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Technical Differential expert's ! Weird pinion gear

Discussion in 'The Hokey Ass Message Board' started by Johnny Gee, Apr 21, 2016.

  1. Larry T
    Joined: Nov 24, 2004
    Posts: 7,675

    Larry T

    This is a pretty common failure with a stock carrier. Most of the killer drag cars that use 9" rear ends are pretty reliable --------------------------- after they put in aftermarket nodular carriers, "Daytona" pinion supports, spools/lockers, etc. If you really start making horse power, you add 35 spline pinions, bigger axles, etc.
  2. Lol, time for an update and stall on the Chevy vs Ford thing that we all like doing :p. I spent some time this morning looking at the original wear pattern. The whole story is right there. The coast side of the ring gear favors the outer edge and the drive side run's just below the CL therefore looking for the ideal ring pattern is out the window. When I match that to the original wear pattern on the pinion all turn's like snot on a glass door knob. If that's ever happened to you ?
  3. Larry T
    Joined: Nov 24, 2004
    Posts: 7,675

    Larry T

    After that there's always this. You break it, just call Mark Williams and tell them what you want. Koby rear end 002.jpg
  4. That's a bit much for a 32' Ford Pick Up with a stock 327 !
    Larry T likes this.
  5. Hombre
    Joined: Aug 22, 2008
    Posts: 847


    I have been using ford 9" for a very long time. Until recently I never owned a Hot Rod without one and I have had a lot of Hot Rods. Now with that said I am not joined to Ford 9" rears by any means. They work and last, I have drag raced them and put many, many miles on them on the street and never had one fail. Doesn't mean they won't fail but it has never happened to me (YET).

    The purpose of this post is a question. It is stated that the Ford 9" is used because of marketing. Just who is doing this marketing? I have never seen a Junk Yard ( where most of the rear ends I use come from) market anything much less a rear end. I also have never seen a Ford ad stating the virtues of there 9" rear ends. I heard for the first time about the Ford 9" in a word of mouth way from another Hot Rodder is that the marketing that is being spoke to? Another words if we are all being dupped by the marketing Guru's about the Ford 9" just who in the hell are these marketing wizards?
    slack likes this.
  6. The know it all's at the car show's that brag's about a 9" to another know it all. You know the type ? Right ? ;) Word of mouth is the best marketing money can buy.
  7. Yeah, the 9" ford is tough but go back a few years at the HAMB drags where Dave Weber [D.W.] came smokin off the line and made it about 75 feet out when his 9" spat the pinion right out the front of the case! It was impressive and I had a great photo of it 'till I switched computers and lost the image. He held up the pinion and took a bow for the crowd.
    Still the best choice for street/strip cars.
  8. Larry T
    Joined: Nov 24, 2004
    Posts: 7,675

    Larry T

    "If a little's good, more's better, then too much is just enough" ................................................ and that's traditional. :D

    I'm glad to see you got things figured out on your ring gear and pinion.
    squirrel likes this.
  9. And Golf Cart's. Now there's an "Add" early Currie may have used ? "You'll never break one of our rear ends".
  10. Although these gears are not the type Jim mentioned. There is something to be said about an even number pinion gear ? If it was an odd number pinion would the worn wear pattern do the same ? The heck with it, let's pop a top. It's Friday !
  11. 69fury
    Joined: Feb 24, 2009
    Posts: 1,416


    I think the main reason they are popular for racers is that you can swap ratios at the track really easy. just load in another centerchunk and now your ratio fits the track better (Slight ratio adjust for road tracking or drive to the drags on the 3.23s and race with the 4.10s, etc). Of course you have to purchase and pre-set the chunks. Also they are stout from factory and VERY stout when upgraded. They have a higher hypoid measurement which robs a bit more HP but adds strength. Since Hotrodders tend to copy race tech, you get a lot of that as well. Then the reputation also helped out. They were also extremely common and easily found. -rick.
    Hnstray likes this.
  12. squirrel
    Joined: Sep 23, 2004
    Posts: 43,638


    3.25 should be partial non-hunting. Each tooth on the pinion doesn't mesh with every tooth on the ring gear, like it would if it were a 3.23 ratio. Something about the teeth numbers having a common divisor, in this case 3 (12 and 39 are both divisible by 3).

    Since you found another explanation for your problem, don't worry about it...but at least a few guys learned something new about the old Ford rearends...
    slack and Johnny Gee like this.
  13. oj
    Joined: Jul 27, 2008
    Posts: 6,150


    Very interesting read, a proverbial HAMB thread.
  14. Engine man
    Joined: Jan 30, 2011
    Posts: 3,476

    Engine man
    from Wisconsin

    I've seen the cases break both on the outside and internally where the bearing on the gear end of the pinion sits. Usually happens under wheel hop but don't they all? We always looked for the nodular iron cases but they're scarce. Most use an aftermarket case for racing. The NASCAR boys had steel carrier housings made to use bigger bearings and 35 and 40 spline axles.
  15. moefuzz
    Joined: Jul 16, 2005
    Posts: 4,951


    Given the context,
    this is particularly obtuse.

    Johnny Gee likes this.
  16. moefuzz
    Joined: Jul 16, 2005
    Posts: 4,951


    I think the main reason that they are popular with " Hotrodders"
    is that their original factory gm 10 and 12's spat themselves out of
    every 6 or 8 cylinder in less than 100,000 miles
    all the while there were millions of good used 9" under each
    and every Ford truck that had less than a quarter million
    miles on it in the scrapyard.

    From factory, -Generally good for ~500 hp in a 4000 lb car
    and fair reliable in a light weight rail or modified into the 9 second mark.
    Got 15 or 2500 hp? then build it up using easily found
    generally quite reasonably priced parts

    ..In the 1960/70s, and when required/from the factory,
    All things like 500+ foot pounds of torque big blocks in 4000+ pound
    factory equipped cars would come equipped with a dual ribbed and/or nodular case.

    -Not all nodular iron cases are cast with an 'N',
    the majority of dual ribbed Nodular iron carriers
    do not have the tell tale "N" between the ribs.

    Irregardless of the rare Nodular carriers,
    If you broke one you'd just yank another at the junk yard
    -and with that said,
    99% of the 'used' replacements were being installed
    without a rebuild or even a quick check of lash/knash or trash
    irregardless of the 150,000 mile boat they out from/under.
    Most 9s came from grandads Lincoln or F100 and and other than
    checking for gear oil, they were never touched.

    ..In 82 vehicles and 46 years , I have broken one 9" (spiders) and that was from severe abuse on a quarter million mile 4400 pound truck hard dropping the clutch on dry pavement in second gear because that was always a reliable way to 'really' get smoke from a stoplight. That truck/chassis was 26 years old at the time with exception of the torque monster engine and clutch. I parted the truck out a few years ago at it's tender age of 44 and Still have the gearbox with overdrive as well as the factory 4:10 track lok that I had swapped out of a '69 4x4 18 years prior.

    Irregardless of some fools saying that Ford designed/built them weakly
    and then somehow "compensated" for their "poor design",
    millions of 9's are still roaming the street with 50 years on the clock
    and some of them may even have original oil in them.

    Johnboy34 likes this.
  17. It seems your perception of what I've said has been misunderstand. Never have I said the 9" is no good. It has it's plus's for sure and I can see why it's popular. Myself I like that it has a shim that's easy to get to for the pinion. I like that it's a drop out. I like that there everywhere and parts are easy to find as compared to a Old's/Pontiac 9.3. I only refuse to worship it like so many do that don't even have a vehicle worthy of a 9" and then they couple it to an S-10 manual trans. Do you see what I'm getting at. It's not the product. I'll close with this >
    Last edited: Apr 23, 2016
  18. The explanation I was told to identify the various gear sets was if the pinion and ring gear tooth counts are both even OR odd and both evenly divisible by the SAME prime number, it's a non-hunting set. If the pinion count is odd and the ring gear count even (or vise versa) and both are evenly divisible by the same prime number, it's a partial non-hunting set EXCEPT if the ring gear count is a multiple of the pinion count, in which case it's a non-hunting set. If both gear tooth counts can't be evenly divided by the same prime number, it's a hunting set....
    Last edited: Apr 23, 2016
    BigChief and H380 like this.
  19. squirrel
    Joined: Sep 23, 2004
    Posts: 43,638


    That sounds right. I have no idea how you remembered that...but yeah, it makes sense. 3.0 is non hunting (13/39), 3.25 is partial non-hunting (12/39), and 4.11 is hunting (9/37)
    henryj1951 likes this.
  20. GearheadsQCE
    Joined: Mar 23, 2011
    Posts: 2,153


    I remember my H.S. Autoshop teacher taking a long time explaining that. Later, as an Auto teacher, I didn't spend any time on it. After 50+ years, this is the first time I can remember it coming up.

    I think it may have been more critical on non-hypoid R&P gear sets. Example being early Ford V8, the non hunting gear sets being more prone to being noisy as the same pinion teeth contacting the same ring gear teeth in a repetitive sequence.
    Are there other considerations?
  21. Here's a wild one then. I'm sure Jim has the resources to find this information. And Jim you'll get a kick out of this if all things point in the direction I'm asking. Was there ever a 3:00 gear set with a count number of 36 12 ? I ask because as it turns out my pinion has the hash mark on it. Now if there was a 36 12 I can't tell you how it got there. Did it leave Ford this way or did someone miss up afterwards. We've all heard of the different things that have happened on the assembly line. Some of them minor like my Father's Maverick he bought new with missing door window trim on one side of the car. Or tool's left behind and even missing pistons in engines are just some examples. It just all boils down to some answer's can never be answered. But along the way we learn other things from it. I know I did here on this thread. Thanks Jim and I'm sorry that some folks took my reply to your humors remark about "better idea". I pretty sure we, at least I did pick up on the hint about engineering issue's that happen when a simple idea can suddenly have other unforeseen affect's.
  22. squirrel
    Joined: Sep 23, 2004
    Posts: 43,638


    The 3.25 gears in my picture have the hash mark on the pinion, but not the ring gear. They do have paint. I think that's how they did it on that ratio? I haven't spent much time looking at them to see what's what....I do have several sets I could examine if I get bored.

    Just another day on the hamb
    Johnny Gee likes this.
  23. ;) :cool: :)
  24. henryj1951
    Joined: Sep 23, 2012
    Posts: 2,306

    from USA

  25. Relic Stew
    Joined: Apr 17, 2005
    Posts: 1,113

    Relic Stew
    from Wisconsin

    I remember an ad (late 50's) touting the lower pinion allows a lower floor pan for more rear seat leg room.
    It may have also mentioned the high-hypoid gears being quieter.

    Magazine article for a Mercury points it out here.

    Last edited: Apr 23, 2016
    Johnny Gee likes this.
  26. Amusing way of taking advantage of a pinion that has to be low to begin with. The pinion has to be low to allow room for the 3rd bearing other wise the carrier won't clear nor allow the ring gear to come in contact the pinion and not designed for passenger comfort as stated.
  27. How do you know that? Which came first, the low pinion or the third bearing? Unless you have special insight into Ford's design process, it could have been for either reason or both...
    Johnny Gee likes this.
  28. Careful because that could be viewed as evidence to the theory of why the 3rd bearing is there ? ;)
  29. seb fontana
    Joined: Sep 1, 2005
    Posts: 5,924

    seb fontana
    from ct

    Early Ford [pre 49'] have the third bearing and centered pinion so the third bearing came first?.....
    Johnny Gee likes this.
  30. metlmunchr
    Joined: Jan 16, 2010
    Posts: 725


    Kinda weird failure I had on a 9" Ford. 79 F150 4wd, 3.50 axle, bought new and never abused. 351M and auto trans. Not enough power to abuse itself.
    Stopped at a traffic light one day and as I started to take off I hear this strange grinding noise and the truck won't move. Stick it in 4WD and there's no noise and the truck moves as normal. Just a couple miles back to the shop and I get there with no problem.

    Once there, take it out of 4wd and it won't move and the noise is back. Pulled the axles (31 spline) and the splines on one of them are chewed up. Pulled and disassembled the third member, and one of the side gears was cracked thru from ID to OD. Any power applied and the gear was opening up enough to allow the ID spline to spin around the OD spline on the axle.

    Truck had around 90K miles on it at the time, but I assume the gear either had a material defect or a heat treat problem from the day it was born, and just took that long to finally show up.

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