a_r_fowler

1993 Z71 with a 4L60E trans. lost all but 1st and 2nd gear little over a year ago while pulling a 15' boston whaler. Replaced with a new heavy duty4L60Etransmission and put @10,000 miles on it and it has done the same thing while pulling a gooseneck trailer. attempts to shift to 3rd but "slips" and the engine just revs up. Any suggestions would be appreciated.

ZX1100F1

With only 10,000 miles since installed it may still be covered under warranty?

dleonard2844

im having the same problem, mine went when i was hauling a 63 chevy. From what i've read in a bunch of posts its probably something electrical. it could be solenoids, but on mine (and aanother guyspost i saw) the speedo needle goes crazy and then stops working, and the brake light comes on. Im still a little confused as to what exactly he did to fix it (and it did fix it) but it had something the do with the acc power wire for the speedometer. I guess the electronics for the tans use information from the speedometer to control shifting. I just saw this post today, and i'm checking it out first thing when i get home, i'll keep you posted on my "findings"

dleonard2844

OK so i was reading up on other forums and found this. dear God i can't wait till i get home and check this out!






I have a 1994 Firebird that has the 4L60-E Automatic Transmission.

On the same day my transmission quit shifting, (all gears) my speedometer also quit working. All the transmission people tell me I need to re-build my transmission.

I am not buying that the ELECTRONIC transmission that relies on the car speed to shift and the speedometer both going out at the same time being independent problems.

I suspect it is the PCM or the speed sending unit. I do not know exactly how the PCM gets speed information used to shift. Does this input come from the transmission or how can I determine if the PCM is getting the car speed?

Would this information be in the diagnostic codes? (With the car not moving while testing for ?can you read car speed? would this be a test?)

It is my understanding that the speedometer itself is just a analog meter displaying what the PCM tells it to, (not the sending unit to the PCM) the PCM must get an input from somewhere, (thinking straight from the transmission) and that is the part I need help with.

I need to determine if the PCM is getting the speed input it needs on the current car speed but do not know how to determine that, not knowing exactly where that input comes from.

Anyone have a speed sensing problem cause 4L60-E problems?

Any Help would be GREAT!

Thanks![/align]







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06-12-2006, 08:57 AM
#2


LS13RDGEN
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The transmission has a gear on the output shaft. A sensor on the tailshaft reads the gears teeth as a digital signal (ones and zeros) and sends this signal to the pcm. The pcm then sends a voltage to the speedometer on the dash board to display how fast you are going.
First thing I would do would be to check grounds on the block, frame and chasis. Then check the connections on the speed sensor on the tailshaft (make sure it hasn't come loose) then check continuity from the connector to the pins on the pcm itself.
As far as seeing if the speed sensor is actually sending a signal to the pcm, you will need an instrument that can read a pulsing signal.
A DMM might work if you put the car up on jack stands, key on, engine off, splice into the two wires on the speed sensor with the DMM, put it in drive and have a buddy sping the tires or drive shaft. [/align]__________________
Paul
Columbia, TN
92 RS LS1 T56 Rally
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06-12-2006, 12:40 PM
#3


RedEye
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Thanks [/align][hr]

THANKS!

That is pretty much what I think the problem is due to both the speedo and shift going at the EXACT same time.

I will do the continuity between the trany sensor and the harness at the pcm to be sure it o.k. (as far as you know the wire should not stop anywhere else betweeen the tranmission and the PCM?)

Also since this is a car moving only signal, do you know if a diagnostic will pick up anything if the VSS if not sending info?

Finally someonme that is not telling me to rebuild my transmission!

Can I measure the voltage on the 1-2 shift solenoid? Should this solenoid have voltage when the PCM is telling it to **** into 2nd? Have any Idea what voltage?

Thanks again![/align]







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dleonard2844

hey i changed my vehicle speed sensor and everything works now.