Hippo said:

I don't think this gives the correct results.

When lifting the wheels on one side only yer measuring from that wheel to the prop, which is different to measuring both wheels turning on the lifted axle pair to the prop. Hence why I think yer results show 0.2 instead of 0.8 which is what I think it should be. Reason for this is the turning goes through the sun gears in the diff instead of the crown wheel.

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Well - I am not so familiar with the guts of a IRD but - if this was a series landy it would be valid. All the diff would do is half the prop revolutions 'cos only one wheel rev is being input instead of two as the other side is fixed - then reverse the process at the other end as both diffs are identical. It would be exactly 1 to 1 - Is there some asymetrical gearing in an IRD differential? Would you not think that if I jack all four wheels up and perform the same test both sides simultaneously I would get the same result? - I will try it tomorrow.
- good fun innit (;-))

You have hit the mail on the head
If one complete side of a Freelander is lifted, and say a rear wheel is turned, the front will also turn. Because of the gearing difference between front and back, the front should turn slightly more for each revolution if the rear. This assumption is based on the VCU not slipping, absorbing the difference.

Nodge68 said:

You have hit the mail on the head
If one complete side of a Freelander is lifted, and say a rear wheel is turned, the front will also turn. Because of the gearing difference between front and back, the front should turn slightly more for each revolution if the rear. This assumption is based on the VCU not slipping, absorbing the difference.

Click to expand...

Yup - Just to prove to myself before starting this morning this morning I am not having a senior moment - I jacked her up and checked that 20 revs one front wheel gave EXACTLY 20 opposite turns other front wheel (prop locked by handbrake) - No surprise there then. No asymmetry in the behaviour of the diff in an IRD.

I repeated my previous test but with 4 times the sample size (40 total wheel revs instead of 10)
I marked up all wheels relative to the car and the VCU to both sides of itself (checked afterwards that the VCU had not slipped at all)
20 revs of each front wheel in turn with matching rear free (other wedged) - measured lag at each rear wheel 3.3"
Second test same but all output to one rear wheel only (as keeping backlash consistent is the biggest potential error) - measured lag 6.6" 6.6"/2 = 3.3"
Rear tyre diameter 26" - therefore circumference 81.69"
Taking the ratios from Hippo's thread "Freelander 1 IRD Drive Ratio"
I would expect a lag of 0.008819 rear wheel revs/front wheel rev for a normal IRD
20 x 0.008819 x 81.69" = 14.4"
I would expect a lag of 0.002024 rear wheel revs/front wheel rev for a V6 IRD
20 x 0.002024 x 81.69" = 3.315" - measured lag was 3.3"
QED - I have an IRD with the same ratio as a V6
This is a 2005 TD4 Auto HSE with a 2005 GKN VCU in good condition (probably the original) and therefore quite likely to have the original IRD

dfossil said:

Yup - Just to prove to myself before starting this morning this morning I am not having a senior moment - I jacked her up and checked that 20 revs one front wheel gave EXACTLY 20 opposite turns other front wheel (prop locked by handbrake) - No surprise there then. No asymmetry in the behaviour of the diff in an IRD.

I repeated my previous test but with 4 times the sample size (40 total wheel revs instead of 10)
I marked up all wheels relative to the car and the VCU to both sides of itself (checked afterwards that the VCU had not slipped at all)
20 revs of each front wheel in turn with matching rear free (other wedged) - measured lag at each rear wheel 3.3"
Second test same but all output to one rear wheel only (as keeping backlash consistent is the biggest potential error) - measured lag 6.6" 6.6"/2 = 3.3"
Rear tyre diameter 26" - therefore circumference 81.69"
Taking the ratios from Hippo's thread "Freelander 1 IRD Drive Ratio"
I would expect a lag of 0.008819 rear wheel revs/front wheel rev for a normal IRD
20 x 0.008819 x 81.69" = 14.4"
I would expect a lag of 0.002024 rear wheel revs/front wheel rev for a V6 IRD
20 x 0.002024 x 81.69" = 3.315" - measured lag was 3.3"
QED - I have an IRD with the same ratio as a V6
This is a 2005 TD4 Auto HSE with a 2005 GKN VCU in good condition (probably the original) and therefore quite likely to have the original IRD

Click to expand...

Your results are what I'd expect to see.
In this test, all IRD's will show the same result. The V6 IRD ratio change is at the drop gear, not the axle ratio gear which is what you are measuring.

Nodge68 said:

Your results are what I'd expect to see.
In this test, all IRD's will show the same result. The V6 IRD ratio change is at the drop gear, not the axle ratio gear which is what you are measuring.

Click to expand...

Hold up a sec, I'm not sure if I've got this right but do you mean that the propshaft -> front diff ratios are the same regardless of IRD?
(I may have misread that)

Cuz;
V6 : Propshaft to Front driveshafts (or diff) - 3.206
Non V6 : Propshaft to Front driveshafts - 3.186

They're slightly different as all of the gears inside the V6 ird (apart from the crown wheel and pinion) are different, not just the drop gears...

Front to Rear wheel rotations will be different.

VCU Locked:
Non V6: 1:1.0088 front to rear ratio
V6: 1:1.0025 front to rear ratio

Sorry, I may have got the wrong end of the stick here because I've mostly skim read the thread as at work, will do a deeper read at home.

But, remember the test (as has been pointed out) is invalid unless all four wheels are off the ground and axle pairs are turning synchronised.

I can work out the 1 wheel to 1 wheel ratios when I get sat down in front of my pc much later on.

EDIT: I'm an idiot, it doesn't actually matter that there's two differentials in play, one cancels the other out in the multiplication chain

A differential ALWAYS acts as a doubler with one wheel locked regardless of how many teeth are in it, as with one gear locked you have one rotation of the internal gears AND one rotation of the whole gear SET. They are fixed - remember if you've got both front wheels off the ground spinning and you grab one, the other doubles in speed.

This means that dropping the diffs into the conversion factor if you're going wheel to wheel makes no difference as you end up with ( 2 x (diff A) x 1/(diff B) x 1/(2) )

I think? His results should be valid?

The V6 ratio change is done inside the IRD after the gearbox input but before the front diff and output to the rear. This is why only one rear diff is needed across the engine /gearbox range.
There's a thread on here somewhere, although it's been hacked to bits due to Troll activity.

Nodge68 said:

The V6 ratio change is done inside the IRD after the gearbox input but before the front diff and output to the rear. This is why only one rear diff is needed across the engine /gearbox range.
There's a thread on here somewhere, although it's been hacked to bits due to Troll activity.

Click to expand...

Changes BEFORE the IRD diff and output are about gearing. Changes AFTER are about the front to back ratios - you are right about the gearing - but it does not invalidate my argument.

(Edit - deleted the comment on diffs - yes there may be only one rear diff - but there are
effectively different pinion ratios at the front)

Also I have taken no account of the overall gearing - anything before the final drive train. I imagine the gearing would be something
similar to the Manual TD4 rather than the V6 as that's got more grunt. I have no way of examining that with an auto box without a stripdown - (or revcounter/speedo or revcounter to/GPS) I am only commenting on my vehicle by the way - not trying to tell others that ALL AUTO TD4s are same as mine - it just looks like a possibility - easily evaluatate by my two wheel up test.

I think it warrants a fresh thread - Peeps - get back to measuring you wheels for Hippo on this one - I have highjacked it more than I should have.

Nodge68 said:

The V6 ratio change is done inside the IRD after the gearbox input but before the front diff and output to the rear. This is why only one rear diff is needed across the engine /gearbox range.
There's a thread on here somewhere, although it's been hacked to bits due to Troll activity.

Click to expand...

Because of the way the gear train works in a U shape and the fact that the output crown wheel comes off the intermediate step when you change one of the two ratios in the box you have to change both if you want to keep the input and output shafts centralised.

Have a read of:
https://www.landyzone.co.uk/land-rover/freelander-1-ird-drive-ratio.280728/
Where hippo took the two types apart and counted teeth.

Remember that the power comes off the intermediate shaft for the prop and see that the intermediate shaft is part of the drop gearing process...

You'll notice that the gear ratio to the pinion remains the same, regardless of actual final gear ratio used in the IRD.
Well you would if I could upload a crop if Hippo's picture

Nodge68 said:

You'll notice that the gear ratio to the pinion remains the same, regardless of actual final gear ratio used in the IRD.
Well you would if I could upload a crop if Hippo's picture

Click to expand...

Yes - I have studied that thread again - yes the front pinion stays the same - what I said above in #87 was that the effective pinion ratio changed - ie when taken together with the gears

(incidentally there is a great little tool - google it - called Snipping Tool -which allows you to make a selection of anything - bits of webpage, thread, whatever, and save it as a .jpg - then you can paste it wherever you like - very useful) - example the picky above

Nodge68 said:

You'll notice that the gear ratio to the pinion remains the same, regardless of actual final gear ratio used in the IRD.
Well you would if I could upload a crop if Hippo's picture

Click to expand...

Yep, but the gearing to the shaft that the crownwheel and pinion are on from the diff changes...

Apologies if this sounds condescending, I just want to make sure we're on the same page and I've explained it clearly.
So if you look at both the IRD pictures in his thread, start from the front diff in the top left corner (the bit with 11 and 16 teeth, but ignore its internal teeth,) this will always be spinning at front axle speed (aka the same RPM as the wheels.)

In the V6 version:
This is connected to the gear immediately to it's right, with 39 teeth.
This 39 tooth gear engages with and transfers power with the 22 teeth gear underneath it onto the intermediate shaft.
This is the same shaft as the 38 tooth crownwheel on the bottom right,
This crownwheel transfers power with the 21 tooth pinion and towards the back of the car.

This means that from the front wheels to the propshaft you have traversed:
39 teeth -> 22 teeth ( ratio of 1.773 ish)
38 teeth -> 21 teeth ( ratio of 1.810 ish)

Total ratio so far is 1.773 * 1.810 =~3.21

With me so far?

Now look at the second picture for the TD4 (1.8K/2.0L) version and follow the same path.
The front diff is connected to the gear to it's right with 37 teeth this time
This meshes with a 21 tooth gear. This gear mesh is different...
This then goes to the same 38 tooth crown wheel
and out through the 21 tooth pinion

This means that from the front wheels to the propshaft you have now traversed:
37 -> 21 teeth ( 1.762 ish)
38 -> 21 teeth ( 1.810 same as v6!)

This means on the non v6 box the total ratio is approximately 1.762 * 1.810 = 3.19 which is slightly different to the figure above.

The second and third pictures in his thread above are very informative about how the power flows through the box

EDIT: Have a gander at the following, this is how power flows from the front wheels to the propshaft:


The top left is going out to the front right wheel from the diff, the output to the front left wheel is the INNER shaft on the input shaft top right. (This is a photo of the bottom of the IRD)

Sorry @Hippo for stealing your images!

That thread is really good but I think Hippo got the tooth count on the TD4 and V6 IRD round the wrong way. The pictures show the V6 has a lower ratio than the TD4. Or maybe I've just had a long day?

Nodge68 said:

That thread is really good but I think Hippo got the tooth count on the TD4 and V6 IRD round the wrong way. The pictures show the V6 has a lower ratio than the TD4. Or maybe I've just had a long day?

Click to expand...

The second picture on that thread shows the power path to the front wheels

V6 = 30 -> 23 teeth, 22 -> 39 teeth = 0.77 * 1.77 = 1.36
1.8 = 29 -> 24 teeth, 21 -> 37 teeth = 0.83 * 1.76 = 1.46

This means that the V6 is longer geared than the 1.8, it spins slower for the same speed as it has more torque. Lazy geared!

Wow a lot has been said since I last looked. To save going back and finding bits to quote...

Lifting 2 wheels on one side to measure difference when turning one and seeing the other turn... I did this some time ago and was told my result wouldn't work due to the sun gears. Can't remember the full story but I never followed it up. I always thought it was strange it was considered wrong.

Regarding Td4 auto being different to Td4 manual... if yer take oft the pinion gear yer can count the teeth behind it when turning things to see how many teeth they have.

Teeth count... never been told the teeth counts are wrong or crossed over before. I still have them so I can count them again if required. Do the ratio's I calculated match those of the rave etc. That's my first questioning.

Hippo said:

Lifting 2 wheels on one side to measure difference when turning one and seeing the other turn... I did this some time ago and was told my result wouldn't work due to the sun gears. Can't remember the full story but I never followed it up. I always thought it was strange it was considered wrong.

Click to expand...

Differentials confuse the hell out of people because they have weird teeth numbers in them and apparently operate on witchcraft. But standard planetary gear driven differentials are dead simple, they have an equation:
Input RPM x 2 = LEFT RPM + RIGHT RPM
This means if LEFT RPM = 0 (wheel on ground) the equation is Input RPM x 2 = RIGHT RPM

Because you have two differentials in a path Front Right wheel to Rear Right wheel, the RPM changes cancel each other out, the test is still valid.

Hippo said:

Regarding Td4 auto being different to Td4 manual... if yer take oft the pinion gear yer can count the teeth behind it when turning things to see how many teeth they have.

Teeth count... never been told the teeth counts are wrong or crossed over before. I still have them so I can count them again if required. Do the ratio's I calculated match those of the rave etc. That's my first questioning.

Click to expand...

I think peering in at through the pinion aperture won't tell you much - the difference in the VCUs is in the gearing between the main shaft, intermediate shaft and input shaft IIRC?

Apologies for the complete thread hijack, but constructive discussion was happening!

When taking oft the pinion gear yer can see to the right the gear with 23 or 24 teeth, depending on version of ird yer has. This would be enough to confirm which ird it is.

Hippo said:

When taking oft the pinion gear yer can see to the right the gear with 23 or 24 teeth, depending on version of ird yer has. This would be enough to confirm which ird it is.

Click to expand...

Ahh, didn't realise there was a way through to the right, can't see it in the pitchers.

B34R said:

The second picture on that thread shows the power path to the front wheels

V6 = 30 -> 23 teeth, 22 -> 39 teeth = 0.77 * 1.77 = 1.36
1.8 = 29 -> 24 teeth, 21 -> 37 teeth = 0.83 * 1.76 = 1.46

This means that the V6 is longer geared than the 1.8, it spins slower for the same speed as it has more torque. Lazy geared!

Click to expand...

That works for me - I just checked my TD4 Auto at 2500 revs 70mph - that converts to 84 at 3000 - your chart says at 3000 I should be doing 79
If I take 84/1.46 x 1.36 I get 78mph at 3000 - close to your chart - which gives another confirmation that my particular 2005 TD4 HSE has the v6 IRD
The Tomtom was confirming the roadspeed to within 1 mile/hr - I don't know where in these cars the road speed sensor is in the geartrain but it suggests that the thing is calibrated right for what it can see of my geartrain from wherever it is to the road.

Hmm, interesting!

We need a larger sample size, wonder who else has a TD4 auto we can knobble.