Can we talk about the Detroit Bull Gear?

Discussion in 'Trucks [ Eighteen Wheelers ]' started by Hanadarko, Mar 27, 2012.

  1. Hanadarko

    Hanadarko Independent Owner/Operator

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    I'd like to get a thread going with information on the Detroit Series 60 bull gear, especially in the 12.7 motor.
    My engine was overhauled by the prior owner about 800k ago and while he lost the paper work, I was able to contact the shop.
    They did NOT replace the bull gear.

    So, what I am wondering is...what is the deal with this thing, how hard is it to check? - Any tell tale signs of pending disaster?
    I'm looking for ANY information on this rather odd part.

    :biggrin_25524:

    -JD
     
    Truckin2Eat and bullhaulerswife Thank this.
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  3. junkyardhound

    junkyardhound Light Load Member

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    I worked for Detroit diesel for 14 years,the bullgear is almost bulletproof.To check you just check your gearlashes.I dont recall any major problems with it.
     
  4. Hanadarko

    Hanadarko Independent Owner/Operator

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    Well this is interesting. All I have read (or been told) was that this is a horrible part. When it goes, it is utter disaster.
    People have said to replace this at 800,000 (or an overhaul) no matter what. I have 1.43million miles on this part right now.

    Whats up with these people then? - What happens if/when this gear fails?

    How do you check the lash? - Looks like I could take off the drive pulley that runs the alt/AC and perhaps peer inside....but I am not sure if this drive pulley uses silicone or gasket.

    The truck runs good and I want to keep it that way :biggrin_25514:
     
  5. junkyardhound

    junkyardhound Light Load Member

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    First off if it fails it WILL cause major damage.If you take accessory drive on passenger side you will see large gear of bullgear,check for excessive wear ond lash.The accessory drive has either an o ring or gasket.Was the engine inframed or out framed.To change bullgear, front cover has to be removed,you need timing tools.
     
  6. OUTLAW-7

    OUTLAW-7 Bobtail Member

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    I have never seen a failure to wear on the gear, only after bearings start to fail then the gear wobbles and destroys itself and everything around it. I don't know if it's common knowledge but, you can actualy replace just the 2 bearings and races from with new timken bearings from auto parts stores! I have seen gears with well over 2 million miles on them after the bearings were changed at 1 million miles. I'll see if I can find the part number if you guys are interested.
     
    BabyGator Thanks this.
  7. Hanadarko

    Hanadarko Independent Owner/Operator

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    Thanks guys. The engine was IN-FRAME during the overhaul. No paperwork but Winona Diesel that did the work was able to confirm some of my questions.

    The bearings are my worry. I guess if I take off the pully I can peer into there and see how the teeth look and possibly see if it rocks at all (Gently with a small pry bar I suspect) ?

    -JD
     
  8. Dino1968

    Dino1968 Light Load Member

    The accessory drive has an o ring inside, just pull the drive out evenly, you can do it without tearing the o ring if you're careful. As far as the bull gear, it is berry berry important that it not get out of time ! If it goes you'll be looking at an overhaul all over again at a minimum. And yes it will wobble if the bearings are about to go. Also had 1 that made a ratattatat noise which we caught just in time. It was synchronous with the engine, if you sped the engine up the noise sped up, if you slowed the engine down, it slowed down. Yes we were fortunate indeed.
     
  9. Bush chook

    Bush chook Light Load Member

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    Timken 399A USA and Timken 394A USA
     
  10. truckmechanic

    truckmechanic Medium Load Member

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    Usually when the bull gear goes out and you don't catch it in time it takes out the front cover and fills the engine with aluminum shavings not really a hard job just labor intensive since you have to support the front of the engine and remove the front cover fyi there are shops that rebuild the bullgear for you the socket that removes the bull gear from the spindle asyy is hard to find I made mine just some food for thought
     
    Hanadarko Thanks this.
  11. Jfaulk99

    Jfaulk99 Road Train Member

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    Maybe you should tell Detroit that since they changed the service interval from like 1mil mile to around 700k. Only heard that after my friends failed at 800k and destroyed the front gear train.
     
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