installing used transmission


Old 06-07-03, 06:02 PM
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installing used transmission

i'm installing a used trans in my car. the used unit supposedly has 96k on it and has been "tested," whatever that means. it comes with a 4 month, unlmtd miles warranty, so i'm not worried about getting a lemon. however, i've heard about transmission flushes and i'm wondering if i should do this to the new used trans. i'll be cleaning or replacing the cooling lines when i do the installation, so those will be fine. can they flush it when it's out of the car, or should i just fill it, test drive it, and get it flushed? any ideas?
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Old 06-07-03, 06:22 PM
darrell McCoy
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that many miles is a real risk. Dont know the type vehicle. But if it were me, I would change filter if applicable, re-install pan. Then install trans and fill to proper level with proper fluid. Run it till it quits. I would forget about the flush. That however is your decision. Usually about 100 bucks for the flush, and that does not change the filter. Should be flushed while in the car. no way to tell how long it will run. Good luck on this un.
Old 06-07-03, 07:18 PM
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Good chance of doing this twice, three times or more. It is a major gamble like shooting at a dartboard. You might hit, you might not. But the odds are you won't and if you have to do it all over again, a rebuild will look pretty cheap in comparison.

I'd go with a rebuilt and be done with it.
Old 06-07-03, 07:32 PM
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it's for a 1990 bmw 735il. mine went out at 118k. it is unusual for this trans to go bad. i should have gotten 200k + out of it, according to the beemer experts. i'm more than comfortable with a used unit with that low mileage (for this car, anyway). i plan to replace front and rear seals, all fluid, filter and pan gasket. replacing the trans on this car is not a difficult task; once i got it up on stands, it took me less than 2 hours to drop the exhaust and pull the trans out, and this was on my back under the car. so even if i had to do it again in a few years, i'd still be ahead. i guess if the fluid looks very clean in this unit there should be no need for a flush. does the flush do what is claimed?
Old 06-08-03, 01:14 AM
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There's 2 "meanings" to the term flush, in this case.. 1 is to take your average car, hook a machine to it, and replace the fluid by flushing all the old out, and at the same time replacing it with new fluid..The other "meaning" is to flush the trans lines and cooler with a cleaning chemical after the transmission has been removed..Most parts stores carry this flush.
I'd recommend doing this before putting your used tranny back in.. Get the chemical, flush the lines and cooler, blow it out clean with air..Then when you install the tanny, just fill it as you normally would..
1 thing to check on first though, some cars have a check valve built into the cooler, and flushing can cause more problems than you started with.. A good transmission shop, or a good manual should tell you if your car has 1 or not..
Old 06-08-03, 06:36 AM
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Original poster:

Unfortunately when things like this break on a BMW, the acronym "Broke my Wallet" rings true. One of the reasons you'll never see one in my driveway unless someone gives one to me (and then I'd flip it for something else Anything over 100 or 150k on a tranny is really borrowed time in many cases, depending on maintenance.

This is a pretty "top end" vehicle and if it's in good shape, I'd suggest going for a factory rebuilt for it. It will have a warranty, all the upgraded parts and procedures and it will fit and work correctly without a hitch. No telling what the junkyard unit will be, since the history is unknown. You may be dealing with the original fluid in that unit, in such case, changing it could wipe out the transmission.

I have seen some trannies that had the original fluid in them WAY too long and when new fluid is put in, they puke and don't shift.

Sure it may only take you 2 hours to drop the tranny again, but I can think of a lot more productive time spent than under a BMW .
Old 06-09-03, 09:37 PM
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BMW transmission

You would have no problem with used BMW transmissions. These transmissions are rock solid. It is very unusual for these transmission to go out at 118K. Have you been following the inspection schedule?

These automatic transmission are VERY complicated. Even the BMW dealers have to fly in experts to service these transmissions. I would not trust anyone to rebuild these transmissions. Even the BMW dealers would replace it with new because it is usually much cheaper.

I would advise you against doing any kind of power flushing other than dropping the pan, changing the filter, and refilling with (mobil 1)ATF. You want to change it slow, 3 - 4 qt over time. Make sure to replace the rear crank shaft oil seal!
Old 06-10-03, 03:43 AM
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True, but someone is remanning them for BMW. It's unlikely that BMW remans their own units

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