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bsun
08-15-2005, 03:07 PM
Newly BMWs have lifetime transmission and differential fluids that do not need to be changed during the lifetime of the BMW. Dealers even warn you that changing it may do more harm than good.

Now many BMW owners do not believe this and continue to maintain their bimmers according to the older BMW maintenance schedule. Even bimmer magazine recommends that those fluids be changed because they see transmission or differential probblems on 100K and above cars.

My question to these claims is: how do you know the failures are caused by not changing fluids?

Some contend that BMW do this becaure they do not care about maintenance. they are in teh business of selling cars, implying that BMW want your car to break down at about 100K so you can buy new cars from them again. My question again is this: do you think BMW will risk their reputation to intentionally let BMW cars to fail pre-maturely by not changing fluids? If this is so, why do they not recommend lifetime engine oil?

I think before BMW makes this recommendations, they must have done an extensive research which the recommendations are base on.

Lifetime means lifetime, meaning as long as you still drive you car, not changing transmission/differential fluids will not be the reason when those parts do fail.

Nick325xiT 5spd
08-15-2005, 03:48 PM
Lifetime is supposed to be 100,000 miles. And, well, I disagree.

bren
08-15-2005, 05:20 PM
Good luck with that.

SMOODY
08-16-2005, 07:29 AM
I am not sure that I buy into the idea that the fluids should not be changed. I have also had a technican tell me that the transmission fluid should not be changed.

When I changed the rear differential fluid on my 330i, which has a little over 40,000 miles, it came out dirty. I am not a mechanical engineer, but I can't believe that keeping dirty fluid in a system is better than replacing it with clean fluid.

bsun
08-16-2005, 11:23 AM
The following is a post from Jim Cash on Roadfly:
Subject: Transmission Fluid - to change or NOT. (304 views) (568 thread views)

Message: Just when you thought this one had died down for a while someone raises it again - here goes.

Like many of you I have wondered/worried a bit about this "life time fill - no change" issue.

There are some experiences, and lots of opinions being expressed. When faced with that I usually try to go back to industry sources, give them what I am hearing and see what they say.


In this case I conferred/conversed with:
- My service manager (although experience limited to what he sees I value his honest input)
- The BMW Canada senior technical engineer (liason to Germany)
- An engineer at ZF who was involved with the development of the lifetime fill fluids.

To keep this simple the following is a point summary of input/advice.

- Service Manager was originally willing to change my fluid when I asked several years ago, but now he "highly recommends that I NOT do it". They have done it on a couple of 7's (with lifetime fluid units) and have encountered some evidence of slippage. They have had no known failures of lifetime fill transmissions that they could attribute to a deterioration in the fluid.

- I also discussed this with the BMW engineer some time ago, and he had similar advice that I got from my Service Manger - basically that it was up to me but he recommended against it because they had no eveidence to say that leaving the fluid was causing any problems.
Now I had been sending some of the info I was finding on the varios message boards to my Service Manager (for interest) and apparently he was forwarding them to the BMW engineer. Two weeks ago the BMW guy called my Service manager and said to "Tell Jim not to change his fluid" - the current experience is that they are seeing more problems in transmissions that have had fluids changed than those that have been left alone.


- Regarding the ZF engineer I sent him an email summarizing many of the comments and questions that I have seen on the message boards, and asked his opinion.
Following is his reply.

1.) The life time fluid was introduced in 1995 to save costs for the customers and to reduce environmental pollution. The fluids are tested and released for a lifetime which is specified by the car manufacturer. A change of the fluid within that span is not necessary.

2.) If you intend to change the fluid even though (I believe it is not necessary), it is a must to use only the fluids which are specified on the labels placed on the bottom of the transmission oil sump. Please note that these fluids have BMW part numbers and are available at BMW service only (For the 5HP30 there are two different fluids in service, the appropriate one depends on the MY of the car, please refer to the labels).
Please note that fluids acc. to Dexron III spec, which are in current use for other transmission manufacturers, are not specified for lifetime fill in ZF automatic transmissions. A use of non specified fluids will cause unexpected transmission behavior as described in your mail or a complete transmission damage.
Also please note that a single oil change does not replace the whole amount of oil within the transmission, it will be necessary to drain and refill approximately 3 times to completely change the oil.

--
I then asked specifically if changing the fluid could, in itself, cause any transmission damage.

Response.
Jim,
it's correct, you cannot make your transmission worse by changing the fluid as long as the specified proper fluid is used and the refill is carried out correct (especially the procedure to adjust the oil level - this is critical and can really only be performed accurately with the car connected to the diagnostic system).
But there is no relation between the number of drainings and refillings and the statement above. It was an additional hint that a **complete** change can be achieved only by draining and refilling at least 3 times.

-----

Soooooo

Based on all the above my conclusions are:

- don't bother changing (I am not going to)

- but if you do, you have to get ALL the fluid changed (draining and refilling 3 times can be real expensive with that fluid)

- you have to get the level correct - and that is done with the car running and with the transmission fluid at a specific temperature (as read by the system)


Yes, more questions come to mind, especially about the methods or total replacement of the fluid. While some places use special tools to get additional fluid out, all the input I have from the dealer, and ZF say that, without taking the transmission off the car, you can not get the old fluid out of the converter without repetitive drainings and refils.


Summary

Both BMW and ZF are saying the transmission fluid should last the lifetime of the car. And they are recommending against changing it.

And ZF is saying that if you do change it for any reason - you had better do it correctly.

So the real question is "what is the expected life time of the car"?

I have not asked BMW that one, and I am not about to since I suspect the issue is too complicated (depends on a whole bunch of issues - many of which are beyond BMW's control) to get a meaningful answer.

So for what it's worth - that is the information I have pulled together. I am not changing my fluid but you can bet that if my unit ever goes south I will have it analysed - and out will come some of this documentation as part of the negotiations on pricing of the fixit bill.

Cheers
Jim Cash

bsun
08-16-2005, 04:04 PM
I guess I do not mind changing the fluids myself. Only worry is I might do more harm than good.

Nick325xiT 5spd
08-16-2005, 04:12 PM
All of that is for automatic transmissions.

bsun
08-17-2005, 03:27 PM
If it does not apply to manual trans, how come that BMW not recommend that manual trans be flushed on a regular intervals?
My point is, is BMW trust worthy? Is BMW intentionally wanted our trans to be failed?
When they do such recommendations, do they have scientific researches to back them up?
I am really confused.