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IRD/Gearbox... we made it wrong...

Discussion in 'Land Rover Freelander' started by matko, Nov 22, 2019.

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  1. Nodge68

    Nodge68 Well-Known Member

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    That's part of it. But the gearing is different enough to allow for slight compression of the front tyre, and to compensate for the front tyre wearing faster than the rear.
    The VCU is designed to allow for this slow rotational difference between front and rear. The tyres shouldn't be forced to slip, as the IRD and diff aren't strong enough to withstand that kind of abuse for long. This is the reason the IRD fails as a result of VCU stiffening.

    It's difficult to drive perfectly straight, so difficult to prove there's no difference in rotation between front and rear, as well as slightly different diameter tyres skewing the results.

    You can test the gearing difference easy enough.
    If one side of the car is lifted clear, so the front and rear wheels on one side can rotate freely. Mark the tyres at some point, so a rotation difference between front and rear can be seen. Then just rotate the front wheel a set number of turns, and see if the position of the mark on the wheels go out of phase with each other. I did this many years ago as a test, to proved to myself that there is a difference in gearing.
     
    Last edited: Nov 30, 2019
  2. Nodge68

    Nodge68 Well-Known Member

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    This is true, until the IRD goes bang :eek:, then many owners want know why.
    Hippo has done far more in depth work into the VCU than me. I just have an understanding of gearing, and what function the VCU has and why.

    I also test my VCU every time I rotate the tyres front to back, which is done at 6 month intervals, or about 3,000 miles. ;)
     
  3. Hippo

    Hippo Lord Hippo

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    I promised my self i would never get deep into vcu discussion again...

    Deeper tread on the rear. Rear prop turns faster than front. So rear prop is essentually pushing/driving the FL forward. In reality its not as the vcu takes out most of the difference if it's working ok. So it could be considered a drag on engine power instead. I say most as there must be some force applied one way or the other as i can tell if a vcu is fitted or not by the feel of the way a FL drives. I dislike the feeling without 4x4.

    If the vcu stiffens up yer get more stress in the transmission. Stress the original design takes out in the majority, if the vcu is ok. Changing the radius of the tires like the front carrying eggstra weight of engine etc has an affect on the ratio of prop speed because the rolling radius of axle to floor measurement changes. Also tire wear does this by reduction of same radius.

    There was a tire measuring fred i started regarding this. I wanted to know peeps day to day running measurements before putting up what we had found and measured, for discussion. Another fred destroyed... The comparison we needed at the time was what others were running "naturally". Hard to explain in words but we believe from what we did, that the FL1 drive ratio front to rear setup, takes into account the squashed day to day running radius, of axle to floor, when LR chose the design ratio to kind of leave it more relaxed more often, so to reduce average transmission stress across all ages of tire wear. That's if yer have all new, or where yer running part worn. The least warn (deeper tread) go on the rear.

    It's too early to answer more fully with calculations. But on point 3, you can monitor the props turning with a camera. A warehouse floor is more flat than a road if you have one. Camber offset is a killer of fair results on a road with this sort if test. Its easy for me to monitor the wheels and props with electronics. Started with a test logger at first but result retrieval is via pc. Setup is too long so trial and error to get it going took ages. Also difficult to relate back to an interesting result event, to know what was happening at the time that caused it. Lock out of results on a technical problem in the end What we were seeing didn't make sense as we thought it was wrong, but it wasn't. We din't know at the time but had already come to the conclusion we were doing something wrong causing this. We weren't.

    Moved to raw electronics with 7 seg displays displaying wheel fhz, chopped and paused against 1hz clock, repeatedly pausing values for a second, of the previous second. Not recorded unless you put a camera on it. Also difficult to read fast before it changes. I would display fhz difference instead if doing it again as it would be easier to read and that's the info you want to know. But you can still see what's happening live with raw fhz like weight effect when cornering fast and yer lean over. Also effect of braking hard when the front dips down.

    There's obviously a lot more to test in the FL1 transmission than we can practically do. Independent rollers with option of a geared difference is what I'm guessing LR must have used. They did drive a hell of a lot of miles in road when testing the FL1.

    The origional problem we set out to achieve was a way of stopping transmission damage, in a way an owner could monitor it happening for themselves. No eggspensive tool or knowledge needed. A reasonably quick test on a Sunday afternoon after yer just washed it. The OWUT does that. The Turnip Test assists. Discussion of the reasons why and all the past arguements we've had as well as trolling, put peeps oft doing the test. Sadly that puts their transmission at risk.
     
  4. Avocet1

    Avocet1 Well-Known Member

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    ..which is how mine got knackered. My sister and her husband are non-technical and not well-heeled. I don't think their IRD ever had an oil change in all the time they had the car. They used to put any old mixture of tyres (nominally the correct size) on it. They drove for a while with a VCU so seized that they had to slip the clutch to get it to move on a lock until my dad took the proshaft off for them! They also live in a flood-prone area and I have a cracking video (sadly, too big and the wrong format to post here) of them exceeding the permitted wade depth ...somewhat! When I got the car, I noticed a loose pipe, which turned out to be the extended breather on the IRD. The steel part of it was completely blocked with rust, so I imagine it must have built up enough pressure when it got hot, to blow the rubber pipe off the spout at some point.

    Flood vidcap.jpg

    Apart from that, though, their IRD got the best of care...!

    So now, I'm keen to avoid the same mistakes and try and give it the best chance for what days it has left.


    Why do you rotate the tyres though, if the car is set up to compensate for wear, and the best thing to do for the IRD is to keep the ones with the most tread on the back?
     
  5. Avocet1

    Avocet1 Well-Known Member

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    Thanks again!

    Just one question - what on earth is a "turnip test"?!

    Actually, 2 questions. Does the FL1 use any "CAN" systems in its electronics? I'm guessing it does - at least for the chassis systems like ABS and Traction Control? On other vehicles, there are often aftermarket CAN readers that you can plug into various "nodes" in the electrical system so that you can harvest data. Do such things exist for FL1? It just struck me that if you can get signals from the front and rear ABS sensors, it'll tell you how much faster or slower one pair of wheels is turning than the other.

    Last thing, (and this might be viewed as heresy on my part)! I'm beginning to think that the difference in gearing end-to-end, is not to compensate for a reduction in rolling radius of the front tyres, but simply to take any backlash out of the system and maybe alter the handling characteristics slightly. The reasons I am starting to think this are:

    1. If it were the case, it would only really ever work at one particular combination of wear state and tyre pressures.
    2. They could easily have compensated for the lower rolling radius at the front by specifying a higher pressure - it's very common with lots of other cars to have different recommended pressures at each end.
    3. A new car (or a new set of tyres) would not be the ideal setup and yet, in my handbook, they advise replacing all 4 at once. Replacing two (and putting the 2 new ones on the back) is only their 2nd best option.
    4. The manual says nothing about the importance of fitting 4 tyres of the same make (even though there can be differences in rolling radius between 2 tyres of different makes but the same nominal size).
    5. The manual doesn't recommend increasing rear tyre pressure when heavily laden or towing.

    Discuss!
     
  6. GrumpyGel

    GrumpyGel Well-Known Member

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    Turnip test is just feeling the temp of the VCU. Cold means seized, warm means operating OK, hot means being overworked - I just made those results up by the way, haven't a foggiest what the results tell you, its a bit of a turnip test really.

    Your observations are spot on, if you agree with them, and wildly off the mark if you don't. Whether you agree with them or not is dependent on whether you are the first born twin or second.

    Cars with squashed up front tyres will run with the props turning at exactly the same speed when running straight and forwards. @dfossil found this out when he put some RPM sensors on his props and checked the speed of them in different conditions - forwards, backwards, straight, turning, flat, up hill etc. See 2nd post here...

    https://www.landyzone.co.uk/land-rover/vcus-the-sweet-spot.291258/page-7

    All diagnostics on the Freelander is accessible through the ODB port, eg you can connect to the Engine ECU, SRS ECU and ABS ECU. What into you can get from the ABS ECU I don't know. It will obviously know the 4 wheel speed sensors, but whether you can access it as 'live data' as you can with engine data I'm not sure. Although systems may be 'ODB' (or 'ODB2 what ever) compliant - this compliance is very limited to what it specifies such as communications spec and messaging spec for basic functions - such as reading and clearing codes. None of this necessarily applies to the ABS modules either. For the lower level information such as wheel speed sensor output, I think you very much need information from the manufacturers, which they will supply - if you make it worth their while!
     
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  7. Nodge68

    Nodge68 Well-Known Member

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    Any care you give the IRD is going to be better than it received with its previous owners. ;)
    I rotate the tyres every 6 months (approximately 3K miles) to even out the wear. I like to replace tyres in full sets, as I've been caught out in the past, when tyre I have been using was discontinued. This left me having to throw away half worn tyres, which I don't like doing, so I now rotate them to maximise available life.

    The AWD system is fine with matching new tyres (the car comes with a full set when new;)), or rear tyres with more tread. When odd tyres are fitted, or the fronts have more tread than the rear, is when the trouble starts.
     
    Last edited: Dec 1, 2019
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  8. Hippo

    Hippo Lord Hippo

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    Yer worrying about this too much. Take the props and vcu oft if it worries you that much.

    You can watch live data via obdii on the FL1 but the precision and speed of refresh you need, with 4 value capture and pause, isn't available. The hawkeye will show two at a time but the figures are in whole numbers in kph. So not good enough for precise measurement. You only have the option of going up/down the live data list so limited on which two you pick. It would need someone to write their own interface and display abs pulse counts. That's if its available in the list you can pull out. It may only offer the calculated kph values. The FL1 does recognise pulse counts for use with traction control as it can sense slip with less than half wheel slip. All depends if the raw values can be got at.

    The Ternip Test was named after @Vagrent who is a member on ere who sadly doesn't post anymore. I miss him and his wit. It needed a name and he regularly posted the word turnip on its own on different fred's. So I used that.

    The sheering affect in the vcu (how it works) creates heat as a side affect. The more heat the greater the sheering inside. It's a live dynamic test you can do after a drive. 3 miles is enough although I and others tested it over much greater distances over time. Its a valuable test which is free to do with no knowledge or tools. Ambiant temperature does change the results which is part of why this was investigated. The temps measured shouldn't be much different if doing 3 miles or many more. Temps measured with infrared are more accurate.

    Theory is if the vcu is cold after a drive of 3 miles then theres little or no difference in prop speed. Either yer very lucky or the vcu is seized or something is not right like pinion gear cut oft, lay shaft missing, rear diff content missing etc. You may have a dodgy recon vcu.

    If the vcu is comfortably warm after a 3 mile drive then it's working as it should, with some difference in prop speed ratio, and coping ok with it, it is understood. A further longer drive would confirm.

    If the vcu is hot to touch after a 3 mile drive then its working harder than ideal. This points to there being a lot more stress in the transmission which is a concern and should be investigated further.


    Over the years a lot has been said on ere about vcu's. Each fred created in the past ended in long drawn out arguments and got no where. We also had trolls chipping in. So anything vcu related was done out of sight of the forum after a certain point in time until the time was right to post up. When I found out about the 1:1 ratio I asked on ere for wheel measurements but didn't say why. The problem is if you post up a result it will be discussed but not investigated. There will be loads of theory but little testing. Peeps just won't do the test themselves or are put oft posting up results. Some can't do the more advanced tests if they're mechanically difficult which is understandable. The work we were doing all lead to the ratio fred which said some of what had been done and asked for teeth counts. As usual it got trashed then cleaned up by mods.

    We still don't have conformation one way or the other if the ratio changed on all vehicles. Its difficult to get peeps on ere to check this. I can chalk a gear through the ird filler hole and film the teeth turning to count them with the help of an led inside via the filler hole. Its not easy but possible with HippoRamps (TM) and other lifting kit. When pinion gears have been taken oft members teeth counts could have been taken. LR always superspeed part numbers when parts changed. It wiuld be strange for them to not do this on a different ratio ird. It goes against all their convention for other parts and is also part of their production ordering and component control. So we're stuck which on a personal level is annoying. @dfossil was the only one to contact me and come forward with his results. Unfortunately they differ from mine. I'd been collecting broken/cheap ird's to gain more teeth counts. Also approached peeps directly when they were swopping out ird's or repairing them but the project was put on one side then shelved. So in the end we never got a definitive answer. I knew about the sweet spot fred before it appeared as it had been discussed privatley. At the time I was hoping to get more results before it was posted. To this date he's the only one who came forward with the same 1:1 result I had found. Nobody else came forward having done the same tests. But as said, once the result is advertised no one is interested in doing the tests. For me that's annoying. Its possible we may never know. Funny to see theres currently 58,000 views of my video of drilling a hole in my old vcu to watch the content come out.

    Attention then turned to sacrificing my low miles new gkn vcu. We wanted to know it's limits which included a test to see what temperatures were measured and how fast we could constantly turn it. The results of that haven't been posted. I may do next year.
     
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  9. Hippo

    Hippo Lord Hippo

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    For many years I have been swopping my tires front to rear anorl when buying 4 new. Same as above, to get even wear out of them. It means when yer buy a new set yer will have been able to use most of the tire life of the old set. I swop mine every 1,000 miles by choose. Also a chance to clean them. I don't do a large mileage so it's not too often.
     
  10. GrumpyGel

    GrumpyGel Well-Known Member

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    I initially thought monitoring the 4 wheel speeds would be a good idea, however, I'm not convinced.

    What you really need to know is how much torque the VCU is transferring, maybe an external temp sensor pointing at it and checking for abnormal behavior would show signs of trouble.

    Ultimately though, I think the best thing is a TPMS as if all the tyres are at the correct pressure then all is good (assuming they are the same of course!). It will immediately show if there is a problem, it would have saved the transmission on my motor, and so long as you are doing regular VCU tests (ie 1WUT) then there's nothing :)rolleyes:) that can go wrong.
    Yeh, but no but. How often does TC kick in on a Freelander that's got its props attached? I hazard a guess that TC on a AWD Freelander would only kick in on an axle twisting situation, maybe in the wet where a wheel on each axle has lost traction - in these situations a wheel on each axle is spinning uncontrolled much much faster than the other - that's not the same sort of check as would be needed to determine enough difference in 1 corner that's putting the transmission in jeopardy (which this discussion (and most other VCU discussions) is about).
     
  11. Nodge68

    Nodge68 Well-Known Member

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    The TC comes in pretty much instantly, the moment a tyre slips. You could say the TC system is on the ball.
    Agreed. Active tyre pressure monitoring will go a long way to determine a tyre pressure related issues.
     
  12. Jonny H

    Jonny H Active Member

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    If tyres are rotated say every 3k miles, doesn't that mean that at some stage the front tyres will have more tread than the rears, or is the difference so minimal as to not cause any problems?
     
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  13. Nodge68

    Nodge68 Well-Known Member

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    The difference in tread depth is negligible. I measured it at around 0.5mm after 3000 miles, which is nothing.
     
  14. Avocet1

    Avocet1 Well-Known Member

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    Thanks that's extremely interesting! Pity he didn't try it with grossly different tyre pressures at each end just to prove the point. However, it does make me think that there is some tyre slippage in normal use. All tyres do it by a small amount (a tyre can't actually generate grip unless it's moving relative to the tarmac), so it wouldn't be that surprising.

    Thanks. I'm guessing, but I think my 2001 FL will be a tad too old for OBD2. I'd be pretty much out of my depth with it though. You're right, raw data from each ABS sensor is what's needed. That would give very fine resolution.
     
  15. Avocet1

    Avocet1 Well-Known Member

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    I know what you mean about tyres being obsolete. Same thing happened on the X-Trail when Pirelli swapped from Scorpions to Scorpion Verdes (although they were pretty similar). However, each time you swap yours front-to-rear, presumably you'll (initially at least) be in a situation where you have more tread on the fronts?

    Now here's my dilemma. I have 5.5mm on my rear tyres and about 3.5 on my fronts. (Those are "worst case" measurements). The previous owner of that set of wheels and tyres told me he'd been running them at 40 PSI (presumably to improve fuel consumption and reduce noise) so they're more worn in the centre than at the edges of their tread. I want to even-out the wear because I don't really like them, so I'd like to get rid of all 4 at once. Dare I risk putting the 5.5mm ones on the front? (Maybe if I decrease the front pressures and increase the rear pressures a tad until the wear as evened-out a bit more)?
     
  16. Nodge68

    Nodge68 Well-Known Member

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    When I swap mine front to back, the rear end up with 0.5mm less tread than the front. This doesn't seem to notice, but if I were worried, I could drop the front pressure tyre slightly, or raise the rear tyre slightly. This would alter the rolling radius, which will help equalize out the problem.
     
  17. Avocet1

    Avocet1 Well-Known Member

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    Not sure "worrying" is the right term? At the end of the day, this is a disposable car nearing the end of its life. However, I am keen to learn as much about it as I can until that day comes!

    Yeah - above my head, but I know we do this at work for taxi meters and we can get ABS pulse raw data in real time. I might ask some of the "leccies".

    LOL! A sort of internet forum version of Tourette's?!

    Understood. I've done this test a few times (only by hand) and it has felt little more than body temperature. It's certainly never been as cold as ambient or too hot to keep my hand on.


    Damn! I could have counted the teeth on mine if I'd known! Which numbers do you need? The number of teeth on the crownwheel and the pinion or the ones on the two internal shafts
     
  18. GrumpyGel

    GrumpyGel Well-Known Member

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    It was a great series of posts. I think @dfossil did go on to let some air out of tyres to see what the results were, but maybe I just made that up :D
     
  19. Avocet1

    Avocet1 Well-Known Member

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    No, I did see that somewhere in the thread, but he only seems to have done it for his low speed turning tests rather than straight line.
     
  20. Avocet1

    Avocet1 Well-Known Member

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    OK, ta. That's what I was thinking of doing. As I mentioned, I don't really like them (very noisy), so I'd like to get rid of them all at the same time.
     
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