Nodge68
Well-Known Member
Thanks for doin the maths. I was having a bad day yesterday. Today it's looking correct.
B34R - Your post #93 and this additional Hippo picture (see below) really clarified things for me - I had followed Hippo's calcs all the way through from the input from the gearbox and Luckily I picked the right ratio numbers from front axle to back axle from his thread for my two wheel up check - but this picture of his and your post #93 and Nodge68's input have crystalised it out for me.
It boils down to this :-
We can ignore the actual differentials - they cancel out - and it's valid to do the test one front to one back wheel - which makes it easier.
From the gearbox input to the front Diff - we can ignore - that's gearing - not ratio front to back
That leaves as you have shown only the following :- (small differences make it important not to round - so I use all the decimal places my calculator will give)
V6 IRDs (Edit -not just V6 but any later IRD with the 0.2% difference front to back) front diff shaft to rear axle is purely those first two gears, the front crownwheel and pinion, and the rear pinion and crownwheel.
39/22 x 38/21 x 14/45 = 0.997979797 -
1 - 0.997979797 is the lag at the back wheel in revolutions = 0.002020203revs
ie if your rear tyre is 26" Diameter 81.69" circumference - and you rotate the front say 20 turns for a good sample - you should see a lag of 0.002020203 x 20 x 81.67" = 3.3" at the circumference.
Similarly
Other IRDs (Edit - this should be for all older IRDs with the 0.8% Difference front to back) 37/21 x 38/21 x 14/45 = 0.991887125
1 - 0.991887125 = 0.008112875revs
ie if your rear tyre is 26" Diameter 81.69"3.3" circumference - and you rotate the front say 20 turns for a good sample - you should see a lag of 0.008112875 x 20 x 81.67" = 13.25" " at the circumference
So a simple check - jack up two wheels - one front one back - mark - turn front 20revs with no slip from the VCU - if its around 13.25" late at the back it's an older 0.8% IRD
If it's around 3.3"" late it's a later 0.2% IRD
Simples
Let's hear from other TD4 Auto owners out there - I have now checked 2003 and 2005 TD4s both Auto and Manual and found the 3.3" lag. (That's why I added the edit above) Can anyone find an older vehicle that measures 13.25" Lag?
Many thanks folks for helping clarify this for me - and again apologies to Hippo for highjacking his thread (although it's sort of relevant)
It boils down to this :-
We can ignore the actual differentials - they cancel out - and it's valid to do the test one front to one back wheel - which makes it easier.
From the gearbox input to the front Diff - we can ignore - that's gearing - not ratio front to back
That leaves as you have shown only the following :- (small differences make it important not to round - so I use all the decimal places my calculator will give)
V6 IRDs (Edit -not just V6 but any later IRD with the 0.2% difference front to back) front diff shaft to rear axle is purely those first two gears, the front crownwheel and pinion, and the rear pinion and crownwheel.
39/22 x 38/21 x 14/45 = 0.997979797 -
1 - 0.997979797 is the lag at the back wheel in revolutions = 0.002020203revs
ie if your rear tyre is 26" Diameter 81.69" circumference - and you rotate the front say 20 turns for a good sample - you should see a lag of 0.002020203 x 20 x 81.67" = 3.3" at the circumference.
Similarly
Other IRDs (Edit - this should be for all older IRDs with the 0.8% Difference front to back) 37/21 x 38/21 x 14/45 = 0.991887125
1 - 0.991887125 = 0.008112875revs
ie if your rear tyre is 26" Diameter 81.69"3.3" circumference - and you rotate the front say 20 turns for a good sample - you should see a lag of 0.008112875 x 20 x 81.67" = 13.25" " at the circumference
So a simple check - jack up two wheels - one front one back - mark - turn front 20revs with no slip from the VCU - if its around 13.25" late at the back it's an older 0.8% IRD
If it's around 3.3"" late it's a later 0.2% IRD
Simples
Let's hear from other TD4 Auto owners out there - I have now checked 2003 and 2005 TD4s both Auto and Manual and found the 3.3" lag. (That's why I added the edit above) Can anyone find an older vehicle that measures 13.25" Lag?
Many thanks folks for helping clarify this for me - and again apologies to Hippo for highjacking his thread (although it's sort of relevant)
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Hippo
Lord Hippo
What is the P number on top of the auto gearbox? There should be a small plate you can see on the top.
Can you take the pinion off and count the gear teeth on the gear to the right inside the ird while turning a wheel?
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Yes - my oops - edited to read V6 IRD - thanks
Hippo
Lord Hippo
Can you send me your vin number by "private conversation" and I will look it up in microcat to see what LR say was fitted to yer FL.
There's only 2 versions of ird available but there are several part numbers over the years, including new and exchange units. Old part numbers are superseded by new ones.
TAG000230 is for the 4 cylinder engines (L series rover diesel, 1.8 k series petrol and Td4
TAG000220 is for the v6 (6 cylinders)
irdpartno ZQ0mmaQ
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Hippo
Lord Hippo
Yer can see this when removing the pinion. The gear on the rhs is all you need to count to know which ird you have. 23 or 24 teeth.
DSCN1471 pwTEskP
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Hippo
Lord Hippo
Some time ago I tried tuning the rear wheel to see how many times the front wheel would turn, with both wheels on one side lifted in the air. I have a 2001 v6. If I start with markers at the bottom (6 o'clock) on both wheels, how many full revolutions of the rear wheel do I need to get the marker at 6 o'clock on the front wheel to move to the 12 o'clock position?
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Some time ago I tried tuning the rear wheel to see how many times the front wheel would turn, with both wheels on one side lifted in the air. I have a 2001 v6. If I start with markers at the bottom (6 o'clock) on both wheels, how many full revolutions of the rear wheel do I need to get the marker at 6 o'clock on the front wheel to move to the 12 o'clock position?
See post #103 - that quick test I describe will show what you have more easily - I found you cannot drive the front wheels by turning the back without the VCU slipping (the IRD as a machine is less efficient than the simple rear CW/P driven after the VCU from the front) - do it as I describe and 20 turns of your front wheel on a V6 will give you 3.3" lag at the rear wheel. You would need about 248 turns to get 180 degrees of lag at the back
Can you send me your vin number by "private conversation" and I will look it up in microcat to see what LR say was fitted to yer FL.
There's only 2 versions of ird available but there are several part numbers over the years, including new and exchange units. Old part numbers are superseded by new ones.
TAG000230 is for the 4 cylinder engines (L series rover diesel, 1.8 k series petrol and Td4
TAG000220 is for the v6 (6 cylinders)
Brilliant - will do
Hippo
Lord Hippo
Yer but no but I want you lot to calculate me turning the rear wheel to see the offset in the front to see if yer maths is correct.
I put masking tape on both props to make sure the vcu didn't turn. Also applied/removed force gently to reduce shock into the system.
B34R
Active Member
Yer but no but I want you lot to calculate me turning the rear wheel to see the offset in the front to see if yer maths is correct.
I put masking tape on both props to make sure the vcu didn't turn. Also applied/removed force gently to reduce shock into the system.
V6 Ratio is 1:1.0025 front to back
Therefore back to front = 20 turns x 1.0025 = 20.05 turns so you should have gained 0.05 of a turn which should be somewhere about 3-4 inches out.
Turboman
Mab An Gov
Hippo
Lord Hippo
That was the paper version made purely to prove the design concept. The actual ird which went into FL production was a spin oft from the Challenger 1 tank design. The only difference being the ratio change front to rear on the FL was side to side on the Challengers.Probably one that was rejected for moped use as too weak!
Nodge68
Well-Known Member
Probably one that was rejected for moped use as too weak!
I wouldn't describe the IRD as week. It's taking half shaft loadings and survives ok. I bet not many full size LRs transfer boxes would take half shaft loadings so well. The IRD is taking over 4,000 Nm of torque on the V6 Freelander
Turboman
Mab An Gov
Hippo
Lord Hippo
I hope yer not suggesting our ird's are made of tratter half shafts.Nor would I, doubt if it would even last six days!
Turboman
Mab An Gov
Nuttin wrong with the halfshafts!I hope yer not suggesting our ird's are made of tratter half shafts.
Weakest part of a tratter is between the drivers ears!
