Thread: Can I run w/o trans oil going into radiator???

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I was thinking of a sensor in the trans cooling line. Easier to install trans. It will not show the temp going back up into trans but should indicate overall system cooling. What do you guys think?

heatwave, I am sorry to admit I am such a worry wart. I go out to the garage and turn on the small heater but still freeze my face. Today we had snow flurries and it was 48 F in my garage with the outside at 38 F, soooo I am just mostly talking here. I already purchased a #80226 Trans Temp Gauge Kit from B&M and that is exactly how it is supposed to be installed with a T-fitting inserted into either line to/from the cooling unit. On the 700R4 I believe they recommend to put the gauge in the upper (return) line but other transmissions vary as to the upper or lower line being the return. The return line should be cooler than the out line. My problem with that setup is the T-fitting uses copper bead compression fittings which I am wary of regarding a good seal. The other problem for me is that the B&M gauge is a very different style from my other gauges (TPI Antique) and there is little space left in the small dash anyway. I could squeeze it in by moving my ignition key switch but then the gauge will be quite different from my TPI gauges. One further factor is that I checked with the TPI Tech guy and TPI does not have a temp sensor for trans oil that is compatible with the water temp gauge in my quad cluster TPI gauges. As far as using sensors from different manufacturers on the same temp gauge goes, the TPI Tech guy said there are some dfferences and while some resistors like gas tank floats are uniform others are not so it is a guess as to the range, but he did say no harm would come from using mismatched sensors just that the gauge would not necessarily give the right reading. Soooo, I am back to square 1 again and may just install the T-fitting and get the compression fit as tight as possible and use the mismatched gauge. Finally, I called the Tech guy at Derale and he said with the Derale pan and the bottom part of the radiator core he is sure that is adequate for a mild SBC and he thought the temp gauge is not necessary. Then we are back again to the low pan, he suggested a skid plate but I don't see how that would do any good since it would probably block the air to the little tubes in the Derale pan; Maybe a perforated skid plate with a lot of holes might work. In any event the cold garage is holding me back. I work for an hour or so and then come in the house to warm up and then go back but it I am still muddeling around about this trans cooling bit.

Don Shillady
Retired Scientist/teen rodder

If you put a sensor in a trans line, put it in the output line as close to the trans as possible. That gives the best indication of temp. It's probably the best place for a sensor.

I checked the B&M directions and they do specify the return line for the sensor. Of course that would hopefully be the cooler of the two lines so that reading is optimistic.

Don Shillady
Retired SCientist/teen rodder

Originally Posted by Don Shillady

I checked the B&M directions and they do specify the return line for the sensor. OF course that would hopefully be the cooler of the two lines so that reading is optimistic.

Don Shillady
Retired SCientist/teen rodder

Don, like you I don't have a huge bunch of space "under there".. the connections for the radiator : trans cooler are especially tight. My first choice was 90' ell male thread X 3/8" compression brass fittings. Never a second thought! My 3/8" tubing was anodized blue aluminum tubing. I fabbed the tubings to bring the connections to the side of the radiator where I could add some hoses to provide a flex joint. The tubing is clamped to the frame with some of the rubber coated clamps and screwed into the frame.

I've never had a failure with any compression fittings. Until the state of Mass outlawed it back in the 80's we used them on brake lines!
I wouldn't worry about using them.

Originally Posted by Don Shillady

I checked the B&M directions and they do specify the return line for the sensor. OF course that would hopefully be the cooler of the two lines so that reading is optimistic.

Don Shillady
Retired SCientist/teen rodder

OH, almost forgot, I like the idea of putting the sensor in the return line. I think I'd like to know if the trans was getting a "hot" fluid "added in".... If the temp going into the trans was say 140' to 150', you could assume that the coolant from the engine was influencing the trans fluid cooler. If the Engine temp got excessive at say, 200' : 205' yet the trans cooler return stayed at 140' : 150' you'd know you're radiator system was working and a problem was within the motor and not the trans adding to a different problem.

Well, my 2 cents.. IMHO...

OK, guys, you may be overthinking this. Do you want to protect your transmission or determine the eficiency of your of your radiator and or your cooler?

Do you want to know the temperature of the fluid in the trans, or impute it from the temp of the fluid coming back from the cooler? Suppose you have a really, really good cooler, and all you see is 160* fluid in the return line. OK, looks good. However, that cooler is giving you a 40-50* drop, and your trans fluid is really over 200*. You're fat and happy until your trans burns up.

Why would you want to know whether hot fluid was going into the trans? If hot fluid is going in, it's surely going to be hotter coming out, because there is minimal cooling inside the trans. You can tell whether your radiator is working from the water temperature.

An automatic transmission - especially one with an overdrive - can flash excessive heat in a very short time. And, the temp IN the trans is what makes or breaks it. I want the best info at the potential point of damage.

Your mileage . . . or temperature . . . may vary.

Originally Posted by Henry Rifle

OK, guys, you may be overthinking this.
Do you want to know the temperature of the fluid in the trans, or impute it from the temp of the fluid coming back from the cooler? Suppose you have a really, really good cooler, and all you see is 160* fluid in the return line. OK, looks good. However, that cooler is giving you a 40-50* drop, and your trans fluid is really over 200*. You're fat and happy until your trans burns up. And knowing you've got a temp drop over the cooler, if you see 200 degrees going into the trans you know you're in trouble.

Why would you want to know whether hot fluid was going into the trans? If hot fluid is going in, it's surely going to be hotter coming out, because there is minimal cooling inside the trans. . MY point Exactly!

An automatic transmission - especially one with an overdrive - can flash excessive heat in a very short time. And, the temp IN the trans is what makes or breaks it. I want the best info at the potential point of damage.

Your mileage . . . or temperature . . . may vary.

Measuring the oil temp outside of the pan is not a great way to do it. Maybe adding sensors to both cooling lines is the way to go! I'm glad I just hooked it up to the radiator and was done with it. I know some guys who don't even bother with it and just run a short tubing. Just my .02 cents and IMHO!

If we are building a new space shuttle we would like two sensors (in and out) to check whether the radiator cooler is doing any good. Thanks for the reassurance about the inline compression fitting I may yet put it into the line before the cooler; I agree that tells the higher temp of fluid. I will figure out something so the mismatch between the gauges is lessened.

Don Shillady
Retired Scientist/teen rodder

Hi guys. I just found this thread and, in the interest of time, have not read all the details... But to answer the original question about the trans fluid going to the radiator, consider this: My coupe is the fourth car I have built using a TH 350 transmission running with NO COOLER! I simply took a 60 inch steel line and wrapped it around a piece of 2 1/2" tubing to make a coil and screwed it onto the transmission. It fits up next to the trans and requires no lines, flexible fittings, etc.

Some early Powerglides had no coolers; they had big holes in the bellhousing to enhance air flow. I had an old transmission mechanic tell me years ago that on lightweight vehicles, the difference between running a cooler and not running a cooler was about 30% shorter life of the fluid. He said I simply needed to keep an eye on the trans fluid and change it when it started to show signs of darkening or beginning to smell the slightest bit burned. I have had my coupe on the road since March of 2005 and probably put about 20,000 miles on it; it is just now showing signs of the fluid turning from red to brown...

So, do I recommend doing this? It's up to you. If you have room for a cooler, use one; I didn't have room under the car and didn't want to put one in front of the radiator. If you have a heavy vehicle (over 3,000 lbs.), or if you are drag racing or towing a trailer, etc, run one. My coupe is 2600 + pounds. the other 3 cars I did this way were in the 2400 pound or less range. All of them are still on the road...

Okay, this is why I like the forum. Lot of knowledge and exp. I like Henry's deduction : My reason for a trans temp gauge is avoiding the No#1 problem heat. I will try for a temp sendor in pan. I used to run an engine oil temp gauge for funzies and was shocked to see how much higher the oil temp was to the coolant temp!@!!!!
I pan on 5 mph cruzin all day long in Aug heat in Louisville (90-100 degrees)
with my foot on the brake looking @ 10,000 cars and trying not to run over anyone. I used to do this with a clutch but when the clutch got hot, it grabbed and jerked me around making it harder to avoid the spectators LOL.

J. Robinson, the only comment I would add to your experience is that I belive a 700R4 or other OD trans will build up heat much quicker than a TH350. Different thoughts on cooling may apply.

Denny, Good reading. Thanks. However, I would add this based on their discussion and my experience.

On my '34 w/ 700R4, I don't use a radiator cooler, and I have a 180* thermostat. With my aux. cooler setup, the temperature in my trans pan rarely, if ever, even moves the needle off the 150* mark. So, it seems that if I did run through the radiator, I might actually be warming the fluid.

Or, maybe the water temp in the bottom of the radiator would be less than 150, and I'm over-thinking it.

Originally Posted by Henry Rifle

J. Robinson, the only comment I would add to your experience is that I belive a 700R4 or other OD trans will build up heat much quicker than a TH350. Different thoughts on cooling may apply.

I never considered that and it's a good point. Don't 700R4's have a lockup converter? It would be interesting to know (1) does an overdrive trans run cooler or hotter than a non-overdrive [or is there no big difference] and (2) does the lockup converter make it run cooler because it's not "squeezing" the fluid?