Thoughts on why bmw slushboxes fail?

[supark]

I'm thinking about getting a 4.6is X5 which as you probably know only comes in slushbox flavor. As the 540i I believe shares the trans (or at least one that is very similar), thought I'd see what you guys think will increase the life of a automatic. I've noticed that it doesn't seem to matter if it's a ZF or a getrag, they often require replacement around 100k miles.

In my experience, heat is the primary killer of slushboxes - either due to pushing them too hard or some sort of internal design fault that decreases lubrication/cooling efficiency. I know that something a lot of people use on work trucks and vans is install a secondary transmission cooler - which definitely helps when hauling large loads which invariably creates more heat. That combined with auxiliary transmission fluid filters and/or regular transmission fluid changes every 30k miles or so can yield a couple hundred thousand miles out of a getrag slushbox.

Thoughts/experiences? And please no bullsh!t arguments in this thread about the efficacy of transmission fluid changes. It's a non-starter discussion for the purpose of this thread.

[02Pilot]

A few factors to consider:

- Modern transmissions, like every other component, are being reduced in size and weight. In the case of transmissions, they are also being required to handle larger amounts of torque as engines become more powerful (to move increasingly heavy cars). Smaller internals, smaller overall volume for lubricant, and increased demand are not going to help the longevity of transmissions.

- Obviously, heat buildup is increasingly problematic as well. Larger transmission coolers offer potential benefits, but lowered frontal area and tighter packaging in the front of the engine bay make such a solution difficult in some applications, not to mention the increased cost.

- Transmission oils suffer from considerably higher shearing loads than engine oils. While designed to handle these loads for a time, the combination of constant shearing and high heat inevitably cause oils to slowly lose their ability to function properly, eventually causing transmission components to be damaged by normal operation due to lack of proper lubrication. Reducing either factor (by use of larger mating surfaces on the gears or additional cooling) or increasing the quantity of lubricant all mitigate this, but for the aforementioned reasons, these are not likely to be done by the factory.

- Of the potential solutions, only adding a cooler is within the realm of possibility for the owner. Increased volume plus additional cooling certainly offer some improvement in the conditions under which the transmission operates. Nonetheless, the fluid will eventually break down, with all the attendant problems this creates. If the owner intends to keep the car for a long period of time, a transmission cooler, preferably a thermostatically-controlled one, is certainly a sound investment.

[supark]

^ EXACTLY the kind of discussion I was looking for - thanks for your insight! Tons of great tranny coolers out there too - from pretty stripped down ones to fancy ones with coolant fans built into them: http://www.bmracing.com/PRODUCTS/Hi-Tek-Automatic-Transmission-Cooling-System

[Jackcat559]

They seem to rated for alomost the exact power of the engine with no buffer. It would be nice if they built to take more load, and only used to say 70-80% of capacitity. Lack of fluid changes on these 'lifetime fill' trannies is not helping either.

[02Pilot]

Unless you want to go to the trouble of figuring out the precise thermal requirements, just get a moderately sized cooler that will be relatively simple to install and a thermostatic control valve. There is no reason you will need a large cooler in this application, nor is there any requirement for a separate fan unless you are mounting the cooler somewhere where there is little or no cool airflow when the car is in motion. The thermostat is necessary for street use; too cool is just as bad as too hot, though with different specific consequences.

[dinan e39]

i didn't realize getrag made auto's??? learn something new every day.

supark,

don't forget that the X5 is considerably heavier than the sedan which will prematurely wear the tranny. in addition, i don't know if all wheel drive puts more stress on every shift but something to consider. my wi

[Jason5driver]

Great discussion!
If I had a preference, I would choose the Getrag transmission.
However, I thought Supark was looking for a Mini Cooper S 6-speed manual???

Why the large SUV?
If you are looking at SUV's, why not a Lexus, or an Infiniti that will be much more reliable?

Plus, in order to promote long life of an automatic transmission, the fluids should be changed regularly.
Not per BMW's maintenance schedule, which is a joke.

[kbsilver]

My understanding is most modern BMW auto trans fail due to a design issue or not changing the fluid. For both the E46 and E39, loss of reverse is the most common failure. While different transmissions and different manufacturers are used, the each lose reverse due to part failure, although the part that fails is different between the GM or ZF units. In one case the reverse drum cracks. Once the weak part is replaced with an newer design replacement, then they last as long as any other trans.

If your towing, get a cooler. Not towing, then believe BMW designs with more than adequate cooling. Just change the fluid at least every 50K miles.

[ME264]

Modern transmissions are exceedingly complex. This complexity is driven by the desire to squeeze an extra 1-2 mpg out. Thus extra gears, lockup plates and the like are put in along with a computer or two to manage it all. It's a great reason to avoid them if you buy 2nd or 3rd hand cars...

I wouldn't be surprised if the life expectancy hasn't dropped 30-50% since the 1960s (when every other part has increased in life expectancy). I know that when GM switched to a 5 speed in the corvette in 1989 (for mileage reasons) it went from a 100K wear item to a 50K wear item.

[OJwerks]

ive decided that when my auto tranny fails.... ill most likely do a 6 speed swap

[bimmerE36freak]

dont do it sung!

[02Pilot]

A quick check of the parts database shows that E39s, along with E34s, have transmission oil coolers from the factory. I have no idea exactly where these are located, nor how big they are, as my cars are all manuals and the diagrams are rather generic. On the E60 it appears that BMW has gone to an oil-to-water heat exchanger arrangement. Again, this is based solely on the parts listings and diagrams. I would be curious to see just how these coolers are placed - given the rather dubious design of the air-cooled alternator ducting on the I6 cars (prone to blockage by debris), I wonder if airflow to transmission coolers is an issue; if it is ducted from the lower grill area, it certainly could be. Worth a look for those of you with automatics.

[DuffmanE39]

My transmission cooler is right next to the power steering oil cooler...

[gtxragtop]

In the 60's you were lucky to get 60K miles out of a automatic transmission. Rebuilds between 40-60K were common. Engines were good for about 100K and then needed a complete rebuild. How many of you would put up with that. Now go back to the 40s and 50s. Ring jobs and valve jobs were the norm every 15-20K. So the good old days really were not all that good.


Modern transmissions are exceedingly complex. This complexity is driven by the desire to squeeze an extra 1-2 mpg out. Thus extra gears, lockup plates and the like are put in along with a computer or two to manage it all. It's a great reason to avoid them if you buy 2nd or 3rd hand cars...

I wouldn't be surprised if the life expectancy hasn't dropped 30-50% since the 1960s (when every other part has increased in life expectancy). I know that when GM switched to a 5 speed in the corvette in 1989 (for mileage reasons) it went from a 100K wear item to a 50K wear item.

[Wolfen]

The trannies are actually quite good. But they like any mechanical component need to have their oil changed. Every 30K is prudent IMO. Also a good quality synthetic lubricant should be used.

Basically do to your tranny everything you do to your engine to make it last, just less frequently.

Too often the tranny is a out of sight out of mind piece of eqp that never gets any love. Then we wonder why the finally failed. It's almost comical.

When i bought my 540 the first thing i did was change the tranny fluid. Then over the course of bout 10K miles i changed it 1 more time. Logic dictates that the failures, barring defects, are all happening due to the fluid, much like engine oil, just wearing out. The tranny uses the fluid to move and transfer power AND for lubriation and cooling. So i agree that the shearing forces will be tremendous.

[ViBren]

What OP needs to answer his question is search out empircal information on desired model and model years by transmission type.

FWIW doing forum searches, autobox failure can happen at 200k and it can happen at 30k. There is no fixed and it doesn't necessarily have to do with driving style.

What I do have from a reliable mechanic who works on nothing but BMW autoboxes, he says something along the lines of: if you have been replacing transmission fluid every 30k, this is excellent. But if you start doing it to a high mileage car, you are asking for trouble.


FS : 4.10 final drive ratio unit, for E39 525i, later 528i, 530i

[supark]

Great discussion!
If I had a preference, I would choose the Getrag transmission.
However, I thought Supark was looking for a Mini Cooper S 6-speed manual???

Why the large SUV?
If you are looking at SUV's, why not a Lexus, or an Infiniti that will be much more reliable?

Plus, in order to promote long life of an automatic transmission, the fluids should be changed regularly.
Not per BMW's maintenance schedule, which is a joke.

haha yeah I change what car I want every couple months. I'd been thinking about a cooper because I thought I might be staying in SF for a bit longer, but I think I'm going to move back to Seattle in the near future. I've wanted an X5 for a while - and driving my cousin's for a week convinced me. Not a super rational decision - just liked how it drove, looks great IMO, etc.

[NNY528I]

Automatics fail because they contain a large number of parts which wear as a part of normal operation. If you have a manual transmission you would not be suprised or even annoyed to discover that you needed a new clutch every once in a while(hey it a wear part) Well Automatics also have clutches yet for some reason everyone seems to think that they will never wear out. Well guess what they do, and they wear out in direct correlation to the driving style to which they are subjected. If you always run your car hard, there is a greater chance that your transmission will have problems sooner than somone with lots of steady highway miles.

[supark]

They seem to rated for alomost the exact power of the engine with no buffer. It would be nice if they built to take more load, and only used to say 70-80% of capacitity. Lack of fluid changes on these 'lifetime fill' trannies is not helping either.

If I recall correctly, the ZF in the 540i is rated for 340-350ish hp.

[Jackcat559]

Could be. I had the spec sheet on both the e39 zf 5hp-19 & the 540 version. The I6 wasn't much above the factory hp rating of the engine. Could be mistken tough. It was a while ago.

This wasn't the file, but the only thing I could find quickly.

http://www.zf.com/na/content/media/import/zf_na/startseite/sso/passenger_car___light_truck/car_driveline/product_catalog/5HP19.pdf

[epeppino]

until auto transmissions mimic manual transmissions, that is, backing off the throttle during shifts, they won't last.

[Cyrix2k]

In the 60's you were lucky to get 60K miles out of a automatic transmission. Rebuilds between 40-60K were common. Engines were good for about 100K and then needed a complete rebuild. How many of you would put up with that. Now go back to the 40s and 50s. Ring jobs and valve jobs were the norm every 15-20K. So the good old days really were not all that good.
hmm, the 2-speed powerglides were known to last for 100s of thousands of miles. My buddy has an I6 1967 chevelle that has 260k miles on the original powerglide. Still shifts fine...

[dinan e39]

until auto transmissions mimic manual transmissions, that is, backing off the throttle during shifts, they won't last.

they do nowadays.

[nodoubts2k]

they do nowadays.

What about the new CVT transmissions that are all the rave. They dont shift at all (i.e Nissan)

[amancuso]

What about the new CVT transmissions that are all the rave. They dont shift at all (i.e Nissan)

CVT sucks, boring ass transmission, you cant even feel the shifts.

[Orxan4ik]

CVT sucks, boring ass transmission, you cant even feel the shifts.


because there are none :D its continuously variable :)

[supark]

What about the new CVT transmissions that are all the rave. They dont shift at all (i.e Nissan)

well - CVTs are nothing new (used in scooters for quite a while now) but from what I've heard the nissan and mini cooper ones have had issues with reliability.

[bimmerE36freak]

dude just dont do it. why not just get a 5/6 speed manual x5? best of both worlds!

[supark]

dude just dont do it. why not just get a 5/6 speed manual x5? best of both worlds!

There's a chance that I'll be working for the evil empire over in redmond, and having done the commute - I'd rather have an automatic when I'm sitting on 520 for an hour and a half. I'm planning on getting a motorcycle for sunny days though and to cure my speed cravings :) We'll see, if I end up working in Seattle I'll probably get an 02 M5 (that way I can keep my linea corses).

[BabyfartMcGezax]

In the 60's you were lucky to get 60K miles out of a automatic transmission. Rebuilds between 40-60K were common. Engines were good for about 100K and then needed a complete rebuild. How many of you would put up with that. Now go back to the 40s and 50s. Ring jobs and valve jobs were the norm every 15-20K. So the good old days really were not all that good.

Interesting. How many miles would you say we get out of the E39s and E46s?

[epeppino]

they do nowadays.


haha, i assume the e-throttle controlled e39's have this in their favor. mine does not.

do cvt transmissions slip?

[jerkstore]

haha, i assume the e-throttle controlled e39's have this in their favor. mine does not.

do cvt transmissions slip?

continuously

[Wolfen]

There's a chance that I'll be working for the evil empire over in redmond, and having done the commute - I'd rather have an automatic when I'm sitting on 520 for an hour and a half. I'm planning on getting a motorcycle for sunny days though and to cure my speed cravings :) We'll see, if I end up working in Seattle I'll probably get an 02 M5 (that way I can keep my linea corses).


I had a few bikes to cure my need for speed. My last one was a CBR 1100XX
The 540 cured all my needs and i was able to sell the bike.

[noahtheviking]

you can use higher quality trans fluid as well royal purple makes a great product that exceeds esso specs and will help trans stay a little cooler but not by much. Remember the esso fluid or the shell is not a new technology but it was new when bmw started using it 15 or so years ago so most new synthetic fluids are more than sufficent to cover the old bmw fluid recomendations but if you have a new bmw use what they say to use.