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4L80-E Vent line

Discussion in 'Chevy Trucks' started by ABES, Sep 27, 2008.

  1. ABES

    ABES PlowSite.com Addict
    from MN
    Messages: 1,322

    I was looking around underneath my truck the other day and I saw that the vent line is just sort of hanging off the side of the transmission with about a 45 degree cut at the end. I bought the truck used and it looks like the transmission has been out before (marks on the bellhousing and crossmember bolts). Also there is really no stop or breather like the one on the back differential which is nice and securely mounted up on the frame. So I guess my question is does anybody know how and where to securely mount the vent line ?


    Thanks
     
    Last edited: Sep 27, 2008
  2. B&B

    B&B PlowSite Fanatic
    Messages: 12,777

    Most never had a cap or even an external rubber vent hose on the trans like your used to seeing on a diff for example. But there's no reason you can't add one and run it higher to prevent water/dirt intrusion if you use the truck off road. Be sure it's not pointing near anything to hot like an exhaust component in case it ever pushes any fluid out.
     
  3. ABES

    ABES PlowSite.com Addict
    from MN
    Messages: 1,322

    I guess I will have to try to extend the vent line and mount it up a little higher. I will be extra careful not to mount it to anything too hot, I learned in class the other day, Heat + ATF = Big flames lol.
     
  4. 70monte

    70monte Senior Member
    Messages: 468

    I have a 98 K3500 4x4 RCLB with the 7.4/4L80E. I just looked under mine and the tranny vent tube goes up and comes up between the firewall and the back side of the driver's side head. There is a metal shield part way up that the vent tube goes behind. Up near where the driver's side pre-cat O2 sensor plugs into the wiring harness. It also has a metal clip attached near the top of the vent tube that has a hole, almost like it slides over a stud or something. Mines not attached at the top and just laying on a metal line. Might be the fuel line. Tomorrow when its light out I will see if I can find an attachment point up top. Mine also still has the plastic vent in the end of the tube. I hope this helps you.

    wayne
     
  5. B&B

    B&B PlowSite Fanatic
    Messages: 12,777

    Most of the 7.4's did use that setup Wayne...as did 99% of the S10's/Blazer/Bravada stuff. Don't see many on the 5.0/5.7's of that era though.
     
  6. 70monte

    70monte Senior Member
    Messages: 468

    I'll have to see what setup my 98 K1500 has. I've never looked for the tranny vent line, just the front and rear diff ones.

    Wayne
     
  7. LHL Inc.

    LHL Inc. Member
    Messages: 92

    I Have 2 1998 k3500 RCLB 4x4 W 7.4 and 4L80 wondering what the max temp you should run the tranny to before shutting down? We have alot of large accounts and we put temp. gauges in and have been running them to about 220 degrees and shut them down for awhile can i run them hotter? I flush the trannies once a year is there anything i can do to keep them cool? they will run up to 250 or more if i let them.
     
  8. B&B

    B&B PlowSite Fanatic
    Messages: 12,777

    Smart to install the temp gages in the first place, but no you definitely don't want to run them any hotter.

    220* is already a little hotter than you should be running them on a regular basis. If you can keep them at 200* and preferably less you'll prolong the life. Best way to do that is to add additional cooling by use of a larger/more efficient trans cooler.

    Upgrading to better/bigger trans coolers is money well spent in a plow truck application, next to the temp gages you already have.
     
  9. ABES

    ABES PlowSite.com Addict
    from MN
    Messages: 1,322

    The hottest Ive had mine was 210 on a 95 degree summer day pulling a jeep on a 16' flatbed at 60-80 mph. If it got any hotter I would have let it cool down a bit. (This is with the sender in the pan). If your seeing temperatures like 220-250 everytime you plow with the truck I would install a large trans cooler. A lot cheaper than a new transmission

    * Dang B&B beat me to the reply lol
     
  10. LHL Inc.

    LHL Inc. Member
    Messages: 92

    Thanks for the reply. would it be better with a synthetic fluid? Shaeffers, conklins of something like that?
     
  11. Milwaukee

    Milwaukee 2000 Club Member
    Messages: 2,180



    Don't shut down it. You need keep engine run with transmission in neutral it will help much. That what I learn from this long time ago.

    Why if you shut down but how transmission get cool by just sit nothing. But Neutral keep fluid pump but in park it just sit nothing.

    I am not sure put synthetic fluid in that if it already leak ATF.

    And you need upgrade cooling system to more bigger one that will help cool transmission fast. Do you use in O in D? Not 1 or 2 gear? use D mean it shift gear all time cause heat fast.
     
  12. LHL Inc.

    LHL Inc. Member
    Messages: 92

    cooling the tranny.

    I always leave the pickup running but does it cool faster in nuetral than leaving it in park letting it run and why is that?
     
  13. Milwaukee

    Milwaukee 2000 Club Member
    Messages: 2,180

    They say leave in park mean fluid are not circulation it just sit but in neutral it circulation.
     
  14. B&B

    B&B PlowSite Fanatic
    Messages: 12,777

    That only applies to Dodge transmissions. GM transmissions have full cooler flow in ALL gear positions.
     
  15. Milwaukee

    Milwaukee 2000 Club Member
    Messages: 2,180

    Oh now I learn new stuff is Ford and Jeep is different from Dodge? How cool down?
     
  16. LHL Inc.

    LHL Inc. Member
    Messages: 92

    Where would be the best place to get a bigger cooler? Thanx for all the info!!!!
     
  17. ABES

    ABES PlowSite.com Addict
    from MN
    Messages: 1,322

    summitracing sells many different ones.
     
  18. B&B

    B&B PlowSite Fanatic
    Messages: 12,777

    A local trans shop or auto store may have some of the better coolers but most any of the big performance geared on-line places will have good coolers as well...Summit, Jegs etc.

    Try to purchase a "stacked plate" style cooler as they're more efficient in cooling capacity than a "tube and fin" style cooler in the same comparable size. Look for cooler brand names such as B&M or Long as most of there coolers are of the stacked plate design. In fact Long manufactures all of B&M's coolers...as well as many of the coolers used by the big three OEM's.
     
  19. B&B

    B&B PlowSite Fanatic
    Messages: 12,777

    Only the Dodges need to be in neutral (rather than park) for full cooler flow.
     
  20. LHL Inc.

    LHL Inc. Member
    Messages: 92

    Thank you for all the info! this is a very helpful site..