Trans cooler vs. secondary fan?

[ZSK]

I've been tossing the ideas around how to lower transmission temps specifically while towing. Naturally transmission fluid needs to be in a proper temperature zone to get the best results. I'm curious what would be a better setup for both DDing and towing. Run a second large capacity cooler or to swap the stock cooler for a large one, and install an E-fan on the cooler. Of course with a switchable fan you'd be able to control temps from both too hot and too cold, but would it be worth it when not towing?

[Wicked_Sludge]

i guess it depends on what type of towing you primarily do. if its all highway, air flow is not a problem and you need more surface area (eg. auxiliary cooler). if you do mainly low speed towing then an additional fan would help tremendously.

most people find just adding a second cooler is more then enough to handle their demands.

also, whatever you decide to do, do NOT bypass the stock tranny cooler. its much more efficient then any aftermarket cooler. on top of that, it also acts to warm the tranny fluid to get it to operating temperature as fast as possible.

[ZSK]

My towing will be about 40/60 city and highway and around 3000# give or take. I guess I'll just have to hook up the trailer, take a trip and see what my temps are.

[BDAB]

i guess it depends on what type of towing you primarily do. if its all highway, air flow is not a problem and you need more surface area (eg. auxiliary cooler). if you do mainly low speed towing then an additional fan would help tremendously.

most people find just adding a second cooler is more then enough to handle their demands.

also, whatever you decide to do, do NOT bypass the stock tranny cooler. its much more efficient then any aftermarket cooler. on top of that, it also acts to warm the tranny fluid to get it to operating temperature as fast as possible.


We went through this, the transmission heats up the fluid nicely on it own. however, don't by-pass the radiator cooler, it brings the trans fluid temp down to 190* before going into your aux cooler.

I would run this

http://www.transmissioncenter.net/HPIM1002.JPG

(23"x9.5"x1.5", 13 plates, 45,000 BTU rating, and a cold weather by-pass)

with this somewhere near the transmission

http://www.transmissioncenter.net/Fan2.jpg

this has an available thermostat that turns the fan on when the fluid reaches 180* in the pan.


you want to keep your transmission fluid as close to 165* as possible.

[hairyboxnoogle]

On a similar but different topic... why that your trans should be at 165* yet the motor should be at 210*?? I was told 210 is the optimum temp for oil longevity and ultimatly less friction. Is the difference because trans fluid is thinner?

And now really off topic, is it normal that after driving for an hour you rearend is so hot you cant touch it but for like 2 seconds. Its full of 85,95 semi syn. and no noise, nor is the pinion or the the axles loose. Ive never noticed a rearend do that before. its a 7.5

[BDAB]

On a similar but different topic... why that your trans should be at 165* yet the motor should be at 210*?? I was told 210 is the optimum temp for oil longevity and ultimatly less friction. Is the difference because trans fluid is thinner?

And now really off topic, is it normal that after driving for an hour you rearend is so hot you cant touch it but for like 2 seconds. Its full of 85,95 semi syn. and no noise, nor is the pinion or the the axles loose. Ive never noticed a rearend do that before. its a 7.5

could not tell you why tranny fluid needs to be around 165*, just that is starts breaking down around 200*

I can run my Suburban all day pulling 8000 pounds and my rear diff is warm to the touch. I don't know if that is normal, but I do know semi-synthetic and full synthetic run hotter than dino oil in a rear end. I avoid synthetic in my big trucks and my diffs run around 200 on the front diff (primary) and 180 on the rear diff (secondary), also just warm to the touch.

this is not as good as the chart that will has, but it is still useful.
http://web.archive.org/web/20050304080821/http://www.transmissioncenter.net/FluidChart.jpg

[Wicked_Sludge]

i run full synthetic in all my gearboxes and have never had any of them too hot to touch (even towing almost 3,000lbs through eastern WA.)

[ZSK]

Did my first real good test. Running empty I had 165°F Trans and 195°F Water temp. Towing my 6x12 at 65mph (3100 RPM in drive) I had 195°F Trans and 210°F Water temp. Are these numbers pretty normal or do I still have some work to do?

Temps are measured on Autometer electric gauges.

[samsonitesamsonite]

get that tranny temp down. that 165 is PERFECT. so a cooler wouldn't hurt. I run coolers on all my trucks and suvs.

[BDAB]

yep, get the temp down. 195 is way too hot. I don't care for synthetic oils but I just bought a 4L80e from Raptor Transmissions and he recomemded raptor blood for it. If he is recomending raptor blood Knowing he has to warranty my transmission then I think i will believe his claims....... it has more friction modifiers in it to reduce slipping, has heat conducting capabilities to help the trans run cooler, and because it is synthetic it resists heat better. Normally I would not believe the claims but like I said, he made the claims knowing he has to warranty my transmission.

[jtfoxman]

Swap the original cooler for a larger one or stick a fan on it. That should do the trick.

[Wicked_Sludge]

replacing the stock cooler with an aftermarket unit is a huge downgrade. if you want to add another cooler, then ADD one...dont bypass the stocker as its much more effective then aftermarket air cooled ones.

[Will]

yep, get the temp down. 195 is way too hot. I don't care for synthetic oils but I just bought a 4L80e from Raptor Transmissions and he recomemded raptor blood for it. If he is recomending raptor blood Knowing he has to warranty my transmission then I think i will believe his claims....... it has more friction modifiers in it to reduce slipping, has heat conducting capabilities to help the trans run cooler, and because it is synthetic it resists heat better. Normally I would not believe the claims but like I said, he made the claims knowing he has to warranty my transmission.

I'm under the impression that friction modifiers lubricate only light clutch contact and then are sloughed off during heavy contact. They won't prevent slipping but would smooth out clutch engagement under low throttle shifts.

On my Gear Vendors they specify some weird low pressure fluid without anti-foaming agents only offered by GM, or a synthetic fluid. I called and asked what the difference is in operation (both satisfy the warranty) and they said the synthetic they tested and specify is smoother when it engages. They had no conclusion on any other benefits. It has a planetary setup with a pump and a cone clutch so it sees a lot of the same beating that auto tranny fluid sees. Since it isn't actively cooled you have to change the fluid 20x more often than auto tranny fluid.

[Black_Splash]

could not tell you why tranny fluid needs to be around 165*, just that is starts breaking down around 200*

I can run my Suburban all day pulling 8000 pounds and my rear diff is warm to the touch. I don't know if that is normal, but I do know semi-synthetic and full synthetic run hotter than dino oil in a rear end. I avoid synthetic in my big trucks and my diffs run around 200 on the front diff (primary) and 180 on the rear diff (secondary), also just warm to the touch.

this is not as good as the chart that will has, but it is still useful.
http://web.archive.org/web/20050304080821/http://www.transmissioncenter.net/FluidChart.jpg

At one of the shops I go they had a brochure that said for every 10* cooler your transmission is you double the life of ypur transmission.

[BDAB]

hey will ...... solved the transmission problem in Satan's Motorhome......... the dip stick tube came loose, the bolt that holds it on has a chain on it and the bolt was banging against the bell housing. gonna drive it today to verify that that was actually the problem.

[ZSK]

I took your advice and installed a second cooler this past week. Man, that stock cooler is tiny. Fluid flow is now out from the radiator into stock cooler, out stock cooler into second cooler, then back to the trans. While towing temperature was at a steady 165°F cruising down the highway/e-way and only rose to about 175°F around town in stop and go traffic. Empty I'm running about 145-155°F consistantly.:icon_thumby:

[Wicked_Sludge]

sounds good :beer: