true trac writeup

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  1. #1
    CelicaSupra.com Member williamb82's Avatar
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    true trac writeup

    True Trac part number
    911A342

    Toyota part numbers
    90366-35023-77 Inner pinion bearing
    90366-30022-77 Outer Pinion Bearing
    90368-50006 Carrier bearing (2 required)
    90311-38010 Pinion seal
    90311-38011 Side seals (2 required)
    41182-22011 Cover gasket
    41231-22010 Crush sleeve
    90179-18001 Pinion nut

    Solid pinion spacer if you opt for this instead of the crush sleeve.
    https://www.justdifferentials.com/SK...p/skcst7.5.htm



    First off, you need to make sure you have all the parts necessary to do the conversion. Second, make sure you have a differential with a good ring and pinion. You will need a large bench vise to make this easier.

    First drain the fluid from the differential, then clamp the nose of the diff in the bench vise, and remove the nut that is on the nose of the diff. You'll have to use a small punch or screw driver and a hammer to bend the notch out so it will unthread.

    Once that is out, slide a long punch/prybar between the differential case and the side output shaft. then smack the punch/prybar with a hammer to pop the output shaft out of the differential. Do this for each side.

    Next, remove the 8 bolts holding the cover in place and remove the cover. Now remove the 4 bolts that are holding the center section in place. You'll have to use a long breaker bar or an impact gun as they are tight.

    Once they are out, remove the caps, but mark them so you will remember which side they belong to. Also, when pulling the center section out, there is a shim on each side. KEEP THESE!!!! You will need these and may need an assortment of them to get it adjusted right after assembly. Most 4x4 shops can get you a shim pack for a decent price.

    Now that the carrier is out, remove the pinion bearing. Remember how everything went together! Take pictures if possible. The outer pinion bearing will slide out from the nose. Now, if replacing the inner pinion bearing, you will want to use a punch and a hammer from the front of the diff and drive the race for the pinion bearing out. If replacing the outer pinion bearing, you will use a punch to push the race out from inside the case.

    Next, the differential case needs to be cleaned. You can have it hot tanked at a machine shop, or, do what I did. I put it in a 5 gallon bucket and then poured purple stuff engine degreaser in till it was completely submerged. i let it sit for over an hour then scrubbed it with a stiff bristled brush. there is a black coating on the inside of the diff that will probably not come off. Do not worry about this. After I took it out of the bucket, I then scrubbed it with soap and water to get the degreaser residue off, and to prep it for paint. then i put the ring and pinion gears in to let them soak as well. When painting, make sure to block all the holes for the bolts and also make sure no paint will get inside the diff case.








    Now, if you do not have a shop press, you will need to take the True Trac and the carrier bearings to a machine shop to have them pressed onto it. Also take the pinion gear with you to have the old bearing pressed off and the new one on if replacing it. Make sure the shim is left on the pinion gear when they press the new bearing on if these gears came out of the case you are using and you are not changing them. If you are changing gears, you will need a pinion depth shim kit, which can be purchased at most 4x4 shops for Toyota 7.5in differentials. Setting the pinion depth is critical! Once all that is done your almost ready to assemble.






    Dave soaked all the bolts and whatnot in carburetor parts cleaner for several minuets to remove all the gunk that was on them. I have found that a sonic cleaner with HOT water and a little bit of Purple Power, or dawn will work as well. Next, you will need a seal/race install kit(Brass punch in a pinch) to drive the new pinion bearing race/s into the diff case. Make sure you do this carefully as it must be perfectly straight, and you do not want to damage the surface that the bearing contacts. .



    Once they are in, slide the pinion gear in, then put the new pinion seal in and make sure you slide the parts back onto the pinion shaft in the correct order(remember the pics I said to take?), and make sure you put the new crush sleeve/solid pinion spacer in there and not the old one. Be sure to use the new nut use a new nut. If using a solid pinion spacer, you should be able to measure the length of the OLD crush sleeve to get a starting point for the shims that come with it. You likely will need to add a small amount on top of this thickness to account for wear and tear on the original crush sleeve. Adjust until the preload on the pinion bearings are correct.

    Once together, you need to very very slowly tq the nut (if using crush sleeve) until it takes ~3.5-5.2inch lbs for a used bearing or 10.4-16.5inch/lbs for new bearings to turn the pinion gear. If you tq it too much you must pull the nut back off and get a new crush sleeve so be very careful. Too much preload on the pinion bearings will destroy them very quickly! If using the solid spacer setup, once the bolt is tq'ed, check the preload. If it is too low, add another shim. if it is too much, remove a shim. Repeat until it is correct!

    For he solid pinion spacer, Marlin Crawler says to hit the nut with the impact. Yotatech says about 90lbs. For Ford 7.5, 8.8, 9in diffs, the tq spec is 125ft/lbs. Your call.

    http://www.ratechmfg.com/fordspbs.htm

    Next, you will have to use a small flat head screw driver and a punch to bend the little tabs back that lock the bolts that hold the ring gear to the center section. then use an impact gun to remove these bolts. Then you need to use new tabs when bolting the ring gear to the True Trac. The bolts need to be tq'ed to 71ft/lbs, then push the locking tabs up against the nuts as they were before.

    Next, insert the True Trac in with the races on each bearing and for starters use the shims you had removed before. The shims are used to adjust end play and the preload on the carrier bearings. The preload should be ~3.5-5.2inch lbs as should the total preload. The backlash should be 0.0051"-0.0071". You may need to install different thickness shims to ge the preload right, and adjust them to move the carrier from left to right or vice versa to make sure the "wipe" pattern is correct. Once the right end play and preload is set install the caps and tq them to 58ft/lbs and recheck that the preload and backlash are still within spec.










    Use a new diff cover gasket and coat it lightly with ultra gray rtv sealant. It is best to rub a lil on your fingers and then smear it on the gasket so that there will be no excess to squish out. Then install the diff cover and tq the bolts to 16ft/lbs. Reinstall the axle stubs, and then fill the diff with the proper amount of fluid, and its ready to be installed.

    I used standard 75-w90 for the initial break in then switched to Amsoil Extreme duty 75-90 synthetic after maybe 1,000 miles.





    Here is a very helpful link.

    http://www.cygnusx1.net/supra/librar...ra/RA_018.html

    http://new.photos.yahoo.com/williamb...60762348387882

    This is why I needed the True Trac.







    Last edited by williamb82; 05-22-2018 at 02:12 PM.
    william
    Black 84 7mgte/R154, MS2, truetrac, bbk, etc...soon to have 2jzgte and t56
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  3. #2
    CelicaSupra.com Member BoostedTDI's Avatar
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    Good stuff. Question on the ring tabs when bolts onto the truetrac, did you get these at the dealer?
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  4. #3
    CelicaSupra.com Member williamb82's Avatar
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    yes, they are a dealer item. i dont have a part number. ill have to look it up.
    william
    william
    Black 84 7mgte/R154, MS2, truetrac, bbk, etc...soon to have 2jzgte and t56
    Blue 85 Beater. TRD Header, HKS Exhaust, custom 3in intake pipe, cone filter
    Black 86 Triple Weber 6m Eventually
    Rusty 85 Frankenstein 6M/w58 with DIYPNP

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  6. #4
    CelicaSupra.com Member ZZT231's Avatar
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    William,

    How much did it cost you to buy all the listed items above for you (if you did)?

    Cheers.

  7. #5
    CelicaSupra.com Member williamb82's Avatar
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    true trac part number
    911A342

    ~325 shipped

    toyota part numbers
    90366-35023-77 inner pinion bearing
    90368-50006 carrier bearing (2 required)
    90311-38010 pinion seal
    90311-38011 side seals(2 required)
    41182-22011 cover gasket
    41231-22010 crush sleav
    90179-18001 pinion nut

    ~$150 total

    then i bought a 3.727 non-lsd diff from the pick and pull for ~$60 with corecharge and tax. then the purple stuff degreaser and paint ~$20 then the money for the machine shop to install the bearings ~$40 then ~$10 for gear lube so a lil over $600 total.
    william
    Black 84 7mgte/R154, MS2, truetrac, bbk, etc...soon to have 2jzgte and t56
    Blue 85 Beater. TRD Header, HKS Exhaust, custom 3in intake pipe, cone filter
    Black 86 Triple Weber 6m Eventually
    Rusty 85 Frankenstein 6M/w58 with DIYPNP

  8. #6
    ZZT231,

    I need to get bearings for mine, and my brother in law works for a mob that has a toyota dealership, so armed with the part numbers (thanks William) I'll see what I can do for prices

    Cheers

    Michael B

  9. #7
    CelicaSupra.com Member ZZT231's Avatar
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    Quote Originally Posted by bbaacchhyy
    ZZT231,

    I need to get bearings for mine, and my brother in law works for a mob that has a toyota dealership, so armed with the part numbers (thanks William) I'll see what I can do for prices

    Cheers

    Michael B
    bbaacchhyy,

    Please do! I will buy a backup set as I already done 8,000kms on the diff and it's back in the shop to get a new set of bearings... Thanks William for those part numbers, it makes life soo easy

    Cheers.

  10. #8
    CelicaSupra.com Member williamb82's Avatar
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    i doubt you had the wrong bearings. if you did they wouldnt have fit, i bet they set the preload too tight. that will kill bearings fast.
    william
    william
    Black 84 7mgte/R154, MS2, truetrac, bbk, etc...soon to have 2jzgte and t56
    Blue 85 Beater. TRD Header, HKS Exhaust, custom 3in intake pipe, cone filter
    Black 86 Triple Weber 6m Eventually
    Rusty 85 Frankenstein 6M/w58 with DIYPNP

  11. #9
    Great work William...making this a sitcky for a while so everyone has a chance to see it.

  12. #10
    CelicaSupra.com Member ZZT231's Avatar
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    What type of Oil do you use for the TruTrac? I was told to use the Standard Diff Oil (85W-90) is that correct? :?

    Cheers.

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