Are Ferrari differential internals common to anything else? | Page 3 | FerrariChat
Buy

Are Ferrari differential internals common to anything else?

Discussion in 'Technical Q&A' started by luckydynes, Oct 5, 2008.

This site may earn a commission from merchant affiliate links, including eBay, Amazon, Skimlinks, and others.

Page 3 of 4
  1. luckydynes

    luckydynes F1 Rookie

    Jan 25, 2004
    3,931
    CA and OR
    Full Name:
    pit bull
    #51 luckydynes, Oct 12, 2008
    Last edited by a moderator: Sep 7, 2017
    So I noticed the new thrust washers have an extra .03 of tab and I also decided to loctite them in. I'm putting all new guts in so we'll see how she does.

    Here's some more pics. I tried to break the edge on the wear in the carrier with a file. I'm waiting for the loctite to set for a while and then I'll button her up and see how much end float she has.

    One guy with a lot of diff experience reccomended I just make/buy a new thrust washer and not worry about the tab ... hmmmm. I going to send him a spare 308 diff I have to get his .02.

    Cheers
    Image Unavailable, Please Login
    Image Unavailable, Please Login
    Image Unavailable, Please Login
    Image Unavailable, Please Login
    Image Unavailable, Please Login
    Image Unavailable, Please Login
     
  2. luckydynes

    luckydynes F1 Rookie

    Jan 25, 2004
    3,931
    CA and OR
    Full Name:
    pit bull
    #52 luckydynes, Oct 12, 2008
    Only thing that's got me a bit nervous about slapping her back in tonight is I wanted to magnaflux the crown gear bolts. Anyone care to weigh in on that one? Someone scared me with a story about these bolts shearing but who knows what life that car had seen.


    Anyone?
     
  3. Verell

    Verell F1 Veteran
    Consultant Owner

    May 5, 2001
    7,022
    Groton, MA
    Full Name:
    Verell Boaen
    #53 Verell, Oct 12, 2008
    I had a crown gear bolt shear on me about 3 years ago, went after the car had about 35K miles. Found it when I was doing a trans fluid change & shift shaft seals. It must have happened when I was driving the car up on the 2x12s I use to get enough clearance so the lift arms will go under it. I've fastened those plastic 2 bump parking mats on top of the front wheel 2x12s. I get up to about 6 mph, then depress the clutch & coast up over the 1st bump & stop it with the brakes. I came in a little too slow & it didn't quite make it over the bump & I felt it just start to roll backwards off of the bump, so let out the clutch. Felt a little jerk as the clutch caught, then the engine pulled the car over the 1st bump & into parking position. NOT a big jerk, no more than if I"d been stopped at a light, maybe rev the engine up to 2500 or so & accidently let out the clutch a little fast. Certainly not something I'd expect to snap a crown gear bolt.

    When I pu lled the trans sump cover, there was the head of a 10mm bolt lying in the bottom of the sump.

    See: http://www.ferrarichat.com/forum/showthread.php?t=43305

    As you'll see in the thread, it took me awhile to figure out where it came from. It was the head of a crown gear bolt!

    I've had several professional mechanics tell me that sheared crown gear bolts are fairly common in cars that are regularly tracked.
     
  4. luckydynes

    luckydynes F1 Rookie

    Jan 25, 2004
    3,931
    CA and OR
    Full Name:
    pit bull
    #54 luckydynes, Oct 12, 2008
    Last edited: Oct 12, 2008
    Thanks Verrel. I've seen a bunch of "12.9" bolts in some of the diff's I've been pulling apart that don't have the ground shank but I didn't measure it to check the difference.


    When I put this gearbox together I felt one "yield" while I was tq'g it and ordered a used one from the typical sources (350 run hrs ago :)). I don't recall exactly but I'm pretty sure it was a "12.9" that I felt this happen to.


    It looks like it was one of the original Ferrari bolts with no markings on it that broke with the ground shank in your situation yes? ... please confirm this V 'cause I've seen anywhere from 1 to 4 in the diff's I've pulled apart.

    I skimmed thru that thread pretty fast ... didn't see a pic of where it broke and had someone been in that box before? Also were the other bolts loose when you took it apart?

    I'm right at that point right now.


    cheers,

    Sean

    edit: okay noticed you mentioned it broke right under the head.
     
  5. luckydynes

    luckydynes F1 Rookie

    Jan 25, 2004
    3,931
    CA and OR
    Full Name:
    pit bull
    #55 luckydynes, Oct 12, 2008
    You know anything about that car? Wasn't it a certain 4v that had the crap tracked out of it?
     
  6. luckydynes

    luckydynes F1 Rookie

    Jan 25, 2004
    3,931
    CA and OR
    Full Name:
    pit bull
    #56 luckydynes, Oct 12, 2008
    looks like you think it was a Ferrari bolt.

    I don't understand how one can fail if the others weren't loose even if you loaded the crap out of it jerking the clutch. It's the clamping force from all 8 bolts with the coefficient of friction between the two metals that holds the gear to the diff carrier. I'm assuming the other bolts were tight, so I'm going with "was junk at installation". Like I said I felt one yield during assembly when I built this box so I'll use my same intuition.

    thanks for chiming in. Guess you never looked inside to see the condition of the spiders and output shafts on that box did you?


    cheers
     
  7. luckydynes

    luckydynes F1 Rookie

    Jan 25, 2004
    3,931
    CA and OR
    Full Name:
    pit bull
    #57 luckydynes, Oct 12, 2008
    Might wait to chat with my Porsche diff guy.
     
  8. f308jack

    f308jack F1 Rookie

    Jun 7, 2007
    4,300
    Cape Town, South Afr
    Full Name:
    Jack Verschuur
    #58 f308jack, Oct 14, 2008
    So may it be concluded now that the whole problem was caused by the tab of the washer? And that the washer is superceeded by a new part with a beefier tab?

    Interesting observation regarding the oil level differences Ferrari versus P-car diff. That wouldn't be so difficult to change, but it affects a lot of other things. Any thoughts?

    To what end-float did you shim the output shafts, or did you assemble as is obtaining an acceptable float? IMO this is quite critical.
     
  9. luckydynes

    luckydynes F1 Rookie

    Jan 25, 2004
    3,931
    CA and OR
    Full Name:
    pit bull
    #59 luckydynes, Oct 14, 2008
    Last edited: Oct 14, 2008

    I think that's what caused the problem on this diff. I thought I had replaced the washers in this diff a couple years ago (edit: I definitely checked the tabs were still there and measured everything) when I did the motor but they definitely had a smaller tab than the latest ones I bought. FWIW the diff specialist I was chatting with told me the later G50 diff's don't have a tab on the thrust washer period.

    Regarding the oil level the only thing it's effecting is the diff internals so I don't really know what to think about that. I'm going to run some high end gear oil from now on also.

    I haven't final assembled in this carrier yet but had .012" and .016" end float (passenger/driver respectively). What do you think about those numbers? There's .003" clearance on brand new spider gears to spider shafts.

    Thanks,

    Sean
     
  10. f308jack

    f308jack F1 Rookie

    Jun 7, 2007
    4,300
    Cape Town, South Afr
    Full Name:
    Jack Verschuur
    #60 f308jack, Oct 14, 2008
    I was thinking about the tabs and their necessity. Could there be merit in deleting them? If the new ones are built stronger, I think I'd leave them where they are.

    In terms of final drives I think that endfloat is still excessive, and I'd shim it out, if not for the spider gears do it for the bearings and ultimately the seals. Bear in mind though that the gears you're working with are quite small, and any movement may be small in absolute size but relative to the size of the gear quite large. .oo3 sounds very reasonable.

    If you're in doubt of the consequences of float on gears, just make a small drawing of 2 interlocking gearteeth in their correct form, and you'll see what it does. Better, look at the gears you pulled out.
     
  11. FandLcars

    FandLcars F1 Rookie

    Aug 6, 2006
    3,057
    Tempe, Az
    Full Name:
    Rick Schumm
    #61 FandLcars, Oct 14, 2008
    Oh - guess I scanned too quickly. I've only had the covers off my 348 box. Never mind :) Actually, a friend of my who I trust a lot (ex-GM engineer) did some work in his 328 box, and said it was a very easy one to work on. Still great to see the pics, and this can only help other DIY'ers.
     
  12. luckydynes

    luckydynes F1 Rookie

    Jan 25, 2004
    3,931
    CA and OR
    Full Name:
    pit bull
    #62 luckydynes, Oct 14, 2008
    Just put the new pieces in carrier that came out of the car with 350 hrs and checked the end float ... .004"/side!

    This is the only one that did not have the spinning thrust washer failure for an extended period. Now I'll measure that feature on the other carriers and hopefully see about .010" difference from the thrust washer spinning and eating into that surface.

    Very cool.

    Cheers,

    Sean
     
  13. luckydynes

    luckydynes F1 Rookie

    Jan 25, 2004
    3,931
    CA and OR
    Full Name:
    pit bull
    #63 luckydynes, Oct 14, 2008
    I share the .005" end float with my diff expert and he responds with "way too tight ... that's why the thrust washer tabs are breaking".

    So I measure that feature on both diff's to see if there's any wear in the carrier .... NONE.

    So I put the "tight" diff back together and smack the shafts with a mallet as I'm snugging it up to make sure the clutches weren't binding ... they were. Now I have .014" on passenger and .020" on driver ... pretty much what my diff guy reccomends. This diff was about .005" looser on each side that when I put her in 350 hrs ago. Another interesting thing would be to measure the end float now with the old gears to see how much it increased over the 350 hr cycle.

    Regarding the end float, I'm getting the feeling it's not wise to shim it any tighter than this. Also a good sign is the thrust washer spinning in the carrier did not take any material out. Now I'm wondering if I should just bust the tab off the thrust washer? Like I mentioned in another post the newer G50 style diff's did not have a tab on this thrust washer.

    Cheers
     
  14. f308jack

    f308jack F1 Rookie

    Jun 7, 2007
    4,300
    Cape Town, South Afr
    Full Name:
    Jack Verschuur
    #64 f308jack, Oct 15, 2008
    What is your diff guy's motivation for not shimming out the float? There must be a reason, because it wasn't shimmed from new. It could have been deemed unnecessary, but there could be a mechanical reason, but that eludes me.

    If you decide to run without the tabs, I'd machine some new washers so as to obtain a smooth un-interrupted surface all the way.
    Given the much higher oil-level in the P-car, be convinced that there will be enough oil to lubricate this in the F-car; the fact that you don't see wear in that area even after running with a busted tab is encouraging.

    Does anyone know what the end-float on a new 348 diff is?

    (this is getting dangerous, as I am starting to feel the urge to pull my diff....)
     
  15. Artvonne

    Artvonne F1 Veteran

    Oct 29, 2004
    5,379
    NWA
    Full Name:
    Paul
    #65 Artvonne, Oct 15, 2008
    I dont know if it would (or how it would) relate to the end float question, but most all the ice racers up here ran locked spider gears. They would braze between teeth on the side gears so that when assembled, the wheels would be locked, but really loose. Someone found many many years ago that they had to be fairly loose or they would break. I wonder if this has anything to do with your diff experts reasoning?

    Has anyone yet determined why the 348 diff has no clutch pack preload?
     
  16. luckydynes

    luckydynes F1 Rookie

    Jan 25, 2004
    3,931
    CA and OR
    Full Name:
    pit bull
    #66 luckydynes, Oct 15, 2008
    Pulled apart yet another diff. This is the one out of the original gearbox/motor that was in my car when I bought it in '95. I replaced the thrust washers & bearings end of 2004 and burned an exhaust valve in early 2006 so a little over a year run time but the engine was stock.

    I was surprised at the witness marks on the back of the thrust washers ... a lot more of one on the driver's side.

    This made me realize it's probably too hot for the loctite to have any chance of holding the thrust washer against the correct surface ... not letting it lift off.

    Thoughts on that?

    Cheers,

    Sean
     
  17. luckydynes

    luckydynes F1 Rookie

    Jan 25, 2004
    3,931
    CA and OR
    Full Name:
    pit bull
    #67 luckydynes, Oct 15, 2008
    Last edited by a moderator: Sep 7, 2017
  18. luckydynes

    luckydynes F1 Rookie

    Jan 25, 2004
    3,931
    CA and OR
    Full Name:
    pit bull
    #68 luckydynes, Oct 15, 2008
    Last edited: Oct 15, 2008
    Just spoke to my aircraft inspection guy and bolts are okay ... gave him 3 sets just in case :) ... so should I just slap 'er back in and test my loctite theory???

    edit: he gets a free plug ... he's dropping them back by here at 4:00 a.m. on his way out of town :) ... "Aerohoff Inspection" if you're in San Diego :) ... cheers
     
  19. f308jack

    f308jack F1 Rookie

    Jun 7, 2007
    4,300
    Cape Town, South Afr
    Full Name:
    Jack Verschuur
    #69 f308jack, Oct 16, 2008
    Has anyone yet determined why the 348 diff has no clutch pack preload?[/QUOTE]

    Maybe they put a pre-load on the 308 diffs to avoid chatter, and found it unnecessary in the 348? Are the cluches and ramps identical?
     
  20. Artvonne

    Artvonne F1 Veteran

    Oct 29, 2004
    5,379
    NWA
    Full Name:
    Paul
    #70 Artvonne, Oct 16, 2008
    Maybe they put a pre-load on the 308 diffs to avoid chatter, and found it unnecessary in the 348? Are the cluches and ramps identical?[/QUOTE]

    I dont know about the ramps, but the clutches are at least the same material/friction cf.. My question is why, after the 308/328 having a preloaded diff, did the 348 go to a non-preloaded diff, and why did the 355 revert back to a preloaded diff.

    I am still curious of any theory to explain why there is more wear on the left (drivers) side. Could it perhaps be from right hand turns? Turning right generally creates a tighter turning radius than turning left. Turning right would force the left side gear to make more turns while being in the lowest gears creating the greatest amount of torque. Thoughts? Perhaps our brothers who drive on the wrong side of the road have seen an opposite wear pattern??? Or dont they make left turns in the UK? :)
     
  21. f308jack

    f308jack F1 Rookie

    Jun 7, 2007
    4,300
    Cape Town, South Afr
    Full Name:
    Jack Verschuur
    #71 f308jack, Oct 16, 2008
    There may be some merit in this theory, as the torque transmitted through the most loaded wheel is potentially much higher than that under full power on a straight road.

    This begs the next question though: do you corner harder to the right or to the left? My guess is that you corner harder to the side of the driver, in either a LHD or RHD car, which would suggest the opposite consequence for diff wear.

    Maybe I will get some more info on uneven wear un Sunday (Cape Town Ferrari track day)
     
  22. Artvonne

    Artvonne F1 Veteran

    Oct 29, 2004
    5,379
    NWA
    Full Name:
    Paul
    #72 Artvonne, Oct 16, 2008
    No, the differential splits torque equally (50/50 torque split) to both sides at all times. Thus the torque applied to both wheels remains equal at all times.

    In a straight line there is no differential action, and there would be zero wear in the carrier assembly. It is only when turning, where the outside wheel covers a greater circumference, that the differential comes into play, and the tighter the turn, the greater disparity of the two arcs, the greater the wear would be seen in the one that turns the greater distance.
     
  23. luckydynes

    luckydynes F1 Rookie

    Jan 25, 2004
    3,931
    CA and OR
    Full Name:
    pit bull
    #73 luckydynes, Oct 16, 2008
    From talking to the Porsche diff guy I think it's all about lubrication ... or lack of it. Both the diff's that I tore apart still had assembly lube in 'em ... after 350 known hrs on the one. I really would have thought the assembly lube would have rinsed out of there after this long.

    The only way the diff is getting oil is form the spray from the crown gear ... and if you look at the shape of the diff cover and where the gear is positioned, on the right or passenger side the oil can run right down the side of the crown gear and diff cover into the diff ... it can't do this "as easily" on the driver side ... it has to go over the center of the diff to get inside if running down the gear and the diff cover's curvature isn't as steep on that side ... how about that??? :)

    So UK and Aussie cars should see this identical wear, although I'd come up with a cornering scenario that wears the gears more but I don't think that's it.

    cheers.
     
  24. luckydynes

    luckydynes F1 Rookie

    Jan 25, 2004
    3,931
    CA and OR
    Full Name:
    pit bull
    #74 luckydynes, Oct 16, 2008

    I know for a fact I have not been taking right handers as hard as lefts with engine oiling issues ... are we all doing this subconciously? :)
     
  25. f308jack

    f308jack F1 Rookie

    Jun 7, 2007
    4,300
    Cape Town, South Afr
    Full Name:
    Jack Verschuur
    #75 f308jack, Oct 16, 2008
    I think it is because you sit on the left side. Here in South Africa we sit on the right and right handers get driven harder (or so I feel).
    My engine sump is always over-filled at least a quart, no problem with surge.
     
Page 3 of 4

Share This Page