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Thread: Dropping a front Differential on a Toyota IFS

  1. #1
    Made in Brazil JackSilb's Avatar
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    Default Dropping a front Differential on a Toyota IFS


    Hello,</div>
    </o:p></div>
    I would like to start a discussion on dropping the front differential on IFS. More specifically, discuss these on Toyotas 4Runner 3<SUP>rd generation and <st1:City w:st="on"><st1:place w:st="on">Tacoma.</div>
    </o:p></div>
    While removing my Fabtech (Fox) shocks for rebuilding, the guys at ProTrux recommended me dropping the front differential. It was an easy install, just two spacers about 2 each. I have a picture on my phone to add here later.</div>
    </o:p></div>
    As a loan, they installed a TRD front shock coil over from a <st1:City w:st="on"><st1:place w:st="on">Tacoma. I did not realize until was too late in the trail, but it seems that I have less than stock clearance on the front now. I hit several rock and I easily passed before. Sure I had the Fabtech installed.</div>
    </o:p></div>
    Questions:</div>
    </o:p></div>
    - By dropping the front differential, one looses clearance?</div>
    - The drop diff mod allows you to lower the angle of the half axels and release some stress on the CV. Therefore one can raise more the adjustable coil over. Right?</div>
    - When I install my Fabtech again, and raise it above where it was before will I have more or the same clearance at the lower point bellows the front diff? I mean will really gain anything?</div>
    - If I drop the diff ~2 and raise the suspension 2 what exact will I gain? One is in a straight line (drop diff) the other will be reflected as an angle on the suspension arms. </div>
    - Am I adding any stress anywhere by lowering the front diff?</div>
    </o:p></div>
    I did not like much the mod. It is basically two aluminum cylinders. The original interface between the front diff and where it connects (name?) has a male / female setup. The spacers are flat. I wish they were machined to replicate the perfect fitting from the original setup. It seems that all the stress is being held by the bolts that go through the spacers. </div>
    </o:p></div>
    Please give me some feedback because I may remove the drop dif this week while re-installing the Fabtech shocks. Reliability is very important for me.</div>
    </o:p></div>
    I hope this discussion will be useful for others.</div>
    Thanks in advance.</div>
    -JACK</div>


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  2. #2
    Graduate Member GoodTimes's Avatar
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    Jack, when you drop the front differential on any IFS vehicle (not just toyota's), you will lose ground clearance under the differential. What you will gain is better angles on your CV joints, which equates to them being in a stronger operation position, and you will have longer CV boot life. This will also allow you to lift your front end higher if you want. The problem with going too high with IFS is the angle of the control arms that you mentioned. Since the upper and lower arms are different lengths, you will see a more radical camber curve as your suspension cycles (because they are both lower in their arc of travel), which can lead to some bump steer, and some odd handleing characteristics (keep in mind that they will be very slight, but they will be there). Also, the higher you go, the more of a angle your tie rod ends will be at, relative to your drag link. This is what creates the bump steer, and depending on steering system design, this can accelerate wear on your idler and pitman arms, and make it easier to bend your tierod &amp;/or drag link.</div>



    Any time you lift a IFS vehicle, you will run into those problems. The higher you lift, the more pronounced the problems will be. It is not a linear scale between the amount of lift and severity of problems, it is closer to a exponential curve (remember, every component of IFS and IFS steering systems travels in a arc--the farther down that arc the components are, the more horizontal travel they will have for every inch of vertical travel). Anything over 2 or 3 inches if lift, you will have to start modifying more and more things to compensate for the problems you created bythe lift. </div>



    The diff drop is one of those things that was designed to compensate for large lifts.....that mod brings your CV joints and boots back to a better operating angle (at the expense of ground clearance). Next, you will see the bump steer (if you lift your 4-runner more), so you end up dropping the lower control arms (similar to how you dropped the diff)and putting long travel upper arms on it....then you get tired of the bump steer, so you use a aftermarket steering system....then you.......blah blah blah.....it just snow balls from there.</div>



    Ok, to answer your questions, yes, yes, no/yes, more clearance under everything except the diff (until you put bigger tires on it), yes (but it is minimal, and I doubt it will ever be a concern).</div>









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  3. #3
    Sophomore Member RTaylor's Avatar
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    2" spacers?!?!

    i have some 1.25" spacers and people tell me they are too much. Revtek sells 3/4" spacers with their 3" lift kits and Cornbred sells 1" spacers with his kits.

    the logic behind dropping the diff is a good one, but it doesnt actually help that much on our IFS system. our front diff is supported by three mounts (2 front, 1 rear). the diff drop spacers lower the front 2 mounts while the rear mount doesnt move. this actually pivots the diff on those mounts causing a pinion angle that some argue is not good. (this has been argued a lot on TTORA)

    they say adding a diff spacer X in height is the equivalent of having X/2 less lift (1" spacers on 3" lift means the CVs are equivalent to 2.5").

    so would i want to increase my lift after adding diff drop spacers? NO! IMO the diff drop spacers should be used after a desired ride height is acheived for some extra ease of mind.

    if you notice those, your CV boots are at about the same angle, just slightly angled.


    [jack] see attached picture

    Post Edited By Moderator (JackSilb) : 5/25/2004 12:48:05 AM GMT
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  4. #4
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    JackSilb said...


    </o:p></o:p>
    - The drop diff mod allows you to lower the angle of the half axels and release some stress on the CV. Therefore one can raise more the adjustable coil over. Right?
    Goodtimes covered this very well. I will just add that another reason not to lift more is because the more you compress those coils, the less performance you will get from them. They will be too pre-loaded. You will also be stressing the ball joints more. IMO, if you want to go more than 2.5" (2.75" max) on the Tacoma/4runner 3rd gen IFS, then you need to step up to custom (longer) arms (a.k.a. Camburg, Total Chaos, etc).

    GT mentioned increasing boot life. I am not so sureit matters as muchon this particular setup (Taco/4Runner). I had 100,000 miles on my original CV boots before I replaced them (they finally started todry-rot). About 47,000 of those miles were with a lifted suspension.


    JackSilb said...


    </o:p>

    - When I install my Fabtech again, and raise it above where it was before will I have more or the same clearance at the lower point bellows the front diff? I mean will really gain anything?
    IMO, no - you won't really be gaining much. The diff. will indeed be lower, but everything else will be higher. So it depends on how you look at it. If you are able to add a little taller tire as a result of the additional lift (cranking your coilovers to 3" or more) then you would get more clearance back from the taller tires. But as I mentioned above, lifting this high with the coilovers is a bad move in my opinion. I don't think the gain is really worth mentioning if there is any.

    Ryan brought up a good point about pinion angle. Your front driveshaft has to connect to that diff - and by dropping it, you change the angle of that connection.

    In a nutshell, I think that dropping the IFS differential might improve the life of the CV joint a little bit, but I'm not sure how much. I just added a locker in the front, so if I end up breaking a CV with it, I might go ahead and drop my diff a little to try and get a little bit of extra strengthfrom the CV joint. But IMO it's not a big enough deal to do it until I break my first CV.

    Also, I think Ryan brought up a good point - 2" spacers seems like too much to me.

    </div>



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    Puertecitos Casa BajaXplorer's Avatar
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    Jack, you also got my attention with the 2" spacers. I am now running the All-Pro coilovers and a-arms with 1/2" differential spacers (3" lift over stock =2 1/2 coilover and 1/2" tire) which keep the CVs at a good angle. I am not familiar with the 4 Runner set up, but 2" got my attention. </div>
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  6. #6
    Made in Brazil JackSilb's Avatar
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    Thanks everyone for the information. This is goos stuff. I apreciate the time and detailed replies.

    Here are the pictures I took with my phone. I may have mislead you. From the picture it seems less than 2". I can't tell anymore.

    I have to decide to remo these or not by Thursday.
    How about my question on the bolts coming loose and too much stress on them?

    -JACK


    </div>


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    Post Edited (JackSilb) : 5/25/2004 1:16:02 AM GMT
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  7. #7
    12V Fridge Enthusiast BajaTaco's Avatar
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    Jack, I can't accurately measure mine without taking the skid plate off, but it looks like those mounting cushions (that the bolts go through) are about 2' deep. So it looks like your spacers are probably around 1' to 1.25' or so. Maybe a little much, but I don't know for sure. Those actually look like Roger Brown's spacers ( http://www.4crawler.com/4x4/ForSale/DiffDrop.shtml )

    I'll bet you will be okay if you leave them on. It's one of those things that you'll just have to try and see what happens. It would have been nice if you could have measured your pinion angle before and after the install.

    As far as the bolts go, I would just make sure they used grade 8 bolts and it should be fine. Lots of Taco/4Runner people are 'wheeling the diff drops these days and I haven't heard of any of them coming apart.



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  8. #8
    Made in Brazil JackSilb's Avatar
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    > As far as the bolts go, I would just make sure they used grade 8 bolts and it should be fine. Lots of Taco/4Runner people are 'wheeling the
    <> diff drops these days and I haven't heard of any of them coming apart.

    I would not know. How can I find out about this?

    -JACK


    So much to see, so little time. Try using your 4WD tosee and do more.
    Tread Lightly! empowers generations to enjoy the outdoors responsibly...
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  9. #9
    Jeep Nut TimB's Avatar
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    To ID bolts for grade:
    http://www.engineersedge.com/hex_bol...tification.htm

    I had a 1994 4-runner for a while - hated the diff drop but was tearing the CV joints up a lot. I put the diff back up in the stock location and installed some hubs from Mile Marker. I only locked the hubs when I needed them and the CV's never gave me any more trouble. I can find the part number for the hubs if you want - still have the solid drive slugs in the box the hubs came in. I think my milage went up too but that may have been all in my head.




    Post Edited By Moderator (JackSilb) : 6/30/2004 5:10:47 AM GMT

  10. #10
    Sophomore Member RTaylor's Avatar
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    im bumping this thread because of a recent discussion that got me thinking, heres the post from a different forum:

    'The diff drop procedure improves CV angles on lifted trucks when they are sitting level. This is a good thing. Moreover, at full droop the angles are also better. However, at full droop there isn't much weight on the wheel and hence not much torque flowing through the CV so I would think there is less chance of breakage. When the wheel is fully stuffed, the CV angle is worse than before and if you have a locker up front there is more torque flowing through that CV shaft since so much weight is on that wheel.

    Do you think it would make it more likely to break a CV because of this reason? '

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