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Thread: 4BD1T - auto conversion with 6R80??

  1. #11
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    Quote Originally Posted by oka374 View Post
    I would steer clear of the 4L80E too, I put the strongest version factory version from a Hummer H1 into an Oka which while it is heavier is powered by an asthmatic Perkins Phaser turbo diesel of 3.9L.
    Basically it boils down to the fact that the clutches, especially the torque converter clutch can't handle the torque load from a big 4 cylinder diesel.
    I was one of the first to fit the 4L80E to the Perkins in Oz and all the later adopters have had the same problems despite "indestructible" builds by the transmission experts.
    What works in a relatively light performance vehicle doesn't necessarily work in a heavier vehicle with a a torquey diesel.
    The Allison 6 speed fitted after that debacle, now that is a great transmission but way too heavy for a Landy or Cruiser, altough there have been a few fitted to 200 series Tojo's when Duramax has been fitted.
    Thanks - that's good feedback. I've been mainly a manual bloke, and very little auto experience aside from the 6cyl falcons I had as daily drivers in the 90's and 00's.

    Were you running a flywheel as well as the flex plate - or just the flex by itself? I've noticed that the factory 4BD1T auto has a 2 piece flywheel + flex plate arrangement. I'm assuming it was done to dampen some of the torque impulses and make it a bit nicer for the converter and trans.

    Are the ratios in the Allison similar to the 6L80, and what sort of weight are you at in the Oka?
    If the 6L80 had held up OK - would you have stuck with it, or were there other things about it that that you didn't like? Just trying to get a feel for what the driveability was like and how that's likely to correspond to the 4BD1T. I haven't had anything to do with the Phaser, but a quick search online looks like they are even lower revving that the Isuzu, and produce most of their power down lower too.

    Steve
    1985 County - Isuzu 4bd1 with HX30W turbo, LT95, 255/85-16 KM2's
    1988 120 with rust and potential
    1999 300tdi 130 single cab - "stock as bro"
    2003 D2a Td5 - the boss's daily drive

  2. #12
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    Steve we're usally around the 5.5 tonne mark when loaded for a trip.
    The ratios in the Allison 1000 are
    1st.....3.10...........3.51
    2nd....1.81...........1.90
    3rd.....1.41...........1.44
    4th.....1.00...........1.00
    5th.....0.71...........0.74
    6th.....0.61...........0.64(06-up models only)
    Rev.....4.49...........5.09
    Mine runs the LHS side ratios which has it sitting on 1850 rpm at 100kph with 37's
    Yes the perkins adapter kit for the perkins ran an industrial stepped flywheel into which the adapter bolted then the flex plate plate bolted to what was essentially a piece in the middle which was the same as a chev 350 crankshaft.
    The flywheel weighed around 50kg so there was plenty of dampening going on but a lot of inertia as well.
    The adapter kit was designed originally for aircraft tugs in the US which were apparently manual back then to fit Th400 auto transmissions to enable them to get larger aircraft moving off the mark.
    My using it for a vehicle was a first apparently and as a whole it worked well except the transmission couldn't handle the combination of the Perky's torque and the weight of the Oka.
    I later fitted a Cummins 6bt and that took less than a few thousand k's to destroy the 4L80E's torque converter clutch. I was using a Compushift to control the transmission.
    The 4l80E's torque converter clutch is about 120mm in diameter and about 12 mm wide in surface area so not much at all, combined with a typical hydraulic pressure of 30psi to clamp it isn't much at all.
    The Allison is running much higher pressure, up well in excess of 100psi and the clutch surface area is about 10 times the 4l80E and much larger diameter so is well able to handle the torque from an intercooled 6bt

  3. #13
    TonyC is online now Master Silver Subscriber
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    Quote Originally Posted by steveG View Post
    I'm aware of the Wholesale Automatics 4L80E conversion, but TBH if I'm going to mess around with an auto its going to be to get the extra gears so a 4 speed isn't going to cut it!

    Steve
    Hi Steve,
    I wasn't suggesting the 4 speed.
    Just thinking that the bellhousing/ flywheel/ flaxplate might be the same or similar, and that may save you some work.
    Tony

  4. #14
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    Quote Originally Posted by steveG View Post
    Is that the factory TCM that you can tune - or the Quick6 I mentioned earlier?

    Steve
    I meant the original Ford TCM.
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  5. #15
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    Left field here................

    Dunno why anyone would want to put a 6 speed electronic auto behind an Isuzu, with a flat, abundant torque range.

    Call it primitive............. I put a Ritters C9 / LT 95 TC conversion behind a 350 maybe 20 years ago in a 74 RRC.

    Sure the C9 is only 3 speed, but you don't really notice it with a motor like that. There are no electronics and a rebuild to handle 700 hp is south of 1K. An Isuzu would have more torque than a 350.

    There's a solid overdrive (20 something percent) for LT95's available now for less than $4K , with temp sensor, gauge, etc which would mean I could have a really strong transmission combo with no electronic expense or complication, with 12 speeds............. 6 forward, 2 reverse, 2 neutral and 2 in P.

    I know I still owe Bearman pics of what this looks like from underneath, using stock TC mounts and propshafts.

    cheers, DL

  6. #16
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    Fair comment.
    Do you do much heavy towing or sand driving with that combo or is it mainly just general road work.
    With no converter lockup I’d be concerned about the cooling aspect.

    Steve
    1985 County - Isuzu 4bd1 with HX30W turbo, LT95, 255/85-16 KM2's
    1988 120 with rust and potential
    1999 300tdi 130 single cab - "stock as bro"
    2003 D2a Td5 - the boss's daily drive

  7. #17
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    In case anyone is interested, here's a good article on how the hydraulic side of the torque converter clutch (TCC) works in the 6 speed ZF variants, and the common issues and symptoms.

    Sonnax Six Ways from Sunday: Diagnosing ZF6 & Ford 6R60/80 TC-Related Drivability Concerns

    Knowing SFA about modern auto transmissions, I'd always assumed that the lockup clutch was applied by hydraulic pressure.
    Apparently not the case - the clutch is actually RELEASED by pressure.

    EDIT: After having a good look at the hydraulic circuit diagrams and doing a bit more research, the lockup clutch is both applied and released by pressure.
    Essentially pressure to one site applies it, and pressure to the other side releases it. Controlling the pressure on the release side will reduce the clamping force - the more pressure on the release side the less clamping.


    I can see now why the tune of the trans is critical to both how it behaves, and longevity.
    Also how important it is for the converter clutch to have sufficient torque handling for the application. I'd go as far as to say that monitoring the TCC slip would be critical in any conversion, since if its slipping under power when it should be locked its just a matter of time before it fails.
    Like anything, if you know its happening then you can modify your driving style to help - in this case reducing the torque at that point and let it lock rather than driving on blindly for thousands of km's and eventually killing the converter/trans.

    Steve
    1985 County - Isuzu 4bd1 with HX30W turbo, LT95, 255/85-16 KM2's
    1988 120 with rust and potential
    1999 300tdi 130 single cab - "stock as bro"
    2003 D2a Td5 - the boss's daily drive

  8. #18
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    Have a look what they are doing with the 6r80 in the US, getting around 1000hp through with just an ecu tune.

    You could import a 6r140 if you're worried about killing it.

    I couldn't think of anything worse than a 3 speed 4bd1t! The more gears the better for the slow and low revving big diesel. You really need to get those revs down on the hwy.

  9. #19
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    Anyone happen to know if the 6R80 in the Ranger is physically the same in the 2.2 and 3.2 diesels?

    I’ve found a couple of bits of info online that suggest the same trans fits both, but nothing concrete.

    Steve
    1985 County - Isuzu 4bd1 with HX30W turbo, LT95, 255/85-16 KM2's
    1988 120 with rust and potential
    1999 300tdi 130 single cab - "stock as bro"
    2003 D2a Td5 - the boss's daily drive

  10. #20
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    Quote Originally Posted by steveG View Post
    I know there has been talk about it, but looking for hard info if anyone has actually done it - or done detailed research into it.

    ......
    Steve
    Yes have done it. Yes is available as a kit. Yes works very well.

    1.003 transfer with 32" tyres and she cruises at 120 with ease 😎
    4.17 first gear ratio gets you going with a load easily.
    Currently averaging 9.5 litres per 100km.

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