Gotcha, I for some reason would make this up and state it as my personal experience... why?

If I worked in the transmission industry like other posters above.... I too would SAY you must change it bla bla bla.

Its a sealed system, do you change your power steering fluid? If the manual said to change the summer air for winter air would you do it?

Enjoy.

I�m only guessing you make it up because you don�t know any better. Your obviously wrong. It is not a sealed system, it�s vented and the fluid breaks down over time due to heat cycles and yes contaminants.

I asked the guy that rebuilt my trans a couple years ago when should I change the fluid in it. He said if I got 315,000 miles on my last one towing every weekend and working construction I should probably keep doing what I had been. I've never changed trans fluid in my life and that was the first problem I've ever had out of one.

Straight bs. A vent doesnt make a hydraulic sytem a open system or introduce contaminants. Thats like saying you can catch a cold from a fart going out your azz.

Exactly like I stated in my original post would happen, people who want to make money off others will chime in..

You and 99 percent of the population....

I make no money off of transmission services and have nothing to gain by recommending it. Sure you can get lucky and get high miles without a problem or without servicing one but if you want a reliable high mileage transmission in the big picture it�s going to require service bottom line.

More than 99% of the pop will trade long before they need to service or before the big problems emerge or likely right when the first signs of problems emerge.

Yeah I have 208k on mine, one at work has 953,000. I think they're great too, just wondering from the dude that seems to have lots of experience with transmissions.

I changed my fluid/filter about 10,000 miles ago. The fluid was just clear red, no metal shavings at all anywhere, just a very clean transmission. I still change my spin on filter every oil change.. I put Valvoline Dexron VI synthetic in it, but I think next go around will be Castrol TranSynd. I don't run mine hard at all, but from what everyone tells me, I'm sitting on borrowed time with a 100hp tune.. They're probably right, but I baby my truck. Either way, I'm waiting on it limp it's first time so I can build it. But, that may never happen.. Most folks said I'd limp it within the first few hundred miles of having the tune.. That was 11,000 miles ago.. still the smoothest shifting truck I've ever driven

That one at work with 953k is an '07 LBZ so it has the 6 speed. The motor has had it's typical repairs (alternator, water pumpS, etc..) Most major repair done to it was injectors around 650,000. BUT. That Allison has never, ever been opened up.. Just fluid/filter changes, nothing more. 953,000, all original from the factory, and she still shifts as good as mine. That, my friend, is a Cummins owners DREAM.

My brother owns a welding shop, and his entire fleet of work trucks have been Duramax's ever since the LLY came out in 2004. He's had his issues with motors here and there (mostly electrical and fuel related), but not once in that time frame has he ever had a single problem with the Allison's bolted to them.. I'll say too, they are poorly maintained.. But those Allison's yet to give him a problem.

I don't make money doing services. We have kids that do that. I make money when people don't do services.

For one it is recommended that you change your power steering fluid. This sealed system thing shows you don't know what you're talking about. Only sealed system I know that is service free are bearings. It's not dust or dirt that kills the transmissions but the worn internal parts that contaminate the system and cause sticking in the valve body among other things.

Please Jeff keep doing what you've been doing. My wife wants a new Yukon.

Thanks for your permission to do what I want.

Your poor wife should set her standards higher than a yukon.


A TRANSMISSION is a CLOSED loop system. A VENT or Overflow does not make it a open system. Wow.

I have a so called sealed transmission. Lack of a dipstick is the only reason people call them sealed. Mine has a drain plug, fill plug, and a test plug. I change it every 60k even though draining the pan only removes maybe 25-30%. It is really less trouble than the old drop the pan and change the filter type. Just put back in a little more than you drained, warm it up to operating temp and pull the test plug. I wish they were all like the Escape my daughter had. Pull the drain plug, let it drain, replace plug and fill.

Your brakes, engine, cooling system, hydralic power steering, transmission, front differential, and rear differential are all sealed system. All require maintenance.


or don't do it so my wife can get her a new yukon

Which is it? Sealed or not sealed?

Not sealed they are all vented. When they get hot air and fluid inside expands and pushes air out. When they cool everything contracts pulling outside air, moisture, dust, dirt, whatever is on the vent in. They don't need to be serviced as often as the oil because they are not dealing with blow-by carbon and unburnt fuel from he cylinders etc. but they do have a finite life span.

Im not big on servicing the differentials but its probably not a bad idea, the transmission is different. Diferential have gears and bearings and that's about it, transmissions have extensive valve bodies clutch packs seals etc and degraded fluid will affect their function.