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Transmission/Overdrive Questions
  • Jim KildayJim Kilday
    Posts: 207Gold Member
    Does lubricant flow between the transmission and the overdrive unit or are the sumps separate?



    I understand that the transmission hold 2 pounds of lubricant after a drain and refill and the that the overdrive holds 1 1/4 pounds after drain and refill.



    I am about to drain and refill both units in my '46 Coupe and in mousing around on the Internet I find that Fifth Avenue Internet Garage offers a special lubricant for Borg-Warner overdrive units called GL-190 Gear Oil. The site says to "not use any synthetic gear oils. Use only API rated GL-1 oil. The sulfur and related additives in modern lubricants will destroy the bronze parts inside of the Borg-Warner overdrive."



    Is the above statement correct??



    Would a 1946 car have a Borg-Warner overdrive? Should I be using the above-mentioned Gear Oil??



    Thanks for your help.
  • Geoff C., N.Z.Geoff C., N.Z.
    Posts: 2,267Platinum Member
    That statement is baloney! the Hudosn specs are to use EP90 oil in the transmission. There are no bronze components in an overdrive. The transmission and overdrive share the same oil, butyou dohave to drainboth ends if you are changing theoil, as there willbe some residual oil in the overdrive housing. Modern oils do not have sulphur in them. No oiil company would market a product that would destroy components.
    If you're stuck in a hole, stop digging.
  • Park_WPark_W
    Posts: 2,051Platinum Member
    Yes, the '46 has a Borg-Warner OD. Same from 1941 ( the '40 may also be a B-W unit, but it's quite a bit different from the '41 and later ones). B-W made two series of OD units, one for heavier, more powerful cars. Hudsons have the lighter duty one (but still plenty strong), and they have a 30% reduction instead of the 28% of the heavier units.
  • nick snick s
    Posts: 696Platinum Member
    Geoff C., N.Z. wrote:
    That statement is baloney! the Hudosn specs are to use EP90 oil in the transmission. There are no bronze components in an overdrive. The transmission and overdrive share the same oil, butyou dohave to drainboth ends if you are changing theoil, as there willbe some residual oil in the overdrive housing. Modern oils do not have sulphur in them. No oiil company would market a product that would destroy components.

    Geoff,
    I like you, thought that the gearing is all steel so the EP grades would not be a concern anyway.
    But there are lubricants specifically sold for bronze applications. Manufacturers of worm boxes (which typicaly do have a bronze worm gear) warn against using EP lubricants because of damage from sulfur and or chlorine. There are spefic grades e.g. AGMA 7 and AGMA 8 which are known as worm gear oils and do not have the harmful additives. (I've been through this recently do to some worm issues - not oil related but it did come up because of amounts not type) It's not that they make oil's that are marketted to destroy componants its just that they are engineered for specific applications i.e. there is a reason the castrol catalog defining their available grades of oil's and greases is an inch thick.
  • EssexAdvEssexAdv
    Posts: 515Moderator
    Jim Kilday wrote:
    Does lubricant flow between the transmission and the overdrive unit or are the sumps separate?


    There is a passage between the OD and the trans. However, don't make the mistake of thinking you can fill one and the fluid will transfer to the other; it won't. Fill them both up and check them both.
  • Jon BJon B
    Posts: 4,761Moderator
    Interesting. The '40 OD (Borg-Warner, by the way) may indeed be different in this sense: I think it is filled from one plug only, and drained from one plug only. (At least I hope so, because I've been filling it this way for 31 years. If I'm wrong, it's probably due to explode into a million pieces, from lack of lubrication, LOL!)
  • hudson8hudson8
    Posts: 353Platinum Member
    Jon B wrote:
    Interesting. The '40 OD (Borg-Warner, by the way) may indeed be different in this sense: I think it is filled from one plug only, and drained from one plug only. (At least I hope so, because I've been filling it this way for 31 years. If I'm wrong, it's probably due to explode into a million pieces, from lack of lubrication, LOL!)
    Hi Jon---My 40 overdrive transmission has 2 separate filler plugs for lubricant. Better check yours.---Cliff Minard.
  • Geoff C., N.Z.Geoff C., N.Z.
    Posts: 2,267Platinum Member
    There are two seperate filler and drain plugs, but the oil circulates through between the o/d and transmission.
    If you're stuck in a hole, stop digging.
  • Clutch guy
    Posts: 811Platinum Member
    The overdrive and the main transmission cases are separate. They do not circulate between each other. The gearlube from the O/Dr. can transfer into the main case with driving, but they are 2 different reservoirs and make sure you check BOTH. Usually the O.dr. will be the one that is low so MAKE SURE TO Check and fill it.
  • EssexAdvEssexAdv
    Posts: 515Moderator
    Jon, my 49 has 2 sets of plugs .. me thinks you have been lucky... or well sealed
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