Well in that case. Your IGNORANCE is a sign of your AGE.
Does NOT make a damn just how much motor you have, evidently you don't understand Automatic Transmission's. So here's a free lesson for you.
Automatic Transmissions 101:
1. 9/10 Transmissions fail due to heat. That is NOT an estimate nor is it my opinion, It is a PROVEN FACT!!!!!!!
Transmission Temperature is effected by 3 major variables. Care to guess which one your transmission is going to fail from?????
1. Fluid Condition
2. Cooling capabilities
3. Transmission slip %
Transmission fluid breaks down over time for a few different reasons, such as Poor Maintenance, Improper cooling capabilities (HEAT). As the fluid Breaks down it looses its lubricating properties, which in turn WILL cause excessive slip (HEAT).
Transmission Coolers are only half the battle to having a long lived Transmission. As fluid breaks down and passes through the cooler, it leaves behind tiny particles inside the cooler. These tiny particles will reduce the cooling efficiency of the cooler, in Return this WILL cause Transmission Temperatures to increase.
Transmission Slip %, is the other half of the battle for a long lived Transmission. The secret to the Right amount of Slip is NOT in how much power your engine has, actually it is the exact opposite. The way to Lower the Transmission slip percentage is, FINAL DRIVE RATIO. Higher gear ratio's cause EXSESIVE SLIP (HEAT). The same is true for wider tires.
MIGHT I SUGGEST THE NEXT TIME YOU MAKE A THREAD ASKING FOR HELP TO FORGET EVERYTHING YOU THINK YOU KNOW. AND LISTEN TO WHAT OTHERS ARE TRYING TO TEACH YOU, OTHERWISE WHEN YOU NEED HELP THE NEXT TIME PEOPLE WILL REMEMBER JUST WHAT KIND OF A DICK YOU WERE THE LAST TIME AND WILL NOT EVEN CARE TO ENTERTAIN YOUR PROBLEM!!!!!!!!!!!!
I'll agree with with all that but 1 thing, and it's the same with motor oil. Oil Companies use these terms, "Break Down" to claim their oil has better properties than their competitors, and to make recommendations on EARLY change intervals so you will spend more of your money to buy new oils and fluids. Just like Motor Oil, ATF DOES NOT "Break Down". What it does do is become diluted and contaminated. By diluted, this can be from water caused by condensation in the crankcase or the transmission pan. Keeping your fluid levels to proper leverls helps in condensation since that leave less space in the pans to be able to condensate, and even then the risk is very small except in extreme cold weather where the after the motor or trans oils are very hot or warn, the pans thin metal that is not covered with oil inside cools rapidly creating sweat inside the pan. Contamination comes from bearing wear and combustion in a motor that is able to sneak past the rings and get into the crankcase, so a new motor with good rings is obviously to contaminate much less than a motor with very well worn rings. IN A TRANSMISSION, what contaminates the fluid is thrust washer and bushing wear of extremely fine particles that are caught easily in dacron or screen filters AND WORN CLUTCH material that become sludge and mud caused from CLUTCH SLIPPAGE which generates even more heat, then more slippage, then more heat and so on. Consider Clutch slippage as a snowball affect. Once it starts, the damage is being done, the fluid is becoming contaminated, and the life span of the transmission is decreasing rapidly. Contaminated fluid also retains heat longer because it loses it's heat discipation capability. Point is, Oils and Fluids DO NOT "Break Down". There is a Cause and Effect. Prevent the Cause, you don't have the affect. In this case, keep the trans from getting to hot, and clutches from slipping which is CAUSED by things like taller gears, bigger tires, more wind resistance and heavier weight that a full size truck has over a passenger car, and you won't get the EFFECT which leads to a short lived transmission.
In a perfect scenario you would NEVER have to change your fluids because they NEVER "Break Down". But, you can't get around dilution and contamination. You can however limit dilution and contamination and with good quality filtration keep most of the contaminants out of your fluids for a very long life. Keeping your fluids clean, also drastically slows down the wear process and that in itself also helps keeps your fluids clean. Once you allow the fluids to become over diluted now the process again works like the snowball effect.
Keep a trans from slipping clutches and getting hot, it will last forever up until the point of thrust washer and bushing wear come to a point where shafts go catty whompus, or drums start tipping and riding center on shafts due to bushing wear and then a catastrophic failure happens eventually. Do you know how long that would take? Put it this way, many builders don't even replace most bushings or thrust washers when they do a rebuild. You're lucky if they'll replace Common Wear Bushings. Point is, even our clutches and seals can last a very very long time. But, it's not going to happen in a full size truck with 3.08 rear gears, not even in a 2013 year model, not even with a big trans cooler, and not even if you don't tow.
Chances are though, tha 3.08's will serve your purpose so long as you're not carrying heavy loads and towing and you're probably OK with it's transmission life expectancy too. In a real world guesstimation, with 3.08's and no towing you can expect about 80,000-100,000 mile life from a Turbo 350 in a full size truck so long as you're not abusing it. Where as if you had the 4.10's you could probably expect 150,000-200,000 miles depending on how often you DID carry and tow loads, because you CAN carry and tow loads and do minimal wear. If you didn't carry or tow loads with 4.10's, and the transmission never sat for long periods of time allowing seals to get hard, you could probably expect 250,000-300,000 miles out of it.
In your case though, I get it. You had the 3.08's axles at hand for no charge, so you've sacrificed gear ratio for fuel mileage, and also have intent to do an OD trans swap and back to the low gears, so it's really no big deal so long as the trans lasts until you get to your point of your swap, and the 3.08's are a temporary thing. Not everyone knows that because I'm sure they didn't read the entire thread and they don't visit daily, but fact is, they are giving accurate sound advice. Just not for your temporary situation.
, and my engine helps compensate with power(10:1 flat tops, mild cam, etc.....) Honestly, my truck is like "oh look, a set of gears, no problem" .
