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Posted

This has been mentioned but never really discussed. A straight answer hasn't really been provided.

 

I'm writing this for my Jaguar, but I think it has plenty of merit with our cars as well since many people install transmission coolers.

 

There are 3 possible scenarios here.

 

1. Use the built-in transmission cooler in the radiator

2. Route the transmission cooler lines from the radiator, to the aux trans cooler, and back to the trans

3. Bypass the radiator and go straight to the aux trans cooler

 

Obviously, we know that our transmissions heat up to the point where the stock radiator is not enough to cool them. Buck reported that under heavy driving, his 05 GTP's 4T65E-HD would hit 260 degrees F. We also know that heat kills transmissions, and that temperature is rather high. Therefore, it can be assumed that the stock radiator is insufficient in cooling the transmission. This is primarily because it cannot cool the transmission below what the temperature of the radiator is, which during a typical summer day will sit nicely around 190 degrees F. IIRC, our w-bodies won't switch on the primary fan until the temperature reaches 235 degrees F. Correct me if I'm wrong here. The transmission will only get hotter than that.

 

If one routes the transmission cooler lines through the radiator and then to the aux trans cooler, the radiator does some slight bit of cooling, and the transmission cooler does the bulk of the cooling thereafter. In my experiences, with a large transmission cooler flush mounted to the condenser, the engine could be running at even 220 degrees F, and the transmission will stay steady at 190 degrees, so the cooler is obviously making a big difference. Obviously its less than ideal to flush mount the transmission cooler, and I'm working on that. My concern with this approach is that the transmission can potentially be cooler using only the aux transmission cooler, which brings me to my next point.

 

How cold is too cold? I've read that someone called valvoline to ask them that question, and the response was flat out "30 degrees F." I'm not sure how much validity there is to that claim, since I've also heard from around here that you can run a transmission too cold. Well how cold is too cold? I don't want to hear guesses here, but rather constructive feedback. Would it be detrimental to bypass the radiator entirely and have the aux trans cooler take care of all of the cooling? Has anyone done this and reported back on their temperature readings in different conditions? Another thing to consider with this approach is that the car itself will run cooler as a result of not having the heat of the transmission lines going through it.

 

In regard to the aux trans cooler, I'm referring heavy duty coolers in the $50-$60 range, built for RV's.

Posted

You always want to run it from Transmission-> radiator -> trans cooler -> transmission

 

you are loosing efficiency if you just run it into the trans cooler.

 

and you are right, at minimum the trans temps are ambient engine temp with no trans cooler, and generally only go up. I wish I had more hard information but when we added a trans cooler to digitaloutsiders regal the trans temps dropped about 20*c from what they had been (its been a few years now, what that number was I don't know).

 

I think in most climates it would be rather hard to bring a transmission to below freezing temperatures under any sort of normal operating conditions. I really don't think most people really have to worry about running a trans too cool.

Posted

Also, I have read back and forth arguments on bypassing the factory trans cooler vs. running it in series with the aftermarket auxiliary cooler. Here's the arguments I'm seeing:

 

Using only the aftermarket transmission cooler will result in a more significant temperature drop. Since the difference between the fluid inside the cooler and the ambient air can be almost 200*F, you will get the greatest cooling effect.

 

Running it through the stock trans cooler, then to the aftermarket cooler, than back to the trans- While it does cool, you will be picking up the ambient temperatures through the radiator. The ambient temperatures will be rather warm, and through that, you may only get a 20-60*F temperature drop. However, on hot summer days, you may actually be heating the fluid up while it's passing through the stock cooler in the radiator. Now, the big part about the argument here- Running it in this configuration, during the winter time, the running it through the stock cooler in the radiator will help in heating up the transmission fluid.

 

 

Yes, the fluid can be too cold. I've read 160-180*F is the lowest you will want to get the fluid. Myself, I would go no cooler than 180*F. If you are worried about this, cardboard and zip-ties over the aux. cooler during the colder months will keep it from cooling the fluid.

Posted

Yeah, but there's not much you can do in these cold parts in the winter (short of letting your car warm up for like a half hour or more) to keep the starting temp of the fluid from being ambient outside air temp, which on nice days can get down to -40* or less. I've let my car warm up for upwards of 20-30 minutes that the heater was hot and when I put it into D, it still took about 2-3 seconds for it to *clunk* into gear. On a normal summer day, it would be instaneous. And with all that cold weather starting and driving, any of my vehicles have been just fine. So, I agree: HEAT KILLS. But, the cold really won't hurt it though.

Posted

Hmm.....

 

A) I have this severe fear of the trans lines breaking in the radiator, ruining the trans. I would be much more comfortable bypassing it entirely.

 

B) How can I set up a Trans temp gauge?

Posted

a trans temperature guage should be simple as the trans already reports temperature. Don't. Worry about the lines leaking. Rather unlikely.

Posted

a trans temperature guage should be simple as the trans already reports temperature. Don't. Worry about the lines leaking. Rather unlikely.

 

But this is me you're talking about. Just because you said that, I'm sure a crack has developed.

Posted

Yeah, but there's not much you can do in these cold parts in the winter (short of letting your car warm up for like a half hour or more) to keep the starting temp of the fluid from being ambient outside air temp, which on nice days can get down to -40* or less. I've let my car warm up for upwards of 20-30 minutes that the heater was hot and when I put it into D, it still took about 2-3 seconds for it to *clunk* into gear. On a normal summer day, it would be instaneous. And with all that cold weather starting and driving, any of my vehicles have been just fine. So, I agree: HEAT KILLS. But, the cold really won't hurt it though.

 

Cold won't hurt anything except proper operation.

 

A lot of newer transmissions actually open and close flow to outside lines to help warm up the fluid during cold conditions.

Posted

In the winter my transmission cooler gets hot in just a few minutes.

Posted

I've been told before that 160 is just about as low as you want to go by a rebuilder. He explained that while the fluid is perfectly happy at almost any temperature, o-rings and other soft parts are less pliable at lower temps, and that extended operation at those temps seem to shorten their effective lives. I don't honestly know if he was telling me his opinion, or if it was something he'd seen.

 

That being said, why not simply run one additional line, with a cutoff valve, which would allow the radiator trans cooler to be bypassed in hot weather, and not bypassed in very cold weather? Should be simple to do, cheap, and gives you the flexibility to do either option as conditions warrant.

 

I added a factory cooler to my '95 LQ1 this summer. I did run it as the factory did, going to the radiator first, then the cooler. Average temp dropped from 215-220 to around 190-195....except when in stop-and go traffic. The reduced airflow while stuck in traffic meant at times even with the cooler, temps were around 210-215.

Posted

So how would one go about installing a trans temp gauge, or would that warrant a new thread?

Posted

So how would one go about installing a trans temp gauge, or would that warrant a new thread?

x2!

Posted

I imagine you could fit one into the transmission pan like you would a drain plug kit. Two copper washers or rubber o-rings, a temp sensor, a locking nut, and a hole drilled into the pan.

Posted

When I did the install into Matt's Cutlass, it was as simple as taking out the plug on the top of the transmission, screwing in the sensor, and running the wires for the gauge. It was no more than 20 minutes of actual work. And, I didn't have to deal with touching the transmission fluid.

Posted

When I did the install into Matt's Cutlass, it was as simple as taking out the plug on the top of the transmission, screwing in the sensor, and running the wires for the gauge. It was no more than 20 minutes of actual work. And, I didn't have to deal with touching the transmission fluid.

 

Is the fluid just sitting there at level with the top of the trans or what?

Posted

It's been a while, so I really do forget most of the details.

 

Buck, if your car is OBD II, you can get the Aeroforce Scangauge, and plug it into your OBD port. It will give you any and all information that you will need http://www.zzperformance.com/grand_prix/products1.php?id=878&catid=107 <--- You should be able to find it cheaper.

 

Holy mother of god, that thing has EVERYTHING!!

 

Where could I get it cheaper?

Posted

I'd just search around on the web a bit. I remember it being much cheaper a few years back.

 

EDIT: Looks like normal price is now $250. Still not a bad price to see everything that's going on. Granted, not a full scanner/tuner (in fact, you can get pretty good scanners for pretty cheap), but it's nice to have on the fly.

  • 2 weeks later...
Posted

the aeroforce gauges are really handy, and look pretty bad-ass in my opinion.

 

well worth the money asked for them.

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