KyAllroad (Jeremy)
KyAllroad (Jeremy) PowerDork
1/17/18 4:45 p.m.

So this afternoon I got in the Suburban to drive home and was disheartened to find the trans doesn't pull below 2,000 rpm and feels really bad.  Stop and check the dipstick.....dry.  A friend from the machine shop gives me a gallon of Lucas universal hydraulic and ATF.  Add a quart and notice the pool forming under the front of the truck.  Sigh.

Diagnose that the trans cooler line has popped off and is just pumping fluid out. (Did I mention it's 18 degrees outside?). Screw line back on and add more fluid and it goes but it just doesn't feel "right". SWMBO picked me up and I'll drive the Altima tomorrow but do I need to do anything else with the Suburban?  A friend told me that it wants Dex6 ONLY and that I need to drain and refill before I tear anything up.  

Advice please trans gurus....

dean1484
dean1484 GRM+ Memberand MegaDork
1/17/18 4:48 p.m.

Yes proper fluid is critical in modern transmissions. 

Curtis
Curtis GRM+ Memberand PowerDork
1/17/18 5:21 p.m.

Proper fluid is needed, but fortunately in your case all you need is Dex3.  The 4L80E is an evolution of the old TH400.  It just needs plain ATF

The stuff you put in is not for automotive transmissions.  Its for hydrostat and shuttle shift equipment like tractors and hydraulic stuff.  A drain and fill is necessary.

You likely didn't damage anything, but that fluid is not right and continuing use could be icky.  Hydro fluid has added high-film components so they work in a wider variety of shear loads like the gears and things of a pump.  They are likely phosphorous compounds.  Hydraulic fluid is kind of like ATF with the additive package of gear lube.

This is one time I actually recommend a flush instead of just a pan drop.  A pan drop only changes about 1/3 of the fluid in a 4L80.  A 5 gallon bucket, some 3/8" fuel hose and three gallons of ATF.   Take the cooler lines off and start the truck for a moment to see which one squirts fluid.  It might take a minute.  Attach the rubber hoses and put the "out" hose in the empty bucket and the "in" into the first gallon of ATF.  Fire it up and let it suck in the new stuff while someone goes through all the gears.

Streetwiseguy
Streetwiseguy UltimaDork
1/17/18 5:24 p.m.

The proper fluid and a bit of time to get the aeration out of the oil should fix it up.  The good thing about blowing a line right off is that it really doesn't have time to bake anything.  It just stops moving.

I like synthetic atf, because I live where the air hurts your face.

KyAllroad (Jeremy)
KyAllroad (Jeremy) PowerDork
1/17/18 6:12 p.m.

Thanks guys. (Curtis, you amaze me with your depth of transmission knowledge)

Looks like a 5 gallon bucket of Miles ATF is 68 bucks on Amazon, do we like that?

Also, do I need to do it in place or can I drive it home and tinker in the back yard (5 miles, no stress)?

rslifkin
rslifkin SuperDork
1/17/18 6:31 p.m.

If the 4L80 is like most tranmissions, it won't suck up the ATF with the method Curtis suggested, as the "in" hose is just a return to the pan.  You'll have to pour the ATF in through the dipstick tube. 

Generally when I've flushed a trans of that size with this method, I start it, let it pump 2 - 3 quarts, stop, refill and repeat.  Avoids worrying about whether I'm pouring too fast or too slow.  As long as you don't let it pump out enough to suck air before you stop and refill, you're good. 

scottdownsouth
scottdownsouth Reader
1/17/18 7:31 p.m.

Not to hijack the thread but was going to ask, is a shift kit a good idea for one of these for towing? New to me 01 2500 suburban that I got to pull my toon with and I'd like to keep this thing forever. 

KyAllroad (Jeremy)
KyAllroad (Jeremy) PowerDork
1/18/18 9:31 a.m.
KyAllroad (Jeremy) said:

Thanks guys. (Curtis, you amaze me with your depth of transmission knowledge)

Looks like a 5 gallon bucket of Miles ATF is 68 bucks on Amazon, do we like that?

Also, do I need to do it in place or can I drive it home and tinker in the back yard (5 miles, no stress)?

Bump for new day.  My apologies for being slow on the uptake.

rslifkin
rslifkin SuperDork
1/18/18 9:39 a.m.

If it's shifting acceptably-ish, I'd drive it home and then take care of it.  Any ATF that meets the spec should work, so buy what you can get.  

Curtis
Curtis GRM+ Memberand PowerDork
1/18/18 3:27 p.m.
rslifkin said:

If the 4L80 is like most tranmissions, it won't suck up the ATF with the method Curtis suggested, as the "in" hose is just a return to the pan.  You'll have to pour the ATF in through the dipstick tube. 

Generally when I've flushed a trans of that size with this method, I start it, let it pump 2 - 3 quarts, stop, refill and repeat.  Avoids worrying about whether I'm pouring too fast or too slow.  As long as you don't let it pump out enough to suck air before you stop and refill, you're good. 

You might be right about that.  I thought it was on the suction side of the pump but I could be wrong.

Probably safer to do it rslifkin's way.

Curtis
Curtis GRM+ Memberand PowerDork
1/18/18 3:38 p.m.
scottdownsouth said:

Not to hijack the thread but was going to ask, is a shift kit a good idea for one of these for towing? New to me 01 2500 suburban that I got to pull my toon with and I'd like to keep this thing forever. 

To me, not worth the expense.  4L80Es can benefit from a reflash.  The line pressures are partially controlled by a PWM solenoid.  At full throttle, it defaults to full pressure anyway, so programming it won't change anything at full throttle, but you can tell it to have higher pressure everywhere else.  Unless you tow a lot at WOT (which happens a lot for heavier towing), I don't see the need for a shift kit.

Mountains and towing 8000 lbs? yes I would consider a shift kit for overkill.  Towing 5000 lbs of flatbed with a car on it, nah.  I frequently towed 10k with mine and couldn't kill it, but I'm pretty conscientious about backing off the throttle when I know a shift is coming, pulling it down to D going up a hill before the computer does it for me, only using OD with a temp gauge and on flattish roads, etc.

Curtis
Curtis GRM+ Memberand PowerDork
1/18/18 3:40 p.m.
KyAllroad (Jeremy) said:

Thanks guys. (Curtis, you amaze me with your depth of transmission knowledge)

Looks like a 5 gallon bucket of Miles ATF is 68 bucks on Amazon, do we like that?

Also, do I need to do it in place or can I drive it home and tinker in the back yard (5 miles, no stress)?

I'm rapidly forgetting so much, but thank you.

I'd do the Miles ATF.  At the shop we got bulk quantities of the cheapest ATF we could and gladly put a 5 year warranty on our builds.

I guess I can't speak intelligently about what the hydraulic fluid will do in 5 miles.  I would personally do it, but I can't feel warm and fuzzy recommending it to you and then have it toast clutches and your next drive is to PA to bitch slap me.

KyAllroad (Jeremy)
KyAllroad (Jeremy) PowerDork
1/18/18 5:55 p.m.

Interestingly, I made a call today to the local automatic transmission guru.  Old man by the name of Cotton who only rebuilds and services automatic trannys.  Locally famous among motorheads for the quality of his work.  He recommended just making sure the fluid level was right and just driving it. Said the Lucas ATF was good stuff.

Called another place and they recommended a flush but with their "100% compatible with everything" fluid.

I swear automatics are only a step behind computers for being run on belief and witchcraft.

KyAllroad
KyAllroad UltimaDork
11/23/21 3:11 p.m.

Bringing this one back up since I'm wondering about the longevity of the trans.

It appears to be holding up for now but it certainly could be improved.  At 215K miles and often towing I'd like to get as long as possible out of it.  It's probably time for the next fluid flush, do we like any fluid additives or just straight DEX6.

 

Pete. (l33t FS)
Pete. (l33t FS) GRM+ Memberand MegaDork
11/23/21 7:10 p.m.

Just use whatever, it's an electronically controlled TH400 with an overdrive bunged in.

The main advantage to Dexron VI in this application is that it is usually synthetic, so it can handle higher trans temps.  But, if the torque converter clutch is working, that eliminates most of the reason why transmission fluid gets hot in the first place.  Not all, but most.  High trans temps cook other things besides the fluid, though, but a cushion is a cushion.

codrus (Forum Supporter)
codrus (Forum Supporter) GRM+ Memberand PowerDork
11/23/21 7:45 p.m.
KyAllroad (Jeremy) said:

I swear automatics are only a step behind computers for being run on belief and witchcraft.

Nah, the people who build both of those know how they work.

Back when I worked at a company who did cellular phone stuff, we had a heirarchy of "black magic".  The software guys (like me) looked at the computer hardware as black magic.  The hardware engineers looked at the RF (radio) hardware as black magic.  The RF engineers in turn looked at the antenna design as black magic.

The antenna engineers?  They pretty much agreed. :)

 

Curtis73 (Forum Supporter)
Curtis73 (Forum Supporter) GRM+ Memberand MegaDork
11/24/21 4:27 p.m.
KyAllroad (Jeremy) said:

Interestingly, I made a call today to the local automatic transmission guru.  Old man by the name of Cotton who only rebuilds and services automatic trannys.  Locally famous among motorheads for the quality of his work.  He recommended just making sure the fluid level was right and just driving it. Said the Lucas ATF was good stuff.

Called another place and they recommended a flush but with their "100% compatible with everything" fluid.

I swear automatics are only a step behind computers for being run on belief and witchcraft.

ATF is a lot like motor oil in that the cheapest stuff out there is probably just re-labeled Castrol or Valvoline.  We got ours at the shop in bulk (like 250 gallons at a time in a tank) from the cheapest possible supplier which was Gulf back then.  Gulf ATF at the time was the same generic stock that went into most FLAPS brands, and also what GM stocked at the factory and what goes in the GM parts-counter bottles.  There were a couple other well-known brands that filled their bottles with Gulf as well.

The Lucas stuff you listed (when you said Hydraulic and ATF) threw me.  They make a Hydraulic/ATF that is specifically for things like tractors and equipment and it's a whole different ball of wax.

I did learn once that industrial hydraulic fluid works nicely in a 4L60E.  I was late for an interview and my car had developed a leak.  I needed a quart and all I could find was a 5 gallon bucket in dad's barn, so in it went.  I fixed the leak a month later and refilled with ATF, but no one died and nothing exploded.

Pete. (l33t FS)
Pete. (l33t FS) GRM+ Memberand MegaDork
11/24/21 4:32 p.m.

In reply to Curtis73 (Forum Supporter) :

"Tractor fluid" is popular for drag racers to use in automatics.

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