Project Money Pit

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Project Money Pit Planning

I have been running my present Suzuki for almost three years now and have learned a lot about what works and what doesn't.  I was getting ready to tube the back end when it came to me, maybe I want to start a new one, something built from the ground up with rock crawling in mind.  The basic idea is to slowly build one up on the side, keeping my present trail rig useable so I don't feel the need to rush the project vehicle along.  My design goals are much the same as when I started my original Zuk:

1.  Keep it light.

2.  Rockcrawling abilities are the #1 priority.

3.  Keep it street legal (although it will be trailered).

Here is the general plan:

Chassis: Samurai frame, front Shackle reverse with YJ springs, rear coil with 4 bar link.  Wheelbase to be extended to 95-98" depending on final drive train.  I plan to cut the factory frame and tub off behind the passenger compartment and replace it with a tube structure.  The front end will be similar to what I have now for clearance. I'd also like to find a way to raise the rocker panels up to just below the door sill.

Axles:  At the end of the project I will swap my existing Toyota truck axles to the project rig.   I plan on shaving the front axle for more ground clearance.  In order to setup the rear coil links I will need to locate a bare rear axle housing.

Drive train:  I would like to try an automatic transmission and I definitely want dual transfer cases for a wider selection of gear ratios.  Ideally with an automatic transmission I think something around 100:1 would be great, with a manual I would double that.  The hard part will be making sure I have enough gearing options so I am not too low for the easy parts of the trail but still geared high enough in high in case I have to run some freeway to get to or from a trail.

Misc:  As time permits I would like to make a custom dash and run some sort of hydraulic assist steering.  I plan on using a fuel cell and would like to setup the back end so tools and spare parts are securely stowed and easily reached.  I have a feeling this may be the toughest thing to get right and may require a little experimentation.  I also want to run with a full-size spare, or at least have the provisions to mount one for remote runs.

Tires:  At this point I am aiming for 36 x 12.50 TSL's but that may change depending on what the wheelbase ends up being. 


Crunching Numbers

So with the plan in place I am starting to look at drivetrain options since this will determine how long my wheelbase will have to be.  After a little digging I have found there are a ton of different motor/gearing options which is going to make it hard to decide which way to go.  My rig will primarily be a rockcrawler so I am looking for a wide range of gearing ratios between 200:1 and 90:1.  If you run sand, mud, logging roads or a little of everything, you may benefit from more ratios from 150:1 down to 50:1, basically having a gear for every situation. Here's a breakdown:

Stock 1.3l - The Suzuki small block (literally).  Horsepower is right around 64 in a carbureted version, torque is around 45-50 ft-lb? (I couldn't verify this spec). The only available option for a dual case setup was a second 4:1 transfer case w/adapters made by Klune.  Unfortunately they pulled that kit off the market, no word on when it will be back.  The Klune replaced the intermediate driveshaft and allowed you to run a stock transfer case behind it.  Although you can't put an automatic behind a 1.3l, the Klune and a 4:1 gearset would have provided some very good gear ratios.  I used the RPM gearing spreadsheet located at Off-Road.com for all the following calculations.  I used my existing 5.29 ring and pinion ratios since I will be using the same axles.  Note you could put a GRS II or 6:1 behind the Klune for even deeper gears, but I felt the options with a 4:1 gave a better range and the 4:1's are half what a 6:1 gearset runs. (321:1, 171:1 and 125:1 are deep enough yet spread apart enough to give you some cool options).  The only downside was the price, when the Klune was available it ran roughly $2400.  

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Klune, 4:1 with Stock 5 Speed

Some people have been experimenting with mating two stock Samurai transfer case together.  I was not able to find any real world feedback other than they dump oil out on side hills due to having to clock the first transfer case.  You also have to deal with the added complexity of having two more connections in the drivetrain (some sort of driveshaft/coupling between the transmission and 1st t-case, then another between the two t-cases).  Lastly the Samurai transfer case is actually geared 1.4:1 in high range as a sort of displacement compensator.  Stacking stock cases makes your high range even deeper and can really hinder your top speed on the freeway.  Here's what your gear ratios look like with a 6:1 and a stock transfer case.  I ran the numbers with 37" tires, so your rpms go up as your tire size goes down.  Costs are estimates, don't take into account core or installation charges, and you'll have to add money for making new mounting crossmembers and getting new driveshafts if needed (rear may have to get shorter, front longer).  I think $100 for the couplings needed is light, but if you can do it yourself you can probably do it for that.  Lastly look at the high range, your top speed will realistically be around 45mph.

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6:1, Stock Case with Stock 5 Speed

1.6l -  These motors are commonly found in a Sidekick or Tracker.  Two versions exist, an 8 valve and a 16 valve.  The 8v is good for about 80 horses, the 16v about 100.  Couldn't find torque numbers on the 16v, the 8 makes about 94ft-lb at 3300 rpm.  This is a nice jump over the stock 1.3l and the engine is pretty much bolt in to the Samurai frame.  With the appropriate harness and ECM I could add the fuel injection, a nice bonus and a 3spd automatic transmission is available.  Doing some web surfing I discovered several companies that make adapters that bolt to the 1.6l's bellhousing which opens up a lot of dual case gearing options.  The first one I looked at is running the stock Sidekick 5 spd transmission, transfer case and buying an adapter to mount a Toyota transfer case to the back of the Sidekick transfer case.  The adapter also requires you to send in the Sidekick transfer case to remove the front drive portion of the case, basically it becomes a hi/low box.  I would install a 4.7:1 gearset in the Toyota case and leave the other one stock (although a 4:1 is available is you want to go lower).  This setup falls a little short of my overall gearing goal but it's simple, no extra couplings since all the cases are attached to each other and relatively cost effective (assuming you can find a parts car for the drivetrain for a couple hundred). 

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Stock Sidekick T-case, Toyota 4.7 T-Case with 5 Speed Transmission

Another thing to pay attention to in the above numbers is the high range, the Sidekick t-case is 1:1 in high so you are only factoring your ring and pinions in while on the road.  OK, so if that's not low enough?  You can add another 4:1 to the sidekick case but right now they are expensive ($890).  Also, in my searching I noticed that Marlin (they make Toyota crawler boxes) does not recommend putting a 4:1 reduction box in front of a 21 spline Toyota transfer case (the most common ones).  If you need deeper gears they recommend upgrading to a beefier 23 spline transfer case.  After I discovered this I really don't think dual Samurai cases will hold up since they have even smaller components than the Toyota transfer cases.

So how about the automatic?  The first gear is much lower than the first gear in the 5sp transmission.  The torque converter will make up for this and many people consider the torque converter equal to another 2:1 reduction.  For my charts I did not make this assumption.  One reason not to go too low of gearing with the automatic is it will have a tendency to want to creep forward in some situations, the lower your gears the worse is can get possibly to the point of overpowering your brakes.  

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Stock Sidekick T-case, Toyota 4.7 T-Case with Automatic Transmission

Another interesting option for the 1.6 is to use two Toyota t-cases via a divorce mount adapter.  This combo results in lower gearing but adds some complexity with the need for an extra coupling and adapter.  Just for reference the same setup below except with an automatic transmission results in a 136:1 lo gear.

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Stock T-case, Toyota 4.7 T-Case with 5 Speed Transmission

22R - With all this talk of Toyota transfer cases why not just drop the Toyota drivetrain in?  The motors are a 2.2l four banger, the carbureted 22R making 103hp @ 4800 rpm and 133 ft-lb of torque @ 2800 rpm.  The EFI 22R-E is even better with 116hp @4800 rpm and 140ft-lb of torque @ 2800rp.  In a light rock buggy that's a lot of useable torque. Another bonus is the gear ratios in the 5spd, they are a little lower than the Sidekick ratios which will help on the street and on the trail in first.  Also, if you can find a 5 speed from a turbo truck, you can have a 4.30:1 1st gear!  For this swap to work I think I'll need more room up front, but since I'll be cutting the fenders off that shouldn't pose a problem.

 
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Stock T-case, Toyota 4.7 T-Case with 5 Speed Transmission

For an all around machine this option looks attractive.

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