1. This site uses cookies. By continuing to use this site, you are agreeing to our use of cookies. Learn More.

Converting the 4wd gearbox to 2wd

Discussion in 'Drivetrain' started by Stig, Mar 13, 2011.

  1. Stig

    Stig ST162 Guru Donated!

    E Gearbox Identification
    There have been at least 7 different GT-Four gearboxes, possibly more.
    So how do you tell them apart if you find one at a wrecker?
    Toyota don't stamp their gearboxes with the type number, so it isn't easy.

    E50F1 ST165 Only fitted to 86-87 Japan spec models. No viscous coupling, locking centre diff.
    Not a good performance choice. Has a large pneumatic actuator fitted to the transfer.

    E50F2 Fitted to all 87-89 models (post build number -0002274). Introduces viscous coupling.
    Available with 4.285 final drive (Japan) or 3.933 (export). These have a pressed steel clutch fork.


    E150F Normal early ST185 gearbox. Identified by the cast steel clutch fork.

    E151F RC gearbox. Improved dual cone synchros. Fitted with 3.933 final drive in all homologation models.
    This gearbox may have also been fitted to other post 91 facelift ST185's. Not sure on their specification though.

    E152F I believe that this is the gearbox from the Japan only GT-Four Rally model. This has different ratios.
    I don't know how to identify the different ST185 gearboxes! Without stamped markings, they all look the same.

    E154F ST205 Revised gearbox with different ratios for better accellaration. Dual cone synchros are used as per the RC gearbox.
    The fwd selector lever has been removed. Obviously this is the gearbox to buy!
    Easily identified by the lack of fwd selector lever and the small rubber vent below the shift fork.

    Ratios: (JDM)1st 2nd 3rd 4th 5th Reverse Final Drive
    ST165 3.583 2.045 1.333 0.972 0.731 3.583 4.285
    ST185 3.384 1.913 1.333 0.972 0.731 3.545 4.285
    ST185 RC 3.583 2.045 1.333 0.972 0.731 3.545 3.933
    ST185 Rally 3.230 2.142 1.518 1.258 0.731 3.545 4.285
    ST205 3.384 1.913 1.258 0.918 0.731 3.545 4.285
    MR2 Turbo 3.230 1.913 1.258 0.918 0.731 3.545 4.285

    These numbers are from the Hyperrev so export and US spec models may differ.
    The RC gearbox ratios are what have been found in two RC gearboxes locally,ratios may vary.

    Converting from 4wd to 2wd
    Converting the AWD "E" to a FWD tranny is not as hard people would think, and when finished,
    it will be exactly as an MR2 Turbo tranny, except with the shifter cables already going in the right direction.
    Also, with this method, your center differential won't burn since it will be completly removed.

    Goodies needed :

    -Alltrac tranny.
    -GT4 shift cables.
    -MR2 turbo differential (open, OEM Toyota VLSD, aftermarket LSD)
    -MR2 differential cover plate.
    -Speedometer drive for the differential if it does not come with the diff.
    -2 axles seals (optional, but recommended and cheap).
    -1 set of alltrac outer axles.
    -1 set of inner MR2 axle with passenger axle carrier (get LSD inner axles if going with the OEM Toyota MR2 turbo VLSD unit).
    -A puller and access to a press to replace 5th gears on transmission.
    -An Alltrac crossmember with the transmission rear mount (or modify your existing one).

    I'll try to do a step by step guide (I will really need to post pictures later):

    1 - Remove the transfer case by unbolting it from the bellhousing case, store it, sell it.

    2 - Open transmission by removing 5th gear cover. Remove 5th gears. Remove bellhousing case.
    Remove shifting forks. Finally you can remove the center/front differential from the bellhousing.

    3 - Change drive axle oil seals from the bellhousing if your tranny has high milage (cheap at dealer).

    4 - Buy an MR2 differential. I suggest getting an LSD unit, since opening that tranny is a pain
    and getting LSD with a 3sgte is a must IMHO You either can buy an open MR2 turbo diff, a OEM toyota VLSD diff,
    or better yet, aftermarket torsen diff. The MR2 differential will work perfectly in the AWD tranny.
    The bearings will sits nice and thigh.

    5 - Remove ring gear (Crownwheel) from the AWD differential by removing the 16 bolts, and tapping it with a brass hammer
    (or place a piece of wood and hit it).

    6 - Place the ring gear on the MR2 diff, place the 16 bolts with Loctite.

    7 - Order a speedometer drive from Toyota dealer (cost me 80$ can, but I bet you can get a better price than that).
    Place the speedometer drive on mr2 diff.

    8 - Install diff. If your AWD tranny grinds, and you'd like to replace the synchros for not too much,
    now is a good time to do it.

    9 - Re-assemble the tranny: Place the input/output shafts, selecting gear forks, oil cooler lines,
    bellhousing case, 5th gears, 5th gear cover.

    10 - At this point, you'll need the differential cover plate from the MR2/V6 that will bolt on where you removed the transfer case.
    You can get this from a toasted MR2 tranny. This cover has the passenger axle seal.
    Replace it also if worn or old.

    11 - Get MR2 turbo inner driveshafts. You need axle with turbo and LSD if using the OEM Toyota VLSD diff.
    Otherwise, if using open differential or aftermarket LSD (TRD, cusco, etc) use the normal turbo axle.
    The normal Mr2 turbo non-LSD axle can be modified also to fit the OEM Toyota LSD diff.

    12 - You need to make hybrid axles. Use the celica alltrac OUTER axles, and the INNER MR2 axles.
    The outer axles is those that enters the hub with bearing at the wheels.
    The inners enters the transmission to plug into the diff.
    You can separate the outers and inners axles by removing 6 8mm Allenkey bolts.

    13 - Install the new alltrac/mr2 hybrid tranny. Use the celica alltrac shifting cables,
    use either electronic or cable driven speedo by swapping the correct one on tranny.
    Use 3sgte clutch/flywheel/pressure plate (Or Camry V6/Late 5S flywheel etc).
    Place the alltrac/mr2 hybrid axles.

    14 - The rear transmission mount may be different. This also happens if you swap the MR2 transmission.
    You need to get an alltrac crossmember, or modify your existing one (the mount is not at the same place).

    15 - Drive

    Ok I know this isn't a detailed step by step guide, but this should give a good lead to any of us that wants to convert their tranny.

    NOTE: Keep in mind that you should use the BGB to disassemble and assemble the tranny.
    Also this guide is intended for the 2nd gen E152 on a ST182 celica.
    However, this should work on 4th, 5th and 6th gen celica, and all version of alltrac AWD
    transmission but maybe with some minor differences.
  2. ST185GT

    ST185GT Member

    Ok, so just to clarify i will only need a MR2 diff and cover plate. The rest is nothing.

    Question: I losened off the bolts/nuts of the transfer case and it still didnt separate from the gearbox bell housing, am i missing something.
  3. Stig

    Stig ST162 Guru Donated!

    Yes, but youi'll need to swap the ring gear, speedo drive, bearings and get it
    all measured up correctly.

    It should just pull out
  4. ST185GT

    ST185GT Member

    So this is the cover plate >

  5. ST185GT

    ST185GT Member

    Just a quick double post.

    From my conclusion, what i have done is 100% fwd mode already. The only difference is that the transfer box is retained and the input shaft is internal (no need for a mounting point on the block), and just use the external cv and shaft with the bolt system.

    Overall, the real 4wd to 2wd conversion just removes the transfer case housings and the 2nd diff.

    Weight wise, the only major weight of the transfer box is just the 2nd diff.

    Im doing my homework folks, just bare with me and my questions and answers.
  6. Stig

    Stig ST162 Guru Donated!

    I have no idea what you are doing?
    Sounds like you're trying to emulate the diff switch which isn't recommended for normal driving.

    You can't just remove/disable the 2nd diff - from what I've seen/heard there's stuff
    to be welded & modded inside and it still isn't reliable.

    Look at this pic, if the shaft were one piece it would be simple to just eliminate the transfer diff,
    yoke and all inside the outer case & make a new shaft.
    But I think it's either
    a) 2 piece unit that actually transfers power BACK to the diff via a viscous coupling. (according to the BGB power diagram)
    b) Each shaft has a seperate function, ie the outer works the transfer diff and the inner goes all the way to the RH wheel (according to what I see in the BGB)


    You'll have to split it and post pics, the BGB isn't clear on the functions and wer'e new to this but there are some very clever dudes here.
    I see the outer shaft is pressed into the diff, could be why tou have problems splitting but
    it should pull out with a puller.

    I need to see pics of the selector collar and fork and how it influences the shaft/diff engagement.
    Also whether the inner shaft is solid and goes all the way to the RH wheel thru the transfer diff centre.

    I had links to all this but they are gone, best is to seach the Lotus and MR2 sites for how-to's

    Best route is still to find a V6 box


Share This Page