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What gear oil to use in manuel tranny to help reduce grinding shifting

Discussion in 'Truck & Equipment Repair' started by G.M.Landscaping, Jan 11, 2008.

  1. G.M.Landscaping

    G.M.Landscaping Senior Member
    Messages: 362

    This is for my 91 F250 Manuel 5 speed tranny. When plowing going from first to reverse, it almost always grinds. I bled the slave cylinder hoping it would make a difference. The clutch doesn't slip at all. I usually have to go from 1st to 2nd a few times before going into reverse.

    What lube might work to better on the syncro's. Royal purple? Other? Synthetic?
     
  2. sweetk30

    sweetk30 PlowSite.com Addict
    Messages: 1,588

    i looked in my shop oil spec book. it calles for merc atf. yep std old mercon auto tranny fluid.

    should be in the 3-4 qrt range. to fill from empty. but lets see if anyone else has had better luck with any other kind of oil in them.
     
  3. oman1999

    oman1999 Senior Member
    Messages: 198

    The reason that it grinds to reverse is a great deal of build-up on the shafts. How often do you change your fluid.

    1. I have had good luck with draining the fluid and re-filling with diesel fuel. You can either support the rear-end with stands and run the transmission through all the gears for several minutes to clean out the transmission and or varnish.

    2. Drain and re-fill with full synthetic Mercon V ATF, also add 2x the recomended amount of Sea-Foam transmission tune-up.

    3. Amsoil makes a 5w30 Manual Transmission fluid that really works well.
     
  4. Milwaukee

    Milwaukee 2000 Club Member
    Messages: 2,180

    Will those work for 4 speed manual transmission or it different?

    I want change my manual tran's oil since it seem to be hard to shift when outside is 40 degree like gear oil have water and frozen it.

    And what oil for transfer case?


    I have try find those amosoil oil at Murray it seem to don't have it.
     
  5. G.M.Landscaping

    G.M.Landscaping Senior Member
    Messages: 362

    Thanks for the advice.
    Well I didn't flush it, but I used Mobil 1 synthetic Mercon V ATF fluid. The next time I plow I'll know if it made any difference.

    The tranny sounds noisier now thou:realmad:It had no noise before but it sounds like a slight bearing noise. I thought the synthetic would of been quieter.

    The seafoam they sold was for automatic tranny only. But I wonder if it would of worked since it uses mercon fluid. I didn't use it. They had the lucas for manuel trannys. Might have to try that or flushing next .
     
  6. sweetk30

    sweetk30 PlowSite.com Addict
    Messages: 1,588

    thicker like std oil & lucus = quieter oporation.

    the correct = less hard shifting and better working. but little more noise.

    so use what you want. :salute:
     
  7. TEX

    TEX Senior Member
    Messages: 606

    im guessing you have the ZF trans so you will need 4 qts (6.8 pints) of ATF. a good synthetic like amsoil or mobil 1 is what i would use.

    if you guys need any amsoil stuff just let me know.
     
  8. TEX

    TEX Senior Member
    Messages: 606

    the 4spd stick is calling for engine oil, and ATF for the T-case
     
  9. adksnowo

    adksnowo Senior Member
    Messages: 370

    Little bit o sawdust in the tranny wil quiet it right down! Or you could use heavy weight gear oil. All kidding aside the input/shaft bearings sometimes wear on the ZF tranny, keep idling in neutral to a minimum and run asoil or Mobil1 and hope for he best.
     
  10. G.M.Landscaping

    G.M.Landscaping Senior Member
    Messages: 362

    Well I finally did some plowing today. The Mobil1 synthetic made it better but still wasn't perfect.

    I'm going to try the lucas.
     
  11. tuney443

    tuney443 PlowSite.com Addict
    Messages: 1,847

    Try Schaeffers synthetic gear oil with their propietary moly formula.I changed out the factory GM grapejuice at about 10,000 miles in my C7500 Chevy with a 10 sp. RR tranny and it made shifting almost effortless,where before it was like I dreaded going from gear to gear.Any product Schaeffer offers is top of the line--you won't be sorry.Oldest oil co. in America.
     
  12. BREAULT69

    BREAULT69 Member
    Messages: 97

    If nothing else works you could try a very light weight synthetic and change it back out to a heavier oil in the summer. Another thought is to make sure your clutch is working properly, as well as verify your engine idle speed is correct. The lucas may be too thick of an additive and may make the problem worse. Reverse is a non synchro gear like the granny low of older transmissions so it cannot have any movement of the input shaft in order to engage without grinding.