Hilux 4x4


Install a Dual Transfer Case in A SFA Toyota Hilux

Article by Andrew, you can follow the topic by clicking here.

Well, with my previous project being complete, I suddenly felt a vacuum as I have been used to grafting in the garage on something to keep the brain ticking over :crazy: , so I decided that I will investigate the installation of a Marlin Crawler ( http://www.marlincrawler.com ) additional reduction transfer box on my Hilux.


I have often found 1st gear low range a bit fast when driving over really rocky patches and wished I could go slower.

After reading Simon's (Syron Conversions) article http://www.hilux4x4.co.za/simon/marlin_ ... /index.php I decided to have a look. Marlin Crawler are having a year end special pricing until end December so that interested me immediatley :thumbup:

I did some browsing of the parts I'll need, and after much time piecing it all together in my head, I've figured out how it all works, and what I'll need.

You basically need the MC07 kit, speedo extension, 23 spline rear replacement shaft and output shaft (recommended as stronger to deal with the extra torque) and some other bits which I must still clarify.

Transfer case

I aquired a full spare G52 gearbox that I'll use as the donor box for the transfer case.

With the help of the instructions from the Marlin Crawler site ( http://www.marlincrawler.com/tech/guide ... taller-old ) I decided to strip out the transfer case from my spare gearbox to see what goes on inside.

I have never opened a gearbox before :shock: , so here goes. Hopefully I learn something :lol:

Here is the donor gearbox (G52) and transfer case (RF1A - Gear Driven forward shift with 2.28:1 reduction ratio and 21 spline input shaft - Can be identified by the 7 bolt rear cover )

I then drained the all the oil from the gearbox and transfer case and removed the rear output flange.

I then removed the rear 4WD gear cover

Then I slid off the speedo gear, oil slinger, bearing etc from the output shaft

Stripped some more parts...

I then split the transfer case from the main gearbox

Then, I split the transfer case from the rear 4WD section

Here is the transfer box output side view, followed by the input side view

Here is the main output shaft and gear removed. Next job is to remove the gear from this shaft, so it can be re-used with the adaptor.

I will try to finalise what I need to get from the USA next week, and the prices. Looks about $ 450 for the parts, but I'm sure the shipping will be the killer :wth:

As you can see, the title of this project changed a bit. After battling with Marlin Crawler in the USA to just get simple answers, I got fed up with their customer service and contacted Ronald (Dieseldog) as per Jonathan's (Toybox) advice.

He brings in the Trail Gear ( http://www.trail-gear.com ) range. I have dealt with Trail Gear on the internet, and they actually get back to you when you make an enquiry!! They have everything I need, especially the forward shift to top shift conversion kit for the rear transfer case which Marlin Crawler no longer sells.

I had a long conversation with Ronald this morning, and he was really helpful. Lets see where we go from here !

OK, so I made up my mind, quickly :shock:

I have ordered the following from Ronald:

1........... 100006-1-K..........Trail-Creeper Dual Case Kit, 23-Spline
1........... 105001-1-K..........Trail-Creeper 4.70 T-Case Gears, 23-Spline
1........... 100122-1-K..........Top Shift Conversion Kit C
1........... 120005-1-K..........T-Case Crossmember, 4cyl, 1984-1995
1........... 182501................Rubber Shift Knob, 2.28
4........... 100069-1.............Transfer Case Shift Detent Spring, Heavy Duty
1........... 107510-1-K..........Twin Stick Shift Boot Kit

 transfer case levers

Now I just have to wait for the parts... :cry:

Andy asked:

"Andrew, just enlighten me here a little .... with that setup, would you still have an H4 option, or would it be just L4 and Crawl-4?"

Andrew's reply:

Andy, to borrow another pic from another forum,

Setup is:

Gearbox - 2.28:1 Front Crawl box - 4.7 rear transfer box and 4WD section.

Front Crawl box has:
Gear selector Hi/Lo for selecting 1:1 or 2.28:1 ratio
Rear Transfer box has:
Gear selector Hi/Lo for selecting 1:1 or 4.7:1 ratio
Gear selector for selecting 2WD/4WD

A total of 3 gear sticks + your normal gearbox stick for 5 speed.

You do not loose your high range and can run like this:

Front Crawl box 1:1 then Rear Transfer box 1:1 = normal 5 speed high range.
Front Crawl box 2.28:1 then Rear Transfer box 1:1 = 5 speed low range range.
Front Crawl box 1:1 then Rear Transfer box 4.7:1 = 5 speed extra low range.
Front Crawl box 2.28:1 then Rear Transfer box 4.7:1 = 5 speed super duper low range.

Total of 20 forward gears, and 4 reverse combinations :shock:

My setup will look similar to this pic, except that my front crawl box will remain a forward shift box (the front box here is top shifted).

Rear box will look like the pic.

Hilux dual transfer case

Yip, only one hole to cut. It will end up looking like Simon's Marlin Crawler mod below,


You can just put 4.7:1 gears in the existing transfer box, which is much cheaper, but then you have normal H4, or very slow L4, no intermediate ratios. 3rd and 4th gear aren't as strong as 1st and 2nd, and you'll end up riding in 4th L4 in some cases which could potentially lead to gear damage.

Since I got a nice pair of snap ring pliers from SWAMBO for Christmas, I decided to work off the Christmas over-indulgence this evening and carry on stripping the donor transfer case. I ended up buying a pair of 90 deg jaw ones as well since they were "only" R 145 ea :shock:

Here is the transfer case stripped of all the internal gears etc.

With all the parts stripped, I needed to get the get the low speed gear off the main shaft as it will be re-used with the adaptor kit. To remove the gear, you first need to remove the 6208N bearing from the shaft.

I supported the bearing on two 8mm steel plates on top of my wood vice and then tapped out the main shaft with a nylon hammer. It came out quite easily, so a press was not needed.

I then re-assembled all the parts I will not need again for this project. They will be my spares :wink:

Shown below are all the parts that will be re-used once my Trail Gear adaptor kit arrives. I am going to bead blast the transfer case housing to clean it up when I am back at work.

I am also playing with the idea of re-using the 4WD indicator switch on the front case, but tapping the blank hole on the opposite side and installing it there so it can be used as an indicator switch for the crawl box to show if it's in low range. I will have to grind a cam slot into the high/low shift rod to activate the switch. Will have to see how hard the material is.

After I thought I would need to buy a speedo cable extension due to the transfer case moving backwards, I was advised that it is not necessary, and that the speedo cable can be re-routed to allow extra slack.

I re-routed the cable this afternoon, and did gain a bit more length. Whether this will be enough, I'll have to see.

I also removed the front output flange from my spare 4WD transfer case which I will re-use on the rear output as I will probably go the route of removing the center bearing altogether and install a lengthened front propshaft in reverse with the double cardan joint.

Here you can see the difference between the front and rear transfer case output flanges. Different diameters and bolt hole PCD's.

I also ordered two new flange nuts and two new transfer case drain plugs from Toyota today.

Click here to continue to page 2


Questions and answers:


what transmission does your truck have?
are u going to convert the crawl box to a top shift setup?
if u have any questions about reassembly, let me know, ive assembled over 10 of these.


Hey Philip, my Hilux has the same transmission as the one I'm stripping above. As far as I can tell, it's a G52.

Trans Date Range 1st 2nd 3rd 4th 5th Rev T/Case
G52 1984-86 3.928 2.333 1.451 1.000 0.851 4.743 Gear

Output Spline T/C Shift Notes
21-spline Forward 25.5" long, 80x20mm open-face input bearing

I plan to forward/remote shift the first crawl box, and I'll have to top shift the rear transfer box. Just got to find out what I need to be able to do this.

Is dual stick top shift for the rear box the only option, or can you top shift in the conventional "J" pattern?