line on every 1.3l carb I've rebuilt had lost tension and would have leaked, reducing power.
Fuel pump could be dying, they seem to do that around this age.
Check your dizzy advances like it should, I had one that didn't.

Get some transfer gears (or diff gears if all you drive is sand and road) if you want proper highway performance. Properly geared a reasonably healthy Sierra on 31s wont have to many issues cruising at 110.

10-11l per 100 on the road is pretty normal for a Sierra on 31s. Obviously you'l use more on sand.

[wolfyy395]

sideways wrote:

31s with no gearing will do that. I don't think any 1980s 4wd would still have a useful 5th high after going up 5" in tyre size. If you're going off the odometer reading then your big tyres will be throwing that off by about 18%, so you'l have actually gone 18% further than it says.

So, in regards to gearing, how would i go about getting this looked at & altered, I'm planning on doing a lot of off roading hence the zook purchase, so ideally I want something that would cruise along easily at 100 but be able to crawl over rocks and other obstacles with little difficulty.

I was told that the speedo would be thrown off by about 10km/h, but for the route I took it was 158 there and back, wouldn't image 6 hours on the dunes ( 1.5 bogged hard) would've made too much of a difference, wasn't going too hard on the ole' gal on the dunes, but it was ridiculously hard trying to cruise at even 90 ( 80 on speedo ) on the way back.

sideways wrote:

If it's running the original exhaust get it replaced, it'l be well buggered by now.

I think it's had extractors installed, would this mean aftermarket pipe?

[sideways]

wolfyy395 wrote:

sideways wrote:

31s with no gearing will do that. I don't think any 1980s 4wd would still have a useful 5th high after going up 5" in tyre size. If you're going off the odometer reading then your big tyres will be throwing that off by about 18%, so you'l have actually gone 18% further than it says.

So, in regards to gearing, how would i go about getting this looked at & altered, I'm planning on doing a lot of off roading hence the zook purchase, so ideally I want something that would cruise along easily at 100 but be able to crawl over rocks and other obstacles with little difficulty.

I was told that the speedo would be thrown off by about 10km/h, but for the route I took it was 158 there and back, wouldn't image 6 hours on the dunes ( 1.5 bogged hard) would've made too much of a difference, wasn't going too hard on the ole' gal on the dunes, but it was ridiculously hard trying to cruise at even 90 ( 80 on speedo ) on the way back.

Get some 6.5:1 (or 6.4, 5.14 ect) transfer gears from lowrangeoffroad.com or somewhere like that and get them fitted by a transmission rebuilder or a Suzuki specialist. That will make your high range like stock and your low range 187% lower than it is now.

Your speedo should be roughly 18% out, but that assumes it was accurate to start with which is unlikely. GPS it to check.

wolfyy395 wrote:

I think it's had extractors installed, would this mean aftermarket pipe?

Probably, but not necessarily.

[wolfyy395]

sideways wrote:

Get some 6.5:1 (or 6.4, 5.14 ect) transfer gears from lowrangeoffroad.com or somewhere like that and get them fitted by a transmission rebuilder or a Suzuki specialist. That will make your high range like stock and your low range 187% lower than it is now.

So essentially, it'll have more pickup in the lower RPM, but evens out in higher RPM?

[sideways]

You'l be doing more RPM which will allow you to go faster because you'l have the torque to actually achieve that speed.

[wolfyy395]

Thanks for the help, i think i'll be investing in 6:5:1's so i can cruise normally.

[brookesy]

On the way back from Lancelin in the arvo you would likely have been heading into the sea breeze... This and the small hills on the way back won't help much with the fuel consumption either.

[Moph]

My tintop ran around 10.5L/100km stock, increased to about 11.5L/100km with 235/75R15's and is currently running around 12.5L/100km with 31" muddies, 2" body lift, 6.5 transfer gears and a reasonable amount of weight (steel bullbar, rear shelves, fridge and a heap of tools/recovery gear). Chucking the trailer on the back bumps me up to around 13.5L/100km. You can't really expect a carbied 1.3L engine pushing something with the aerodynamics of a brick to be thrifty

As far as your gearing goes, you will definitely want to do something with either your transfer gears or diff gears if you're going to keep the 31's. Driving on 31's with stock gearing is truly horrible.

With my setup, I run about 13* advance with 98 RON and can hold 110km/h in 5th on the freeway without drama (hills excepted). With standard 10* advance and 91 RON fuel I really had to be in 4th to keep at 110km/h most of the time. Running premium isn't an issue for me as it's a toy not a daily driver.

[alien]

As everyone said above...

Your speedo is likely out by about 10-15%. Mine with new 31's was out by about 12%. I had it corrected and GPS checked and it now reads 60km/hr when i'm doing 58km/hr... or 103 doing 100.

Keep in mind also, the 1.3 loves to rev! Most people try to drive around 2000rpm, that just doesn't work in a sierra. Life begins at about 3000rpm. It will happily sit on 4000rpm all day long.

Before diving into gearing from Lowrange - wait until the 5th Jan and talk to Brian at Suzistore. He may have some 6.5's in stock and be able to fit them nice and fast as opposed to waiting god knows how long for lowrange to despatch and deliver!

Also Regarding the speedo - go to Applied Instruments in Balcatta. They can modify the speedo to suit your tyre size - they do this by removing the cluster and modifying the spring. Costs about $100 IIRC.

One last thing to keep in mind - if you install reduction gears in the tcase, you WILL want to brace it. Lowrange and a few other places sell cradles etc to do this. If you don't, the extra torque will just rip through your transfer mounts! Also - your sierra looks quite lifted - check that your driveshafts have enough spline engaged when flexing, and that your brake lines are long enough. Last thing you want is to be in the middle of nowhere and lose brakes or bust a driveshaft.

[AckerDackerly]

Nice truck!

Try the gear calculator at Ack's FAQ - http://acksfaq.com/gearcalc-01-04-07.php to play with the gearing values on a Sierra/Samurai.

Measure your tyre diameter so that you can plug that value in and get a an accurate ground speed at different engine RPMs and gearing.

I had your problem with my '88 SJ413 equipped with a G16 8-valve on 30" BFG AT/KO mud terrains. It was fixed with a set of TWO FRONT AXLE (rear difs will not work) 4.625 ring and pinion gears out of a 1st- or 2nd-gen Vitara (what we call a Suzuki Sidekick or Geo Tracker in the States) and a set of spider gear pin "cans". You may be tempted to use the entire aluminum third member (they do actually swap if the sidegear spline counts match!) but hard wheeling will cause the case to shatter.

This mod gave me back 5th gear while keeping the improved offroad capabilities.

Transfer case gears will do the job, but you might be able to save a lot of money going the differential route because shipping and customs from the USA might raise the price a lot. On the other hand, 4.625 (automatic gearboxes) or 5.12 (5-speed gearboxes) differentials are pretty cheap and plentiful at the auto breakers/recyclers/salvage yard.

I hope that this helps!

[alien]

Biggest issue with diff swap only is that you dont reduce low range gearing, and stock sierra low range is pretty poor. Most aftermarket tcase gears take low range down 150% or more while affecting high range 10-20% or so to account for the tyres on the highway.

[AckerDackerly]

alien wrote:

Biggest issue with diff swap only is that you dont reduce low range gearing, and stock sierra low range is pretty poor. Most aftermarket tcase gears take low range down 150% or more while affecting high range 10-20% or so to account for the tyres on the highway.

While that may be true alien, the complaint of the original poster was about operation in the 2-high mode - ie. driving on public roads. A dif swap certainly does not hurt off-road performance. Plus, my 4.625 dif swap DID give me back fifth gear on the highway...

Another benefit of the differential swap is the reduction of torque load on the drivetrain (u-joints, transfer case mounts, etc.) as the gear reduction occurs at the axle instead of the transfer case.

To prevent this from becoming a flamewar, I heartily agree that transfer case gears is an IDEAL method for improving off-road performance! There are a lot of t-case gearsets available for Sierras/SJ 413s - perfect for matching the engine to a particular set of tyres or offroad driving condition.

That fact alone indicates the value of a transfer case regearing.

I hope that this helps!

[Gwagensteve]

I'm sorry AckerDackerly, I'm going to have to disagree with you.

Firstly, with the notion that diff swaps are cheaper than transfer gears. They're not, mostly because of the install costs.

Transfer case gears are easy to install, and perfectly offset a 31" tyre (in the case of 6.5:1 gears) for road use.
because
4.6:1 diff gears do, also, perfectly offset 31" tyres for road use. However, 4.6 front ratios are very hard to find here. Thats partially because they are desirable, but also because they come from the least common variant of Vitara, the carburettor 3 speed auto. If you find these ratios they will likely cost approximately $150 each.
Buying and shipping the cans and install kits will run about $400 landed. The install costs to get a diff shop to do the gear install into the sierra carriers will run at least $150 each. So that's a $1200 job all up. Then, it makes sense to upgrade front axles and lockers at the same time as you're already paying for install.

Transfer gears run $600+shipping, and if the transfer is currently in decent condition, there's nothing more to spend. Self install is quite possible and doesn't really require much in the way of special tools.

And in my opinion, thats not even the problem with diff gears.

The problem is that they don't lower low range enough. Sooner or later, the owner generally wants a bit more reduction. So now they look towards transfer gears, and that screws with the high range gearing, because even the tallest transfer gears run 12% reduction in high range, so now road revs are too high.

Axle gears in conjunction with transfer gears are excellent when tyre sizes exceed 32", but in my opinion, they are a bad solution for 31's.

Steve.

[AckerDackerly]

Gwagensteve wrote:

I'm sorry AckerDackerly, I'm going to have to disagree with you.

Firstly, with the notion that diff swaps are cheaper than transfer gears. They're not, mostly because of the install costs.

Transfer case gears are easy to install, and perfectly offset a 31" tyre (in the case of 6.5:1 gears) for road use.
because
4.6:1 diff gears do, also, perfectly offset 31" tyres for road use. However, 4.6 front ratios are very hard to find here. Thats partially because they are desirable, but also because they come from the least common variant of Vitara, the carburettor 3 speed auto. If you find these ratios they will likely cost approximately $150 each.
Buying and shipping the cans and install kits will run about $400 landed. The install costs to get a diff shop to do the gear install into the sierra carriers will run at least $150 each. So that's a $1200 job all up. Then, it makes sense to upgrade front axles and lockers at the same time as you're already paying for install.

Transfer gears run $600+shipping, and if the transfer is currently in decent condition, there's nothing more to spend. Self install is quite possible and doesn't really require much in the way of special tools.

And in my opinion, thats not even the problem with diff gears.

The problem is that they don't lower low range enough. Sooner or later, the owner generally wants a bit more reduction. So now they look towards transfer gears, and that screws with the high range gearing, because even the tallest transfer gears run 12% reduction in high range, so now road revs are too high.

Axle gears in conjunction with transfer gears are excellent when tyre sizes exceed 32", but in my opinion, they are a bad solution for 31's.

Steve.

Thanks for the reply, Steve! And there is no need to be sorry to disagree with me. The last person that thinks I know everything is me...

That is why it's called a discussion forum folks!

Ignorance on my part does grant you the fact that 4.625s are rare. The FI 1.6 16 valve automatic 2-door equipped with 4.62s were the second-hottest selling truck after the 5.12 5-speed version here in the States. What a bunch of lazy bastards we Yanks are! Automatic gearboxes...

The other half of the cost argument posits that one MUST have the ring and pinion professionally installed. There is no doubt that transfer case gears are much, much simpler to install - which affects the overall cost. However, I did it for $450 US with the help of a more knowledgeable friend, buttloads of documentation and a little planning. They have been running quite nicely on- and off-road for 5 years.

Then there is one's perspective in the discussion - and this can be important. There are two groups in the Zuk World. Group 1 - which is the larger group - wants their Zuk to successfully challenge any obstacle. Large tyres, super flexy suspension, air lockers, power and GEARING! Group 2 is populated by folks who want to have a truck they can legally (and affordably) drive every day to work or to buy stuff at the hardware store and have some weekend fun offroading - what the folks in Blighty would call Greenlaning. Or perhaps a day on the dunes. Sometimes members of Group 2 migrate to Group 1. Sometimes.

Guess which group I belong to...

The fourth - and most important - argument is the fact that I have more time than money when it comes to a hobby. If I believe that dif gearing is a good AND cheap solution to my build problem and I can save money with a DIY trip to the salvage yard for parts and the purchase of some pizza and beer, then that's what I'll do. Plus it's fun to make the process social. Naturally, the same applies with a transfer case gearswap!

Finally, your mileage may vary, sold by weight, not volume - some settling may occur during shipping, the choice of a lawyer (barrister) is an important one and should not me made solely on advertising alone and offers cannot be combined.

Again, thanks for the excellent reply, Steve!

PS: I once was the proud owner of a 1973 Styr-Puch Pinzgauer 710M...



This, of course, qualifies me for the title of being BatShite Crazy...

[Gwagensteve]

Nice Pinzgauer. I went on a trip with one of them years ago - a 6X6 running 34" tyres. Its performance was interesting - seemed to lack gearing for very steep terrain but certainly had plenty of traction.

I would strongly discourage anyone that doesn't have a high degree of mechanical aptitude from having a go at swapping a ring and pinion. I have seen many sets of gears destroyed by poor setup, even when carried out by so-called professionals.

In my opinion, anyone running 31" tyres on their car is what you'd call "group 1" - they are interested in off road performance.

To the OP, you need to have a good think about the balance of your use. if you predominantly drive sand, *perhaps* 4.6 diff gears would be preferable, as 6.5 transfer gears won't be ideal in sand. (too low) It's also worth considering the taller transfer reductions such as 4.9. Whilst you'll still be revving slightly lower than standard at 100km/h you will get 5th gear back, and low range will be more broadly usable. 6.5 is pretty low unless you're into quite technical driving (with 31's)

[sideways]

From what I'm seeing on Facebook groups, 80% of people running 31s on a Sierra are more interested in checker plate door trims than off road performance.

For the average SJ50/70 Sierra build (standard gearbox, 31s) there's almost no point in running just diff gears. Transfer gears are just such a perfect, cheap and easy solution. Diff gears have their place with excessively large tyres, alternative gearboxes/transfers, special use vehicles (that don't see road use or only see sand and road) or on models like Vitaras, Hiluxes, Patrols and SJ40s/LJs where it's not possible to lower (or adequately lower) high range at the transfer.

You can argue diff gears can be done cheaper but they only do half the job. Even worse, you'l have to swap back to stock diff gears when you put transfer gears in.

A 1.3l Sierra is the easiest mainstream 4WD to effectively gear. In nothing else can you correct high range for bigger tyres and make your low rage 2.5x lower using one set of new parts with nothing but basic tools for $800. That's thanks to transfer gears.

[MrRocky]

Recent trip down south i averaged 10ltrs per 100km running 32" muddies and 5:14 transfer gears, factory 4.1 diffs fully loaded with alot of spares and camping gear. I also run the efi 1.6.
By comparison the mildly lifted 2011 jimny on the trip with 29" all terrains averaged 12-13ltrs per 100km and the carby 1.3 sierra with 5:16 gears and 31"s averaged 14-16ltrs per 100km.