Here is a quick introduction:
- R72 gearbox is used on petrol Jimnys with M13A VVT engine and electric (push-button) controlled 4WD transfer box.
- These were produced from 2005/2006 to 2018 and ongoing.
- R7ME gearbox is used on petrol Jimnys with M13 engine (and maybe with the oldest G13BB engine too) and mechanically (shift lever) controlled 4WD transfer box.
- These were produced up to circa year 2005.
- As far as it is known, all diesel (DDiS) Jimnys have gearboxes specific to them, so this article does not apply to DDiS Jimnys.
Reasons, benefits and risks
- The R72 gearbox is known to develop issues in some vehicles, even at very low mileages in some cases.
- However, your mileage, literally, may vary!
- There is a long lasting, but expensive repair solution.
- The wiki article "Gearbox R72 rebuild" explains the repair procedure in detail.
However, alternative solution to repairing a broken R72 gearbox would be to replace it with the older R7ME gearbox, which has no weaknesses.
Another reason why some people would want to do this swap is to obtain lower overall transmission gearing ratio, which then counterbalances the negative effects of increased transmission gearing ratio when using humongous tyres.
However, the swap is not a straightforward "bolt on" job.
The swapping procedure
This forum topic (among others) contains some useful information about the swapping procedure.
UPDATE: new guide with more pics and better info... 
Page last edited on 21/02/2019 by user Bosanek