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Question for Transman - GM 4T45E

Picked up a 2010 Cobalt LS last week. I was wondering what a reasonable interval would be for a trans filter/fluid change (not flush)? I’ve read Dexron VI has a much longer life than Dexron III but I’m not comfortable with a 150k interval.

Driving conditions are semi-rural, 40-50 mph with the occasional stop sign or traffic light. I’m a fairly calm driver, that may change when my daughter gets her license though.

Pan and filter every 30k is the standard answer from most corners.

Interesting post. Our 08 GM car’s owner’s manual (V-6 engine) specifies that auto trans fluid is to be changed at 100K miles unless severe service. Possibly GM has learned more since 08 about their new trans fluid in use or else there are differences in recent GM transmissions that indicate a difference.

It is my observation that people who are aware of car use and maintenance, including myself, are often slow to realize or admit to changing reality that does not match up with their experience or preconceived notions. Trans fluid change at 30k miles may have been good and needed in the past. If if still applies with GM cars, then GM is in for trouble if it ever becomes apparent that they made a terrible error in recommending 100k or 150k mile trans fluid changes. I can’t believe that after all they have gone through that GM will let this happen. I feel confident that they have talked it over among their engineers and marketing people with management in the loop.

most guys on here know better than GM.

GM is in the business of selling cars. They will give you a 3/36 and sometimes even a 100k powertrain warranty. After that, its all on you. Every transmission tech I know would recommend 25-30k mile fluid/filter changes as I do. Its cheap insurance so why not??? Owners manuals, especially service intervals in the owners manual make great bathroom reading and come in real handy when the paper is out (Ouch)… Like Cigroller said and what I always recommend, 25-30k pan drop fluid/filter changes regardless of what the owners manual says. I can guarantee you that after 27 years with my face inside automatics building them and experimenting with them, 25-30k is very reasonable. I sure wont complain though, its those who improperly or inadequately service their trannys that keep my shop doors open. Come on, daddy needs a new dyno…LOL…


My knowledge of automatics is very skimpy when compared to Transman (mostly Subaru) as most of my transmission work has been with manuals.
However, Transman is dead-on with the 25-30k mile intervals and the way it was explained to me many years ago at as service school is that the fluid does not necessarily go bad; it’s the additives in the fluid that break down.

A lifelong friend of mine is 57 years old and started working part time in the transmission shop (which he now owns) with his dad. Needless to say, he knows automatics inside and out while blindfolded.
He also says that the vast majority of transmission problems that come through his door have a root cause of running low on fluid due to a leak, etc. or as per the usual; never changing the fluid.
He’s also in agreement that if fluid changes are not performed regularly, then fine with him. The kids have always needed new shoes.

Thanks for all the replies. The trans is not easily serviceable (no dipstick), but I’ll let my mechanic worry about that.

I’ll go with the 30k pan drop and filter. After the trans on my 95 Dakota started acting up at 66k miles, I got into the habit of changing the fluid/filter every 35-40k miles on my vehicles. Other than shortening the interval to 30k, I’ll do the same for the Cobalt.


Ed B.

edb1961, Here is a site that says good things about Dexron VI.

If you Google “Dexron VI improvements” you can find plenty more that is positive about Dexron VI. Possibly the car repair community does not have enough experience with transmissions using Dexron VI to say that nothing has changed regarding trans fluid change intervals.

I was thinking too about changing the trans fluid at 30k miles but now am reconsidering, might let it go to 50K.

Guess that settles that. We all know a marketing director is the final authority on all things mechanical.

No, only a start of a good guess. Marketing director, engineering people and management. I have some experience with living in a corporate environment and know very well that such decisions are not made without input from everyone who stands to lose if such a decision turns out wrong. Otherwise, such a decision, if made independently by marketing without consulting with engineering is playing with corporate suicide. It’s easy to see that GM can not afford to mess this up.

Unfortunately, the line mechanics out there are the ones who have to face irate customers due to management/engineering/marketing decisions and line mechanics are often the ones who sort out the problems. Many a TSB has been issued due to input from mechanics; leaving the impression of course that the “factory boys” figured it out.
Matter of fact, very very few factory service reps (the go-betweens from regional) could even make it as a mechanic.

Just a few weeks back I was telling my wife of an idea I had for a prime time TV show. At 9:30 on Friday evenings bring on an automotive engineer and let him get grilled by mechanics on why he did this or that. An illogical answer means a televised tail whipping, and my feeling is there would be a lot of bruised up engineers.

Mechanics see things all of the time that leaves them wondering what in the world were the slide rule boys thinking of when anyone with even a lick of common sense could see the design was an accident waiting to happen.
(Early Subaru plastic govenor drive gear in the auto transmissions are a case in point. A building full of engineers and not one of them raised their hand and wondered aloud how long a plastic drive gear was going to last under fluid pressure. It only took Subaru 4 years to figure this out and when they did they simply reversed the procedure; the drive gear became steel and the driven gear plastic. They simply stripped out in reverse of what had happened earlier. The latter was an easy fix; the former required a complete diassembly of the transmission, which went over pretty well with car owners. Many of those car owners said the same thing; what the hxxx were they thinking of?)

You are so right. I STILL scratch my head at some of the things I see. PLASTIC accumulator pistons… THEN comes the TSB to watch out for cracked plastic accumulator pistons. Just what do you think PLASTIC is going to do?? Heres a good one, Chevy Equinox. 2 identical plugs on the side of the transmission. One of them is used to fill the trans with ATF, the other anchors the 2nd gear band. Remove the wrong one and you’ll spring the band. There is NO OTHER way to reset the band other than removal and disassembly of the trans. Now if THAT doesnt kick some fast lube joints in the can after paying for a couple of those, I dont know what will. I have seen a few of those already. Quick $$ for the R&R guy as well as myself. Gotta love this business sometimes.