Trans temp vs engine temp

[JohnEd]

In my old S&S Winnie I have a 440 and a Dodge 727 trans(TX).  The PO managed to lunch both of those.  I have put approx 50K on her and I have some idea of how she works.  One thing that i have never had a problem with was engine overheating.  On Grapevine the engine temp goes to 195 while it usually reads 185 on other non 7 degree 10 mile hills. 

The trans is a different story.  While the old 3 speed 727 with a lock-up was/is considered the most durable TX ever made for light trucks, it does need its share of cooling.  With the stock system of oil to water heat exchanging I got a reading of 230 and climbing when I pulled over to let her cool and connect the aux air to oil cooler I had installed for the eventuality that the stock wasn't enuf.  It sure wasn't and I then knew how the PO had managed to cream the 727 part of the drive line.  Now that old girl was carrying 15,000 pounds and pulling another 5,000 pounds of pickup so the load was definitely there.  One thing I did when I saw the temp hit 210 was shift into 2nd gear from 3 locked up.  The temp started to soar.  My TX guy said that that was to be expected as the TX in 2nd was pumping a lot more fluid and doing the same work maintaining the same speed.  He thought I had a net gain in heat load by down shifting and not slowing.

So here is the rub:  when you have an overheating engine you "must" increase r's by down shifting.  I never heard anybody say "but you have to keep an even closer eye on your TX temp gauge."  It seems that you have to cut your speed for both their sakes.  Personally, I don't have any temp problem as both my TX and engine run well within limits on any hill I have so far encountered.  Good ole Dodge RM 400.  And, she has positraction!!!!  Go figure.

Thoughts...laughs....ridicule....feel'n lucky here,

John

[compedgemarine]

for one when you pulled it to 2nd out of the locked in 3rd the converter is now slipping so it will produce more heat than when the converter is locked. also in 3rd the trans is 1 to 1 so less stuff is going on in the trans than when in 2nd.

[Airbag]

Just a note on the subject. Here in Marana AZ where it 115 in the shade we have 132 buses with a variety of engines mostly Cummings and Catipillar coupled to the common denominator Allison transmissions.

We get an incredible amount of miles and service from these buses, The kicker is every transmission temp gauge is disconnected because they run in the red, it does not hurt them. If they were connected dispatch would be over loaded with distress calls.

It is just like when Northrop tested the N-9 flying wing, head temps on the six cylinder Franklins were off the scale. What did they do? Put tape over the gauge and finished the test program. No balls, No air medals.

[JohnEd]

Airbag,

I gotta love ya.  You must be an x Marine or at least have dated one once.  No guts, no air medal....priceless. Taking nothing away from what you have said.....the 727 is a different beast and will not compare to an Allison in any way shape or form evidently,  IMHO.  "Regular" TX will live a very short time if run above 210.  They like 180 and will do that for 100K plus.  They have a scale on the subject and when you start running at 300 degrees they time the life span in hours and it ain't a big number.  But that is car stuff and that's different.  But this post was a good deal for me as I was clueless that the Allison was so bullet proof as to shrug off temp.  It does use 40 wt oil for fluid though, right?  I would have shut down at 260 degrees transmission temp with this knowledge.

Thank you both,

John

[Barn Owl]

For the sake of discussion here, it takes the same amount of work to go over a hill fast or slow. When you go over slow, you are allowing a greater amount of time for the cooling system to shed the heat generated by that fixed amount of work.  Even though more heat is generated by a tranny not in lock up, you can compensate for it by reducing your speed even more, and having someone go out back and push; therefore, transferring some of the generated work heat off your RV and onto your helper.

[JohnEd]

BO,

I want you to keep that plan to your self cause when it comes to getting out and pushing I always seem to have my turn coming no matter how many turns I take.   Yeah, she's only 5 feet tall....but!

Things must be wired different at your house.

John

[JohnEd]

BO,

Now I am talking car/truck stuff here but I thought the same procedures apply....they don't.  But, that's how this got on a bus board and I am still getting great info that i will use.  Everything you said was true.....but with a twist.  Yes, it takes the same amt of power...total to get over the hill.  BUT, if you go faster that takes more horsepower and that equals heat.  Like you said it will create the same amt of heat but in a shorter period of time.  When this was my problem I first maintained the same speed in second as I had in third(locked) but I might be mistaken about the locked part.  Any way the temp started climbing faster in second and when I slowed down it was too late as the thing looked like it would peg the meter in another minute.  Sitting in N with a couple grand on the tack started to cool the TX down.  With the air to air hooked in after the radiator she never got much past 220 and it took a while for that to happen on the way up.

I think that synthetic would run a lot cooler and would give you better MPG.  Has there ever been a down side to that stuff except price?  Because of the added lubricity and lower heat you might even be able to run 20 or 30 wt oil instead of 40 and still have the same protection.  I understand there is data that states you can drop down on the weight of your oil and still meet needs but I don't know where that info is.

Thanks for the advice,

John

[TomC]

At least on my V730 I can get lockup in every gear.  The top part of second and all of third is a given.  But what I discovered is that when you're pulling a hill and the transmission is in second-when you slow down enough that the transmission slips back into converter operation, pull the gear shift lever down to 1st. After it down shifts it will be revving around 2200.  Then just pull up on the accelerator about an inch and you'll feel the transmission bump back into lockup-then you can continue up the hill at about 32 mph with the engine revved happily up, with your foot on the accelerator by about 3/4-almost perfect scenario for climbing a long grade.  Good Luck, TomC

[Sojourner]

JohnEd...all American made automatic transmissions are design to withstand 240° to 260°F for every day use. However, if you install a thermocouple in a tee fitting right at the torque converter oil outlet to cooler line that go to radiator. You will have the most important temperature fluctuation...it where the high temperature begins. All chassis dynamometers work I did at GM Tech are torque-converter out temperature to be watched so it never goes over 300°F for more than a second or two, otherwise oil gets burnt and the red dye changes toward yellow (from red to brown to yellow). It is only whenever the torque converter is in unlocked mode while in acceleration or heavy load.
So if you or anyone wants much more instant responding temperature reading, remove pan thermocouple and install with a tee at the torque converter oil outlet that connect to the cooler line. You can tell instantly if you're climbing a little grade with it. It gives you peace of mind to know where and what the temperature is while traveling at all times. Pan temperature is the average of the highs and lows torque converter temp.

Post here to gets more parts detail if you are interested.

FWIW

Sojourn for Christ, Jerry

PS...you may have a slipping locking converter...a no, no.

[JohnEd]

Jerry,

I guess I did the right thing when I panacked at seeing the temp pass 260 at a rapid clip.  From your description of the points of various temps I was headed for trouble.  My sensor is installed in my pan.  I think I will leave it there cause I only see 220 there now and the max must be reasonable.

Your post was very interesting to me.  You mentioned "modern automatic TX" being designed to withstand 260 degrees.  Mine, in that S&S, is a 73 vintage Dodge 727.  When I read up on this a little, the article said that they wanted 180 degrees as an operating temp.  They thought that 210 as a operating temp was getting into trouble and 260 was not to be seen except at the crest of a hill for a minute or two if ever.  I can accept that times have changed but we are still using the same ATF and the first thing I did on the Winnie was change the burnt brown ATF.  The only other vehicle that burned the ATF was my Thunderbird and that cooked the stuff enuf to justify a yearly change.

Have they been increasing the acceptable operating temp or has the formulation of the oil changed as it has for the motor oil? 

Thanks for the informed opinion and info Jerry,

John

[Sojourner]

JohnEd...You are always welcome and I appreciate your nice comment however; you added a word "opinion". The word "opinion" is not a fact.
All my posts are either from my true pass experiences from mid 40's till whatever I am working on or from the internet search with a link. I always try to add the word "I believe" or "think" or "felt" or "feel" about whatever subjects that I was referring to as a opinion. Otherwise it the fact and true. BTW...it always possible I am behind of any unknown technology and always willing to learn for newer things.

About automatic transmission oil temp....today I just search the subject to try to find someone else who been there such as myself to explain about this subject. So here a link that back up of what I said in earlier post but in must more details. Remember, transmission pan contain a body of oil is the average temp from many high & low converter's temp. And the warmer the oil up to a point is better fuel mpg. Otherwise cold oil cause more fiction in between stack clutches not being engage while the other one is engage.
Look for subject "TRANNY  INFORMATION"
http://users.sfo.com/~eagle/CRANKS.html

I love this MAK board to learn what I didn't know and to help anyone to my best ability. I try to let anyone know the shortcuts about fixing or solving a problem from my personal experience and knowledge.

I always learn from the first mistake 

FWIW

Sojourn for Christ, Jerry

[JohnEd]

Jerry,

"opinion"  is "a judgement based on special knowledge and given by an 'expert' ...as in 'medical opinion expressed by a Dr.' " from The American Heritage Dictionary.  You signed off with FWIW and I want you to know it is worth a lot even if you are not 100% and I don't know of that happening.  I place a great store in intention and yours has always seemed honorable.  To be fair, I see a lot of that around here so we are in good and like company.

When you look for what someone "really" means by that, you have to consider the source and their probable intention.  Another valid definition of opinion is "unsupported by facts".  Ya have ta read between the lines my brother.  If I were to call you a "natural guy" you might think that a complement and from me to you it would be but I have said that to some special men and they got a puzzled look and I know they went and looked it up.  Buried in there is NATURAL means "Woods Colt" as one born without the benefit of legitimacy or intentional breeding...ie Bastard.

Stay frosty Jerry,

John

[Sojourner]

JohnEd...Thanks you very much.

Sorry to confuse anyone about FWIW on true subject.

BTW...I modify via adding a subject title above the link so you can quickly get to point of trans temperature.

Have a great day.

Sojourn for Christ, Jerry

[JohnEd]

Jerry,

That link is terrific.  I found that my info on the hazard of running at 300 degrees was over stated a small bit.  The reference said the vehicle would be expected to travel only 800 miles at that temp.  Any way you cut it 300 is bad.  They did confirm the info I had about low temps robbing you of power and MPG but the aspect of accelerating clutch wear took me aback.  Looks like there is no up side to running a cold TX.  BMW must be right when they say to start it and start moving promptly at a conservative speed to accelerate the warming process and not to idle the engine and trans to get them warm.

What I didn't see was a reference to a "locking" converter.  I thought that was standard in this ERA of fuel efficiency.

Been a real good post for me...thanks,

John

[Sojourner]

Slipping lockup torque converter will cause increase temp.....slipping clutch & turbine/pump is a double heater. If so, either weak oil pressure or metal compound in piston area to cause it to slip.

Sojourn for Christ, Jerry