4L60-E Transmission Slipping from 2 to 3

[rpreeves]

Hi,

I have a 1997 Blazer Sport with a 4.3L. The transmission runs great in first and second gear, however as the time nears to shift to 3rd gear (about 45 MPH) it "slips" and acts as if it got shifted into neutral. The motor revs up but doesn't accelerate.

I am a computer programmer by trade and have written a program that sends/recieves any codes or live data to the vehicle, but I'm not sure what components I need to check to determine the problem. There are currently no trouble codes logged, but I have heard that some things like the trans solenoids can fail but not log any errors. Does anyone know of anything I need to monitor?

Thanks for the help in advance,

Ryan

[MT-2500]

Welcome to AF.

First step is to find a good engine /transmission capable scanner.
Snap on or GM makes good scanners for transmission testing.
Read out all transmission shift data and solenoid data.
Watch the shift error seconds and solenoid switching.
Check for history or past or present codes.
Not all problems will set the check engine light.
Most good scanners will have some built in test and also a pressure test.
Remember the 97 is a bad year on ign switches.

A all Data on line sub has a lot of info on transmission problems.
http://www.alldata.com/products/diy/index.html
Good Luck
MT

[rpreeves]

Thanks for the reply.

Can you elaborate on "shift error seconds and solenoid switching" ? I'm new to electronically controlled shifting.

Ryan

[MT-2500]

Originally Posted by rpreeves

Thanks for the reply.

Can you elaborate on "shift error seconds and solenoid switching" ? I'm new to electronically controlled shifting.

Ryan

A good transmission capable scanner reads out all shifting info.
It records and reads the time it takes each gear to shift and the actual transmission slipage.
A slow shift or slipping or no shift sets off a shift errow in scanner data.
It records the shift time in .100th split seconds amd records and reads out the shift time errows in 100th of seconds.
All all transmission shift adaptive data.
Most of the read out trasmission control pressure solenoid and shift solenoid data.
Also it will do some shift testing to check solenoids and read what solenoid is on or off.
Most shift problems will set a code past or present.
Basic you can watch and read transmission shifting data on scanner and most scanners can shift or test transmission shifting.
MT

[rpreeves]

Well I am certain I have no trouble/error codes, so there is no help there. I had this verified by a local transmission shop.

I really need to know what OBD-II commands I can send to either retrieve shift data or to test the solenoids. Do you know?

Also, if there is something mechanically defective within the transmission, would there be an abundance of metal in the oil pan?

Ryan

[MT-2500]

Originally Posted by rpreeves

Well I am certain I have no trouble/error codes, so there is no help there. I had this verified by a local transmission shop.

I really need to know what OBD-II commands I can send to either retrieve shift data or to test the solenoids. Do you know?

Also, if there is something mechanically defective within the transmission, would there be an abundance of metal in the oil pan?

Ryan

OBD11 does not read transmission data or codes.
You have to get into the transmission VCM data.
I do not know what they tap into or how they do it.
All data has a wiring diagram of the transmission/engine VCM and diagnostic plug if that would kelp you.
I always leave that up to Snapon and my MT-2500 and Solas pro scanners.

You can be losing transmission pressure or have burnt clutches or bad solenoids or valves in the transmission with no metal in bottom of pan.
Also lose of one gear can be anywhere in plantary gears or sprags or sun gear shell.
So always a good idea to check filter and for metal or other stuff in pan.
Good Luck.
MT

[blazes9395]

I agree with MT, you need to get a bi-directional scanner on there and see what the transmission parameters are showing, EPC cycle, solonoid function, tranny temp, etc, etc.


With the bi-directional scanner, the tech can command shifts manually and see what the transmission will do. If your slipping from two to three, and no four, then that could be an indication of burnt 3-4 clutches.

What does the transmission fluid look/smell like? If its burnt and smells bad, its usually a further indication of overheating as a result of slipping clutches.

A pan drop is also a good idea too, but usually I would say the last step after all the above is looked into first.

And lastly, make sure your transmission has the right amount of fluid in it.

[rpreeves]

I will work on retrieving the transmission data, but I don't know enough about the results to know what is normal. For example, what is normal temp and pressure suppossed to be?

Also I got to thinking. This problem occurs whether the gear selected is ODrive or non-ODrive. This tells me the solenoids are ok because the solenoids are not taken into effect when driving in non-ODrive gear selection. What do you think?

[MT-2500]

A good transmission scanner has all of the info and test built in it.
On transmission pressure you can read actual and desired pressure.

Your solenoids work in all forward gear.
1 gear 1-2 on 2-3 on
2 gear 1-2 on 2-3 off
3 gear 1-2 off 2-3 off
4 gear 1-2 on 2-3 off