C4 towing overheating...Cooler flow tests?

Originally Posted by gregaust

I have been doing a lot of testing with temps last few weeks on one of my C4's in a friends car. Is one of my C4's using a stacked plate cooler from PWR (PWO1223- 280x255x19mm)with -6 lines. Has the usual pump mod and deep pan etc and full manual valve body runs up to 210psi with a high stall 9" converter. With a temp gauge in the pan it is hard to get it warm. After a 10 second pass trans temp is showing just on 160*F .

I found the same thing with mine, as part of my morning warmup ritual the tranny temp gauge has to move. Starts at 120ish and has to be over that, so I sit in the pits against the tranny brake heating it up.

But especially when I was racing the Fairmont with the cooler up front once the tranny got hot it was hard to cool down. Just not enough fluid or surface area in a C-4. The Fairmont also though I could not keep the lines away from the headers because the cooler was up front.

The T-Bird is very easy to keep cool with the lines running back to the trunk



Has to be a fairly warm day before I hear the fan running. I have not had a chance to come close to hot lapping the T-Bird but the Fairmont would put the temp over 220 doing that.

Take a close look at where the lines run for the car you are working on.

So I disconnected the return line at the transmission and put it in a bucket, nice steady stream about .5L in 10 seconds.

But even at that I did not like my 5/16 steal cooler lines, as they were a little bent up and ran really close to the headers. In the process of swaping in a 5.0L C4 in where a 2.9 A4LD used to be I had joined C4 and A4LD cooler lines with compression couplers. So I replaced the steal cooler lines with 3/8" line I picked at the hydraulic shop. I also installed another transmission cooler the same size as the first, I actually have more transmission cooler area now than I have rad.

This seems a little extreme but I question the efficiency of these coolers (old tube and fine style).

Basically I have 2 options if I have good flow, my transmission is making to much heat or my coolers suck.

These coolers can't suck that bad so if I still have a problem I will have to assume something is wrong with my converter.

I attached pics that you can see the rad only and now with the dual coolers

I use Derale coolers which are tube design and never had any issues. No where near as big as yours . My testing i mentioned above though is a plate type .

The first thing I would do is to turn those coolers 90 degrees. With the with both inlet and outlet on the bottom you can have air trapped in the top of those tubes. then make sure that the front cooler line goes to your radiator first (or one of the bottom tubes if you are not using the radiator cooler) then a line from the top of the first cooler to the bottom of the second cooler and from the top of the second cooler to the rear fitting on the C4. That will eliminate any trapped air.

I can not move those coolers, This is a baby Bronco II, that is the only way they fit. I have the rad cooler completely bypassed. It makes sense that there may have been air trapped in the tops of those coolers, but I doubt it is still there after 600 miles of hard towing.

I did go on my trip and did not have any problems, the fluid looks good and does not smell burnt. I hit 250 deg at the top of a couple killer long hills. The rest of the time it would run between 220 and 230. Still warm, but I am not uncomfortable with that temperature while working things that hard.

If you transmission is running 220F all the time it won't last long. The friction materials need to run cooler than that. The optimal temp to run a C4 is between 165 and 180. For every twenty degrees over that you can cut the life expectancy in half. That means that you can expect to be rebuilding you C4 in about 25000 miles.
You need to address your heat problem.

That just seems way hot. I been doing more checking .Checked one the other day after some driving and with a temp gun on the pan was only 60-70 degrees C.
I've run the coolers vertical before and never had any probs but as Paul says need to look into all possibilities to drop the temp to make it last.

I have watched a C6 and now 2 C4's with temperature gauges. I also have information about a stock C6 in an old Ford truck with big tires on it. In all cases temperatures have run over 200 deg F pretty steady.

I just opened up my other C4 that is in my ranger behind a 500hp 2.3. I have seen 250deg plenty on that one with the transbrake on. I had no color on the steal and did not have any more than normal clutch dust.

I have also noticed there is only one chart out there about the transmission fluid temps and transmission life, and everybody quotes from it like it is honest truth. All this temperature VS fluid life is from one source it seems, and that source sells transmission coolers.

The problem I have had is with getting consistent data as well. I have 2 different temp gauges that read 20 deg apart, I have taken readings from different parts of the transmission (pan, cooler line) and they are up to 30 deg apart. So when you look at a general chart that has been around in since the 70's and comes up in every transmission temperature thread I run across on the internet, then I wonder how much data backs it up, and how much variation is in that data.

Found some information from an engineer who works in the thermodynamics side of the Ford Motor company and he did not feel 220+ deg under server duty was a big deal. That was still within manufactures tolerances.

Also have information from towing with a 700R4 which was seeing 240 degs.

Also found a company that does transmission fluild breakdown testing which was running a 4l60E over 300degs for hours on end in a test stand.

Also note that fords E4OD's temp warning comes on at 300deg.

And consider that 90% transmissions only cool from the rad tank which is not as hot as the engine, but still only offers minimal temperature drop for a transmission to actually run at 165 deg.

I had all this information above before I started this post, but I wanted more real data and I am thankfull for that.

So i realize that I would be better off with lower temps, but I think it is one of those things that maybe is not a problem untill you have information to worry about. Maybe I should take the gauge out (J/K). I am not saying that I will not have to do a fluid flush sooner under these conditions, but the fluid in my C4 after a trip seeing lots of 250 deg looks and smells better than half the vehicles I work on. I could certianly not honestly suggest a flush to a customer if they owned my truck, based on the condition of the fluid. It looks and smells like new.

If my transmission does die in 25,000 miles I will rebuild it again and probably put a good converter in it. I think most of my extra heat is coming from an old tired converter that came out of a C5, as the transmission itself is not slipping to generate this heat. I wonder if this was a C5 lockup converter and that lockup clutch is slipping.

The temps stated in the posts are for optimal tranny life.
Also most posters here race there C4's.
They want to keep them as cool as they can.

Towing will induce more heat.
Your 220-250 Deg. F max. temps I still feel are a bit high for all the cooling area you have.
I also feel the C5 converter is a heat problem.
I am a amature C4 rebuilder. SO take my data with a grain of salt.
My first rebuilt C4 seemd to get hot I thought. Ran about 220 Deg. F max. At the drag strip if i made a couple of hot laps.
I was running a stock C5 converter non lockup.
When I had to go through the tranny again (pump gear broke) I noticed a slight burn smell and the clutches looked worn. Had 50 on it passes or so.
Installed a Broader performance direct clutch kit with new clutch materials and bands.
I also installed a small tranny cooler. (14x9)
Put a Redneck 3500 stall conveter on it to replace the C5 converter.
Now when i hot lapped it the temp. never got past 190 Deg. F.
Put maybe 30-40 runs on it before i tore it down again.
Wanted to install a transbrake and see how the clutch material looked.
This time no burnt smell and clutches looked almost new.
Now with the Transbrake and hot lapping it it still never got past 190 Deg. F.

I think the C5 Converter was making all the heat.

It is good to have more information.

My 2.3 turbo ranger also has a 9.5" converter in it from Redneck. I have a medium size tranny cooler on it (smaller than the ones in the bronco). It stalls at 4500 RPM with 500hp. Running around town with 3.55 gears and 305/45R18 (28.7") I get to 180-190 deg pretty quick. With the transbrake on it makes heat wicked quick. I can only do 2 hot laps before I see 230-240 on the gauge.

Staging a 4 cylinder turbo with 30 psi boost is not a nice thing. Even with a 55 shot of NOS it takes about 4 seconds to hit full boost, so I have to start building boost on the prestage, once the boost gets up high enough the foot brake can't hold it then I get pushed into the full stage beam, at which point I have to "catch" it with the transbrake and finish building boost.