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Where is a 10mm bolt used in in the 308 Transaxle?

Discussion in 'Technical Q&A' started by Verell, Dec 28, 2004.

  1. Verell

    Verell F1 Veteran
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    Speaking of unwelcome 'surprises' in sumps,
    I just pulled my trans sump cover to do a shift shaft alignment. I found the head of a 10mm bolt (ie: hex socket size 17mm). The bolt was sheared off flush with the bottom of the head. Head is black metal.

    WHERE IS IT USED?
    Looked all over the trans & couldn't see where it might have come from, couldn't spot anything.

    Then went all thru the FPC trans & diff pages. I haven't been able to spot where a 10mm bolt is used in the entire trans/diff. Found lots of 8mm & the ring gear bolts are 12mm. What am I overlooking?

    Only place I'm familiar with a similar 10mm black metal bolt being used is to secure the flywheel to the crank. Can't envision a way a bolt head could migrate from the bell housing into the transaxle tho.

    Confusedly,
     
  2. spider348

    spider348 Formula 3
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    Verell, from my recent 348 gearbox rebuild experience, there are a series of black anodized(?) bolts that secure the differential halves/ final drive gear, if my poor memory serves. Cannot recall size but 17mm head size sounds close. Does the 308 have a similar differential system? I imagine it would. This is a possible source. Cannot for the life of me figure how 1 could shear! Check your parts manual for the series of bolts that secure the final drive gear to the differential unit. Good luck, John.
     
  3. spider348

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    Verell, reviewed a schematic of the 308qv differential online. Appears there are a series of large bolts with castle nuts securing the driven gear to the differential, as well as clamping the differential halves together. The torque speced for this bolt/ nut is 80nm. If this is the source of the bolt head, the body and castle nut are still somewhere in the gearbox. From a stress viewpoint, I cannot understand how the bolt would fail under the head. Should fail at the threads due to reduced cross section. Again good luck, let me know if you need a hand. Ferrari gearboxes can be fun!
     
  4. Verell

    Verell F1 Veteran
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    #4 Verell, Dec 29, 2004
    Last edited by a moderator: Sep 7, 2017
    John,
    The ring(driven) gear bolts were my first thought also (see cross-section dwg below). However, I could not find any specs on them other than the torque spec.

    However, when I saw the torque spec I figured I'd found where it came from. Given an 80N-m(59ft-lb) torque spec and Ferrari's consistency in using the same torque values wherever the same thread size & pitch are used, I'd expect the ring gear bolt to be the same size as other bolts with the same torque specs. eg: the half-shaft bolts are 10mm, & the torque spec is 8Kg-m(57.5 ft-lb). Thus most likely the ring gear bolts are also 10mm.

    Uncertainty crept in:
    The cross-section drawing indicates that the ring gear bolts have long shoulders that are larger diameter than the threads. making the shoulder most likely 12mm dia, thus the break at the head would be 12mm not 10mm.

    Of course, the cross-section could be exagerating the size of the shoulder, relative to the threads & the shoulder is really 10mm. Another (IMHO unlikely in a high stress application like this) possibility I thought of is that the shoulder was undercut at the bolt head.

    The other possible contra-indication is that drawing shows the half-shaft flang bolts are shown as similar in size to the ring gear bolts. The torque spec section of the WSM lists these bolts as 12x1.25 torqued to 9Kg-m(65 ft-lb).

    So, does anyone know what size the ring gear bolts are?
    Image Unavailable, Please Login
     
  5. tbakowsky

    tbakowsky F1 World Champ
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    With the trans pan removed you should be able to see the ring gear on the diff carrier through the bottom of the trans. Just rotate the wheels and check to see if any of the bolt are missing or loose. This is getting to be quite a common problem with these things..age I guess
     
  6. Birdman

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    Damn, this is the week for misc. hardware turning up inside 308 engines. All I can say is I'm waiting until NEXT week to change my oil!

    :)

    Birdman
     
  7. Verell

    Verell F1 Veteran
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    #7 Verell, Dec 29, 2004
    Last edited by a moderator: Sep 7, 2017
    Tnx Tom,
    Went back & looked again. Took a while to get the angle & light right. Rotated the ring gear & sure 'nuff there the rest of this sucker was(sigh). Hanging mostly out of the ring gear hole & starting to cut a groove into the side of the diff. housing.

    Must have just broken because the groove isn't much more than a mark, maybe 1/2 mm deep. Also there weren't any Al chips in the trans lube or sump when I drained it.

    Tried to get a pix, had a lot of trouble getting light up into that spot. You can sort of see the bolt, the nut, & the groove the nut is starting to make in this image:
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  8. BigTex

    BigTex Seven Time F1 World Champ
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    I found a Slinky in mine, one time......darn fun loving Italians........

    Happy Holidays!
     
  9. spider348

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    Verell, you are 1 lucky Ferrari owner! Difficult to believe considering the circumstances but you are well aware of the damage that could have resulted if not detected early! I speak from painful experience!
    Is this a repair that can be done without gearbox removal and subsequent teardown? All the bolts should be replaced I would think. If 1 fails, the 2nd is generally not far behind!
    A lot of fellow area owners owe you favors Ferrari Godfather! If you need help, a legion will be there! John.
     
  10. Birdman

    Birdman F1 Veteran

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    Send in the cavalry! Are we taking your engine out Verell? Or can this be done in place?

    Birdman
     
  11. tbakowsky

    tbakowsky F1 World Champ
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    You can reove the diff with the engine in the car. Removal of the rear exhaust muffler and manifold is required. Once those are out of the way, the cover will come off. Depending on the year..the forward most studs on the diff cover may have to be removed with the double nut trick, inorder to get enough hight for the cover to be able to slip over top of them. Once removed just lift it out and jimmy it around until you can remove it form the car. It will come out the bottom..but you can remove try a pull it out through the engine bay aswell..it works both ways.
     
  12. Verell

    Verell F1 Veteran
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    Just checked ring gear bolt prices at Ferrari.uk. Boy is the exchange rate unfavorable these days ($1.92/£ )!!!Replacing all 8 bolts is going to be a tad expensive & my wallet's flat after Christmas:

    [8] #106777 CROWN WHEEL BOLT
    Unit price: £15.20 $29.22 USD
    Quantity required: 8

    [9] #104011 SELF LOCKING NUT
    Unit price: £3.80 $7.30 USD
    Quantity required: 8
    This part supersedes: 14511, 14795

    $36.52/nut & bolt pair * 8 = $292.16 !!!!

    Would like to hear from the professionals as to the need to replace all 8 differential bolts vs just replacing the broken one. Also don't want to be penny wise/pound foolish.

    I don't stress the differential by such things as popping the clutch with the engine rev'd, but do downshift to get engine braking on the highway. This is literally the 1st differential I've had a problem with in almost 40 years of driving cars!
     
  13. Steve Magnusson

    Steve Magnusson F1 World Champ
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    JMO, but I'd judge the need for replace all or replace one by what's found inside (I'm wondering where the "long" part of your bad bolt is ;)):

    1. If there's no evidence of a serious impact -- e.g., the bolt's head fracture (or most of it) occurred during the original preload installation, and you've been driving around sans 1 working bolt for many years -- just the one.

    2. If there is serious impact evidence showing that all the bolts took a whack I might be more conservative.

    Is there some specific "replace all" in the WSM documentation? At 180~230 lb-ft maximum possible torque from the engine I'd think that "exploding" the differential wouldn't be a big concern either way.
     
  14. spider348

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    Verell, would seem to me, with your vast knowledge of all things automotive, you should be able to match up the original Ferrari nut and bolt with an equal, or superior, metric replacement. They do not appear to be a special machined item. Establish the class, size etc and replace. A lot cheaper than Ferrari OEM. Just a thought. John.
     
  15. Verell

    Verell F1 Veteran
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    See above.

    What kind of evidence can I look for?

    Not that I've found, just recommended in a prior post in this thread.
     
  16. Steve Magnusson

    Steve Magnusson F1 World Champ
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    My bad Verell -- I'm getting lazy and just blurt out when I please without reviewing the whole thread.

    With regard to the "evidence" if you don't see a big "ding" (or a missing 1/2 tooth ;)) in the ring gear I think you could safely assume that no undersirable impact/shock loading was transmitted to the other bolts. If you want to go forensic on the broken bolt, see if the fracture surface has more than one distinct looking area -- e.g., a partial break/crack occurs in the bolt surface at initial preloading and the crack propogates slowly over time until the remaining cross-section breaks suddenly (usually the two regions appear different).
     
  17. Verell

    Verell F1 Veteran
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    Well, I'll pull out the last of the studs tomorrow AM, then will have the diff's cover off. Discovered that the studs for the left side seal holder/flange can't be removed w/o removing the half-shaft flange, so had to pull the left half-shaft.

    Found one of the half-shaft bolts was missing it's head! No way to tell if it's related to the broken crown wheel bolt. Looks like the head's been gone quite a while, there was some very dark old looking rust on the end, not bright red like fresh rust.

    BTW, anyone know of a lower priced source for the half-shaft & crown wheel bolts?

    Any idea what grade they are? 10.6 ? 12.9?
    Guess I can't go wrong with 12.9 other than spend a tad extra.
     
  18. spider348

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    Verell, here at the plant we use: http://www.metricscrew-toolco.com/
    Located in Wakefield, MA. Convenient for us, a haul for you. They generally stock a large selection of metric fasteners. We use them all the time for repairs to our CNC Machining Centers. Good luck. John.
     
  19. Birdman

    Birdman F1 Veteran

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    Hey John,
    Is that place in Wakefield a retail place that I can walk in and buy stuff? That's good to know. Wakefield isn't far from me (15 minutes). Verell, I could pick stuff up for you if you need me to.

    Birdman
     
  20. Birdman

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    Verell,
    Are you taking pics of all this for your forthcoming book? :)

    Birdman
     
  21. spider348

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    Birdman, should not be an issue. Pay at purchase. Purchase under your corporate name. Underwater equipment requires a lot of large metric fasteners! John.
     
  22. Verell

    Verell F1 Veteran
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    HERE WE GO AGAIN!!!

    Yesterday AM I pulled all the studs out of the diff cover, EXCEPT for the last one. It's stuck! Of course it's the one that's way in next to the block with minimal clearance! The others came out vy easy w/my stud pullers.

    The last one the stud puller rounded the threads a bit, but didn't break the stud loose.

    Cleaned them up with a SnapOn thread chaser, then double nutted them. Only room for top nut to go about 3/4 way on. Stripped the $!#@$ threads!

    Tried my trusty small pipe wrench, not quite enough room for it to get a good bite on the threads.

    Bought an S-K stud puller (one w/off-set hole & round toothed wheel driven by a 1/2" socket. Wheel's teeth were too shallow, just filed a flat on the stud.

    New pair of medium vice-grips can't quite grip it hard enough to keep them from turning on the stud.

    After 6 hours fighting it, called it quits for yesterday.

    Ordered a set of S-K impact screw-on/drive-on stud pullers (female easy-outs). Had to buy a set to get an 8mm one. (Already had the large Craftsman set, smallest size is 10mm(sigh), should have bought the $20 smaller set.

    If that doesn't get it, then will weld a nut on the end of the stud...

    Next to last resort will be to lift the diff cover up until it's as high on the stud as the block overhang will allow, then saw the stud & hope I can get it out with the pipe wrench once the diff cover is out of the way.

    Last resort will be to pull the engine & split the tranny/diff case off of course(deja vu fer sure...)

    BTW, the T.Rutlands crown wheel list price for the bolts is ONLY $43.66/bolt, $6.35/nut. BTW, nut is same F. p/n as conn. rod nut.

    Spider348, tnx for the pointer to a local supplier. Found a couple of metric suppliers here in Nashua as well. Now I just have to figure out the performance class for these bolts. So far 12.9 is highest class I've found.
    (Anyone know the perf. class for conn rod bolts? S/B same for these bolts.

    Sure hope these bolts don't have a machined body.

    Birdman, Haven't been taking pix as too much of a PITA w/my Kodak. However, my FZ20 just arrived, but the SD card is still in route. Figure I'll take pix during reassembly. BTW, my 8 mm stud puller seems to have developed problems, may be why it didn't deal too well with the last stud. Am going to pull it apart to see if anything's fixable. It's has a lot of use between my timing driver project, the JWise timing drive project, & this one. Thought it might have gotten oil/grease inside & tried cleaning it out w/brake cleaner, but it still isn't working right. Suspect I'll end up just ordering that set w/the 3/8" drive for the smaller studs.
     
  23. ham308

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    Verell, you shouldn't use a 12.9 bolt unless you have to (in order to get the pre-load). They are more brittle (less ductile) and more likely to break.

    Tell me what size the thread is, M10x1.? and I can tell you what the safe torque is for a 10.9, 12.9 etc.

    Richard
     
  24. Verell

    Verell F1 Veteran
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    Don't have the threaded end out of the tranny yet, but I suspect it's 10x1. The WSM torque spec is 80 N-m.

    Still fighting with that last stud. Couldn't whack the drive-on stud pullers hard enough to drive them down to where they wouldn't strip instead of turning the stud. Only have about 40 or 50 mm to swing a hammer, less when you deduct about 30mm for the thickness of the hammer turned sideways. Just couldn't get any momentum up.

    Next step is to try welding a nut on. Maybe the heat will help loosten the stud.
     
  25. tbakowsky

    tbakowsky F1 World Champ
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    Verell...Sometimes you can manouver the cover just enough to clear that stud! On some cars I have had to fight to get the stud it out..others I fought with and I did manage to weasel the thing out with the stud in place.
    I would give it one last try..Maybe if you put your underwear on backwards..and hold your tougue to left check and push at a 30degree angle against it?
     

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