Trans Fail Safe mode-P0720

[Saj8986]

so...never had any issues with the tranny until this morning. Starts and drives great as usual...but after a quick 10 min drive park and start back up....it acts like it doesn't want to go into lower gears. Reverse is fine. got the P0720 code...went online to e38.org...it is called a couple of different things. "output speed sensor circuit" and "pulse generator". I can do a lot of things but not sure if I feel comfortable diying this. any suggestions? made appt at the dealer for tomorrow unless i hear from the wise and knowledgeable folks on this forum>

[IcemanBHE]

Basically, when in a gear, the transmossion output (rotational) speed does not match what the computer says it should be.

This could be due to clutch slippage, bad torque converter, or something along those lines.

Maybe a bad sensor.

But...its not going to be an easy fix. Good luck.

[IcemanBHE]

Forgot to mention..

I would do a battery reset FIRST. Maybe that will fix it.

[Saj8986]

So....battery reset. Sorry to be a newb, but i'm thinking that means taking the neg terminal off and then reconnecting? If so, I did and it cleared the check engine light and when I started it back up, shifted into reverse....everything was good, but when I went into D, bang "tran failsafe etc" came on again. BTW....bought in January 2011....trolled this site for 4 months before joining. Put 20k on the lovely lady in 10 months. Gorgeous car and I now understand the passion for these cars. I've owned Audi, fiat, Volvo, mb's and virtually all brands of Asian and american cars. But I've never had the same feeling as I do for my BMW. 2nd Favorite of all those was a 1979 MB 450 SLC.

[IcemanBHE]

Well then Im afraid you need more diagnostics. Have a trusty Indy?

btw...I would have left the cables (yes both) off the battery for 5 mins or so then touch them both together for 30 seconds, be fore reconnecting to battery.

Try it..but it probably wont help.

[Saj8986]

cars at the dealer...authorized diagnostic for $125. Hopefully good news or at the very least....moderately bad news would be fine.

[Edwin NL]

Fingers crossed!

[Saj8986]

ugly news....dealer called and said it was a transmission gear monitoring failure which would require a whole new trans. and would ONLY cost $7000. going to take it to an indy and see what they say. strange how the tranny would go from great to crap overnight with no signs whatsoever.

[IcemanBHE]

Well...we already knew that.

Timm seems to be pretty handy on this topic. Maybe he will chime in.

[ryan77]

Probably a failed A- drum clutch basket on the input shaft, it splits along the snap ring groove then the clutches slip causing a fail safe, I just disassembled a transmission that had the same code, plus a few others, and that was the issue, another board member chief jimbo did a write up on the repair, I was quoted $125 for the A-drum input shaft at transtar, I plan on getting one and will share the results soon, if you can find a mechanic that will remove the trans from the car, disassemble and confirm and switch the part you may be good to go. If all goes well the repair will be the 125 plus filter and fluid for me. Good luck, o and this transmission is easy to disassemble, not as hard as they make you believe.

[Timm]

Timm seems to be pretty handy on this topic. Maybe he will chime in.

You boys seem to be doing a perfect job without me!

There doesn't seem much doubt that one of the clutches has failed - The output speed sensor error is due to the turbine spinning aimlessly due to the loss of transmission of energy through one of the clutches. As soon as the selector is put into Drive, the turbine should stop rotating until the car is moving, if a clutch fails the turbine will turn at the same speed as the impeller - the EGS sees this and expects the output shaft to be rotating - when it doesn't an error code is logged and the gearbox is put into failsafe mode.

There are a couple of things worth checking, firstly, ensure the battery is new and fully charged, it could be that a solenoid has failed to move causing the clutch to not engage - and that could be due to low battery voltage.

Check that the selector cable is moving the selector on the gearbox and is adjusted correctly:

http://www.meeknet.co.uk/E32/E32_Shi...Adjustment.pdf

The tell-tale signs of a clutch failure is nothing immediately happening when the selector is put into Drive - followed by a thump and 'trans error prog' appearing on the OBC as the spinning turbine is halted by the 4th gear engaging.

[Saj8986]

hmmmm...after my wife became slightly less cranky I was able to return to the forum. She has this weird love/hate thing with this car. Loves to drive and ride in it...but hates the cash outlay. Told her lifes a bitch and then you die...get over it.

Timm mentions below exactly what is happening

The tell-tale signs of a clutch failure is nothing immediately happening when the selector is put into Drive - followed by a thump and 'trans error prog' appearing on the OBC as the spinning turbine is halted by the 4th gear engaging.

So I'm gonna do as has been recommended by Ryan77, Timm and the iceman. I truly thank all of you for the advice and direction.

First things first....get a new battery cross my freakin fingers and hope. But expecting the worst, will also do my research and find an indy and explore the other options mentioned. This is a gorgeous black on black 7 that runs like....well like a BMW. Have put well spent $$ into it so far and with some due diligence, i'll get this sweet little thing back up and running. its 6pm somewhere and time to knock back a couple and relax.

[Chronic]

Hey, keep me updated on this... I've had the same problem with mines and I was thinking about buying a transmission, or having the one that I've got now worked on....

[Timm]

First things first....get a new battery cross my freakin fingers and hope. But expecting the worst, will also do my research and find an indy and explore the other options mentioned. This is a gorgeous black on black 7 that runs like....well like a BMW. Have put well spent $$ into it so far and with some due diligence, i'll get this sweet little thing back up and running. its 6pm somewhere and time to knock back a couple and relax.

A drink is a good plan. As you have a '98 model, there are loads of replacement gearboxes around, usually for around $500 - $600, it is just a matter of finding one!

[Saj8986]

So...picked up the car from the dealer and this is what they diagnosed...

- - - - - - - - - - - - - - --
J# 1 26BMZ AUTO TRANSMISSION ... ' HOURS:' .... 1.00 TECH(S) :540
CUSTOMER STATES THE VEHICLE IS IN TRANS FAIL SAFE MODE.
CAR IS LACKING POWER AND NOT SHIFTING CORRECTLY. CHECK
ENGINE LIGHT IS ALSO ON.

TRANSMISSION IS DEFECTIVE
THERMOSTAT IS DEFECTIVE
RAN VEHICLE TEST. FOUND FAULT 106 FOR STALL-SPEED MONITORING
AND 134 FOR GEAR MONITORING 4.
FOUND FAULT 139 FOR MAP COOLING.
ADVISED CUSTOMER

I did as was advised in previous posts. Unhooked both cables from old battery for 10 minutes and touched the cables together for 30 sec. No luck. Bought new battery and tried that. No luck. As far as driving....the car starts off Slooooow but once she's up to speed she does fine. But not having any gears besides 4th ain't gonna cut it. Calling an indy tranny shop to see if they will order and install a new clutch(s).
The week started pretty nice but has become a real downer.

[ryan77]

when you find someone who will remove the transmission, identify the bad part and call http://www.transtar1.com/ and buy it, like I said my bet is its the $125 A-drum has split, any good honest mechanic should be able to replace it(that may be the hard part...lol


http://www.bimmerboard.com/forums/posts/490896
link to a similar story

http://www.google.com/imgres?imgurl=...ch&um=1&itbs=1

click on the break down exploded view, there are other manuals that call out the internal parts names as well, even thickness specs for measuring the thickness of the clutches, and a clutch set on ebay is $400 or so and includes all the o rings and seals too....just gotta look around, like I said my guess is its a $125 part, may be what I described, may be a bearing and seal just gotta get a mechanic to take it apart and find out, then decide to fix or replace,it has to come out anyway, it took me 15 min to take it apart and find the problem and I'm not even a mechanic. as far as fixing the trans you have... it is nice to know what you have in it and whats replaced and what checked out good, a used unit may be on the edge of failure.

[Chronic]

Hmmp, Sorry to hear that you got bad news after getting your car back... I was praying that you got good news, cause mines is a 97 and its doing the same thing yours is doing.... Someone told me that it can probably be that I'm low on fluid, and the only way to check it is to have it up on a lift, where the car is level, to get a better idea of how much fluid is in there. Don't know if you check that also, but I have not either... Good luck, and I hope that you get some good news. If so please let me know.....

[BimmerBrad]

Just put in a nice used tranny from ebay for $900 and be done with it. That's what i'm gonna do when mine goes.

[Saj8986]

found an indy willing to dismantle and diagnose. Dropping it off tomorrow morning. Will report back the results-hopefully positive.

[Chronic]

There's this guy in my town selling a 2001 il for $250, the price is sweet, but I'm kinda doubting if its any good... He claims that it was in a front end damage, and the transmission is good he just took it out 3 weeks ago... Either this guy needs the money badly, or the tranny is no good....

[ryan77]

Yea there are a few of those cheap used tranny in my area too, many were pulled because of errors, then layed around a shop for awhile and changed hands a few times, now for sale as a" I think it's good" unit and eBay is worse, they don't have to deal with you face to face, much easier to lie, I bought a bent motorcycle wheel once from eBay....lol

[Chronic]

Lol, So Ryan77 you think its best that I just take it to a Mechanic to find out what the deal is...

[eddiem]

I did a job on mine these last two weeks... replace the gaskets on the loosely tightened cooling manifold. When I put her back together, and since it's been two weeks, she wouldn't start. 'Insufficiently charged battery...,' gave her a jump and ran smooth all yesterday. This morning I go to start her up, sluggish, not the usual start, then the trans failsafe prog. Turned her off a few mins and started her back up, like nothing ever happened. Going to get the battery properly charged see if that's what the problem was...

[ryan77]

Chronic, what's it doing, codes? Slipping?, how many miles, if high and it slips in drive revs then pops in failsafe mode then either it's a valve body issue of not sending fluid to the specific clutch pack, or it's a clutch drum issue they were known for splitting along the snap ring groove, and I've heard of the seal and bearing failing between the A and B clutch packs, bad seal no pressure....so it could be a few things, also low voltage, and abs sensors can cause problems for failsafe issues, when you clear the failsafe by disconnecting the battery and connecting the cables together for 30min. Then with a fully charged battery start it and see when it goes in failsafe, if it goes right away at start up, then it may be electrical related, water intrusion in the trans cable connector near the pan, and abs problems may be your problem, but it it only pops in failsafe after you go in drive and rev it up trying to go and it slips, then the computer has detected a internal slip inside the trans from my earlier stated problems, valve body, clutch packs, seals, or drums

[Chronic]

Sorry it took me so long to respond Ryan77, but I just took it to Sam's Automotive in Jacksonville, Fl... Their taking looking a look at it... but it drives and as soon as the transmission gets hot it goes into fail safe mode, it drives but drives real slow when that happens... If I put it into reverse it has no problems what so ever.... Just waiting now to see what news I get back....