Weird Transmission Issue Dropping Out Of OD

[dangerousdave]

Lots of great info here, specifics help simplify things;
Year, model, modifications>
Thanks to all.

 

[THEFERMANATOR]

Funny thing happened last Thursday . . . At highway speed, the tranny started to flutter the TCC (unlock - lock) and 4 - 3 - 4 shifts. Looked over at the Edge and noticed that the ECM's coolant temperature was all over the place (dash gague was rock-steady). When it dropped into the 150's, the motor sounded like a machine gun. When it dropped under 130 F, the tranny started to unlock the TCC and shift down to 3'rd.

Changed the ECT sending unit in the thermostat housing last weekend and now the ECM's temperature is rock-steady and no more machine gun or fluttering tranny.

CTS's routinely cause these kinds of issues. They can REALLY drive you nuts when it hits a dead spot internally, and causes such a rapid fluctuation that teh scan tool won't read it. Seen them read what looked like a normal temp, but you would have to backprobe it to see the fluctuation that was causing the issues.

Over the years I have dropped big bucks into the 4L80e what I found is that it is fully functional at 28 deg f. however pure synthetic should be used to protect it at extreme low temps dino fluids don't offer the low temp protection. Using conventional trans fluids in extreme old you must warm up the vehicle longer for longevity of transmission.

Look at the temp tables you find 157 deg f. is max recommended operating temp for the 4L80e I'm below that on the hottest of days I run 3 coolers the radiator, the large fin plate B&M super cooler w/fan and a large low pressure drop fin plate cooler.

There are those who claim running the trans so cool allows condensation to add lots of water to the mix this is not true because the converter always gets hot enough to boil off any water resulting from condensation so it vents.

I would like to see a copy of literature that says 157 is the max temp for a 4L80E. These things routinely run at temps well over 200 without any issues.

 

[JayTheCPA]

CTS's routinely cause these kinds of issues.

Yeppers! Were it not for the Edge, I would have *NEVER* made the connection and figured that it was the tranny. Or that the Burb was outright possessed and the Wife would finally get her wish of me getting another ride . . .

I would like to see a copy of literature that says 157 . . .

For the educational value, X2.

Read somewhere that GM's TFT 'Hot' value (in the ECM's code) for the 4L80E is 270 F . From other things I have read, plan on a fluid flush and prep for a rebuild if it goes that hot . . .

 

[FellowTraveler]

Actually it's at idle and warm 120 deg.f to 158 deg f. page 95, ASE 8 ENGINE PERFORMANCE 6.5TD, MODULE 16 as read via TECH 2.

I stay below 158 deg f. at speed.............

 

[THEFERMANATOR]

Actually it's at idle and warm 120 deg.f to 158 deg f. page 95, ASE 8 ENGINE PERFORMANCE 6.5TD, MODULE 16 as read via TECH 2.

I stay below 158 deg f. at speed.............

Do you have a copy of it? So far you are the ONLY person I have EVER heard say this 157 degree max temp, and even on google and bing searches you are still the ONLY one who has said it. I HAVE found SEVERAL GM documents stating 180-200 as being the NORMAL DESIGNED trans temp to run, and 235 as being the max reccoemnded temp with DEX III or 270 with DEX VI. So I would like to see a copy of this document. Even my ATSG doesn't have anything in it about this 157 degree max temp. Even all the trans bulletins from aftermarket shops stil lall reccomend running 180-200 as converter outflow temps will be high enough at that temp to remove any moisture in the fluid. So until I see otherwise, I will stick with 180-200. Even brand new trucks with the 4L80E i nthem will run 175 running down the road empty.

 

[Will L.]

So, a stock transmission cooler is in the radiator where the coolant is anywhere from 180-220 depending on engine. This is to cool the trans fluid? If 157 is max how could it cool it with a hotter fluid? My 01 suburban has a stock trans temp gauge, and at idle with engine at 215-220 the trans is 160ish. Driving the hi way for 1/2 hour it is 190.

I'm thinking your dealing with a typo and it should say 257 maybe. That's around red zone on the gauge (maybe 270?)

 

[FellowTraveler]

Do you have a copy of it? So far you are the ONLY person I have EVER heard say this 157 degree max temp, and even on google and bing searches you are still the ONLY one who has said it. I HAVE found SEVERAL GM documents stating 180-200 as being the NORMAL DESIGNED trans temp to run, and 235 as being the max reccoemnded temp with DEX III or 270 with DEX VI. So I would like to see a copy of this document. Even my ATSG doesn't have anything in it about this 157 degree max temp. Even all the trans bulletins from aftermarket shops stil lall reccomend running 180-200 as converter outflow temps will be high enough at that temp to remove any moisture in the fluid. So until I see otherwise, I will stick with 180-200. Even brand new trucks with the 4L80E i nthem will run 175 running down the road empty.

Yep, it's 9.02 mb pm me an email to send it too.

As temps go GM and transmission repair shops have one thing to consider "a transmission that will live through it's warranty period."

Colder running transmission with synthetic lasts longer but you already know that.

 

[FellowTraveler]

So, a stock transmission cooler is in the radiator where the coolant is anywhere from 180-220 depending on engine. This is to cool the trans fluid? If 157 is max how could it cool it with a hotter fluid? My 01 suburban has a stock trans temp gauge, and at idle with engine at 215-220 the trans is 160ish. Driving the hi way for 1/2 hour it is 190.

I'm thinking your dealing with a typo and it should say 257 maybe. That's around red zone on the gauge (maybe 270?)

Perhaps a typo however it maybe closer to real operating temps for the trans to last much longer.

As you know the trans cooler is installed on cool side of radiator to initially cool down much hotter than coolant trans fluid coming from converter.

My first rebuild was after the warranty expired and that's with the aux cooler too I've since gone to over build and not looked back.

The Amsoil synthetic fluid is as clean as the day it was installed back 2009.

 

[THEFERMANATOR]

Perhaps a typo however it maybe closer to real operating temps for the trans to last much longer.

As you know the trans cooler is installed on cool side of radiator to initially cool down much hotter than coolant trans fluid coming from converter.

My first rebuild was after the warranty expired and that's with the aux cooler too I've since gone to over build and not looked back.

The Amsoil synthetic fluid is as clean as the day it was installed back 2009.

Actually many trans coolers were installed BEFORE the trans fluid reached the radiator. Do some flow checks and you will find this out. GM KNEW a liquid to air cooler is more efficient cooling higher temp fluid, plus in doing this they could maintain a more ideal 180-200 degrees trans fluid temp. They have flip flopped through the years on this, but many still got put before the radiator. And my email is [email protected]. I'd like to see this and compare it against factory info.

 

[FellowTraveler]

Actually many trans coolers were installed BEFORE the trans fluid reached the radiator. Do some flow checks and you will find this out. GM KNEW a liquid to air cooler is more efficient cooling higher temp fluid, plus in doing this they could maintain a more ideal 180-200 degrees trans fluid temp. They have flip flopped through the years on this, but many still got put before the radiator. And my email is [email protected]. I'd like to see this and compare it against factory info.

DOC (pdf) ASE 8 MODULE 16 GM 6.5 TD copyright 2002 sent, interesting to see how it compares to the GM shop manuals..

As GM goes efficient was not the rule from my experience I went w/very hard shifts and extra cooler capacity and could not be happier w/results.

 

[THEFERMANATOR]

You misunderstood what that table is for. That is not an ideal temp range, that table describes a typical valu one would see if they started the engine and let it idle until the lower radiator hose was hot(as in stats opened and flow made it all the way through the radiator) with it idling and no load applied. It is in no way a table saying the min or max desired temp, its just a typical valu chart used in a training course to tell technicians what standard values they should see under controlled conditions. I've been through actual training courses, so I've seen these kinds of manuals before. If you go back and look you can see it even says student workbook on the sides of the page. You may want to correct where you have quoted this info as you have misunderstood this materials intentions.

 

[FellowTraveler]

You misunderstood what that table is for. That is not an ideal temp range, that table describes a typical valu one would see if they started the engine and let it idle until the lower radiator hose was hot(as in stats opened and flow made it all the way through the radiator) with it idling and no load applied. It is in no way a table saying the min or max desired temp, its just a typical valu chart used in a training course to tell technicians what standard values they should see under controlled conditions. I've been through actual training courses, so I've seen these kinds of manuals before. If you go back and look you can see it even says student workbook on the sides of the page. You may want to correct where you have quoted this info as you have misunderstood this materials intentions.

Well, thanks for the correction and will correct, thanks.

 

[FellowTraveler]

Actually it's at idle and warm 120 deg.f to 158 deg f. page 95, ASE 8 ENGINE PERFORMANCE 6.5TD, MODULE 16 as read via TECH 2.

I stay below 158 deg f. at speed.............

FERM has corrected me on misunderstanding what was presented in in the above statement, sorry for the error.

I can say however the colder temps I run have served me well running empty or towing.

 

[JayTheCPA]

FERM has corrected me on misunderstanding what was presented in in the above statement, sorry for the error.

Meh, no biggie. Live, learn, and grow thick skins. Personally, I lost count on how many times I got corrected



So . . . Back to the ECT / Tranny behavior.

Looks like the combination for TCC lock is ECT at / above 132F and TFT at / above 70F. Already knew about the TFT figure from prior observation. From last week's episode with the failing sending unit, was only able to loosely affiliate the TCC lock with 130F as the temp swings were too wide and too fast. Last night ran some errands and had a situation where the ECT started at 120F and TFT was 100F. TCC would not lock until the ECT got to 132F.

 

[ak diesel driver]

On my track the tc won't lock until the dash gauge reads 170.

 

[JayTheCPA]

See if you can get a reading from the ECM.

My dash gauge leads the ECM (shows warmer quicker). With the 506 block it was usually by as much as 20F. With the P-400, the gap until the motor is warm is wider with 40 - 60 F. These observations are without heating the block.

Guess I should have clarified that the TCC lock is at 132 ECT and TFT 70, both as measured by the ECM

 

[FellowTraveler]

Meh, no biggie. Live, learn, and grow thick skins. Personally, I lost count on how many times I got corrected



So . . . Back to the ECT / Tranny behavior.

Looks like the combination for TCC lock is ECT at / above 132F and TFT at / above 70F. Already knew about the TFT figure from prior observation. From last week's episode with the failing sending unit, was only able to loosely affiliate the TCC lock with 130F as the temp swings were too wide and too fast. Last night ran some errands and had a situation where the ECT started at 120F and TFT was 100F. TCC would not lock until the ECT got to 132F.

I suspect my some-timers is acting up again and looked past the part of under what condition those temps I stated applied perhaps a brain far_ was the cause.

Anyway, my transmission has been run cold for many years now and I haven't noticed the temps when I move on to the 5 mile causeway to the mainland and the trans fully functions into OD/LOCKUP, I do warm up a bit and engage first after stepper motor drops rpm's no matter the outside temp and the box fully functions I'll monitor the temps. It's been awhile since I've been in really cold sub temps but I remember all the clatter and did warm up the 6.5 more.

I've spent most of the past 3 months in the hospital ICU and just now getting back to being mobile and had to replace my toughbook in the Burb w/newer CF53 so I'll be data logging and monitoring things so I can give an accurate picture of how my trans works after all the $ in upgraded parts to include the TransGo HD-2 and extra cooling.