1995 Chevy Blazer 4x4, 4.3L V6 Vortec. Up until yesterday everything was fine with the truck and got a new muffler installed about a week ago. Haven't did anything out of routine or different. Parked the truck at my office, came out a half hour later, started it and took off noticing the truck was very slow to take off. Having some knowledge of cars/trucks, when I came to a complete stop and went to take off the truck was not downshifting to 1st gear. Found the trans was low on fluid which was normal for this truck with 270K miles. Added fluid and headed home once I hit 45-55mph I noticed that it was not shifting into overdrive, running at almost 3K rpms at 45-65 which usually is 2,200-2,500 rpms. I parked it for the night and drive to work this morning but still the same issue. I have no idea about transmissions but have worked on my truck for years. I have read about solenoids but dont know how to troubleshoot, etc. Any suggestions?

 

Its likely that your shift sylinoids on the bottom of the valve body are bad.They not very expensive so change both of them while your in there.Also when was the last time the filter and fluid was serviced?If it hasn't been done you need to do this.My trans was giving similar problems the steps I mentioned above fixed it.I also did a flush on all the fluid.With the vehicle running and the outflow line removed and truck running,along with 3 large drain pans and 20 quarts of new fluid I kept pouring it in till the fluid was coming out nice and pink.If you go this route make sure you don't let the fluid stop running out of the outflow line or you will burn your front pump out.I had a partner watching and helping me when I did this.Make sure you don't overfill!

 

I appreciate your help very much. Once I pull the pan how will I know which solenoid is bad or which one is the one I am looking for?

 

There are two them both part numbers are the same.They are in the front of the valve body once you remove the filter.There 2 clips that you can use a screw drive to pry out,doesnt take alot of presure.Its been a minute or two since I had mine out but the new ones might come with rubber rings that hold them snug.Once you remove the crossmember if its in the way of dropping the pan Its quite simple of a procedure.hope this helps you.

 

One last question..... so once I drop the pan there are going to be two shift solenoids, A and B, which are exactly the same but one controls 1-2 and the other controls 2-3 correct? I should go ahead and replace both solenoids while I have the pan off correct? If that is the correct then what about the transmission not going into overdrive? Usually on the highway, 65 mph, I run about 2200 rpms- 2500 rpms, instead since I lost first gear I can tell its not going into overdrive plus I am running at 2800 rpms- 3000rpms. I just want to make sure I am replacing the right parts because my truck will not show anything when the diagnostic machine is hooked up for some reason. I plan on dropping the pan, replacing the solenoid(s), the filter, and flushing the system as you suggested, 1sttimejimmyowner, anything I missed or steps I should add? Thanks

 

Yes your correct replace both,1 soilinoid controls 1-2 the other drive and overdrive.Also do you have check engine lights related to computer codes because this will indicate another problem.If your torque converter is locking up like it should overdrive wont work either but it will leave code.You can search the site for definition of codes as there are many threads related that issue.Also look for a lot of debris in the pan once you have it off.If theres not much everything is good like the clutch pacs inside the tranny,if not you have serious issues.