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Disco Td5 autobox: replacing torque converter

Discussion in 'Land Rover Discovery' started by MTurri, Dec 3, 2010.

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  1. MTurri

    MTurri Active Member

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    My autobox Disco Td5 developed a slight shiver just before every gear change, between 2200-2800 rpm. Over the past 6 months the shudder gradually turned into a harsh vibration, eventually sounding like ‘coarse gravel agitated in a tin can’ type of noise. ATF & filter checked and replaced regularly. No abnormal slipping or other autobox issues. No fault codes stored in EAT ECU.

    Historically Td5 torque converters fail by cracking at the base plate but upon a visual check through the opening in the bottom of the bell housing confirmed no visible cracks or missing bolts at the TC which TBH was a bit discouraging…

    In addition to being a mechanical weak point, the Td5 T/C suffers from an excessively high stall speed (~2800 rpm) which is better suited for a petrol engine (Td5 engine torque peaks at around 2200 rpm). Many owners concur in that the Td5 autobox changes gears “too late” causing the engine to rev up unnecessarily (throwing gears well above 3000 rpm under medium to heavy acceleration), giving the feel of one being rather driving a 140HP outboard and not a modern diesel engine. A fellow autobox Td5 owner did in fact coin the term “speedboat effect” to best describe this phenomenon.

    So in order to –hopefully—fix the vibration problems, get rid of the speedboat effect, and eliminate the known weakness between engine and transmission (thinking of future remap), opted to replace the torque converter for an uprated version from Ashcroft Transmissions. This is nothing but the T/C used for the 3.9 & 4.0 P38s but with a sturdier billet base plate modified to match the triangular 3-bolt flex plate on the Td5 as well as an altered spigot to fit the 4HP22 oil pump. With a lower stall speed (2200 rpm) it is meant to provide torque to the transmission a lot earlier than the factory standard T/C.

    Had done the Td5 clutch several times but the autobox was totally unknown territory. Went down to my mates place both for his helping hand and pit. Initially thought the job could be tackled in a day if started early enough but this soon proved impossible. Ended taking a total of 20 hrs over 2 days. Encountered numerous difficulties but the complexity lied in the number of details that had to be taken care off. Getting the autobox back in with the new T/C installed and partially filled with ATF was a complete b*tch and had to call for reinforcements at this point. Reckon the whole job would have taken 4-5 days in a regular garage.

    Upon reenergizing the vehicle all kinds of errors showed up, especially within the EAT ECU which did not like at all being disconnected from the autobox, and had to reset it various times before it started talking to the ECM. Filling the whole system with ATF took quite a while as there was air everywhere.

    The last task on the list was resetting the adaptative values in the EAT ECU. The EAT knows the nominal time that each gear shift should take. To counteract for wear in the autobox components as well as differences in the engine torque/power vs speed delivered, the EAT monitors the pressure modulation used for each gear change and applies a pressure adaptation so that shift duration is restored to the nominal value. These adaptative pressure values are stored in a volatile memory within the EAT ECU and in this scenario I thought it necessary to wipe them clean since an essential component of the auto transmission had just been replaced. Unfortunately HawkEye was not up to the task (function not included) and had to resort to my mates DEC system.

    Finally went out for a spin… felt as if was driving a different vehicle!!! Not only was the infamous vibration gone but the driving completely changed! No more gear shifts at +3000 rpm, on a light throttle gears go at 1700-1800 rpm, and 2300-2400 rpm on a heavier foot. Overall the engine runs a lot smoother and even all the time.

    Other noticeable changes:

    1) Engine and auto transmission feel “closer” and more in tune rather than catching up with each other all the time (reduced T/C slippage?).

    2) More “inertia”: the uprated T/C is roughly 2” wider and 10 lbs heavier (plus the extra ATF volume) than the original one which gives an increased flywheel effect. Engine feels firmer, solider.

    3) Gear shifts are a lot smoother (likely also a consequence of having completely changed the ATF) and on T/C locking up no longer feel the slight pull-push the old T/C had, now can only tell by the drop in engine revs.

    4) A totally non-anticipated yet very much welcome side effect: a significant drop in fuel consumption! Still evaluating it but would dare say between 10-15% (quick calculation shows I should be able to repay the new T/C in ~10 months). Logically without the constant revving up it had to burn less fuel.

    Pictures:

    All (3) available T/Cs side by side (photo from Ashcroft Transmissions), on the left the original Td5 T/C (also used on the 300 Tdi and diesel P38), in the middle the medium T/C fitted to the 3.9 and 4.0 P38s (this is the one that Ashcroft modifies for the Td5) and on the right the large one used on the 4.6 P38:
    [​IMG]


    Transfer box & autobox out of the way: flywheel and flexplate:
    [​IMG]

    [​IMG]

    New T/C:
    [​IMG]

    New T/C vs old one:
    [​IMG]

    New T/C base/fix plate:
    [​IMG]

    Old T/C base/fix plate:
    [​IMG]

    [​IMG]

    Bowl & flex plate:
    [​IMG]

    [​IMG]

    Flywheel (the holes line up with the fixing points in the flex plate, for factory mounting of T/C?):
    [​IMG]

    Autobox:
    [​IMG]

    New seal in converter housing:
    [​IMG]

    Rgds

    Matt
     
  2. thebiglad

    thebiglad Well-Known Member

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    Hi Matt, this is a very interesting post to me, as I have at least some of the symptoms that you had. So thank you for taking to time to post the thread.

    When cold my transmission is quiet but as soon as it starts to warm up there is a rattle/vibration comes from the gearbox area. It is only apparent until the TC goes into lockup mode then all is much quieter.

    Lockup works correctly in 3 in that it will go in at about 48-ishmph and if I need to slow down, so foot off the pedal, it will stay in until about 35mph as it should. However in D (4th) it will go in (once warmed up) at about 52-ishmph and then romp away, BUT, if I have to slow down as soon as I'm below this speed with my foot of the accelerator pedal, she will drop out of lockup. If I can manage to keep light pressure on the pedal she will stay in lockup until much lower down the speed range.

    So there are some issues that I would like to sort out, including this apparent disconnection between engine and gearbox allowing the power to be spilt away by what seems to me to be an insufficient Torque converter.

    My questions are (in no particular order)

    1. If I may ask, what did Ashcrofts charge you for this modified TC with plate?

    2. Do you still need to use the triangular plate as well? Or do you bolt the new round plate + TC onto the LR flywheel direct?

    3. I am concerned about the reinstallation, in that there worries concerning the reconnection of the oilpump; Don't know if this is only when you replace the autobox though?

    4. Did you have to refill the TC with oil first, or were you able to refill the whole system via the normal level/fill plug on the front edge of the sump?

    4. It sounds like you had to do an amount of recalibration within EATS. I have Hawkeye but it sounds like that is not enough. How vital is this recallibration.

    Any further advice you can offer would be most gratefully recieved, as I'm getting concerned that sooner or later something is going to break and leave my car stranded


    From what you write it sounds as though your car is now running exactly as I would like mine to do, so I'm all ears for your info please. Don't suppose you have any more pics about the job that you could e-mail me direct?
     
    Last edited: Dec 3, 2010
  3. MTurri

    MTurri Active Member

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    Biglad,

    Uprate T/C from Ashcroft was £250 + £100 refundable core charge (in my case had to shed another £180 for shipping + 50% on customs duties... :(:( ... hey but no VAT!)
    New flex plate £18
    Bolts, plate assy & oil pump seal another ~£50 (from other vendor)
    You should also replace the autobox output shaft seal which I didn't.

    The thick round (base) plate is part of the torque converter and it has a triangular 3-bolt pattern. You still need the flex plate. The T/C expands with heat and the flex plate bends towards the flywheel to accomodate the extra T/C length.

    The oil pump does not need to be taken out from the autobox, the T/C spigot slides out of the oil pump. All you do is replace the seal (see last picture) and carefully reinstall the T/C. This was supposedly the tricky bit but mine went through right away.

    I opted for partially filling the T/C with ATF prior to installing it as I thought it would prevent the oil pump from starting dry. Not sure if this is actually the case. It just seemed the best thing to do. Then upon reconnecting the oil cooler lines filled the sump as would do during a regular ATF change. The T/C was filled with 2 ltrs and the box took another 8 ltrs to completely fill up (previously had blown the oil cooler lines to get as much ATF out of the system as possible).

    No recalibration needed. The EAT continually monitors the most current gear shift pressure values and calculates & stores the corresponding adaptative pressures. Ideally you zero them to start on a clean slate, but this not a must, with time the values in memory will be readapted to the autobox's new performance.

    Had planned this job for months but was yet quite uneasy about it. In the end it was not such a big thing. It is extremely labour intensive but not difficult.

    No more pics available but can provide a rough step by step procedure, though it is pretty much all RAVE material, let me know.

    Hope this helps.

    Rgds

    Matt
     
  4. thebiglad

    thebiglad Well-Known Member

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    Hi Matt, first of all a big thank you for responding so quickly and in such an understanding manner. I too am a little apprehensive about doing this job but after the snow goes and we start to get some better weather - and I've sold a car so have some spare cash:eek: - I want to do this replacement as I believe it will stop the unpleasant noises AND make the car much nicer to drive.

    Incidentally, when I contacted Ashcrofts yesterday they quoted £250+vat for the new TC plus an exchange cost of £250+vat refunded upon receipt of my old TC in serviceable condition.

    Thanks again for your guidance, information and support, it is much appreciated.

    Cheers
    Dave
     
  5. T1G UP

    T1G UP New Member

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    wow! this is just what us D2 auto boys need.

    mines been mapped and far to revvy for a 2.5L turbo diesel

    i'm on the phone now!
     
  6. Rykard

    Rykard Active Member

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    how much will they charge to fit?
     
  7. T1G UP

    T1G UP New Member

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    won't do it the lady said!...they sub the instal out though so i guess the garage who they sub it too would? anyone know who they use to do the change?

    Luton based i guess
     
  8. thebiglad

    thebiglad Well-Known Member

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    If you look on their website, under auto transmissions they talk about fitters near Luton.

    Dave
     
  9. T1G UP

    T1G UP New Member

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    seen that

    have spoke to both.

    can't get it done before xmas at this rate
     
  10. Bogthebat

    Bogthebat New Member

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    In order not to open a new threat, I`ll ask a question regarding torque convertor : can I use a V8 one instead of TD5? I saw that the gearbox are the same.....
     
  11. thebiglad

    thebiglad Well-Known Member

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    It would be possible but you will need to change the flex plate and the flywheel, as the TD5 setup uses 3 bolts but the v8 uses four.
     
  12. Bogthebat

    Bogthebat New Member

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    Ooops, In this case, I ll forget about.....I saw that a torque converter is around 1400 GBP, and since I found a V8 gearbox complete with 500 eur., I thought that worth it ..... But I have to made too many changes.
     
  13. thebiglad

    thebiglad Well-Known Member

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    Ashcrofts supply a modified V8 TC with a modified 3 bolt drive plate for £250+vat
     
  14. Bogthebat

    Bogthebat New Member

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    Thanks for the tip. I send a e-mail to Ashcroft, and I choose HD TC. !
     
  15. Bogthebat

    Bogthebat New Member

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    I receive the new TC from Ashcroft, but seems to have 6 hols for bolts....
     
  16. Bogthebat

    Bogthebat New Member

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    .... And some pictures
     

    Attached Files:

  17. thebiglad

    thebiglad Well-Known Member

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    That's perfectly understandable, if you look at the triangular drive plate on the back of the engine you'll see that the 3 holes in the drive plate will line up with any of the 3 holes in the TC plate.
     
  18. Bogthebat

    Bogthebat New Member

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    Ok, Thank you for wasted doubt regarding acquisition a wrong TC.... The plate didn't arrive yet... ( I'll check it as soon as I will received it )
     
  19. T1G UP

    T1G UP New Member

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    you got yours yet Biglad???
     
  20. thebiglad

    thebiglad Well-Known Member

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    No I haven't yet mate. I'm giving serious consideration to finding a manual box car.

    For me the thing that I can't get past is the fact that, imo, LR have fitted the wrong TC from outset and it really bugs me that I have to pay a substantial sum to put right something that should never have been wrong.

    It's just another example of poor LR car building.
     
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