96 blazer V6/auto LT with 210,000 miles. Let me state before ranting that no codes have been thrown. Recently while stopped at red lights the engine would surge whether hot or cold.This has recently cleared up some and has been replaced by having the engine bog down and stumble when it shifts into overdrive. As soon as if gets past 50mph it seems fine. Also in the past few days (never no when) while cold, I can leave my driveway and after stopping at the 1st stop sign in the neighborhood while in drive the truck will not move.I can rev the engine and nothing. If i cycle the gears say from reverse to neutral and back to drive then it will catch and I am on my way. Once on the highway it will shift fine thru all the gears, but when it's time to shift into overdrive the truck starts to bog down and shake momentarily. It will do this hot or cold and I never know when it will do so but seems to be happening more often .Trans fluid is where it is supposed to be (light red color) and the pan/fluid was never dropped or changed that I know of. Complete tune up 5 mos ago (gm dealership/gm parts) and ran great until about a couple of weeks ago. Fuel pressure @ 60 and holds for over 15 minutes. Seems like a tranny issue,but do not know what to look for. Gas mileage now sucks as I can only get abt 150 mi out of a tank if I'm lucky. Daily driver with two kids in college, need I say more. Would appreciate any and all thoughts or suggestions on what could be the issue.
Thanks to all for a great forum

 

check cat converter. sounds strange but thats what mine was.

 

Dont think it is the cat as it is less than a year old,any thing is possible and will check it out. What about the VSS. I have heard and read that this sensor could cause the very systems that I am experiencing. If it is the VSS where is it location. Is there more than one. I have been told that there is one located on the tranny and one on the transfer case. I have a 96 blazer with a 3 button (2hi,4hi +4lo) switch on the dash. Auto Zone has web shows 2 sensors available, a screw in type and another with a 1 bolt bracket.

 

Update...after sitting overnight and started 1st thing the next morning the truck will go in reverse to back out of the driveway.However, when put into drive nothing. After putting it back in park and I let it warm up for a few minutes it will then go into drive. I have added 2 ounces of dr.Tranny shudder fix and it has helped a little as the shudder is not as profound as it once was but I am still getting the occasional no "drive" in the morning. When i tap the brake during the shudder the rpms jump. Is this normal for this to happen.
I have 205,000 miles on the trans and to my knowledge the fluid has never been changed and still no codes thrown. So what do you all think! Am I looking at a possible TC replacement or maybe a simple trans fluid/screen repair will cure my pain.

 

My 99 had bog at certain throttle positions and milage drop of several MPG. There were no codes but it was the MAF sensor. When I unplugged the MAF the bog went away.

I assume the shudder happens during lockup and tapping the break stops the shudder?

For the No drive issue, did you very purposely try every gear, 1,2,3? Did reverse still work after you lost drive?

 

Had the MAF out and cleaned abt 2 mos ago so I am doubting that is causing my issues. I will unplug the MAF anyway on the way home to see if it makes a difference. Yes, to your response on the shudder. Yes,reverse still was working.
When the no drive issue happens it is always after sitting overnight and after I back out of the driveway, put it in gear and drive to the 1st or 2nd stop sign (less than 2/10 mi) in the neighborhood, step on the gas and nothing.
When this happens (at least 3-4 times already) I shifted into reverse (went in gear), then back to drive (nothing), to neutral and than back to drive where it engaged in gear and I was on my way. Never tried cycling through the other gears. What do ya think....tranny going ???

 

Maybe the filter is clogged or the transmission pump is going bad .

 

I am trying to make arrangements to have the fluid and filter changed hoping that this will correct the problems.As I have mentioned in earlier posts the fluid & filter it is something that I never had done to the truck as long as i have owned it (bought it with 96k and now has 201k) and I do not know whether the previous owner did so.
Tranny expert I am not so.... if it is the pump can it be accessed by dropping the pan or must the tranny be dropped.
Any other suggestions as to what could be causing my issues.

 

I have a 2000 Jimmy with a 4.3 v-6,i was wandering can i leave the back knock sensor unplugged and would it hurt anything?

 

I want to double check the codes, did you have it scanned or are you going off the lack of a check engine light? The shudder can be an pressure or TC issue. Low and reverse are on the same clutch pack so I'd tend to think your getting pump pressure since reverse works. The sprag has a oneway but I think that should work in 1 or 2. So I'm leaning toward a valve body or solenoid issue.
Changing the fluid and filter are well over due anyway.

You have to drop the tranny to pull the pump.