FridgeFreezer Posted September 16, 2009 Share Posted September 16, 2009 Bear with me, this is probably a daft idea but here goes... I'm looking at a Tatra which is a great truck but a bit slow, so trying to work out ways of upping the gearing. The idea has occurred to add a splitter between engine & gearbox (they are divorced with a propshaft in between), and rooting around eBay I've found MJ transfer cases for sale which are also divorced from the main box. A plan is forming So - can anyone tell me about the transfer case? How it works (does it have a differential, viscous coupling, or straight old dog clutch), what the ratios are for high & low range, and perhaps most importantly how strong they are. The Tatra is 250hp / 1000nm, not bad but not outlandish by modern standards. Any ideas for other ways of doing this would also be appreciated, I'm probably missing something much more sensible :??? Quote Link to comment Share on other sites More sharing options...
N.O.S. Posted September 16, 2009 Share Posted September 16, 2009 I'm certain High is 1 - 1, and Low is almost 2 - 1, giving a reduction of 50% in speed (or in your case doubling of speed). Just 2 pairs of gears with a mechanical selection. You also have selectable output drive for front axle, and on some a full-power pto drive. They will cope happily with 130 hp, but I don't think 250hp would do them a lot of good and they certainly would not survive a reversal of drive to act as a speed INCREASER with that available torque :shake:. TM boxes are better-sized but very scarce. MJ transfer boxes are not like the heavy old Militant boxes which I believe have been successfully reversed. Also, the Tatra gearbox would be running at up to twice the speed, you could be leaving yourself wide open to a claim gearbox abuse :cool2: I like your way of thinking though! Quote Link to comment Share on other sites More sharing options...
FridgeFreezer Posted September 16, 2009 Author Share Posted September 16, 2009 Thanks NOS, I suspected the MJ box might not be up to it. What I could do with is a splitter from something that can be easily separated from the main box. Unfortunately I'm relatively new to all this HGV gubbins so have no familiarity with the various bits & bobbins that are out there. Although pushing the Tatra beyond its natural speed limit may be a bit cheeky, they are designed to tow 100 tonnes so I would hope that lightly loaded it would cope with a bit of extra gearing. I only really want to hit 100kph (current max is 80-85kph) to keep up with the crowd. Quote Link to comment Share on other sites More sharing options...
radiomike7 Posted September 16, 2009 Share Posted September 16, 2009 Also, the Tatra gearbox would be running at up to twice the speed, you could be leaving yourself wide open to a claim gearbox abuse :cool2: I like your way of thinking though! Twice the speed but half the torque. Torque breaks gearboxes, power makes them overheat, speed may make them vibrate, take your pick. If top gear is direct (1:1 with the input shaft locked to the output shaft) speed and heat may not be a problem. Quote Link to comment Share on other sites More sharing options...
gritineye Posted September 16, 2009 Share Posted September 16, 2009 A friend of mine has up geared his Cummnis L10 250 engine/Fuller Gearboxed International by inserting a reversed 6x4 Miitant box after the gearbox. works very well, pulls an artic trailer living van. Another strong box he considered was a Leyland Buffalo, which gives a higher ration still. Quote Link to comment Share on other sites More sharing options...
Stone Posted September 16, 2009 Share Posted September 16, 2009 TRUCK, 4t, 4x4, BEDFORD MJ[/font] ALL VARIANTS TECHNICAL DESCRIPTION REPRINTED INCORPORATING AMDT No. 1"] TRANSFER BOX GENERAL DESCRIPTION 1. The transfer box (Fig 1) is manually controlled by two levers in the cab and provides a direct drive to the rear axle for two wheel drive, or a direct drive to both axles i.e. four wheel drive high, or a two to one reduction to both axles (four wheel drive low). On some vehicles, the transfer box incorporates a power take-off which is controlled by a separate lever. 2. The input pinion (1) is supported at its forward end by a ball bearing (14). 3. The rear end of the mainshaft (5) and the front and rear ends of the layshaft (7) are supported by ball bearings and the front of the mainshaft is carried by a roller bearing (2) in a counterbore in the input pinion. Gears dogged to the mainshaft and layshaft are in constant mesh. 4. The layshaft driven gear (11) is carried on needle rollers (10) and is in constant mesh with the input pinion. 5. The front end of the layshaft is splined to engage a front wheel drive clutch (12). Internal teeth on the clutch engage external teeth on the coupling flange when in four wheel drive. 6. A drive for the speedometer is provided at the rear of the transfer box. Fig 1 Sectional view of transfer box Does that help? Stone Quote Link to comment Share on other sites More sharing options...
FridgeFreezer Posted September 16, 2009 Author Share Posted September 16, 2009 Does that help? Only a lot :tup:: Looks like a transfer case from something a bit bigger may be the order of play though. Cheers guys. Quote Link to comment Share on other sites More sharing options...
N.O.S. Posted September 16, 2009 Share Posted September 16, 2009 Reo M54 5 Ton transfer box on Milweb.....:cool2: Quote Link to comment Share on other sites More sharing options...
FridgeFreezer Posted September 16, 2009 Author Share Posted September 16, 2009 Reo M54 5 Ton transfer box on Milweb.....:cool2: This could go on a while... OK, anyone know the ratios & torque handling of one of those? :readbook: I'm much better at useless Land Rover trivia, honest! :coffee: Quote Link to comment Share on other sites More sharing options...
Degsy Posted September 16, 2009 Share Posted September 16, 2009 M54A1 with Mack engine was 211hp and 612ft/lbs Quote Link to comment Share on other sites More sharing options...
FridgeFreezer Posted September 17, 2009 Author Share Posted September 17, 2009 One of my esteemed colleagues has pointed out that transfer boxes live after the gearbox and as such will see engine torque multiplied by the gearbox ratios (eg 250nm through a 4:1 1st gear = 1000nm, give or take) so putting one on the back of the engine before the gearbox you should be able to get away with something quite small. Suggestions from him were Mercedes G-Wagen (full synchromesh, unburstable by all accounts) and Suzuki SJ :shocked: which are well known for being almost insanely strong for a car with a bee in a biscuit tin as an engine. It's tempting to try the SJ version for the sheer perversion of bolting one behind a 17 litre V12 diesel :rofl: Quote Link to comment Share on other sites More sharing options...
N.O.S. Posted September 17, 2009 Share Posted September 17, 2009 You'd best not forget the oil cooler then.......and don't let the engine rpm drop below 1800....... :banana: Quote Link to comment Share on other sites More sharing options...
FridgeFreezer Posted October 2, 2009 Author Share Posted October 2, 2009 Another idea that cropped up today is a Leyland "aux box" as fitted to Leopard coaches and, if the internet is to be believed, a lot of other Leyland trucks. Also as used by Charlie Broomfield on his Merlin-engined Rover SD1 to up the rpm/drop the torque. Can't find any info on the actual boxes (only that they exist) so does anyone know more? Quote Link to comment Share on other sites More sharing options...
Emile Posted March 7, 2020 Share Posted March 7, 2020 Hi I have a TM4X4 Bedford 1982 i have planetary axels and would like to know gear ratios of it and who makes the axels TIA Quote Link to comment Share on other sites More sharing options...
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