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740IL Trans problem - Trans Fail Safe

5K views 35 replies 13 participants last post by  u.nanimous 
#1 ·
I have a 1998 BMW 740IL

Problem noticed today on Interstate when changing lands I noticed kind of like a hesitiation with a clunk sound, let off the gas then resumed just fine with minimal slippage in the transmission.

Later in the day I noticed trans seemed to slip more but if I took it easy, it would resume fine.

Later I tried to go fast, then it did have some very noticeable slippage and then When I tried to go fast and the trans should normally kick down a gear it did not and then the transfail safe program came on the dash. Once that happened, I noticed the lights for the PRD,etc went off and would not resume. I would let the car sit for 10 minutes, then the trans program light would go off and the P,R,D lights would return to normal.

I do have a relatively new battery. Alternator has not been checked, but I cannot see it being bad.

When the trans program light is on, the car will go into reverse just fine. however trying to go, it seems to be limited on power. Almost like it is in 4th gear kind of and hard to go. So it would be time to let it sit.

So your thoughts?

If I have to change the filter, how difficult, Can I get the fluid at autozone, they said they had something at $6.00/ Quart. Then how difficult to pour the fluid in?

Any help would be appreciated.

Thanks,

Kevin
 
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#2 ·
I would suggest checking your shocks, rear control arm bushings etc. Anything is the suspension can set off the fail safe. I had this problem before. Found the solution because i was behind my wife in the car one day and noticed the real wheel had extra bounce to it. Once under the car i found out the problem. Rear control arm bushing was shot. Hope this helps. The transmissions on these cars rarely have problems. Mine has 330K and still going strong.
 
#6 ·
I beleive when the tranny goes into "fail safe" mode it stays in 3rd gear. This would account for the slow take offs you speak of. Sounds like Fail mode is working like its suppose too. Cannot think of the name of the component on our tranny that is known for failure. That lillte computer modual on the tranny. Anyone....some help please.
 
#7 ·
I went to other shop and they said the forward clutches are slipping. Suggest rebuild. However they did not drop pan or anything. You have to rev. real high to get going. Once you do it will drive, best on highway. I tried moving from D to 4 or 3. Nothing. So i put it back in D.
 
#8 ·
Yeah id have to rev the hell out of it. But when mine went into gear it would shift trough all the gears. If forward clutch is going get it rebuild. Or look for a bit trans so you don't have to wire about it again for a long time. Only thing with built transmissions you will loose gas millage.

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#10 ·
Yes fail safe mode keeps the car in 3rd gear. If you punch the gas it won't move, but as you get going it seems fine till you need the car to down shift. There is 2 other thing I'm going to research I'll get back on here soon and let you know.

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#11 ·
I just did another test drive. Took off slow. Put it in M anual mode. Went through all the gears just fine. Upshifted, downshifted fine. Once I went through a couple of stop signs, started slipping on take off and went into failsafe mode then at that point stuck in gear 3. Was wondering if I should add Lucas transmission treatment to the transmission.
 
#12 ·
Did you have anything else looked at besides your trans like bigmike60 said look at control arms, bushings, could be drive shaft abs module, read end, U joints. These are all thing that could make your trans go into this mode. I would not put anything Lucas or royal purple in my bmw.

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#14 ·
Well that's the first thing you need to do. Jack the car up so suspension hangs free and start pulling and shaking ****. If you can move anything with little strength it needs to be fixed. Also you need to have your car hooked up to a computer to see what fault code comes up to male the trans hit fail safe. You can get a obd scanner pretty inexpensive. I hope I'm helping you and not making things worse off for you.

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#15 ·
I really do appreciate all your help. When this all started, I was driving down the exway and it clearly was a tranmission clunking back and forth then went away, within moments the fail safe. I did use a OBD scanner. No codes. Trans shop did use their compute and come up with code 49 & code 53.

I am almost thinking the new tranny is the way to go. Although cannot afford, so I was looking for the miracle.
 
#20 ·
V@ ian^ they can last up to 600,000 miles witch is longer then some peoples life. Never drain fluid unless it has always been done. When you drain an automatic tranny you move around a lot of metal shavings that could have been holding the trans together.

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#23 ·
I don't believe just draining the fluid and replacing it can remove any shavings that aren't just sitting in the bottom of the pan.

I also don't believe that flushing a transmission by using it's internal pump will cause any harm.

What I do believe is that using a powerflusher can dislodge gunk/shavings and cause issues.

As for lifetime fill, even BMW backpedaled and agreed that they really meant 100k miles. Fluid can wear out, it's an oil after all. It should be replaced periodically. Lifetime fill was a marketing gimmick, I should know, I have a marketing degree and a mechanical engineering degree so I know both side's tricks. :)
 
#21 ·
Ok. So the latest. I drove the car to work this morning. About 10 miles. Most of which was expressway. If I take it slow (real slow) without any hills, it will Go from gear to gear smoothly with limited slipping unless I high rpm it. Which if I do it will go into failsafe and stay in 3rd gear until I stop and turn off engine and restart. I did make it in to work without it going into failsafe. Went through all the gears in automatic mode and manual mode. I even pressed the gas at 70 mph and it did downshift just fine. If I started to press gas to hard on interstate it would start to slip a little.

So I think I am at the point of agreeing the tranny is going out so I thought I would take it to Valvoline instant oil change and pay to have them Flush and Fill. Thought if it hurts so what, I need a new one anyway.

Any other thoughts from anyone?
 
#24 ·
1. Don't care about your degree means nothing to me I'll sell snow to a snow man and fix cars all day I work I a very well know shop, it just not good employment for me. 2. Have you ever done anything you are claiming. I have personally watch a bmw in working order get the trans fluid drained out new fluid back in and BROKEN TRANSMISSION.

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#27 ·
i have a 95 740il and sometimes about 40 mile pr hr and give it gas it feels like it slips a little car jerks but then is fine sometimes when first starting out in morning the gears don't shift right away unless pick up speed then it shifts fine this has been doing this for about 3000 miles tonight sitting at a light the trans safe light came on then I jumped on thruway and it did not come back on anybody guide me thru this
 
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