Howdy all,
A friend of mine has a Blazer, that recently had an automatic transmission into the limp mode. The problem was with an AT faulty speed sensor, which was replaced. Luckily the transmission went out of the limp mode, but he noticed, the gears are being shifted at a higher RPMs than usual (i.e. it was 2500rpms before, now is 3500).
His velocity gauge had not been working since long time ago till now, so he cannot refer to the speed.
My idea is that the sensor wasn't installed deep enough, so it is not picking the rpms properly. I gave a call to the person that carried out the replacing job and the guy said, the sensor they got is not the genuine one (made in Taiwan). He says there are no shims for adjusting and dropped me the photo of these two sensors (as per attached).

Looking forward Your opinion.
Cheers, MikeGenuine, old sensor and a replacement

 

The speed sensor is a set length. If you screw it in farther you'll likely contact the reluctor ring and tear the end off the sensor as the tolerance is fairly close. The speed sensor reads PPM Pulses Per Mile and isn't involved in measuring engine rpm's.
What year are we talking about? Is it 2 or 4wd?

 

It's 4WD '95 (2nd gen with rect. headlights, 4.3Vortec).
The rpm gauge is OK, but the speed one isn't (and wasn't) working, Therefore it is hard to judge whether a VSS readings are OK or not.

 

You could try a different Speed Sensor and also look in the hole to see if the reluctor ring is full of crap.

 

Thanks buddy! You're right, if there is a crap in between teeth, it will not pulse properly. I haven't though of it

 

2001 Blazer is in limp mode. Replaced the speed sensor and both shift solenoids. Still in limp mode. I guess I need a new trans. Search "limp mode." to see most of the story.

 

Mike.308
How did you "look in the hole"? It's located where you can't even see it.

 

Actually I did not Luckily not my ride, but a friend that lives 60miles away. But in regard to Your question - my hint: get a cheap endoscope on ebay and a usb micro plug<->usb-A socket cable and turn Your mobile into a remote camera. It should cost You no more than a $15 bucks.

 

Now that right there is an awesome idea! See , knew we kept ya around for a reason Mike.... lol