95 automatic s10 blazer having problem with transmission where it will shift fine if shifting manually but if you try to start in od it will just rev up and slip has had used trans installed and is still doing the same thing. anyone with ideas?

The shifting is electronic/electrical.
Make sure fuses and electrical plugins are good.
Any check engine lights on?

You need to get it on a good engine/transmission capable scanner and check it out.
Post back any codes.

Have the genesis scanner hooked up and there are no codes present. all harness's visually look ok inside and out but I am checking resistance now.

Is it transmission checking and testing capable?
Does it show any solenoids switching or on and off.

Check fuses and for 12 volt power to transmission solenoids.

Yeah it is transmission capable but not all for sure what I am looking for on the scan tool it is new to me. Fuses are good and will check power on solenoids. Yes they are switching on and off on the right gears.

Yes there is power getting to the solenoids and all of the fuses are good. :banghead:

Scanner should be giving some transmission data and sensor readings.
And should pick up a code if not shifting?
Does scanner show gear selector ranges?
Is the speedometer and speed sensors working.
Any check engine lights on?
Fluid level good when hot?
Does it have 3 gear or 2 gear shifting or will it start in 2 or 3 gear range?

It has 2 and 3 shifting it willstart moving in 2 but not start engine in 2. There are no codes either for some reason. yes speedometer is working

it will shift second to third if it is already moving and you are doing it manually before putting it in drive or overdrive. and it will do fine down the highway in overdrive untill it has to down shift. what kind of sensor data other than the selector, solenoids and tcc.

Trans tempt and speed sensor and trans shift time and pressure control voltage to transmission and engine tps ans some show input and out put rpm.
lot of good info.
Any check engine lights or engine codes?
If it is a older OBD1 you can ground pin a to b and read codes.
But some 95 you have to have a special adapter for scanner to read out data.

If it will manualy shift out good you have a electrical or pcm or switch solenoid problem.

It is the OBDII system and there are no engine codes, I was woundering about the difference between a VCM and a PCM, and how doI know which one it has.

It has a vcm.
VCM is the NEW type of computer on them.
Used on 96 up and maybe some 95

It has the a separate vehicle computer and transmission computer but built together in one box.
Mounted on left fender under water tank.

Try unplugging a sensor or two and see if it will set codes for the unplugged sensors.

I unplugged the vss and the shift solinoid and it did not throw any codes. That does not sound right to me.

I could be wrong on the VCM.
The OBD11 VCM is a double pluged computer and if you look at it real close it is two pcm stacked up on top of each other.
95 had at least 3 pcm/vcm types
Is your computer on left fender apron?
Something messed up someplace if it did not sst code.
Did it get a check engine light?
Can you find another scanner to try on it?

That is the only real scanner that we have. The vcm is on the passenger apron. I did get it to set codes but I had to use generic obdII not the pathfinder 3 system.

Sounds like scanner is not hooking up right.
The 95 is a special breed of there own.
A lot of scanners will not work on them for some reason.
You might look in the instruction manual and see if it has a tech support telephone no to call in for help on scanner.
Or try to program in the scanner for one year up or newer.
Good Luck
MT