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Location: North Rockhampton, C
Vehicle: Too many sierra's and 2 GV's

Post Posted: Wed Apr 06, 2016 1:07 pm 
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So you’ve bought your first Sierra, or are considering a purchase, and want bit of information on how to modify it? The first step is to establish your goals for the car. Whether you want a daily driver, a tourer or a hardcore dedicated wheeler most of the following information will apply but if this decision is made early it will save you money and time by choosing the correct modifications the first time around.



Let’s start with which Sierra to get, being in production since 1981 to 1998 there are a series of generations that the Sierra went through:

1981 – 1984 1L Narrow Track
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1984 – 1988 1.3L Narrow Track
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1988.5 – 1996 1.3L Wide Track
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1996 – 1998 1.3L Coil Sprung
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For the purposes of this article most of the information will be based on the most popular models (1.3L NT and WT). Besides the coil sprung late models all the others came in a range of configurations; Short wheel base (SWB) Hard top, SWB Soft top, LWB Soft top and LWB Tray back (NT only). Minimal changes were made between the body designs, basically choose what you like. The longer wheel base models will travel slightly better on and off road while being more stable when climbing hills. Any hardtop model has the windscreen and B pillar as part of the body making it harder for replacement if damaged so if hard core wheeling is your aim perhaps stay away from these, or accept the risk.


Right so you’ve chosen what to get, or already got it, and want to know what to do with your new four wheel drive. If you’re new to Suzuki’s or 4wd’s in general your first reaction will be to look for 4” lift kits and 33/35” tyres, but please don’t bother. If this is you my first suggestion would be to get out and drive your new (to you) car, the lines that you must take in a small four wheel drive are unlike any other car. You will feel the limitations and the following will make more sense.

My personal opinion is that suspension is the single most important characteristic of a four wheel drive, and any car that you are trying to increase performance. In a four wheel drive situation you want soft springs with correct dampening, fortunately leaf springs are very easy to dial in.

“Lift” springs in a four wheel drive increase the static height of the vehicle. They do this in one of two ways; higher spring rate (stiffer springs) or more arch bent into the leaf pack. Neither of these methods will promote better than stock travel and in fact will result in a worse ride. Springs alone will not assist with fitting larger tyres. Stock springs due to their age will look basically flat on level ground with the weight of the vehicle on them.
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If they are inverted over the diff housing they will need to be replaced. To get the soft ride that we are looking for and a chance at better travel there are two options that I choose between for a bolt in fit. OME Comfort Springs or EFS 50mm springs. Before fitting either of these I would recommend removing the third leaf from the top of the pack and the overload spring from the rear. In removing these springs you will not get the advertised “lift” from the spring, the car will settle only slightly higher than stock. If you intend on carrying large loads or towing don’t remove the springs from the rear, you will need them but you will be compromising performance.

To fit a shock dampener to the vehicle you can choose a bolt on option. OME again have good dampeners that will bolt to your vehicle without further modification. If you do not like the bolt on options and are looking to adapt from another vehicle you need to measure your requirements before looking for a suitable shock. To do this remove your current shocks and slowly drive the front passenger wheel forward up a ramp until your rear passenger tyre has lost traction. Apply the handbrake and chock the vehicle. You now need to measure between the shock mounting top and bottom locations at all four corners of the vehicle. Check and see if the vehicle has reached the bumpstop yet, if it hasn’t it is likely your spring rate is too high still and you will need to remove more leaves from the pack otherwise alter your spring rate. Unchock the vehicle and then back the driver side rear tyre up the ramp until you lose traction at the front. Reapply the handbrake, chock and check all of your measurements again. Use your maximum recorded extended length and the minimum recorded compressed length when you are researching new shock absorbers. Remember that when using a dampener from another vehicle you should retune the shock for the weight of your vehicle.

The above springs and shocks will cover the daily drivers and tourers well. You’ll have parts availability if something breaks and you will still have a legal vehicle when driving around. If you are finding the limit of the suspension regularly and want to go further the first step is to research RUF (rears up front). There’s already heaps of information about this with plenty of examples in the build threads, no need to rehash it here.
http://auszookers.com/forum/viewtopic.p ... hlight=ruf

Hopefully I’ve talked you out of the four inch lift, now let’s focus on the 33/35” tyres. The stock tyres on your Sierra are very likely a 205/70R15; this is equivalent to a 26” tyre in imperial. Going to something that is 7” to 9” larger in diameter is going to require significant modifications that are far out of the scope of this discussion, (that is the equivalent of trying to mount 38” to 40” tyres on a Patrol for comparison). For a bolt on fit, albeit still illegal, 235/75R15 tyres are a good choice. They are a 10% increase in diameter; the gearing is acceptable for on road duties and can still be used off road without too much clutch work. There is a large range of tread patterns available, choose a mud terrain radial. To go a little larger a common choice is 31x10.5R15’s. These will require more modifications including gearing and body work to ensure that they do not scrub in the wheel arches. We’ll talk about gearing later, more on body work now.

Bigger tyres obviously fill up a greater amount of space between the top of the guard and the hub, in the case of a supple leaf spring and a 31” tyre this space is far insufficient. This can be solved with a body lift or by cutting the sheet work and welding in a patch panel as required between the inner and outer guard.
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A body lift is just that, it lifts the body up to 50mm from the chassis, giving that much more room for the tyre. In doing this you raise the center of gravity of the vehicle. Most kits also only come with enough lifting blocks for the bolted connections; this reduces the amount of support the body gets from the chassis. The reduced support can lead to bending the mounting points on both the chassis and the body.
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Trimming the body is a better option even though it is more labor intensive. You will need to remove the flare, cut the sheet work, weld it back together and reattach a flare. Plenty of tech around for this, key words to search is “virtual lift”.
viewtopic.php?f=5&t=34550&start=0

With the suspension and the tyres sorted you should go out and play with the car again. Get a feel for it. It will be softer, flex more, sit a little higher due to the tyres. You’ll feel that your car struggles a little more when going up hills due to the higher gearing and higher resistance. You’ll go place you wouldn’t have got with the stock tyres and you’ll lift tyres less. You may get crossed up and lose traction to diagonally opposing wheels. You may get a little more adventurous and start to feel some side angles as you approach tipping point. Either way you’re probably going to want to keep modifying it.
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We can address that struggle going up hills first, and at the same time let’s get more control when we are crawling through the creeks in low range. How do both? Transfer case gearing. Because you have one of the two models I suggested earlier (1.3L NT or WT) you have a good range of options to choose between of different gearing ratios. By now hopefully you’ve done enough wheeling to see what you like and what sort of terrain you will be driving mostly so the following shouldn’t be too hard to pick from:
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4.16 – If you’ve chosen 235/75R15 tyres, or similar, don’t want to go any bigger and mostly drive sand this gear set will be ideal. It will still lower low range considerably but your high range will be back to stock.

4.9 – If you’ve chosen 235/75R15 tyres and enjoy more technical driving. These will slow down the car a lot more in low range, giving you greater control. They are also a good choice if you’ve gone to 31” tyres, bringing your high range close to stock and getting low range nice and low for an all-round vehicle.

6.5 – If you’re set on staying on 31” tyres and above. High range will be unbearable with smaller tyres and low range is simply too low. On 31’s this gear set is far slower than walking pace at idle, you can crawl with precision. You will basically be using high range in sand because you will top out at approximately 40km/h in fifth gear.

The assembly of the transfer case isn’t too difficult; the only specialist equipment required is a shop press. Following the instructions supplied, take your time and you shouldn’t have a problem. Make sure you get the detent balls back in to the right place!


So now the car is controllable, can accelerate up hills, suspension is nice and subtle and tyres are providing about as much traction as your axles can take but you’re still getting stuck every now and then. You’re getting hung up with not enough traction on the wheels that are spinning or you’re just picking that line slightly wrong and ending up in a precarious situation. Two options present themselves here, you can either go for prevention or cure; differential lockers or a winch. Both of these have carry on modifications that are best done at the same time which are discussed below.

A diff locker locks the side gears of the diff together, providing constant equal power to both wheels at that end of the car. When you lift a wheel the other wheel still has traction and you can continue to drive forward. Again there are plenty of products available; it basically boils down to a manual locker, auto locker or a full time locked differential.

Manual locker – most well-known is the ARB Air Locker, this can be turned on and off from the driver’s seat. It is the most expensive option and hardest to install. In the case of the air locker it requires an on board air compressor as well. The ability to turn it on and off is a huge advantage, allowing full stock maneuverability when turned off and 100% traction when on.
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Auto locker – the most common of these is the Lockrite. These cannot be turned on and off by the driver, they are always locked except in the case the car is turning a corner. Through the turn the auto locker allows the outside wheel to overspeed the inside wheel. This can be felt through the car as the locker engages and disengages at each of the dog clutch teeth. In order for this unlock action to occur the driver must coast through the corner. If accelerating as normal the diff will remain locked, adversely affecting the handling of the vehicle.
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Full time locked – this is either a welded diff or a spool. At all times both wheels are receiving the same power, it cannot be turned off.
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Positives and negatives exist for all three, a manual locker is best in my opinion. There’s plenty of debate on this with plenty of other threads to read through if you are trying to make the choice for yourself. Whichever way you go you will feel an immense improvement in traction. It feels like the difference from going from 2wd to 4wd all over again just locking one end. I’d also advise front end first, from personal experience it has been far more useful than a rear. When locking the front it is a good time to also upgrade the axles and constant velocity (CV) joints. The standard front axles are 22 spline at the differential and inside the CV joint. Chromoly alternatives are 26 spline at both, larger in diameter and a far better material. To install them you will need to use a diff center/locker with 26 spline side gears, which is just a rear diff. The chromoly CV’s are far stronger and shouldn’t needing touching for many kilometres of wheeling. Chromoly CV’s are only available for WT diff housings, if you have a NT now is a good time to look up Bogfrog’s NT to WT conversion thread and have a read.
http://auszookers.com/forum/viewtopic.p ... light=diff

A winch is a pretty simple piece of equipment used for self-recovery. For a Sierra you do not need a winch above 9000lb capacity and make sure to get one with synthetic rope to save some weight. These can be installed by either purchasing a winch ready bulbar such as the ARB deluxe Sierra winch bar or you can make a winch bar from plate or tube. Again have a browse through some build threads and get an idea of how multiple other people have gone about it.
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A winch draws a high level of current when pulling a car; the standard alternator is not up to this task. A suitable alternative has been well documented in EF/EL/EA Falcon Alternator Upgrade thread. This along with a good battery will have your winch running well without any danger to the electrics of the car. Depending on your winch and bar choice you may need to reinstall a leaf into the spring pack to make up for the extra weight. http://auszookers.com/forum/viewtopic.php?f=17&t=5529

If you’ve got to the end of this and have followed most of the suggestions above you’re probably looking at your Sierra with WT diffs, locked diffs, chromoly cv’s, 31” tyres, 4.9/6.5 transfer gears, nice winch with a solid bar while sitting low and stable. This formula will result in an extremely capable Sierra. You can still go further adding things that make it far nicer to drive like power steering, engine conversion, better seats, throw a winch solenoid in it so you can winch in and out from the driver’s seat, fuel tank bash guard so you’re not constantly bottoming out on the tank, etc. but the basis of this thread should tide you over until you’ve learnt a lot more about your new car.


Here are some pictures out of the ZOOM articles to show the level of Sierra's on this site;

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Last edited by Zook_Fan on Wed Apr 06, 2016 7:34 pm, edited 2 times in total.
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Post Posted: Wed Apr 06, 2016 6:43 pm 
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Very good
* lwb trayback are available as wt in maruti (indian import) form from 94-99 but only as a 1ltr (f10a) 4spd

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Post Posted: Thu Apr 07, 2016 9:02 am 
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Good tech. Great writeup

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Post Posted: Thu Apr 07, 2016 2:50 pm 
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Can we make this a mandatory thread that must be read on sign up? Haha.

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