OK I did transmission fluid flush on my 02 4.4i

[e30cabrio]

03 4.4?

[740ilDuke]

I havent been under one later than my own as far as looking at the T-Case. I think at that point it was still the 5HP24 5 speed so it should have a plug to drain down low and a plug to fill up top.

[JCL]

Originally Posted by Hoser

There are not many companies around that know more about automatic transmissions than Allison. They had to come up with new oil formulations when GM dropped certification of Dexron. When that happened everyone was open to put burro pee in a can and call it dexron. The engineer who wrote the specs on Allison's replacement synthetic Syntec when retired, joined an RV forum about Allison. They were forced to re-adjust their thinking about lifespan of trans fluid-even with their new super juice. To those who "know" someone who changed their fluid/fliter in their automatic and ended up blowing up their trans- I think I would challenge them to name names. It only stands to reason that removing any of the dirt and byproducts of a piece of machinery with friction surfaces and replaceing the lubricant with fresh new lubricant, can only do good for the same reason it does in an engine. I doubt that any machine manufacturer has their own oil well, oil research section, testing labs, health & safety standards approval section (this stuff is in human contact). I think it is safe to say BMW and others use rebadged cans of lubricants and chemicals. The fact that Ford uses the same ZF6HP26 tranny in a Lincoln Navigator and specs Motorcraft Mercon SP fluid at $8/liter should be a little enlightening to those who are receptive.

TwinTurbo made a good point, above, but I don't want to let your points go unchallenged.

I can point at specific transmissions whereby the fluid was changed, and the new fluid (or more specifically, the detergents in the new fluid) caused a failure in a transmission that was up to then, performing well. These were customer transmissions. They weren't BMWs (but then, BMWs don't have BMW auto transmissions). You can't have their names. You don't have to believe me if you don't want to, but these are not old wive's tales or urban myths. It certainly doesn't mean that changing the fluid at higher mileage will always cause a problem, it simply doesn't. But statistically, it does cause a problem often enough to make shops stop and think about whether they want to take the risk. Many won't, as they don't like being on the hook for a transmission rebuild after they specifically recommended not changing the fluid (same as the vehicle manufacturer), but did it at the customer's insistence. It is more profitable for them to pass on the revenue from the fluid change, and avoid the risk of the occasional rebuild on their dime.

I don't understand your Allison reference. Great company, no worries there. But they were owned by GM Powertrain from the 1920's to sometime in the early 2000's. So, Allison is GM. And GM endorsed BMW's maintenance strategy. So I don't think that their heavy truck experience, as applied to RV's, has any weight here.

The other issue with RVs is that they are famous for being heavier than they should be according to the GVW sticker, and having more aerodynamic drag. Both stress transmissions. I can understand changing the transmission fluid in a vehicle that is regularly overloaded, as many RVs are. It would make sense, as it would shift the risk/reward balance.

You mention dirt and byproducts in a transmission. Fair comment. But a transmission fluid has very low demands for lubrication. That is why it isn't called transmission oil. It is a hydraulic fluid, first and foremost. It is a heat conductor, very important. And it can't foam or oxidize. But the lubrication demands that it is subject to are so low that auto trans fluid is typically a straight 10w oil. It is running in a sealed system, with pressurized lubrication, with no external contaminants (things like byproducts of combustion, water, etc). So, it lasts a long time as long as it doesn't get burnt. Thermal management is very important (back to the RV issues....).

BMW doesn't design or build auto transmissions, or the fluid that goes in them. ZF and GM do a good job of both (and both have their fluids built to their own specs). What BMW does do is alter the control strategies, and the transmission cooling system. Those are BMW items, not ZF or GM (although they are done in cooperation). Items like the BMW cooling system, with the thermostat (keeps it cool, even towing 7700 lbs in Europe, and provides warm fluid sooner on startup to reduce cold wear), and the strategy of backing off the power via the ECM when shifting (reducing clutch wear, and heat, significantly) both extend the life of the transmission fluid. Even more important, the lock up torque converter strategy (much reduced heat when locked up) helps a lot. Not sure what the Lincoln has in this respect, but to say that it is the same transmission is incomplete.

I wouldn't use the Mercon fluid in a BMW, but that is simply because while it is similar, it isn't necessarily the same. ZF went to specific fluids due to their transmission design, primarily relating to clutch engagement characteristics. That is all that is different about the different fluids, at the end of the day. Unless ZF or GM want to publish their friction specs, it is a mugs game to say that the fluid is the same because some parts of the transmission are the same.

Your subsequent post asked about pumping out the transmission via the return line from the cooler. This can certainly be done. It gets more of the old fluid out. If I had a transmission with burnt fluid in an RV (common occurence, for reasons listed above) I would do this. But I wouldn't do it on a modern BMW, unless the fluid was burnt. Take a look at the BMW service procedure. If a tech has to drain the fluid to change a simple item like a temperature sensor, speed sensor, or whatever, inside the transmission, the approved service procedure says to catch the old fluid and put it back in. Think about that. It's a lot of trouble. It would be easier to put new in (and thus cheaper, when you are paying labour by the hour). But they want to keep the old fluid in, because it is better for the transmission than new fluid. There is a paradigm shifter for you.

Always happy to talk transmissions. And I even know where Stettler is (ex Edmonton, and Grande Prairie).

Cheers

Jeff

[upallnight]

If you do a Google search you will find that Allison transmission warn their customers not to use Dexron VI in their trans. Even though the manufacturer of Dexron VI said that their fluid was backward compatible. Customers who changed to Dexron VI started having trans failure with the new fluid. It turn out that some of the rubbers seal used in the trans was not compatible with the new fluid.

Allison trans are not just used in trucks and RVs. Some Corvettes also uses Allison trans.

[JCL]

Originally Posted by upallnight

Allison trans are not just used in trucks and RVs. Some Corvettes also uses Allison trans.

Interesting, I didn't know that. All my Allision experience was with heavy trucks and industrial equipment.

I looked up Allison and the lightest current transmission (model 1000) is rated for 6 ton and up vehicles. I thought the new Corvette was getting lighter? Was it an older Corvette?

[e30cabrio]

Who is the real oe on the filters? I see several saying they are.

[e30cabrio]

REALOEM from my vin says I have AUTOMATIC TRANSMISS. GA6HP26Z - 4-WHEEL

The vin decode says:
Production FROM : 1998/10/01 TO : 2003/09/30
Engine M62
Engine Oil 8.00 Liter
Transmission Automatic
Transmission Model A5S 440Z
Transmission Oil 9.70 Liter
Rear Axle Oil 1.00 Liter
Coolant(w/o Air Conditioner) 0.00 Liter
Coolant(with Air Conditioner) 12.50 Liter
Brake fluid 1.00 Liter
Remarks : 
Transfer box (0,46 l), final drive (front axel) (0,7 l)

Which freaking trans do I have?

[e30cabrio]

Never mind. Somehow it jumped from 12/2002 to 12/2003. I knew I had the 5 speed.

Sorry & thanks

[sunny5280]

Originally Posted by TwinTurboGTR

Good morning. The last time anyone posted on this thread was Dec. of last year. While your information is concise and well written, the topic has been beaten to death. There is a consensus from other members and former techs on this forum that support you don't touch the tranny if it has hit 100k and has never been cracked open before. Using the old adage of "if it ain't broke..." The exception would be if the tranny is experiencing problems, then change fluid. You may be looking at an overhaul of the tranny anyway, so as a last ditch effort to squeeze the last bit of life out, you could drop the pan and change the oil and filter, but end result normally is the same.

Consensus doesn't prove anything. I'm in the camp of changing the transmission fluid. I had it changed in my 2001 4.4i with 108K miles (right after I purchased the vehicle) and drove it to 129K miles before buying my current X5. Never had a hint of problem with it.

I had it serviced at an indy who specializes in German vehicles and the owner hsa over 25 years working as a mechanic and service manager for BMW / Mercedes before opening his own shop. It has been his experience changing the transmission fluid does not result in increased failure rates. To date I have seen no supporting facts showing an increase in faliure rates for transmissions where the fluid was changed after high mileage. Until such time I'm chalking this up to a wives tale.

[Vonbimmer]

I have been watching the outcomes of transmission fluid changes here since 06' and JCL is right on target. The post change failure rate is just high enough to make the process too risksy to be worth pursuing. Add to that, that the dealer won't do it to make a buck and I'm sold on it being a bad idea.