I was thinking that with the amazingly high temps our automatic transmissions run, would it be worth it to go with synthetic fluid? Is there any out there that will meet the requirements for our A/T's and withstand the high heat?

 

I was thinking about synthetic too, Autozone had atf+4 5.39 qt, I think it was vavoline and some cheapo brand name non synthetic 5.39 I was like wtf da lol....the one problem with going synthetic is if you dont drain the torque converter you're only replacing half the fluid, kind of killing the point of switching over.

 

BG Products makes some awesome synthetic trans fluid. It'll probably cost you about $70-85 for the fluid because you're going to want 16 quarts or so and then you need someone to perform a flush on it. Alot of shops have BG equipment to flush your trans. Basically you tap into one of the cooler lines and it flushes the trans using a transfusion type exchange so that you get all of the fluid in the torque converter. Most shops that have BG stuff will have the flushing machine, but not the fluid. We usually use the factory recommended fluid for the line of vehicle. You'll have to ask about the fluid or find a distributor and give them a call. Here's a link. Seriously though, BG makes good stuff. Been using it on customer's cars myself for 8 years
http://www.bgprod.com/home.html

 

The stock fluid is synthetic.

I wouldn't use anything but ATF+4! There were a number of problems in liberty's with the 42RLE when other fluids were used.

 

I had mine flushed and replaced with Amsoil. So far so good! Amsoil A/T fluid comes highly recommended in RV publications and forums for HD A/T's. I ran it in my Allison Trans on my GMC 2500HD. It's great stuff.

 

Another Amsoil user here, although a recent bout with laziness has kept me from changing over the Jeep......I've used Amsoil since the late 80's in everything..

 

The stock trans fluid ATF+4 is a full synthetic made for Chysler by Valvoline. I saw it at WalMart for 4.00 a qt! I thought of changing it out but decided, based upon an extensive Google search, to stay with the stock fluid. Based upon problems when using a non ATF+4 spec fluid.

I think the best thing to do is install a massive trans cooler. It appears that while engines like to be at or above a certain operating temperature for the trans cooler is better.

The below is from "Making an Auto Trans Live":
http://www.high-impact.net/transmiss...makinglive.htm

Making the Automatic Transmission Live
Automatic Transmissions have gotten a bad rap by some. The main causes for automatic transmission failure are excessive heat, and slippage of the internal friction elements. And of course, if your trans suffers catastrophic breakage.

Heat
The worst enemy of an automatic transmission is heat . Run a big enough tranny cooler, do NOT run the tranny fluid through the radiator, and DO use a tranny temp gauge. That simple.

How hot is too HOT?
An automatic tranny is happiest at 190 degrees or less most of the time. They really do not mind getting up as high as 240 on occasion, but you definitely don’t want them there for a long time. A tranny that hits 260 is in imminent danger of having a catastrophic failure and blowing tranny fluid all over the trail, not to mention the rig won’t drive well after that. Also, unlike an engine, it really does the no harm to run them overly cool. Engines get fuel diluting the oil (a little sneaks past the piston rings during compression). If you run the engine warm enough, this fuel evaporates and then gets sucked back into the engine to be burned through the PCV system. Tranny fluid is thinner and works fine at temperatures much lower than it is wise to run your engine at.

Tranny Cooler:
The answer is simple: Use a huge tranny cooler, like an aftermarket unit designed for a 25,000lb towing application. We then prefer to NOT route the tranny fluid through the radiator. The engine is often hotter than the tranny (and when the tranny DOES make heat, like on a long hard climb, it does not add as much of it’s heat to the tranny.

We commonly use B&M PN 70264 as a replacement cooler (mounted in front of the radiator) in 1/2T vehicles, and do not run tranny fluid through the radiator. B&M also makes a couple models of coolers which have their own electric fan. It is thermostatically controlled, and kicks in when the tranny fluid gets over 180 degrees (B&M PN 70297 or 70298). This can be used by locating it where it does not interfere with the airflow to the radiator, it can get a easy flow of cool air through it, and is out of harms way (from rocks, etc). In a towing application, we might be inclined to use BOTH. Bottom line: Your tranny temp gauge will tell you if you have enough cooling or not.

Tranny Temp Gauge
We recommend one highly. Without it you haven’t a clue how hot your tranny is running. It is scary sometimes how hot they can get! If you have an automatic tranny, have a tranny temp gauge. It will certainly help you make your tranny live longer, and could prevent a catastrophic failure.

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This is the trans cooler he was talking about:
http://www.bmracing.com/PRODUCTS/Hi-...2-diameter-fan

This is gross overkill and is rated at 30,000 gvw. I spoke at length to B&M about this and they said it's you can't really over-cool an automatic and the only reason not to use a big cooler was cost. I have one of these sitting on the workbench and need to get around to installing it.

 

+1

I think ATF+4 has some properties that are quite different from traditional transmission fluids. Amsoil is great stuff but if it's compatible with ATF+3 or Dextron it's probably going to be a problem for the 42RLE in the long term. Dextron and ATF+3 are problems for the 42RLE in the short term. There are numerous accounts of quick-lube places using Dextron in Libertys and killing the 42RLE pretty quickly.

 

Amsoil has a new A/T fluid that exceeds ATF+4 standards. Call them, they'll send you test data compared to several other fluids.

I also installed a large A/T cooler.