cant express how important this is, please help


before anybody jumps ahead i was looking for it on the search box but unfortunately there is not a straigh answer and unfortunately i dont realy know how it works. basicaly all i want to know is:

-what is the differential gear ratio (rear and front)
-i am thinking on changing current ones to wider axles so i would like to know wich axles from wich trucks would work perfect
-what gear ratio axles would i need
-how will it affect the engine
-how is going to be the feel of it
-i would like to know everything if possible.

i have a 1986 daihatsu rocky 2.8 diesel, "no turbo", 2765cc,4cyl
4wd, leaf spring all around.

i dont want to change gear box because thats not going to happen at all but thats not my question.

sorry if i sound rude but unfortunately i am looking for a straigh answer from my questions no run around and besides this site is the only on that can answer my questions so i will keep posting the same question until i get an answer because i am ready to start working on my daihatsu.

other things you might want to know is that i dont do hardcore offroad, 70% i am in the city, 20% offroad and 10% high speed around 60 mph. thanks a lot and all this realy helps me with my rocky project.

Work out the drive ratio by

Work out the drive ratio by putting chalk mark on the prop then jack up one wheel and see how many time you have to turn the prop to turn the wheel round once. Simple.
As for the rest cant help much but would tend to stick with the same prop ratio more or less. If you want wider why not get a set of wheel spacers? whole lot simpler than trying to transplant axles . That will potentially be one big fabrication and welding job I guess.

there is another posibility

there is another posibility which hasnt been considered, the rocky is a body bolted to a chassis... its worth looking to see what other trucks are about with wider coil sprung axles on a chassis, then just cut and chop bodies... for example it may be possible to stick a rocky body on a landrover defender or discovery chassis using the lr mechanicals, lengthening or shortening the chassis to fit the body is relatively simple engineering...brake pipes and rear propshaft are the ony other major bits that i can think of that would need altering...ive used lr as an example cos they are readily available here and i also own one,..... but there again why bother... in the uk there would be no point as latter coil sprung rockies are easily available .

There is information on the

There is information on the ratios at . The ratio you will want depends on what other plans you have for the vehicle. If you are planning on fitting similar size tyres to the original you will probably what to stick to ratios that are close to the original, if they are going to be much bigger you will want to increase the ratio otherwise you will kill the top speed.
If I were to do the swap I would probably be looking for Toyota Landcruiser II axles as these have about the right diff offset to match the gearbox outputs. Anything you use though will require some modifications with at least the welding of new spring perches to the axle in the correct locations likely.
I would think carefully about what you want to achieve, if it is just to give a slighty wider track then I would consider wheelspacers or preferably wheels with more offset as swapping the axles is going to be a lot of work. The main advantage I would see to swapping the axles is for offroad use as for axles like the Toyotas items such as difflocks and upgraded internals are easily available. If it is mainly for road use as you suggest I think I would find it hard to justify the amount of work required to do it properly.

just a few general

just a few general observations on all your recent questions, i get the feeling youre not an experienced mechanic or engineer and are coming up with modifications which are beyond your capabilities. you havnt said which country you are from so we have no idea what parts or donor vehicles are likely to be available in your country which makes it difficult for us to give useful answeres.
if your intended use is mainly on road with no extreem offroading a rocky in standard spec will be perfectly adequate.i would suggest you give rocky a complete service making sure everything is working as intended and then enjoy driving it. projects like changing axles or suspension to non standard set ups take lots of time and money to complete , many such projects never get finished and many that do have ruined what was a perfectly usable vehicle

I would have to agree with

I would have to agree with your comment Richard, and i am talking from considerable experience, and with considerable expertise. Having undertaken most forms of modifications, and scratch building, and having the expertise and facilities available to me, i still find it an arduous task.

Fitting axles will mean removing the existing spring hangers, fabricating new ones, and welding them to the axles PROPERLY. Axle ratios will usually need changing and this usually means making other internals fit, along with the considerable machining facilities needed to do this properly, then the capability to build them properly ensuring basics such as gear mesh are correct. Obtaining axle internals is a considerable task, the research alone is very long winded, even when you have most if the technical information to hand. Other problems are the ancilliary items such as brakes, if these are not properly undertaken the rears will be more powerful than the fronts and it will be dangerous.

There are many other problems, but this should give an indication of what you need to consider.


thanks for the comment and i appreciated very much and i would like to mension a few things:

i own a 1987 daihatsu rocky 2.8 diesel non turbo 2765cc engine 4WD. yeas youre right i am not a professional mechanic or engineer but i do have the right people to do it and provide with feedback on the work being done and yeas i know it involves a lot of cutting, torching, welding, measuring, just to mension a few but again i have a professional welder that will do it for me and besides i have all the tools needed for the job. now going back to the differential i might not do it i will probably stick to the original ones but i will cut out the leaf springs and replace with coil springs we already measure everything we just need to know how far will the suspension travel when done and make sure is not interfering with other steering parts just to give you an idea here is what i will do: remove leaf springs, cut out spring hangers and steering parts, remove axles completly, weld new coil spring mounts under the chassis and on top of the axle housing, longer rs9000 rancho shocks, longer panhard bar that will fit just perfect, new stabilizer bar and complete it with 3 lenght control arms located one on each side welded to where the original leaf spring hangers use to be and the third one on top of te differential housing to a special cross frame member welded to the frame directly and just about the same for the back except steering devices. now regarding coil springs i will use same ones from daihatsu independant from ironman suspension and on the front well i havent decide yeat but i will shortly and i am pretty sure i forgot other things that need to be done. i know its a hard job to be done that involves a lot of money,time, personnel, dedication but where there is a will there is a way, its been done to zusuki samurai already and the results are proven that works perfect as it whas a regular manufacture part. i will try to get pictures and send them so everyone can see them, i live in central america panama city and theres not a lot of daihatsu rockys i'll say out of every 100 cars maybe 5 are rockys but again we also have a lot of land cruisers(all the models), hilux, zusuki samurai, fourunners, not many land rovers or range rovers (older models), nissan patrols (a lot of them), nissan pathfinders or terranos, all types of toyota and nissan trucks as well as mitsubishi pajero (montero) old and new models everywhere, lada niva 4x4, among others. now regarding mechanical parts for my rocky well i can find all major and important parts but when it comes to doors, panels, glass, accesories, electrical wireing, complete transmissions or engines, inside parts unless you can find another one well taken care of in a yard or just take it from another rocky while is driving i have to find the way of fabricate a new one to make it fit or order it from europe ( lot of money involve ) because not even the united states have parts for this cars unless your are looking for universal accesories and but than in the other hand if none of this works well than you are just shit out of luck and will have to sell it in parts or for metal recycling. thanks again.

Dont get this one at alll

At the end of the day with skill and imagination any axles will do to make it an off roader with coils, but to use as a main on road driving machine with part off road use just do subtle suspension mods with the leaf springs, unless the correct coil set up is found with the rockys narrow chassis frame it will handle even worse than leaf springs, im thinking that you have brought yourself the wrong vehicle the way you want to change everything about it.

Full of ideas but no time to do them!!
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