Series 111 gearing ?

[Snagger]

Some of the lower gears were lower, but their upper gears and transfer boxes were standard, I believe. I'll happily be corrected on that, though.

My 109 managed 60 mph eventually on the level with the 12J and standard gearing plus overdrive (cruising gear only, acceleration in 4th with OD being non-existent). Without the roof rack, it could eventually wind itself up to 85 mph on the level and cruised merrily at 60-65 on the level, but lost speed on even shallow long hills. The Tdi allowed 85 mph too (rack installed), but became raucous above 65 mph with OD engaged, but accelerating, even with the rack, is easy and you can maintain 60mph even on relatively steep, long hills. With the 3.54 gears (OD disengaged), the Tdi can struggle on big hills in 4th in the same way as the 12J did with the original diffs, typically dropping to 50mph on long steep hills and not having the guts to keep the OD engaged.

OD works really well with the 12J because you can use standard gearing for acceleration and the engage the OD for cruising. The 3.54 diffs are significantly taller than 4.71 +OD, though (another 25% of the OD's increase), so if you try accelerating or driving up a long hill in 4th +OD, and then imagine it even worse, you get the idea of 3.54 diffs.

[Landowner]

Some of the lower gears were lower, but their upper gears and transfer boxes were standard, I believe. I'll happily be corrected on that, though.

My 109 managed 60 mph eventually on the level with the 12J and standard gearing plus overdrive (cruising gear only, acceleration in 4th with OD being non-existent). Without the roof rack, it could eventually wind itself up to 85 mph on the level and cruised merrily at 60-65 on the level, but lost speed on even shallow long hills. The Tdi allowed 85 mph too (rack installed), but became raucous above 65 mph with OD engaged, but accelerating, even with the rack, is easy and you can maintain 60mph even on relatively steep, long hills. With the 3.54 gears (OD disengaged), the Tdi can struggle on big hills in 4th in the same way as the 12J did with the original diffs, typically dropping to 50mph on long steep hills and not having the guts to keep the OD engaged.

OD works really well with the 12J because you can use standard gearing for acceleration and the engage the OD for cruising. The 3.54 diffs are significantly taller than 4.71 +OD, though (another 25% of the OD's increase), so if you try accelerating or driving up a long hill in 4th +OD, and then imagine it even worse, you get the idea of 3.54 diffs.

Doesn't really matter what diesel engine it is, they all rev about the same. Imagine the Landy up on axle stands in top gear with a brick on the throttle, our series would have shown 50 mph only that's about 12mph per 1000 revs

I would imagine a series 3 should be geared about 15 to 18 mph per 1000 to achieve 70 mph, maybe even 20 mph

Not saying any one is wrong, just that this series is very low geared, or was, its now about 15mph per 1000rpm with the defender diffs

[Snagger]

The engine isn't geared, and all LR 4-pot diesels are limited to the same 4200ish RPM. But the engine is important in that it needs to have enough torque to pull the higher gears otherwise speed and fuel economy will suffer. Having small diameter tyres reduces overall gearing considerably, and so running 6.00s with 3.54 diffs would not be such a massive step up as with7.50s, but is effectively a little more than half the effect of an overdrive with standard gears and 7.50s. An 88 will have no trouble on the 6.00s and 3.54s, and a 109 only a hint of performance decrease over standard, but have you ever seen a 109 on 6.00s?

If you're going from 4.71 and 6.00s to 3.54s and 7.50s simultaneously, you are increasing the axle gearing by approximately 45%, and will be in for a big shock at how badly the car drives on a 12J.

[BSF]

It works out at about a 10% or so gearing increase to step from 6.00s up to 7.50s.

As for BSF's comments, I couldn't agree more. A "DI" retrofit is easier and cheaper than doingt he whole Tdi fit and will put less strain on the transmission (though I am one of the many who have had few problems caused by the increased engine torque, the one gearbox failure being more due to my use of OD and 3.54 gears together in third gear). But, for those who don't want the extra performance, why bother with all the hassle of bigger exhausts, intercooler plumbing and the rad change to include an oil cooler. Much simpler to fit a DI and keep the existing rad and plumbing... Horses for courses and all that!

Thanks for your comments and at the risk of going into a rant about torque and gearbox wear….

What effects the torque through the overdrive is the output from the engine and what gear the main gearbox is in, anything downstream of the overdrive (low ratio, diff ratio) cannot effect what is going on in the overdrive.

In the past I have dealt with gear trains in a non-automotive setting. as I see it the problem with over-torqueing a gear train is initially high wear on the gear teeth as the oil film starts to breakdown between the parts. For short periods this is acceptable if you can put up with the shorter life. If you keep doing it for a long time the components start to produce friction heat faster than the oil can remove it, the temperature goes up and eventually you get a failure caused by that over-temperature. The failure might not actually be the gear teeth, but could be bearing or oil seals, it depends what is weakest. I would suggest that engine output torque rarely can cause a catastrophic gearbox failure, but letting the clutch up viciously adds torque from the rapidly slowing flywheel to the basic engine output and that can cause a very loud bang.

Half shafts are different, they fail suddenly because they are where the highest torque is. They get the engine output torque multiplied by the total gear ration (that would be gearbox ratio multiplied by transfer ratio and again multiplied by diff ration) and that can be massive. The safety valve is wheel spin, but big tyres need a lot more torque to slip, so the half shaft goes instead.

Rant over.

[Snagger]

As I said, I have had very few issues (arguably none at all) caused by the Tdi, and nor do the majority of Tdi or V8 users as long as they don't drive with binary pedal use (ie sharp on-off movements). I think my gear box 3td gear failure was entirely down to my misuse oft he transmission - I was using the overdrive in 3rd as 4th is too high with 3.54 diffs for 30mph, and that much torque resistance combined with the Tdi output nailed the gear. It's like a velodrome cyclist breaking the bike chain through having very high wheel resistance from tall gears and massive torque input on the pedals - a smaller input or lower gearing will reduce the load on the chain. So, any gearing alteration will have toque load effects on every component in the system, including the engine crank shaft, con rods, gudgeon pins and pistons. Increase the gearing and everything upstream of the alteration is under more strain while everything downstream under less; decrease the gearing and everything upstream will be eased while everything downstream loaded higher.

Consequently, I refit the 4.71 rear diff, hated the noise and refit the 3.54 again, restricting high range use of the overdrive to 4th gear to protect the rest of the gear box. Low range with overdrive should not create any overload.

The thermal oil issues are significant with higher loadings. That's why it's helpful to use 4th as much as possible, because it locks the input pinion and main shaft, the gears being loaded only with idling forces.

[Phil Hancock]

4 cylinder series apart from 1 ton or stage 1 V8 spec gearboxes were all the same transfer ratio in high, low range was lower on B suffix and earlier series 2a than the C and on were.

[Landowner]

4 cylinder series apart from 1 ton or stage 1 V8 spec gearboxes were all the same transfer ratio in high, low range was lower on B suffix and earlier series 2a than the C and on were.

Aha, but are the gearboxes the same? maybe they are and all diesel series will only cruise at 40 mph and start off in third if asked to and be in top at 20 mph.

The series 3 is now just about acceptable but still too low geared with the Defender diffs (3.45 ?) its not that we are used to modern vehicles, it's because the engine is revving too much at 45mph. The engine revs that we usually change up at (say 2500 to 3000) see very rapid gearchanges and into top at running speed, cruising at say 2500/3000 is usual but the series would only be doing about 30 mph which is not normal even for a series so our gearing somehow is lower than normal,

The skinny wheels have been changed for defender ones but the profile is about the same, stood side by side they are about the same height.

Must be something different with the cogs but don't know what.

Its ok for now as 45 isn't too slow for local but its not nice revving so much over the 'happy' section of the revs if you know what I mean, it sounds like you should be doing 60 or seventy with the engine nearly on the governors

[Tom Fall]

Just to chuck my two penneth in...

I run a S3 88" day to day as my only car, have done since 2006. When I first got it, my Series was on 6.00x16's and a standard 2.25 petrol. It wouldn't go past 60ish without screaming its nuts off. That changed with an overdrive, which made things more comfortable. Then came bigger tyres, then bigger again until my current 235/85R16's (equivalent to a 7.50x16).

All through this though, I had a rev counter fitted.

I can tell you that at 60mph in 4th (no OD) on the 6.00x16's, my Series was doing just over 4200rpm. That tallies perfectly with what everyone is saying here about gearing.

Now though, with Overdrive and 235/85's but still on standard diffs, she cruises at 2900rpm at 60mph. Tyres made a massive 200rpm difference when I went from 225/75R16's to the current 235/85R16's.

[Landowner]

Just to chuck my two penneth in...

I run a S3 88" day to day as my only car, have done since 2006. When I first got it, my Series was on 6.00x16's and a standard 2.25 petrol. It wouldn't go past 60ish without screaming its nuts off. That changed with an overdrive, which made things more comfortable. Then came bigger tyres, then bigger again until my current 235/85R16's (equivalent to a 7.50x16).

All through this though, I had a rev counter fitted.

I can tell you that at 60mph in 4th (no OD) on the 6.00x16's, my Series was doing just over 4200rpm. That tallies perfectly with what everyone is saying here about gearing.

Now though, with Overdrive and 235/85's but still on standard diffs, she cruises at 2900rpm at 60mph. Tyres made a massive 200rpm difference when I went from 225/75R16's to the current 235/85R16's.

That's interesting and it means that ours is lower geared because with the engine on the governor it would just pull 50 mph so 10 mph slower (checked by sat nav)

[Snagger]

All the Series gear boxes had comparable gearings, with 4th always being a lock-up between the input pinion and main shaft (ie no gears at all), so any Series transmission with any non-1-Ton or V8 transfer box (the latter is integrated in the LT85 anyway) will give you the same output to the prop shaft, from the earliest SI to the last of the SIIIs or Santana units. So, unless you have a modified or non-standard transmission, all your problems will best be solved by 750 or 235/85 tyres and an overdrive, but 3.54 diffs will be bad unless you keep cookie cutter wheels and tyres.

Importantly, the speedo will be thrown out of calibration by changing diffs (35% under-read) or tyre size (approx 10% under-read). Only fitting an overdrive avoids the need for recalibration. Using a speedo built for a 109 and use with 7.50s is a simple way to ensure accuracy, overdrive or not, but using 3.54s will need recalibration by a company like speedycables or JDO1 - I used the latter and have been pleased with their work and service.

[discomikey]

Thanks for your comments and at the risk of going into a rant about torque and gearbox wear….

What effects the torque through the overdrive is the output from the engine and what gear the main gearbox is in, anything downstream of the overdrive (low ratio, diff ratio) cannot effect what is going on in the overdrive.

In the past I have dealt with gear trains in a non-automotive setting. as I see it the problem with over-torqueing a gear train is initially high wear on the gear teeth as the oil film starts to breakdown between the parts. For short periods this is acceptable if you can put up with the shorter life. If you keep doing it for a long time the components start to produce friction heat faster than the oil can remove it, the temperature goes up and eventually you get a failure caused by that over-temperature. The failure might not actually be the gear teeth, but could be bearing or oil seals, it depends what is weakest. I would suggest that engine output torque rarely can cause a catastrophic gearbox failure, but letting the clutch up viciously adds torque from the rapidly slowing flywheel to the basic engine output and that can cause a very loud bang.

Half shafts are different, they fail suddenly because they are where the highest torque is. They get the engine output torque multiplied by the total gear ration (that would be gearbox ratio multiplied by transfer ratio and again multiplied by diff ration) and that can be massive. The safety valve is wheel spin, but big tyres need a lot more torque to slip, so the half shaft goes instead.

Rant over.

I beg to differ, The effect of different sized wheels, or ratio diffs, or in fact reduction hubs will affect the amount of internal stress on anything upstream of it in relation to its torque output.

i.e. with reduction hub gearing of 30%, everything upstream, i.e. shafts, diff, xfer box, overdrive, gearbox etc etc, will have a 30% lower internal torque than if the same overall torque output was achieved with standard hubs.

so if you were towing up a hill and lets say required 100nm of wheel torque, and you were in say, 4th hi for example, with standard gearing, that torque would be X amount on the gearbox.

if you were towing up the same hill with the same required 100nm of wheel torque, and you were in 4th with 30% reduction hubs, that torque in the gearbox would be X amount -30% effectively lowering the stress on the gearbox.

which is exactly why tractor brakes are inboard of the reduction hubs. as a result the braking effort required to stop the tractor is much less. requiring smaller brakes and less cost, more serviceability etc etc

also a smaller lighter duty transmission is required.

[BSF]

I beg to differ, The effect of different sized wheels, or ratio diffs, or in fact reduction hubs will affect the amount of internal stress on anything upstream of it in relation to its torque output.

i.e. with reduction hub gearing of 30%, everything upstream, i.e. shafts, diff, xfer box, overdrive, gearbox etc etc, will have a 30% lower internal torque than if the same overall torque output was achieved with standard hubs.

so if you were towing up a hill and lets say required 100nm of wheel torque, and you were in say, 4th hi for example, with standard gearing, that torque would be X amount on the gearbox.

if you were towing up the same hill with the same required 100nm of wheel torque, and you were in 4th with 30% reduction hubs, that torque in the gearbox would be X amount -30% effectively lowering the stress on the gearbox.

which is exactly why tractor brakes are inboard of the reduction hubs. as a result the braking effort required to stop the tractor is much less. requiring smaller brakes and less cost, more serviceability etc etc

also a smaller lighter duty transmission is required.

Sorry, we are going to have to agree to differ here.

You are turning the problem onto its head. The source of the torque is the engine; you can't start an argument with how much torque you would like at the wheels. It is the engine that produces the torque. I am assuming that we are talking about the engine's maximum torque (195 lb/ft in a 200 Tdi) since the original discussion was about torque induced damage to the overdrive. I agree that we do not always use maximum torque from the engine, but it will be that maximum (full right foot at 1800 RPM) that puts most torque through the drive train. If you change the diff ratio you may alter a lot of other things but not the maximum torque in the gearbox/overdrive.

If the engine is producing 195 lb/ft of torque at the flywheel, then that is what is going into the front of the gearbox (let's ignore any mechanical losses throughout this). If you are in 4th gear that is also the output torque from the gearbox and therefore the input torque into the overdrive. (If the overdrive is in high the output torque will be 154 lb/ft)

If you are in 3rd gear the input torque to the gearbox will still be 195 lb/ft, but the output torque from the gearbox into the overdrive will be 195 multiplied by 1.5 (Suffix C gearbox) which is 292 lb/ft. Whatever you do with this torque downstream (again ignoring mechanical losses) the power (torque x RPM) will remain the same and since the RPM is reduced by gearing then the torque will be higher.

As an example in 1st gear, low transfer with a 200 Tdi, the torque at the half shaft will be 7918 lb/ft (it won't, of course, because that amount of gearing will have considerable internal losses). In reverse it would be over 9000 lb/ft. No wonder they sometimes break.

I can't be the only one who sometimes forgets to put the overdrive back in low before pulling away and I guess that we would always push a bit harder with our right foot if the acceleration didn't seem right, which means that overdrives are regularly coping with torques approaching 700 lb/ft, well over 4 times its design maximum.

I suspect that rapid engagement of the clutch coupled with the rather large amount of backlash in the transmission that really does the damage. Mechanical sympathy is required.

[Landowner]

The series is on the same profile tyres as my Defender

I stood one of my 235/85/16 Wolfs next to the 90 tyre, the Wolf is almost 5inches taller that's two and a half inches more ground clearance and a lot higher geared.

Any one know the official top speed of a standard diesel series 3 ?

[discomikey]

Sorry, we are going to have to agree to differ here.

You are turning the problem onto its head. The source of the torque is the engine; you can't start an argument with how much torque you would like at the wheels. It is the engine that produces the torque. I am assuming that we are talking about the engine's maximum torque (195 lb/ft in a 200 Tdi) since the original discussion was about torque induced damage to the overdrive. I agree that we do not always use maximum torque from the engine, but it will be that maximum (full right foot at 1800 RPM) that puts most torque through the drive train. If you change the diff ratio you may alter a lot of other things but not the maximum torque in the gearbox/overdrive.

If the engine is producing 195 lb/ft of torque at the flywheel, then that is what is going into the front of the gearbox (let's ignore any mechanical losses throughout this). If you are in 4th gear that is also the output torque from the gearbox and therefore the input torque into the overdrive. (If the overdrive is in high the output torque will be 154 lb/ft)

If you are in 3rd gear the input torque to the gearbox will still be 195 lb/ft, but the output torque from the gearbox into the overdrive will be 195 multiplied by 1.5 (Suffix C gearbox) which is 292 lb/ft. Whatever you do with this torque downstream (again ignoring mechanical losses) the power (torque x RPM) will remain the same and since the RPM is reduced by gearing then the torque will be higher.

As an example in 1st gear, low transfer with a 200 Tdi, the torque at the half shaft will be 7918 lb/ft (it won't, of course, because that amount of gearing will have considerable internal losses). In reverse it would be over 9000 lb/ft. No wonder they sometimes break.

I can't be the only one who sometimes forgets to put the overdrive back in low before pulling away and I guess that we would always push a bit harder with our right foot if the acceleration didn't seem right, which means that overdrives are regularly coping with torques approaching 700 lb/ft, well over 4 times its design maximum.

I suspect that rapid engagement of the clutch coupled with the rather large amount of backlash in the transmission that really does the damage. Mechanical sympathy is required.

okay, so i guess we will.

what i was trying to put across was if the engine had in effect at peak, enough torque to break something. the effect of a higher gearing further down will increase stress on the components further up. remembering that an engine only produces more torque when it is required, and the engine labours. i.e. torque curve diagrams are plotted when there is a load applied to the engine.

if no/less load is applied, there is no/less stress.

think like when you change down, the engine has an easier time working, imagine if that gearbox was at the tail end. the effective change down would still mean the engine has an easier time, requiring less of its total torque output. the same as changing down in a gearbox, the less required torque to pull the same load, means the less torque applied through the drivetrain from the point of gearing reduction back up to the engine.

so if that gear reduction was in the hubs, everything has an easier time. its exactly the reason why taller tyres break more shafts and diffs and gearboxes than smaller tyres.

[Phil Hancock]

Any one know the official top speed of a standard diesel series 3 ?

It used to be reconed as 65mph at 4000rpm as that was the max revs on a 2.25 of the 2a flavour.

[Phil Hancock]

Aha, but are the gearboxes the same? maybe they are and all diesel series will only cruise at 40 mph and start off in third if asked to and be in top at 20 mph.

The series 3 is now just about acceptable but still too low geared with the Defender diffs (3.45 ?) its not that we are used to modern vehicles, it's because the engine is revving too much at 45mph. The engine revs that we usually change up at (say 2500 to 3000) see very rapid gearchanges and into top at running speed, cruising at say 2500/3000 is usual but the series would only be doing about 30 mph which is not normal even for a series so our gearing somehow is lower than normal,

The skinny wheels have been changed for defender ones but the profile is about the same, stood side by side they are about the same height.

Must be something different with the cogs but don't know what.

Its ok for now as 45 isn't too slow for local but its not nice revving so much over the 'happy' section of the revs if you know what I mean, it sounds like you should be doing 60 or seventy with the engine nearly on the governors

You must have a 1 ton box in there based on those speeds and revs.

[Snagger]

Sorry, we are going to have to agree to differ here.

I used to think that way too, but it's wrong. Try pushing a door open near its handle and try again near its hinges. Your shoulder muscles are just as strong and the door just as heavy, but the leverage (ie gear ratio) is markedly higher - your fingers are working much harder if you push near the hinge line, even though their required movement is less, just like increased gearing in a transmission. If the transmission isn't strong enough, it'll break under the resistance - ask a person with arthritis or osteoporosis to push a door open that way and see the look they give you! That's what happened to my third gear, which was perfectly happy with the Tdi and overdrive, but the addition of the taller diffs killed it.

[BSF]

I used to think that way too, but it's wrong. Try pushing a door open near its handle and try again near its hinges. Your shoulder muscles are just as strong and the door just as heavy, but the leverage (ie gear ratio) is markedly higher - your fingers are working much harder if you push near the hinge line, even though their required movement is less, just like increased gearing in a transmission. If the transmission isn't strong enough, it'll break under the resistance - ask a person with arthritis or osteoporosis to push a door open that way and see the look they give you! That's what happened to my third gear, which was perfectly happy with the Tdi and overdrive, but the addition of the taller diffs killed it.

Again, back to front thinking!

When you open the door by pushing near the handle your muscles may be just as strong, but you are not using the full force of them. The person with arthritis gets pain when he uses a lot of force; his arm muscles and joints are the engine and that is what is not working correctly.

When you floor the accelerator you are using the full torque of the engine which will result in either more acceleration or less speed loss as you go up a hill. You cannot increase the torque output from the engine by using a lower gearing downstream.

[Snagger]

Sorry, BSF, but you're wrong. While the engine torque is unaltered, the resistance to it by the transmission is increased. It's the same reason that triallers and rock crawlers with oversize tyres blow their diffs and half shafts so often. I understand your stance - I used to share it, but it's wrong.

[BSF]

Sorry, BSF, but you're wrong. While the engine torque is unaltered, the resistance to it by the transmission is increased. It's the same reason that triallers and rock crawlers with oversize tyres blow their diffs and half shafts so often. I understand your stance - I used to share it, but it's wrong.

I do rather think you need to read what you wrote again. Without resistance from the transmission the torque from the engine would be zero, perhaps we have a misunderstanding of the term torque? The engine can only transmit torque to the gearbox if there is resistance from the gear train.

The original discussion was about the torque applied to the overdrive, which is a gear train, a broken half shaft is a pure torque induced shaft failure at the point of maximum torque with no safety valve in the form of wheel slip. It actually supports my point which was that no more load is put through the overdrive in transfer low range than in high.

[FridgeFreezer]

Easy guys - You're trading units, torque * revs = work done, so increase revs with gearing you can do the same work at lower torque.

Obviously at either end there are limits to available torque & revs so it's all about compromise.