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Understanding the Toyota E15x series gearboxes, a basic guide to...

Discussion in 'Drivetrain' started by Stig, Mar 12, 2012.

  1. eNtraxGT88

    eNtraxGT88 Well-Known Member Donated!

    i agree with redrkt on this one, when nothing is slipping it's 50/50 based on the video. the power is equally split coming out of the centre differential. but when let's say any one wheel slips, let's say the front left like in the video, then the open centre diff diverts to the front, then the front diff diverts to the left. if it was the rear left slipping, then it would be spinning that rear left wheel only while the other three wheels are not moving. if that was the case, you would lock the centre diff and you'd have both front wheels + rear left wheel spinning now.

    think of a fwd car, normally, the power is split 50/50 between left and right, but when you slip one wheel, the side that is slipping is the one that spins while the other is steady. LSD would fix that and turn both at the same time.

    if you think of the fwd diff as similar to the centre diff, the lock is similar to a fwd LSD in the way it locks both front/back.

    the lock doesn't "activate" the rear, but simply locks the front and back together in case either one slips. by your logic, if it was the rear slipping instead of the front, the car would be rwd and the lock would "activate" the front..
    Last edited: Sep 27, 2012
  2. Stig

    Stig ST162 Guru Donated!

    You guys just don't get it

    The VC is a can with thick fluid in it - literally!

    Take a jar of syrup or honey and stick a spoon in it - you now have a makeshift VC with the spoon being the rear propshaft.

    Turn the jar and the spoon will turn with the jar, there is NO force (zero!) being transmitted to the spoon (in our case the spoon is actually being turned by the rear wheels, not the jar)

    Now hold the spoon and keep turning the jar - you will feel a force transmitted through the spoon (this approximates a difference in speed between the front/rear)
    You will also now feel that there is a lot of "slip" on the spoon - the syrup can't transmit all the force (or half) to the spoon (this is why people are trying to upgrade the VC fluid)

    Now boil the syrup and repeat - you will now feel the effect of an old or overheated VC - even less force is transmitted to the spoon (propshaft)

    There is NO WAY the diff or VC can sense or distribute power from left to right or right to left. Both front and rear diffs are open on the ST165.
    You can remedy this by fitting a LSD to the rear diff but not the front diff - this will eliminate some understeer but not all
    People who have fitted ex TTE front LSD's will tell you the car actually wants to oversteer!

    The WRC cars ran dual LSD's as well as a super stiff VC, ie they had polyurethane instead of syrup in their jars as well as wheel sensing on both axles

    I hope that helps clear some confusion
    Last edited: Sep 27, 2012
  3. Redrkt01

    Redrkt01 Well-Known Member

    I don't know about entrax, but I understand plenty. What you are describing is a plain VC diff, not a VC diff lock. And not only that, it appears you think that the power is being delivered to the open front diff first.

    In my explanation of what is happening torque-wise a few posts ago I noted that there was a 50/50 split until wheel slip occurred. This is maintained by the center diff, which is where torque is transmitted to FIRST. The center diff is driven directly by the output shaft thus splitting the output force between the front and rear diffs. As entrax correctly pointed out, the VC diff lock acts like an LSD. So with a 50/50 power distribution when wheel slip occurs it "locks" and apportions more torque where it is needed. The VC diff lock isn't trying transmit any of the torgue during normal straight-line driving because it doesn't have to. The center diff is transmitting the torque 50% front and back. When wheel slip occurs is when the VC diff "locks" to maintain the 50/50 (or close to) power distribution.

    I know it is confusing, but if you look at the diagrams and read the Toyota literature it is plainly outlined. Look here for the "description page" http://bgbonline.celicatech.com/90alltrac/MT/MT.htm

    Also, there are traction tests involving the Alltrac/GT-Four online. I have a friend with an ST185 that just performed one demonstrating what the 4WD system is doing. As soon as he sends me the link for youtube, I'll post it.
    Last edited: Sep 28, 2012
  4. Stig

    Stig ST162 Guru Donated!

    The open front diff IS the main drive and directly connected to the crown wheel/gearbox, it cannot be disconnected as it is part of the front diff.

    The term "lock" is being used loosely - the VC is unable to lock completely (what they are trying to explain is the way the fluid tries to turn the propshaft) - and in no way can it function as a diff lock, there is a huge difference between a diff lock and a VC.

    The early JDM GT4 (rev1) has a "diff lock" (coupling) in that it can lock the front and rear diffs together to act as one, unfortunately it was prone to breaking and abandoned.
    It was still possible to have a wheel spinning at each end and loss of drive due to the 2 open diffs, ie the car could never tow a boat on a sandy beach

    There is no open centre diff? - only a VC and an open diff each end of the rev2 GT4
    Last edited: Sep 28, 2012
  5. Redrkt01

    Redrkt01 Well-Known Member

    The Toyota Repair manual begs to differ for both the E50F2 and the E150F. Please read both the first and second pages here: http://bgbonline.celicatech.com/90alltrac/MT/MT.htm

    Edit: By the way, I misspoke referring to the center diff as open earlier.......clearly we all agree that it is a VC diff. Although I would counter that it is indeed a VC diff lock (non-mechanical, more like an LSD) stby for link.....
    Last edited: Sep 28, 2012
  6. Stig

    Stig ST162 Guru Donated!

    I'm aware of what the manuals say - what they should say is UP to 50/50 split as the road conditions are constantly changing and the car is accelerating, cruising, cornering, braking etc.
    It's easy to understand why there has been so much misinformation going around.

    From what I can see the centre diff is actually part of the front outer diff casing, it's a solid extension (the short shaft you see in this pic), ie it's directly connected to the crown wheel & final drive sprocket. (I can't turn it!)

    The long shaft is an extension of the inner FWD open diff and not connected to the crown wheel or the VC. (I can turn it easily)

    I'll be taking apart the 4wd and LSD diffs in the next week or two and we can see exactly how the VC derives it's power
    Last edited: Sep 28, 2012
  7. Redrkt01

    Redrkt01 Well-Known Member

    Okay, I know the 50/50 thing is just semantics. Like you say, conditions are variable. But for the sake of continuity and ease of explanation let's just keep saying 50/50. However, even if you don't read page 1 you should read page 2 in the lower left corner where it outlines that the power flows from Transmission-CenterDiff-FrontDiff/RearDiff. That underscores my point that it is truly full-time 4WD. I think your picture is key. I believe (but I'm not 100% sure) that the long shaft pictured is the "differential side gear intermediate shaft"‚Äč.
  8. aaron

    aaron Well-Known Member

    So I went and picked up my new gearbox today.

    It was sold to me as "mr2 lsd gearbox", has the selector on the FWD side with the opposite side blocked off with a welsch plug, has a pinion shaft through the diff and is near impossible to make the output shafts spin opposite ways.

    What do you guys think?



  9. Stig

    Stig ST162 Guru Donated!

    Nice find, looks like the real mcCoy
    Did you get the shafts as well?
    Does it have a pressed cover?
    What model is that from?
    Does it have any numbers near the clutch fork hole?
    What speedo is fitted?
    What colour is the speedo drive ring?
  10. aaron

    aaron Well-Known Member

    It better be, I paid $300 for it!
    I got a set of shafts that look like they're big turbo inners and 162 outers, solid CVs, good boots etc.
    Cover is cast aluminium
    It's out of an MR2 turbo apparently
    S20404112 - What does it mean?
    The speedo was removed, I'll have to find a new one.
    Drive ring is a creamy dull yellow colour.

    The guy I bought it off said he got it to put in his 162, but lost interest in the project.

    I know I need the GTE flywheel (which I have) to fit this to a GE, but what starter motor does it need? My 3SGE ones don't fit.
  11. fernandocelica

    fernandocelica Well-Known Member Donated!

    Nice gearbox you got there bit expensive ,Exactly what I said our starter's don't fit they to short on the bendix side it's good that have mention that as well .I was told the Camry one fit's there but wait for more info for I am not 100% sure still going to pick mine up as well then will find out.
  12. aaron

    aaron Well-Known Member

    It was cheap compared to what a lot of places want for an MR2 box around here :toetap05

    I'll admit I didn't check the wrecking yards first, they want less than $100 for any gearbox but I doubt I would have found a turbo LSD box.
  13. fernandocelica

    fernandocelica Well-Known Member Donated!

    Reason why Aaron I said expensive is that you guy's over there sometimes buy a complete celica for $300 lol.The one I am going to get is also from a MR2 turbo a LSD E series not sure what model going to pick it up next week then will see.The price was R1000 maybe $120+- that's the price I got it for.
  14. aaron

    aaron Well-Known Member

    haha yeah I got my last parts car for $350 and my good celica only cost me $700!
    $120 is a pretty good price for an LSD E series!
  15. Stig

    Stig ST162 Guru Donated!

    Any FE or Camry/later starter will work with the GT4/FE flywheel.

    Over here that's a $750+ deal - without the shaft/shifter conversion, funny that the internals are different to mine.

    You need to find a ST165 speedo drive, nothing else will work

    Made April 1992, sn - 4112, mine is a year older which may explain the changes and the different style diff from 1992-

    The dirty yellow ring denotes a 4.1 diff ratio, which is the same as ST165, ST185, ST205 etc.
    The blue ring on mine is a 3.9 diff found only in the ST185 RC and should give better economy but your 4.1 will accelerate better
    Last edited: Jan 5, 2013
  16. aaron

    aaron Well-Known Member

    Awesome, one of those should be easy to find.

    So is the 165 speedo drive the only one that fits or the only one that's mechanical? I don't mind making an electric-to-mechanical converter, I could even just make a 7-segment LCD display speedo.

    What would the acceleration and economy be like compared to having the S53 box?
  17. Stig

    Stig ST162 Guru Donated!

  18. aaron

    aaron Well-Known Member

    That box is a pretty good deal if it's got a LSD and it's in good condition, it's a shame about the ad being so poorly typed lol

    My friend has an electric to mechanical box in his 165, I could easily rig one up using a stepper motor once I know the pulse rates of the electric speedo drive. If it's voltage based it'll be even easier and I can fine-tune it.
  19. Stig

    Stig ST162 Guru Donated!

    Yeah, obviously he doesn't know anything about the box.
    It's a good buy considering they are so scarce and I had to buy 2 scrap boxes plus tons of crap to make one decent box. It's still all in pieces and waiting for time and money to put it back together properly.

    This is normally what's available - a lot of work to convert it to a ST162
    The MR2 box/shafts is definitely the easier/cheaper route to go unless you have access to a Curren or Solara setup.

    I don't think the speedo is voltage based and I know most systems are pulse fed, on the racecars we had pickups mounted to the propshaft or driveshaft.
    Last edited: Jan 5, 2013
  20. fernandocelica

    fernandocelica Well-Known Member Donated!

    At long last I had the time to go pick my gearbox up here are the picture's I also would like to know what model is it from got the inner shafts as a present lucky me 2013-01-11 11.36.46.jpg 2013-01-11 11.37.51.jpg 2013-01-11 11.38.38.jpg if the no is not visible
    it's S 1020 2703 thanks

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