changing diff ratios

[sambo]

How much do people think changing the ring and pinions on my HJ60 from the standard 3.7 to 4.11 would cost. What is the cheapest way of doing it.

[RUFF]

How much do people think changing the ring and pinions on my HJ60 from the standard 3.7 to 4.11 would cost. What is the cheapest way of doing it.

A 60 series allready has 4.11 ratios not 3.7.

[ROD666]

How much do people think changing the ring and pinions on my HJ60 from the standard 3.7 to 4.11 would cost. What is the cheapest way of doing it.

the cheapest way would be to do nothing, next would be second hand r/p from a wrecker but for piece of mind you should get new that way you know they haven't been abused

[sambo]

My mistake, I would like to change the diff ratio to 4.7 or something similar. Any suggestions on where to get them from

[dumbdunce]

are you doing the work yourself or paying someone to do it?

it's better value for money to put crawler gears in the transfer case and leave the diffs alone - Marks Adaptors has a set with 8% underdrive in high range and 3.08:1 low range which give you the equivalent of a 4.4 diff ratio in high range and 6.3 in low range, it's the best of both worlds, requires less disassembly of your vehicle and unlike the diff gears can be installed by the average backyard mechanic. Transfer gears are pretty hard to break, whereas diff gears are far from bulletproof - if you break your standard ratio diffs, a spare is easy to find. if you change the ratio, finding replacements can be difficult.


cheers

Brian

[sambo]

i was planning on doing it myself. but if the only way to do it is aftermarket then i think i will have to give it a miss. $$$$

I was hoping that i could cannibulise them from another truck. I put 33s on and i would like to get things back to the same ratios.

[sambo]

The 100 series 5speeds have a ratio of 4.3 does anyone know if they will fit in a 60 series diff

[dumbdunce]

you might need to use the whole diff centre, x2, not sure if the ring and pinion can be interchanged. going 4.3 over 4.1 is hardly worth the expense and drama, it's less than 5% change eg if you used to do 2000rpm at 100km/h with 4.3's you'll be doing 2100rpm - hardly worth it.

if you're only running 33'w it really isn't worth changing the diff ratios, 60's came stock with 7.50/16 tyres with 4.1 diffs, those tyres are almost 32" diamter and most 33's are barely more than 32" diamter.

cheers

Brian

[4sum4]

get some 6.2`s

[dumbdunce]

get some 6.2`s

yeah they are cheap if you can find two wrecked stout utes but they aren't real strong.

and an almost 50% ratio change would make for some impressive highway revs. to put it in perspective, you'd need to fit 44 inch tyres to bring your revs back to stock levels at any given speed.

[NICK]

you might need to use the whole diff centre, x2, not sure if the ring and pinion can be interchanged. Brian

no they cant, although they could but you would need to drill and tap the crown.


NICK

[slosh]

So how did the old Stouts perform with gearing like that?

[dumbdunce]

So how did the old Stouts perform with gearing like that?

I doubt they're a highway touring contender...

[sambo]

The reason i was wanting to change is because since i put the 33s on i have noticed a drop in power. And since 31 to 33 is only a 6.4% increase in tyre circumference the 4.3 ratio diffs will do the trick.

The other option is i could add propane injection to make up for the lost power.

And my 33s are actually 33 inchs in diameter.

[dumbdunce]

turning a bigger wheel/tyre combo uses more power, there's no way to get around it. Bigger tyres higher rotational inertia, more rolling resistance, and more aerodynamic drag - added to that the higher stance of the vehicle because of the taller tyres increases the vehicle's overall aerodynamic drag, and when all these things are combined you notice reduced performance. Simply changing the differential ratios will put the engine back into the manufacturer's rpm ranges for given road speed/gear combinations, but it does not reduce the actual physical forces that are working together to slow you down. if you did it, you'd be disappointed.

as for propane injection, it is really only viable on direct injected turbo diesels. If you have a 12H-T in there, then you have the potential to make decent power especially with intercooling and an aftermarket turbocharger. If you have a 2H motor, with or without a turbo, the best you can hope for from propane injection is a slight increase in fuel efficiency at cruise (probably not enough of an increase in efficiency to pay for the propane), and little or no peak power gains.

probably the cheapest way to make your truck faster is to put a V8 in it, which can be accomplished with a holden 253 or 308 for a couple of thosand dollars if you do most of the work yourself (source engine, clutch,flywheel and bellhousing, manufacture engine mounts to chassis, wiring etc). or if you feel sophisticated you can swap in an injected holden V6 or V8 for slightly more $.

If you want to stick with the factory donk, think about extractors or an aftermarket turbo depending on your budget. the 2H responds well to a free flowing exhaust, the factory exhaust manifold is particularly restrictive. If you have a factory turbo and want more go from that, intercooling and a larger aftermarket turbocharger are the go, plus propane if you still want more.

I know it all sounds expensive and complicated but just changing the diffs for a very slightly different ratio isn't going to perform miracles and you will have effectively wasted your time and money.


opinions will vary I'm sure

cheers

Brian

[sambo]

Thanks for the lecture on things i already know and have on my rig.

1. the 2H is already a direct injection diesel and so with a turbo it is a prime candidate for propane.

2. my 2H has an aftermarket Garret turbo fitted to it. which makes it good for propane. As far as i know there isn't any major differences between the 2H and the 12H-T apart from the turbo, the glow plugs are different as well. I think there is a slight difference in the injection timing.

I am not talking about the change in aerodynamics. I mean the difference it has made trying to get up the side of a sand dune, ( i would hardly be doing 100kmh), i can feel the difference in torque from what it used to have.

And as for the suggestion for putting a V8 in. Thats one way to double my fuel bill.

And you can get around the fact that it takes more power to turn a bigger tyre. the truth of the matter is that it only takes more power to turn a bigger tyre if you want it to turn at the same revolutions per minute. so changing the diff ratios will mean that you will have the same power at the same speed but with bigger tyres.

Why do you thing that propane on a 2H with an aftermarket turbo will not make anywhere near as much power as propane on a 12H-T.

I would be interested to hear your opinion.

Regards.

[dumbdunce]

1. the 2H is already a direct injection diesel and so with a turbo it is a prime candidate for propane.

no, the 2H is most definitely not a direct injected engine.

2. my 2H has an aftermarket Garret turbo fitted to it. which makes it good for propane. As far as i know there isn't any major differences between the 2H and the 12H-T apart from the turbo, the glow plugs are different as well. I think there is a slight difference in the injection timing.

there are many differences internally. your 2H with aftermarket garret turbo is (really, trust me on this) indirect injected (12H-T is). it has no piston skirt oiling (12H-T does). it has no boost compensation aneroid on the fuel pump (12H-T) does. the pistons are different, the 12H-T has thicker crowns and skirts to allow greater heat dissipation and a dished combustion chamber in the top of the piston. the hdeads are different - there are no combustion chambers in the 12H-T head. 2H has a 21:1 compression ratio (12H-T is lower to allow more reliable performance under boost) the 2H is not a good candidate for turbocharging at all let alone propane injection. when propane injection is used on indirect injected diesel engines a situation evolves where colliding flamefronts can cause catastrophic damage much like severe detonation in a petrol engine.

I am not talking about the change in aerodynamics. I mean the difference it has made trying to get up the side of a sand dune, ( i would hardly be doing 100kmh), i can feel the difference in torque from what it used to have.

I am also not only talking about the change in aerodynamics. Bigger tyres have higher rotational inertia. that means it takes more energy to change their rotational velocity. they are heavier. that means it takes more energy to change their linear velocity. wider tyres have more rolling resistance. that means it takes more energy to push them along the ground. even if you change your your diff ratios you are not changing the power of your engine (ie the rate at which it delivers energy to the wheels) so even with a diff ratio change you will never return to the level of performance you had with smaller tyres.

And as for the suggestion for putting a V8 in. Thats one way to double my fuel bill.

you can't have something for nothing - more power means more fuel. I agree that a petrol V8 is not an economical choice of engine but if you want power, it's a cheap (until yul start buying fuel) way to get it.

And you can get around the fact that it takes more power to turn a bigger tyre. the truth of the matter is that it only takes more power to turn a bigger tyre if you want it to turn at the same revolutions per minute. so changing the diff ratios will mean that you will have the same power at the same speed but with bigger tyres.

no. at the very least you should be able to understand that you have made your vehicle *heavier* with the bigger tyres. that alone counts for a tiny bit of lost performance.

Why do you thing that propane on a 2H with an aftermarket turbo will not make anywhere near as much power as propane on a 12H-T.

because the 12H-T is by far the better engine for making big power. see facts above.

man, I'm trying to help you, I don't want you to waste the money and time on what really is a pointless modification. Since you have the turbo already, invest in a pyrometer and then fiddle with your boost a LITTLE bit, the 2H can probably handle 9 or 10psi without grenading, at least not immediately - but the bottom line is it's not a strong motor for forced induction. If you've got a few bucks to spend then intercooling and upping the boost to 11 - 12psi is your best bang for buck short of trying to track down a 12H-T (but these babies are pretty expensive). If you are going to play with your boost to get more power then it is also essential to tune the max fuelling for peak power, and to do that you need an exhaust pyrometer. If you're already running high boost then your engine is a time bomb, combustion chamber temperatures will be going through the roof and its only a matter of time before you melt a piston or crack a precombustion chamber and drop half a chamber into the cylinder, which has fairly catastrophic results.

and I'm really not making it up. the 2H really truly is indirect injected. I promise. even Ruff would agree with me on this one and he hates me

cheers

Brian

[RUFF]

and I'm really not making it up. the 2H really truly is indirect injected. I promise. even Ruff would agree with me on this one and he hates me

cheers

Brian

Brian you have got me totaly convinced that you are right in absolutly everything you have said except i have one question. Why do i hate you

[dumbdunce]

Brian you have got me totaly convinced that you are right in absolutly everything you have said except i have one question. Why do i hate you

cos I'm better looking that you, obviously

[sambo]

Dumbdunce

Sorry about the post i put on yesterday, i had a really bad day and was not in a good mood. I agree with wat you are saying about the bigger tyres.

A few Q's about the engine.

The boost compensation aneroid, does that just restricts the fuel pressure until the boost builds up.

I thought that propane injection only caused detonation when to much was being injected.

The rest is news to be and i have no reason to dissagree.

Sambo

[dumbdunce]

Dumbdunce

Sorry about the post i put on yesterday, i had a really bad day and was not in a good mood. I agree with wat you are saying about the bigger tyres.

A few Q's about the engine.

The boost compensation aneroid, does that just restricts the fuel pressure until the boost builds up.

I thought that propane injection only caused detonation when to much was being injected.

The rest is news to be and i have no reason to dissagree.

Sambo

no hard feelings.

the aneroid on factory turbo setups limits the fuel delivery volume under off-boost conditions to reduce emissions and soot loading of the oil. It also slightly improves combustion/exhaust temperatures and fuel economy a bit, but not much. fuel pressure (and consequently, relative injection volume) is controlled by the cracking pressure of the injectors.

for propane to work as a combustion catalyst it has to be well mixed with the fuel and air. In indirect injected engines the precombstion chamber design prevents the propane from effectively mixing with the fuel/air, so instead of acting as a catalyst it just burns on its own. you can turn the propane down to a level where it doesn't cause any problems but the benefit is negligible. I've tried it with turbo and non turbo indirect injected engines and it just don't deliver any appreciable power gains, and sure does make the motor make some horrible noises

cheers

Brian

[sambo]

apart from the piston skirt oiling is the only difference between the two engines the head.

If i were to come across a 12H-T head. could it be bolted straight to a 2H block or is it not worth bothering. Should i just look for a complete 12H-T.
Or even a 1HD-T

Sam

[dumbdunce]

apart from the piston skirt oiling is the only difference between the two engines the head.

If i were to come across a 12H-T head. could it be bolted straight to a 2H block or is it not worth bothering. Should i just look for a complete 12H-T.
Or even a 1HD-T

Sam

pistons are different too - the combustion chamber is in the pistons of the direct injected motor, it's not really viable to convert a 2H into a 12H-T. I'm not saying it can't be done but it would be very expensive. speaking of expensive, low km import 12H-T's are over $7000 I think! - send "Nick" a PM he will be able to give you a realistic estimate. To do a 1HD-T conversion you have to either pick up the bellhousing and flywheel off a 1HZ from a HZJ75 with H55F transmission, and change your gearbox input shaft to a fine spline one (requires full disassembly of gearbox), or get the engine, gearbox and transfer as a package deal from an 80 series, which is big dollars again obviously. other optiions might be a chev 6.2/6.5 V8 diesel but they are also not a cheap swap.

I wish there were cheap answers :(

[sambo]

maybe i will just wait till i can afford a 80 or 100 series.