TerriV

Good day all. My Nissan is a 1998 Sentra. I bought it about 5 months ago for $400 with only 120,000 miles on it.
Lucky me, I have not had to do any major repairs to the car other than a few tires, rear struts and some arm thing also on the back. I have had a squealing going on in the front and thought this was a loose belt but my mechanic told me it was a cover to the timing chain releasing tiny squirts of oil on to the belts and this is causing it to whine. He told me to keep an eye on the oil and he would replace the cover after Christmas. (Quick Fix)
The issue that is really bothering me recently is either my Speedometer or my Transmission.
When I reach around 50-60 mph the speedometer will bounce and drop to
zero. When this happens the tranny downshifts to 3rd. It will do it
several times, take a break for a few miles and start all over again.
Fortunately it's sporadic and the car still drives. When it first began I
still drove it to work,and around town because it was working properly
more often than not.
Two days after it began, my engine light finally went on which is what
makes me think it's a sensor, either for the transmission or something
else. The tranny has always shifted fine, no thumping into gear forward or
reverse.
After cruising around your site, I found some helpful info. that I would love to try before attempting anything invasive.
First of all, after 5 months, I just noticed today I do indeed have an overdrive button. I thought I has a model that was without one. Apparently, my issue has nothing to do with this.
I am interested in looking first into the Instrument Cluster to see if there is a loose wire or corrosion. Can someone please tell me where I am to look for this? I have a repair manual on order, but would like to take a look at this as soon as I find out where it is.
Thanks so much and Have a Merry Christmas!
P.S. Does anyone know what the proper gas mileage on this car would be?

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All horses deserve,at least once in their lives, to be loved by a little girl.

jdg

If you are sitting in the drivers seat, the "Instrument Cluster" is right in front of you, behind the steering wheel, under the dash, between the steering wheel and the windshield, to the left and above the radio, inside the door, about 3ft above the ground, 238,000 miles away from the moon, about 300-ish miles away from the next fillup if you start out with a full tank, somewhere between here and there, next to the dark side of the moon.

As far as the oil squirts go...A timing cover squirting oil? I'm calling some serious B.S. on that one unless you've got an actual crack in the cover itself or the upper tensioner gasket is shot.
How about you try replacing the front crank seal first. Look at the stickies here in the forums. A known problem in higher mileage GA16DE engines. Easy fix. About $3 for the seal. Basic tools. Took me an hour or so first time around on one car (with a couple of phone calls and smoke breaks), took about 15-20 minutes second time on a different car.

__________________
99% of the questions that are "STRANGE" have a dirt simple answer...usually answered by a dirt simple search.

NISSAN GOOGLE

Is it just me, or does the majority overlook the obvious?

Somebody ate a whole bag of dumbass for breakfast.

Why do people continue to run a vehicle when a warning light comes on or starts flashing? Isn't that a clue that something is wrong and you probably should NOT drive it?
Is this whole car driving thing really freekin' brain surgery?

Here's something new for the crowd/clowns...
"A little bit of Google goes a long way!"

Ever notice the one post wonders for info on turbo'ing a GA16 are never heard from again after they figure out the cost???

And if you can read this, you don't need glasses! :)

And yes, I am diggin' it...

TerriV

Thank you for your reply jdg. I spent the afternoon pulling my instrument cluster apart. I took the advise from a few other members, loosening and tightening screws in the panel itself, cleaning connections with PBJ, and putting it all back together.
Unfortunately, this was not the problem. I took it for a test drive with high hopes of everything working properly. At first the speedometer didn't work at all. About 3 min. into my trip it shot up to 50ish and bounced around erratically until I returned home. The engine light is also still lit even after disconnecting the battery to do the initial job. It seems when the speedometer is not working, I have no 4th gear at all.
My repair manual has little to no advise on speedometer issues. Looks like I will have to bite the bullet and pay the $40 and have a mechanic put it on the error code machine, and go from there.

__________________
All horses deserve,at least once in their lives, to be loved by a little girl.

smj999smj

Oil leak- I agree with jdg in that it is most likely the front crank seal. It's a very common problem on GA engines. That said, the oil pump is located in the front cover and there are two oil channels that run from the block to the cover, with collared seals. It is possible that one of these seals has failed and causing oil to squirt out between the front cover and block on the back side of the engine. It's a lot more common on older KA24DE powered Altimas, but certainly possible on the GA16DE, which is very similar in design.

Speedometer concern- I would first pull the vehicle speed sensor and check the plastic gear for worn/stripped teeth. If this is the case, a new gear can be purchased from Nissan. It's very possible that you have a faulty speedometer head unit. Mid-90's Nissans had a lot of problems with the speedometer head's threaded inserts on the back where the four screws mount the speedo head to the back of the cluster and printed circuit. The inserts would crack and cause a poor contact issue. Fix is to replace the speedometer head unit. To check it properly, one would need an oscilloscope and attach the leads to the back of the instrument cluster where the two wires from the VSS attach to the printed circuit. The VSS generates an AC signal which frequency increases with speed. The speedo head converts the AC signal and sends the speed signal to the ECM and TCM. You could use an AC voltage gauge, which would verify a signal exists. Expect to see about 1 volt per 10 mph. While this method confirms a signal, it doesn't verify a "clean" signal, which is why an oscilloscope is prefered. A proper signal to the speedo head but fluctuation or inoperative speedometer would mean that a speedometer head replacement is in order. If you get it through Nissan, they will preprogram the mileage for you.