Speedometer sensor problem. or is it transmission? So about a month ago my car was having a rough shift from 3rd to 4th around 65 mph. i got a tune up and that fixed that problem but another occurred. While accelerating my speedometer is jumping around erratically, and causing my automatic transmission to either not shift or not work all together ( meaning my engine will be roaring but the car is acting like it is in neutral. I replaces the speed sensor as the computer diagnostic test said to do when the check engine light came on. Also, alot of the time the speedometer will read 0 mph and i think thats why my car may be failing to shift. Any ideas or similar problmes?

Sounds like the speedometer is faulty. If the speed sensor were the problem, the odometer would not work correctly, the transmission would not shift correctly, and the check engine light would be on.

You don't give me much information to work with. However, 1st, look at the engine mounts. You may have a broken mount. This will make it feel like the transmission is shifting hard. Other than that, there is only a few things that will cause this. The speed sensor tells the computer when to shift the shift solenoids. It may not be "seeing" a quality signal. If this is the case, the speedometer will be bouncing too. Last idea is that it is skipping a gear. Starts in 1st, should go to 2nd at about 10 MPH. 3rd at 25 to 30 MPH. And, if you have a Overdrive transmission, it should go into overdrive at around 45 to 55 MPH. If it is skipping 2nd, it will engage 3rd at a high engine speed, and will feel like a sudden slam into gear. If this is true, your transmission needs some work. Hope this all helps. Good Luck.

Year, brand, model would be helpful. You sure a speedometer cable is broke? If you have a newer car most of them have speed sensor(s). If a speed sensor is not working, it could be the problem with the shifting. Please rate my answer so I get points awarded.

had this problem myself. it turned out to be a sticky throttle cable from the throttle position sensor to the transmission making the transmission think it was in kick down mode. gave the cable a good dose of WD40 and its worked a treat ever since. and that's about three years to date.

It most likely is a transmission issue, a internal issue inside the transmission.

The transmission may be in Limp mode. The transmission is on the same fuse as the MAF, O2 sensors and at least one other sensor - if an O2 shorts out, it will blow the fuse and the trans will go into limp-home mode. Be sure the trans has power and the fuse is not blown before doing anything else.

What is "limp-home mode" ? This is a fault mode in which the transmission either loses electrical power or the PCM deactivates all of the electronics. The transmission will default to max line pressure. The driver will have Reverse and 3rd, with manual 2nd available by putting the gearshift in 2 or 1 (doesn't matter). 1st, 4th, and TCC lockup will not be available. It will not hurt the car to drive it like this for short periods, but use manual 2nd to get the car moving, and be aware that the trans will generate more heat than normal while operating in limp-home mode due to increased torque converter slippage during 2nd gear starts and no lockup in 3rd gear.

Trans does not upshift out of first, speedometer reads zero at all times: VSS failure. Easy fix on rear of transmission, but xmember must come out to access VSS.

Car goes into gear but feels very sluggish like the brakes are dragging, but it will roll easily (starts out in 4th gear), you manually shift to 2 to get it moving, once it's moving you put it back in OD and the car shifts 3rd to 4th on its own and locks the converter at the appropriate time: ShiftB solenoid failed: Easy fix in the pan. Or a wiring problem from PCM to trans.. or PCM.

No 1st or 4th available; trans shifts 2nd to 3rd by itself in D or OD and locks the converter : ShiftA solenoid failed. Easy fix in the pan. Or a wiring problem from PCM to trans.. or PCM.

Transmission does not shift automatically, only manually. Swap in a known-good PCM, check wiring, check other sensors such as VSS and TPS.

3rd gear starts, can manually shift through all gears. When car has been turned off for a bit, then back on it will run normally.: VSS dropoff w/ Hi-stall converter. The rpms are too high, but VSS is showing no movement. Happens after a tire burning take-off. Doesn't store a code, will not throw a CEL (I've heard that it will store a code if it happens 3 or more times). Cure: Reprogram PCM for VSS dropoff -- PCMforLess knows about it.

Here are just some of the common things you have described with the issues your transmission has. Good luck and keep me posted.

Hi, apparently something in your transmission its causing the speed sensor to go bad. Once you replaced it it ran good for a month. I will check the following
1) transmission oil level 2) check overdrive sensor 3) and then i will take it to a transmission shop
hope i helped thanks

you have a valve body problem, some of the speed sonsor controls are malfunctioning... need to get into the valve body... check fluid condition for dirty and burned condition...

Hi All

I have a s40 1.9d / 2000 plate,
In the last month or so the car loses revs when changing up to 3rd and 4th gear, I can only get 50 mph max in 3rd gear 80mp in 4th.
The car has just clocked 185,000 miles
Its a great car but a pai at the moment, I've had a service including fuel fillter change added fuel cleaners to the deilsel all to no avail


Any suggestions

have a 1998 K3500 silverado 4x4 with 454 motor and 4L80E transmission. I can not get over 55 or 60 mph. At that speed the transmission down shifts from 4th (OD) to 3rd. The speedometer also drifts from about 50 to 65. If I try to speed up it will down shift to 3rd. I have replaced the VSS on the trasfer case. Is there another speed sensor somewhere? Or could it be the TPS? The truck drives and shift normal up to this point. where should i look next. thanks