Got to thinking: Auto Trans Coolers

[ntsqd]

I did a search on the term "trans cooler" just in case I was opening up a can of worms. Only got one hit. So I thot I'd start a discussion on this & offer my thots on the common methods of adding a trans cooler. For clarity I'd like to leave discussion of the different cooler types & mounting ideas or methods to another thread.
I'll be interested to read what others have to say.

I once saw a graph in a trans re-builder trade publication that plotted trans temp with expected life span. The way the graph was laid out curve was exponential and essentially flat (nearly infinite life) to ~180*f where it started falling. At 300*f the life span was only a couple minutes.

First option: Ignore stock in-radiator cooler & replace with after market cooler.
Pros: Easy to do. Used to be the common way to do it.
Cons: May or may not be large enough to effectively replace stock, no temp regulation.

Second: Plumb in series after stock cooler.
Pro: Likely returns the coolest fluid at all times.
Cons: Fluid may never reach a temp high enough to boil out any condensation. (This is sometimes reported to be 160*f)

Third: Plumb in series ahead of the stock cooler.
Pros: Uses stock cooler to regulate fluid temp. Reduces load on stock cooler possibly adding cooling capacity to engine coolant system (little to no re-heating of 'cold' water supply to engine). Likely allows fluid to reach condensation boiling temp.
Cons: Temp cycles the fluid more vigorously, reducing it's service life.

Fourth: Plumb anywhere in series with stock cooler and use a thermostat.
Pros: Likely the best option. Regulates fluid temp and only works when needed.
Cons: More expensive, more failure modes.

My thots on each:

1) The way it used to be done, but not the best by any stretch & not worth considering on anything.
2) Better, but still not as good as it could be. Auto trans' do need some temp to operate correctly. They are designed to function at some minimum elevated temp.
3) The way I do it. I see the fluid as a service item and the trans is not.
4) The way I should do it. The t-stats are available from BAT- Mocal, Baker, Pegasus, and others. These t-stats are designed for engine oil so they by-pass a tiny bit of oil even when 'closed'. The reason is to purge air from the cooler.

No doubt I've missed something, & likely more than one.

 

[slooowr6]

Quick question, looks like you have a stock trans cooler. Why do you need extra cooling for the trans? Do you tow/carry heavy load?
Since your rig has stock cooler already, I would get a gause and check on trans fluid temp before I spend $/effort on it. But that's me, cheap and lazy........:shakin:

 

[Bob_Sheaves]

Without knowing what the max heat rejection is from a given transmission, without knowing what the minimum heat rejection is from the cooler in the radiator, and without knowing what the heat rejection of the aux. cooler (minimum) is, you cannot size, you cannot begin to correctly assemble the proper parts to "improve" the cooling system. You also need to know what the testing parameters are for those numbers. Anything else is a guess, and throwing away money on doodads and snake oil from the aftermarket industry.

For example, if I say a trans has a max heat rejection of 9000BTU/min, do you use oil to air or oil to water for the cooling medium? Or both? Or something else? (yes, this is a loaded question....hehehe)


Best as always,

Bob Sheaves
CEO
catNET Incorporated
http://www.catnetsolutions.com

 

[ntsqd]

I wasn't necessarily referring directly to my particular vehicle, though we can use it as an example if desired. It started life as a 1/2t 4x4 Suburban, with a complete 1/2 ton GM cooling system. I have since converted it to a 14bff & 8 lug outers. It will be used as a tow rig, and I have some reason to expect that on occasion it will be a rescue type operation. Trouble with or failure of the trans cooling is not an option.
I've no doubt that I have & will continue to, on occasion, exceed the cooling system design's constraints. I've already gone thru one TH-400 rebuild in my old '79 Sub. No real desire to do it again with this 700R4. With the oil to coolant heat exchanger in the radiator the engine temp & trans temp are somewhat tied together. This is good so long as the system hasn't started to overheat. Then the trans' elevation of the temp of the cool water supply isn't helping the engine any. That was exactly the cascade that happened to the '79 on the Cushenbury Grade (8-11%).

For most I would venture that auxillary oil to water heat exchangers are not an option price-wise or space-wise. I was confining my thinking to oil to air exchangers for ease of installation and economics.
If we assume that the stock cooler is good for 90% of vehicle operation, with the remainder being the region where we've pushed beyond the design envelope, then the economical though less efficient oil to air cooler need only deal with that 10%

Trans pan was modified for a temp sender though a suitably esthetic location for the gauge has not yet been determined. That being said, I'm not real confident in typical automotive gauges. I may go to the trouble of using a type K to calibrate the gauge & sender.

Matweb does have ATF listings, but Specific Heat Capacity isn't a listed value.

 

[eugene]

Even if your gauge isn't all that accurate it will still give a base line. Say for example just driving to and from work your trans averages 200 after warm up, then you hit a trail and it starts climbing to 250. Then you add a small cooler and it goes to 225 on the trial then you know you still need a bigger cooler. it at least gives you a reference to compare before and after.

 

[ntsqd]

That assumes that such gauges will repeat, which is part of the question. One of Gene Berg's tech articles pointed out that these gauges do not come with any sort of accuracy documentation, yet the $30 pressure gauge from McMaster-Carr has it's accuracy listed right in the catalog.

I didn't start out looking for recommendations on my particular install as it's already done. What I was curious to see was what others think about plumbing etc. Bob's points are well taken, though I don't know how to even get a handle on the numbers needed for those kinds of calcs. One would think that the OE's would design for max cooling of the trans in the worst foreseeable scenario, but I suspect that doing so isn't economically justifiable for them. E.G. I've been hearing that there are rather limiting conditions qualifying the max towed payload claimed for the new Tundra. So while the claimed number is rather high, the actually usable number is noticeably lower. Go past those qualifying conditions and the trans is toast. Literally.

 

[Bob_Sheaves]

We could run through all the calcs and what the conditions mean, if you wish. It IS a fairly complex subject though....people may get bored more about the same time as I get excited about the subject...hehehe.

I agree with using a Type K-cheap, accurate and available dang near anywhere.

Best as always,

Bob Sheaves
CEO
catNET Incorporated
http://www.catnetsolutions.com

ADDENDUM: You are also correct on your assumption about the cost. The typical vehicle used on these forums is nowhere near the same operating parameters or goes through the same testing that a commercial truck or worse, that which a military vehicle goes through in the cooling system design and testing.....

 

[Grim Reaper]

Ohhh I have played this game.

I have a thermal wall I hit with my 454 burb.
Truck has the following
88 that just rolled 88k.
454 Gen IV(?)
factory TH400 (2wd)
FF14 with 3.73
factory height tires at just under 32 inches (factory was 235x 85x16 it now wears 265x75x16). Factory external oil cooler
Factory transmission cooler in the radiator
Did not come with an external transmission cooler.
I run Mobil 1 Synthetic 5w30


With my Burb I have a added a Hayden trans temp gage that reads off the pan. That means it reads the heat AFTER it has been through the transmission before it has been cooled.

I also added a second sender to the engine oil pan so I can see both temps.

I kept having a problem where I would run down the hwy at 75 mph get off the hwy and the heat would be WAY up on engine to about 220. It would take 10-15 minues of low speed driving in ambient temps of 85f up before it came back down.
So I ran the gambit trying to cool it down. New 4 core radiator, new fan clutch, water wetter, 60/40 coolant mix. Still the same complaint

Mine came with a factory electric fan and I improved the shroud on it and still had the problem.
Before adding the large Hayden stack plate (like the B&M everybody raves about) I added the temp sender
Transmission was hitting 220-240 in the pan
Engine oil was getting to over 300 :yikes:

The cooler mounted in front of the AC condenser behind the factory fan helped a LOT but didn't cure it. I am plumbed after the factory cooler.
That got the transmission reading 200-220 after the same run on the hwy. Did not fix the oil temps and only helped a little with the engine temp.

I finally figured out if I ran a max of 65 mph it made all the difference in the world. That 454 does not like spinning 3,000 rpm for extended periods of time.

65 mph has it spinning about 2600rpm. At that RPM the tyranny runs 180-200 depending on load and hills
Engine temp right at about 200-210 (running factory 195 thermostat). Oil temp is around 230-250.
Even with 5500lb of 4Runner on trailer behind it as long as I keep it at a max of 65mph I run about the same temps. The motor just starts making more heat at 3k than the cooling system can cope with.

Couple things I do want to try is getting both the oil coolers out from in front of the radiator. I figure I can tuck them in the nose below the head lights and duct the air to them and dump them in such a way that he air traveling under the truck will pull air through them.

I also want to see if swapping the the flow route to AUX cooler first then factory cooler will help lower engine temp some. The though is the transmission is dumping a lot of heat into the radiator. If I can get its temp down before the factory cooler it will help the engine cooling. It would also help keep the temp of the transmission even year round. Some times when its really cold I am hard pressed to get 160degrees on surface streets. If it over cooled it would come back up to temp in the radiator. Now remember where the engine takes temp is in the heads AFTER it has been through the block. So it is significantly hotter then what is coming out of the radiator.

Where you live....Bigger is better. I really don't think you would ever run into a problem of over cooling except the coldest part of the winter.

Where Bob lives...different story all together.



Bob next time you pass the union hall on Ann Arbor trail there will be a fat POS getting drunk about noon at the picnic tables after getting off their shift....He's my Uncle Fred....scream his name and flip him off for me. Thanks

 

[UnfrozenCaveman]

Fourth: Plumb anywhere in series with stock cooler and use a thermostat.
Pros: Likely the best option. Regulates fluid temp and only works when needed.
Cons: More expensive, more failure modes. ....

My thots on each: ...

4) The way I should do it. The t-stats are available from ...

Hmmm, in series, really?

I don't know how your cooler "circuit" works originally, but the ZF auto trans in the Rovers require a constant flow through the cooler regardless of temp. Additionally, I understand from professional rebuilders that the direction of coolant flow reverses on converter lockup.

These may indeed be unusual operating modes, but are the only reason that I don't have an additional filter in line for the trans.

The Discovery & Defender do have an inline fluid temp sender that simply switches a light on ... but they're a notorious failure item and mine has been unplugged since ~ 1997

Additional cooler = good

Do I know where to put it ... be nice now ... no.

Keep us up to date though!

Thanks,

KAA

 

[Bob_Sheaves]

... Bob next time you pass the union hall on Ann Arbor trail there will be a fat POS getting drunk about noon at the picnic tables after getting off their shift....He's my Uncle Fred....scream his name and flip him off for me. Thanks

Unfortunately, the office is there, but I am not. I am in Portland, Oregon right now. I'll be back home in a few weeks though-I have 3 weeks vacation coming up! After seeing my wife and family 2 times in the past year.......YEEE HHHHAAAAHHHHHHHHH!!!!!!

Back on topic, do your other comments mean you want to go ahead and use your situation as the test case for the calcs?

Best as always,

Bob Sheaves
CEO
catNET Incorporated
http://www.catnetsolutions.com

 

[ntsqd]

The advantage of of using the t-stat is that you could do either series or parallel. My bad on designating a specific method.

The t-stat would "turn on" the aux cooler only when needed, though as stated it would bleed a little fluid thru it to keep it full of oil. When in parallel this bled fluid would by-pass the stock cooler completely. When the t-stat was open that might not be bad, but when it's closed it might not be so good. My intent is to supplement the stock system such that where you live makes no difference. I do live in the SW, but a little over a month ago while camping @ 7800 ft. we woke up to 3.5" of snow on the ground. I don't want a system that will give me trouble then either.

Personally I'd do series unless the pressure drop thru the coolers (think resistors) looked to be a problem unto itself. To that end I make a point of buying Long Mfg (who B&M gets theirs from, try AFCO or similar circle track vendors) engine oil coolers for all aux coolers. These are only a stacked plate design, not the superior stacked plate with fins design of a Harrison or a Setrab.

Bob, is the max thermal rejection for any given trans out there & I haven't yet found it, or is this "in the know" type stuff? My guess is the latter. I was thinking that maybe those calcs should be done in PM's and summarized in the thread? Some people will sink in a mass of numbers........

I'm willing to be the calculation guinea pig......
700R4 behind a TBI 350ci

 

[Bob_Sheaves]

The advantage of of using the t-stat is that you could do either series or parallel. My bad on designating a specific method.

The t-stat would "turn on" the aux cooler only when needed, though as stated it would bleed a little fluid thru it to keep it full of oil. When in parallel this bled fluid would by-pass the stock cooler completely. When the t-stat was open that might not be bad, but when it's closed it might not be so good. My intent is to supplement the stock system such that where you live makes no difference. I do live in the SW, but a little over a month ago while camping @ 7800 ft. we woke up to 3.5" of snow on the ground. I don't want a system that will give me trouble then either.

Personally I'd do series unless the pressure drop thru the coolers (think resistors) looked to be a problem unto itself. To that end I make a point of buying Long Mfg (who B&M gets theirs from, try AFCO or similar circle track vendors) engine oil coolers for all aux coolers. These are only a stacked plate design, not the superior stacked plate with fins design of a Harrison or a Setrab.

Bob, is the max thermal rejection for any given trans out there & I haven't yet found it, or is this "in the know" type stuff? My guess is the latter. I was thinking that maybe those calcs should be done in PM's and summarized in the thread? Some people will sink in a mass of numbers........

I'm willing to be the calculation guinea pig......
700R4 behind a TBI 350ci

Each one is different, based on the operating parameters. What I was thinking is a seperate thread, similar to what we did on the other board for suspension design procedures.

1. Develop the parameters to "operate" the vehicle. (use J688 as baseline)
2. Calc the heat rejection for the engine/trans/driveline
3. Show how changing one parameter would affect the results.

What do you all think?

Best as always,

Bob Sheaves
CEO
catNET Incorporated
http://www.catnetsolutions..com

 

[Grim Reaper]

Unfortunately, the office is there, but I am not. I am in Portland, Oregon right now. I'll be back home in a few weeks though-I have 3 weeks vacation coming up! After seeing my wife and family 2 times in the past year.......YEEE HHHHAAAAHHHHHHHHH!!!!!!

Back on topic, do your other comments mean you want to go ahead and use your situation as the test case for the calcs?

Best as always,

Bob Sheaves
CEO
catNET Incorporated
http://www.catnetsolutions.com

Your main office is not far from where I grew up E-Long lake and Rochester Rd in E-Long Lake Estates. I was born in University Hospital. Mom worked at Chrysler in the 60's is that before you were there?

Back on topic. I'll let ntsqd go first since it is his thread if the offer was extended to me as well. Then maybe we can play and see what the difference is with the 454 and TH400 in my burb. Other then his being 4wd our vehicles would be reasonable comparable just different motor and tyranny. The factors of weight and aerodynamic drag would be about a wash.

 

[ntsqd]

I think a seperate thread for the calcs is a good idea, keep this one more oriented towards placement & plumbing.

In a perfect world I like to see this other thread become some sort of guide towards choosing the right aux cooler or deciding that you don't need one.

 

[CJinCA]

There's a fifth option as well for routing the cooler. Run the cooler in parallel with the stock cooler in the radiator. I've never done it but about 10 years or so ago, I read an article in the Automatic Transmission Rebuilders Association monthly magazine about it. I don't remember all the details, but the jist of it was:

It's possible to overcool a transmission in extremely cold climates, in which case under those conditions the auxilary transmission cooler is run parallel with the radiator instead of in series.

A "Y" from the single cooler line goes to the radiator cooler and the auxilary cooler inlets and another "Y" from the cooler outlets back into the single cooler return line.

ATF does need to attain minimum operating temperature for optimum performance in frigid climates. Running parallel provides added cooling while tempering the absolute max cooling temp that would be possible as when run in series vs parallel.

Also it was mentioned that with parallel coolers, if one cooler should become restricted, the other one still functions and saves the day. And with a ball valve installed in the inlet to the auxilary cooler, the auxilary cooler can be bypassed to help warm the ATF if the ambient temperatures are extremely low for prolonged periods of time.

Personally, I'd only consider running a cooler / radiator in parallel if I was consistently running in temperatures below zero degrees Faranheit. For most of the lower 48 I'd run the auxilary cooler in series, after the radiator, for maximum cooling. You'll see 10,000 transmission failures from heat before you'll even see one die from a cold.