This three part article covers my building of a RockLobster 6.5:1 transfer box. The article parts are:
The kit I am using (Trail Gear) contains gears and parts to replace/add to an SJ Transfer box. Within an SJ transfer box are effectively three gearsets/shafts as follows:
- Input shaft - The Trail Gear set contains a replacement shaft to which you add either the original bearings or new bearings as you prefer,
- Counter shaft - The Trail Gear set contains a replacement shaft and gearset to drop in,
- Output shaft - The Trail Gear set contains replacement gears for the original gears, you either re-use the original bearings or new bearings as you prefer.
I have embarked on building my own low ratio transfer box. I have previously built two boxes, one for my SJ and one for my Jimny but both of these were 4:1 boxes built using the "Difflock" cut & shut gears. This is a frequently maligned process but the current Jimny one has served nearly 10 years so far so they cannot be too bad, however with 32" tyres it is time for something more low range.
Since I did the cut & shut one, a variety of aftermarket gearsets have appeared that provide a "drop in" solution with pre-cut gears. There are a variety available from cheap Chinese versions through to Japanese manufactured ones made in the original factory.
I went for the Trail-Gear 6.5:1 set as it represents a mid priced solution that has been on sale in the USA for a number of years. This should bring back the gearing quite nicely on the road whilst providing a very low gearing off-road.
Also needed is a Suzuki SJ transfer box, either a 410 or 413 will do (except for the very early 410 versions which are useless). See the section in the Wiki - HERE - which tells how to identify the correct box. Late 413 boxes are particularly good as they have the same larger flanges that the Jimny has, however it is straight forward to drill the old ones if necessary.
If you are doing this from scratch you will also need mounting arms, propshafts and a speedo adaptor to fit it to a Suzuki Jimny. Of course, I already have those parts on my as it has a 4.1:1 Transfer box already fitted.
So the build begins......BigJimny's Transfer box.
Very shortly after we drove away from the 2019 BigJimny meet, I heard a very loud bang from somewhere underneath BigJimny. I pulled over and could not see anything, the Jimny still had drive but was giving out a knocking noise.
I suspected the CV joints as they have been clicking for a long time, however I found that the noise was coming from the rear diff (see video below, you can hear the knocking noise if you ignore the disc scraping noise)