375 Ural - Diesel Conversion project

[vtunimog]

I have started swapping out the horribly under powered and petrol hungry V8. I have a Detroit Diesel 6V92t coupled to a Spicer 5/2 speed. My only problem is that I think I may need to change out the rear axle ring/pinion for the later 4320 ratio. Any ideas on that?


I will try to keep everyone updated on this with some photos.


Chris M

[J4garage]

what's about changing the Gear ratio in transmisson box ? It's Possible so let machine two new Gear wheels for it with a higher ratio. A Guy here in Germany changed them on his 4320 to get the Engine rpm down when he drive 80 km/h... Originaly a 4320 runns with 2400 rpm at 80 km/h... now he drive with 1900 rpm. If you want to change the axle ratio, you'll have to change it at all 3 axles !

[vtunimog]

the gearbox will be a "Road truck" 6 speed with dual range (I forget the exact ratios) My thought is to put in new ring/pinion gears in the three differentials. What ratio did the 4320 owner use? or I could put in the gears from a 4320 that might drop my rpms. the Detroit 6v92 will rev up to 2800 RPM but weighs in at nearly 2,000 KG so I may need to put in some heavier front springs.


Chris M

[J4garage]

I think he use nearly 1:1 ratio... original is 1,3:1

[Rob Reznik]

are you sure the gearbox doesnt have an overdrive? - if it does it will save all your problems? - why put an engine in that weighs 2 tonne?

[paulob1]

that must be a monster engine, the 275 bhp c series only weighs in at 1500kgs...and that is a very powerful engine, with 275 bhp and auto box a ural would be a dream to drive....this will be my plan, just need to measure it up and see if it would fit, its a tad longer than a 6BTA.

How heavy is the standard petrol engine, about 700-800kgs...the box is tiny in comparison and very light, just a few tens of pounds...maybe 80kg

If you are fitting a multi speed box I would not worry about gearing you will not be over geared as you have a lot more power you will likely find that driving above 50 mph a bit scary in the old girl unles you fit modern tyres, I usually chicken out at 80kmp h as she is rattling herself to bits by then,...

one thing I have found is that if you open, and drive, with the CTIS operating, all the tyre pressures even out and she runs a lot smoother..even with her massively nobbly tyres...

[KarlJ]

the gearbox will be a "Road truck" 6 speed with dual range (I forget the exact ratios) My thought is to put in new ring/pinion gears in the three differentials. What ratio did the 4320 owner use? or I could put in the gears from a 4320 that might drop my rpms. the Detroit 6v92 will rev up to 2800 RPM but weighs in at nearly 2,000 KG so I may need to put in some heavier front springs.

2000kg?? That's not much less than a Chieftain tank engine (~2500kg)!

[paulob1]

just wiki'd it 253 plus brake horsepower, 9 litre V6 two stroke diesel...sounds damn scary...well popular in the US...but a heavy lump for sure...and doesnt sound the most efficient but it is a V6 and therefore should be compact...max revs 2100, the urals will be running maximum about 4000 rpm. I would think....so you will really need a box with overdrive...at say 1.3 to 1 you will be getting pretty close to 3000 rpm at the transfer box, when I guess it is expecting up to 4000 rpm..but you will likely only have a top speed of around 40-45 mph...I think a gear change in the transfer box is the most likely route to go...will be just one gear change and that will be just a few cogs smaller to increase the revolutions, simple box but may not be a simple change...changing the diffs may be the simplest way to go....can see your point...

No idea what they did to my zil but it is revving at around 24-2500 and doing 70 mph...it flys...I can only assume that somewhere they have changed the gearing...if its via the transfer box or by fitting a bigger ration into the overdrive, it is certainly very tall as it goes from a tough 40 to a very easy 70

[Rob Reznik]

Paul - the zil and Ural petrol engines only rev to about 3200 - you keep talking about 4000

[paulob1]

rob, the rev counter fitted to my zil (micks old one the stormer) shows it going up to 4500 rpm....at 100km/h will take her out and hav another check....unless the rev counter is fitted wrong?

[Abrs]

3100Rpm is the specified max, although this is for 76 octane fuel, but I think you can safely rev one to 3600+/- on our higher octane petrol. Generally petrol engines designed to run low octane fuels rev lower because of the detonation characteristics of the fuel i.e. the knock factor.

Sounds like Paul that your Zil has had the maximum speed governor unhooked if it's getting to those sorts of speeds , 3100Rpm is what it is normally set to, think that works out at about 52Mph IIRC

[paulob1]

yes i think it must have as she is very free revving and will skoot up to over 65mph without much trouble...very stable at that speed even with the old tyres...

[Rob Reznik]

yes they do rev higher if rev limiter removed - had my Zil to over 5000rpm's with the Edelbrock fitted

[Dreadnought]

Just an idea, in the old days of trucking, (especially in places like Australia where they needed to sustain high speed for days on end due to massive road distances) the old trick was to find an old reduction gearbox and bolt it in somewhere along the drivetrain only backwards so it upped the gearing) even if you put in an old two speed g/box. You can keep it in the faster range for road work, and if you don,t want to go to the trouble of manufacturing linkages to bring control of it to the cab, it,s a simple job to nip out underneath with a hammer/big pair of pliers and change it manually for 'off road work'/heavy low speed towing. This is such a simple solution it is often overlooked, mostly because it is not the modern way to do things.

[vtunimog]

Update on the Engine Swap - the Detroit 2 Stroke 8V92 was just way too big a monster to fit into the poor Ural, at 2,800 lbs way too heavy . I finally found a higher revving 5.9L Cummins TD it has been modified with new injectors, tuning and puts out nearly 390 hp revs to 2900 rpm. I thinked coupled to my 10 speed with overdrive I should be just fine. I found a set of 7 Goodyear 1600x20 tires in new condition nearly for around $1,100 (690 GBP) Keeping my fingers crossed that this works.


At 2900 rpm I think I may have to consider swapping out the differential gears or installing as suggest a reverse reduction gearing set.


Chris M

[paulob1]

if your box is geared with an overdrive, you will be suprised how fast you can go...my diesel zil has the eaton five speed box and fifth is an overdrive the 6bta runs 180 or thereabouts and she will cruise at 70 mph all day long if you can stand the noise...i use her at just 60 mph tops...and she run a treat. hard work at 40 mph though as that is when you have to change up to fifth...its a long haul to 70 mph but once at 50 plus she is flying...

[persistence2]

Paul, you mentioned elsewhere that you were putting some diesel V/8s into a couple of your vehicles. A 6.2 chev and a ford powerstroke. When's that likely to happen?
Persistence.

[vtunimog]

The Ural project is starting to gain momentum, I finally chose a 7.3L Ford Powerstroke V8 , 140,000 Miles, 275hp@3,000 rpm. I think a great match. Problems already -

Considerations:

Air compressor - the Russian stock compressor is huge, I would like to replace with a smaller more efficient model, any idea of the specs of the stock compressor ?

Hydraulic pump - I might be able to mount the stock pump , but would the Ford pump work ?

Transmission - The ZF 5 speed Ford has a better .73 ratio on the Overdrive 5th gear compared to 1:1 however the automatic has some interesting features and a .73 overdrive but the first gear is 2.83 which is much higher than the 6? of the stock gearbox. I almost think that the high geared first gear would creating shifting problems and starting problems on hills etc. Any thoughts ?


Input is greatly appreciated


Chris

[persistence2]

Paul, the most efficient air compressor you can get is an airconditioning compressor. Set it up with the pressure switch to the magnetic clutch and put a industrial oiler on the intake
Persistence. and a water/oil extractor on the output and you will be amazed at how little it switches in!
Persistence.

[Zil lover]

Persistance. You would have to be very brave to entrust the braking of an 8 tonne truck to an A/C COMPRESSOR !!!