JONGA - A tribute to Indian army's favourite SUV

Nope, this was a two speed t case so I guess they put a modded tranny by adding a 4th gear.

Franckly, i really dont know if its true at all. The 1-tonner 4 speed does have a single speed x-fer case, but it makes up for it with a 6.52 1st gear.(the jonga has a 2.9:1 first and 2.26 transfer case low, so that makes a 6.56 total ratio). Putting a 4 speeder would be very difficult as it has to be short enough to work, an still be beefier than the 3 speeder to work with a diesel motor, but without the transfer case, you can use a 5 speeder too

 The stock tranny(without the transfer case) is 9.5 inches long, and the 1 tonner is 13.5" long, so thats 4" of difference. Now considering the rear drive shaft is 18" long, you would be left with just 14 of shaft lenght, putting it at an extreme angle, which would be enough to break a lot of crosses even with the stock 3 speeder first gear, let alone the 4 speeders. Coming to that,the only other gearbox that comes even close to this dimension wise(considering it has to be beefier too, and not the mahindra boxes) is the Tata GBS600 5speed gearbox, has a low first and an overdrice too, and Schyros, at 17" long(leaving the rear aside) . And i am not even coming to the axles as yet, which has just a 1.3" shaft. Since i am making a diff-lock for the stock axle, i have observed that the axle is not much stronger than the Dana44 used in the mahindra jeep. The Crown wheel at 216mm dia. is just as big as the Dana44, and so are the shafts. the biggest weak link is the front birfield joint, and i think i would probably use modified longfield birfields to sort it out. the mahindra is stronger with a cross joint up front.

There was a 5speeder awailable abroad that would fit between the stock bell-housing and the x-fer case, and that was made by Marks4WD (aussie) using Nissan cabster parts. Was pretty stout but sadly,not made anymore( and anyways, it would cost you $1500 for a second hand one, without even including the duty and stuff). A lot of my friends abroad are using this tranny.

Don't forget the main shaft of the 3 speed had to be modified from the petrol engine's 17 mm to the HINO's 19mm.

By the way, even the Marks box was 4" longer than the stock, and people did have problems with too short a rear driveshaft. There have been attempts to use the T18 gearbox but i dont know anybody whos been successful as yet. This gearbox, along with the SM420 and SM460, are probably the only ones that have a granny low and 4 speeds to come at just 12.5" long.

Take care,

Bikram

 theres no way a 19 mm shaft can even handle 10kgm torque, let alone a coal burner.

 Its 30mm thick input shaft in the Jonga. the diameter you are talking about must be the size of the pilot bushing.

Bikram

Thats what I meant, its the flange where the shaft mates with the flywheel, the VFJ guys also modded the bellhousing and rear diff as compared to the stock model.

Ok now its getting very confusing. I guess the best idea would be to talk to someone who was actively involved in this project at VFJ.

My source is George Goomes who works at R&D AL and was involved in this project and since I have actively maintained and fixed and run this vehicle till today, I have some idea of its workings and mods that were done to it. I found it out the hard way when I couldn't replace the worn out main shaft with the stock petrol shaft. Also the HINO Jonga uses diaphragm clutch with slave cylinder from Tata 407 truck and the master from Tata 609. The finger mechanical clutch couldn't handle the torque of the HINO so VFJ was forced to mod it. Only negative point being that the travel is very short and therefore, modulation in traffic as well as in off road mud gets to be tricky till one gets used to it.

The best bet for anyone who want a diesel jonga along with a the 4wd intact is to move to the 1ton drivetrain. It did come with the option of diesel, it came from kirloskar motors who at the time were using a 4bt cummins. This motor shares 80% parts with its bigger sibling the 6bt cummins(used in all bigger tata trucks), and as a plus point, it already comes with the nissan 1 ton drivetrain. The bellhousing was modified to mount on to the cummins, and it uses a different pilot bushing, rest all remaining the same. That tranny is strong enough for anything you can put it through.

Bikram

Thanks for the info. Brutus. Never knew much about the Jonga