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Wednesday, December 6, 2023

Doug's Domain

Doug Vetter, ATP/CFI

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Februrary 10, 2005

New Transmission Installed

(Image: New transmission in the box)Hmmm. What can I say that I haven't already said in the last report? Well, I'll start by saying that the new tranny has been installed, and my wallet is $3700 lighter as a result. Yea, that's a lot of money, but I have to look at this in the same way I look at expenses on the airplane. This is not an oil service that effectively lasts 4500 miles. A transmission is a core mechanical device that is supposed to last the "life" of an average car, or over 100000 miles. It just so happens that the BMW 328is, if properly cared for, can last more than twice the lifespan of the average vehicle. So, if I amortize the $3700 over the next five years or 100K miles, the average yearly cost of maintenance rises only $740, or about the cost of an inspection.

I received quite a few emails and did quite a bit of personal research about this problem. Several readers suggested that the transmission could have lasted a lot longer -- had I not believed the marketing hype regarding "lifetime transmission fluid" and changed the fluid on a more regular basis. After all, as one person put it, ATF is nothing more than a lightweight oil with additives, and it breaks down just like engine oil, so why should anyone expect it to handle the stresses of 100K+ miles? Based on my personal experience, I think these people are right. The fact that the engine continues to purr along at more than 110K miles is very likely because I made it practice to change the oil at half the recommended interval.

(Image: Old transmission core)When a manufacturer says that something doesn't need to be maintained for the life of the component, one needs to ask the manufacturer for his definition of the word "life". To me, the expected lifespan of an automatic transmission (GM/Getrag or not) is 150K miles. To Getrag, who makes money selling new and remanufactured transmissions, the lifespan is obviously far shorter.

If you take nothing else away from this, take my advice and change your transmission fluid at some regular interval. From this point forward, I am planning to replace the fluid every 18K miles (at each inspection interval) simply because there appears to be statistically significant evidence that changing the fluid on a BMW transmission extends its life by between 30-50%. The number of people who appear to get at least 150K out of a properly maintained BMW transmission is as striking as the number of people who have needed to replace their transmissions before 120K miles if they did NOT service it regularly.

(Image: New transmission installed)My mechanic got the car in the shop around noon on the day I dropped it off, and was on the test drive the next morning around 9:30 when I dropped by to see him. Assuming he didn't stay late, the transmission swap took him around 7 hours with another half hour for the test drive. The dealer charged book labor of 10 hours, but that's just par for the course with dealers.

Much to my surprise, I learned that it is not necessary to pull the engine in order to replace the transmission because the engine is designed to pivot rearward by a couple inches. The saves a tremendous amount of labor and hassle. Indeed, the right tools and experience are all that is needed to disconnect the bell housing from the rear of the engine. I noticed also that my mechanic had pulled off the entire exhaust system aft of the headers as well, so if you have to pull the tranny, it would be a good idea to replace the exhaust system mounts if you haven't already. As you may recall, mine cracked and were replaced about a year ago.

Parts $2541, Labor $950. Total $3700, Total mileage, 111161.