# 4L80-E Vent line



## ABES (Jun 10, 2007)

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


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## B&B (Nov 4, 2006)

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.


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## ABES (Jun 10, 2007)

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.


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## 70monte (Feb 5, 2008)

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


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## B&B (Nov 4, 2006)

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.


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## 70monte (Feb 5, 2008)

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


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## LHL Inc. (Oct 13, 2008)

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.


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## B&B (Nov 4, 2006)

LHL Inc.;604556 said:


> 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.


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.


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## ABES (Jun 10, 2007)

LHL Inc.;604556 said:


> 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.


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


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## LHL Inc. (Oct 13, 2008)

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


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## Milwaukee (Dec 28, 2007)

LHL Inc.;604591 said:


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


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.


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## LHL Inc. (Oct 13, 2008)

*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?


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## Milwaukee (Dec 28, 2007)

LHL Inc.;604641 said:


> 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?


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


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## B&B (Nov 4, 2006)

Milwaukee;604654 said:


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


That only applies to Dodge transmissions. GM transmissions _have full cooler flow in ALL gear positions. _


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## Milwaukee (Dec 28, 2007)

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


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## LHL Inc. (Oct 13, 2008)

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


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## ABES (Jun 10, 2007)

summitracing sells many different ones.


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## B&B (Nov 4, 2006)

LHL Inc.;604671 said:


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


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.


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## B&B (Nov 4, 2006)

Milwaukee;604668 said:


> Oh now I learn new stuff is Ford and Jeep is different from Dodge?


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


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## LHL Inc. (Oct 13, 2008)

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


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## B&B (Nov 4, 2006)

LHL Inc.;604591 said:


> Thanks for the reply. would it be better with a synthetic fluid?


 The synthetic will take much more heat than a conventional based oil before it causes a fluid based problem with the trans. But if you keep the heat out of it in the first place with the proper cooling your not really gaining anything on that end. But the synthetic will definitely have better lubrication properties...thus it can lower the operating temps _slightly_ and run more efficiently over the life of the trans- so it's money well spent there, but not a solution for an existing overheating problem.


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## LHL Inc. (Oct 13, 2008)

*Overheating*

I looked on b&w website. I found the coolers but how big of one should i get? Can the tranny also run to cool and do any damage? My local machanic thought that some people run the oil through the cooler and then back through the radiator to warm the fluid back up, is this correct?


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## B&B (Nov 4, 2006)

LHL Inc.;605091 said:


> I looked on b&w website. I found the coolers but how big of one should i get? Can the tranny also run to cool and do any damage? My local machanic thought that some people run the oil through the cooler and then back through the radiator to warm the fluid back up, is this correct?


If your looking at B&M...p/n 70274 is the one you want.

You want to plumb the aux cooler inline WITH the factory radiator cooler, and you want to plumb is so that the fluid goes through the factory cooler FIRST and then out to your aux cooler. Do not bypass the factory cooler in the radiator as it will aid in trans warm up during cold temps as well as continue to supplement trans cooling when under demanding conditions.


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## LHL Inc. (Oct 13, 2008)

Hi again, B&B I am going to get that cooler that you recommended from b&m, So do I just replace the factory cooler with that one? Do you think that that will make it run that much cooler?


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## B&B (Nov 4, 2006)

Yes remove the stock cooler from in front of the rad. When you install the new one place it as far left or right as possible, but still in front of the rad. Placing it in that position will promise the best airflow through it from the fan at low vehicle speeds.


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