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  1. #1
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    Default TH400 front yoke length

    Hi
    My set up was from memory was a holden v8 drive shaft with an aftermarket TH400 yoke . Used a HZ th400/10 bolt /sedan .
    uni to uni c/line 1412mm which is correct for application .

    Today
    Using a same style tranny th400 with 4 inch ext housing [same as Holden]


    XXXXX .......Question is what is a factory length yoke measurement ?????
    1/ C/L [ uni centre line ] to tip ---------- this is important
    2/ overall length
    3/ does the factory yoke have a counter bore


    My aftermarket replacement has a counter bore ie suit O ring. Only suppose to come with bolt on yokes . So I`m confused
    Last edited by swampy; 30-12-2021 at 04:01 PM.

  2. #2
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    If no one else replies I'll measure up a HZ yoke tomorrow.

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    OE slip yokes have a smooth bore approx 1 inch long. O-ring helps control the amount of oil to lubricate the splines and reduce the chance of a hydraulic bind which can force the plug out of the yoke.
    The bolt on style yokes have it as well but is often shorter.

    Sometimes you will encounter a problem where the output shaft has an increased diameter in front of the O-ring and the smooth bore bottoms out on this larger diameter.

    A lot of guys throw the O-ring away

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    hi
    Yup

    I can probably remove extension housing [usa th400 ] and check with the length of the yoke for clearance on shaft .
    Yes there were differently shaped output shafts .

    1/ Apparently bolt on versions are Oring sealed shaft to inside yoke . Thats why they have a part inside smooth bore . These yokes have a vent hole in the welsch plug .
    2/ the sliding yoke does not have an o ring but a fully sealed welsch plug in yoke

    But I think Holdens have an o ring with a sliding yoke so a combination of the above
    Remember Holdens hand pick from all GM brands Buick Olds Pontiac Chev

    IT appears the shorter yokes are spline only 5.5 inch ,,etc
    What ever happens if your going to use the shaft O ring you gotta have a counter/smooth bore to match on the yoke inside diameter with the shaft o ring . This all occurs in the running position eg tail shaft close to horizontal and the yoke 1/2 inch gap to bottoming out on the output shaft .


    If I go with no o ring and a fully sealed yoke w /plug this is simpler . Full length spline . STILL NEED TO CHECK FOR FULL SPLINE engagement
    The only thing that I will need to set up is ride height tail shaft front yoke depth eg 1/2 gap to o/shaft
    Last edited by swampy; 31-12-2021 at 02:02 AM.

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    Quote Originally Posted by swampy View Post
    1/ Apparently bolt on versions are Oring sealed shaft to inside yoke . Thats why they have a part inside smooth bore . These yokes have a vent hole in the welsch plug . Wrong
    2/ the sliding yoke does not have an o ring but a fully sealed welsch plug in yoke. Wrong
    Bolt on type have a large diameter washer 3 or 4 mm thick, no hole and a bolt.
    All slip yokes I have ever seen on a 400 have the o-ring, but like I said, people do remove them.

    Just get the tailshaft manufacturer to make the shaft and use the yoke that they provide, if they are reputable then they will be using good gear. Sonnax or Strange do entry level yokes.
    If you get this yoke (in the link below) you'll have no problem if the output shaft has an increased diameter as the counter bore is shortened to accomodate.

    https://www.sonnax.com/parts/3841-slip-yoke

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    hi
    I go on a few chevy and pontiac sites . The chevy vehicles seem to have no o rings and the Pontiacs do . All the other advice has either been Strange or Sonax .
    The local suppliers are either Truck tail shaft or Spicer ,both will do a mild steel only and cast yokes if I ask.

    Just finishing the part orders for driveline just sorting trans yoke and diff yoke hold down clamps .

    For ease I will remove the ext housing and measure the spline length and match with appropriate yoke allowing for 1/2 clearance end float .

    The yoke in my Ozzy Hz th400 is 7.5 inches c/l to tip longest available made outta cast but its an aftermarket unit .
    Last edited by swampy; 31-12-2021 at 07:39 PM.

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    I used to get Strange in the states do all my tailshafts and send them over, it was way cheaper than having them done here. You can order through the likes of VPW etc. if you dont want to go direct.
    Chromoly tube and weld yokes, all the good stuff, the balancing and welding is not like you see here, it's quality.

    https://www.strangeengineering.net/wp-content/uploads/2013/11/Driveshaft-Order-Form.pdf

    Other than that, GJ drivelines down here do the local performance shafts.

    I dont know why you would remove the extension housing, just give them the length from the seal to the diff yoke uni centreline and let them do the rest. They wouldn't even know the spline length or care about it. Dimension "A" on the form is the important one and dimension "B" is to make sure the yoke they use doesnt bottom out.

    I bring that many 400's in from US, BOP's, Chev, Jeep, Hummers and Euro. The vast majority have the O-ring and groove.
    The few that dont have it are usually long shaft box's, odd ball 4wd conversions and the like.

    You have to remember the governor and speedo are right there in that short extension housing, the oil supply to that area is significant.
    The O-ring is just a control measure, GM did it on other transmissions as well but not always in the same manner. Some had a shroud that was attached to the output shaft and the yoke would slip into the shroud.
    Ford did it as well with a rubber concertina on some transmissions.

  8. #8
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    Peter Way did all my tailshafts but havent spoken to him for a looong time.

    First one he did, gave me a billet yoke to bring home so I could measure the length properly.

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    hi
    HQ 368
    Your thoughts steel or chromoly t/shaft . Its suggested by a major player beyond a certain diameter shaft no advantage in weight saving c/moly just strength . This strength is handy when approaching critical balance speed [less run out ] .
    Would try/actually prefer aluminium shaft but I get poor reports of durability .
    Final diameter might be 3.5--4 inch diameter . Pending tunnel /exhaust clearance .
    Anyways that`s for the future coming mths .



    One last mod to complete on the valve body of which u may be able to help ,need a factory size location in v/body of drain or fill hole for vp convertor. Not the welsch plug restrictor ,I have that [inserts in case gallery behind pump] .
    I have all parts needed just the hole details . Even scored an ECU with vacuum/TPS & brake sensor.!!

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    I always go chromoly, there is a weight saving and advantages, can run a reduced diameter for greater torsional strength over steel.

    Not sure what your referring to, the circuit is supplied line pressure from the gallery through the restrictor you mention and into the pump cover where the stator valve is that does the switching in conjunction with the solenoid that is bolted to the pump.

    Thats how the factory does it. Personally I'd just get rid of it all.

    The conventional factory valve body has no bearing on the switch pitch.

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