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Discussion Starter · #1 ·
As you can see from the title I’m currently driving my 03 TB EXT. it’s the V6 with the 4L60E tranny that my husband just put in himself after the first one died on me. Since he put this one in I’ve had trouble with the shifter and the dashboard indicator matching up… I would have to take it from Park down to third and then back up to drive before it would give me any kind of power. Then about three weeks or a month ago, it started slipping. Long story short I’m driving around in third gear at about 3000 RPMs and no matter what I do or how high I get my RPMs it just will not shift into OD. it’s my understanding that in this type of transmission the gears are like pairs that work together. If one works then two should work. if two is bad then one is bad. Same for three and four. So in my simplistic thinking, since I have third gear then my 4th/OD is there and should work right? It is extremely difficult to get it to shift into third gear and I’ve got to get the RPMs up pretty high after the truck is warmed up for a little while, but it does finally go.

so here are my questions:
1.) is it going to hurt my motor driving it everywhere in third gear? I’m avoiding interstate driving so my max speed is about 60 to 65.
2.) Is there anything I can do right now while I’m driving to try to get in to overdrive?
3.) Any ideas on how we can fix this? My husband has change the fluid and he said there were no little metal pieces in the drain pan so that’s good right?

My sincere apologies if this is already been addressed in another thread. Like I said I’m literally driving and I just can’t take the time to look through all of them to try to find the answers. Thank you for any help you can provide.
 

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There's a lot to decipher here and the info MIGHT be wrong as stated.....

3rd gear is really called: DIRECT - or has a drive ration of 1:1.

OD --- as you call it has two factors that sometimes get confused by owner/drivers and I'll try to help you understand that situation first --- OK?
the shift sequence in a typical THM700R4 all the way up to a 4L60E and pretty much any other GM transmission that starts with a "4".

The shifts are as follows ↓ ↓ ↓ ↓ ↓ ↓ ↓

  • 1st gear --- startup from a dead stop.... more on this in a bit though .....
  • 1st gear + Lock Up --- but only in certain do-or-die circumstances as a protection for the transmission. You may not ever get into 1/L-U
  • 2nd gear
  • 2nd gear + Lock Up
  • 3rd gear
  • 3rd gear + Lock Up
  • 4th gear
  • 4th gear + Lock Up.

You stated that you seem to have a low power problem when accelerating --- and I'm guessing that's from a stop.... right?

OK --- if so --- you may actually be starting to roll in 2nd gear.

▲ 2nd gear starts from stopped are useful in very slippery conditions because the conversion factor in the torque convertor is at a mechanical disadvantage and the engine won't rev up and it feels like the engine is really struggling.
▲ This keeps the wheels from spinning in ice and snow and muddy conditions.
▲ This also works for you in 4WD too if you're really stuck - try it some time.

I say that you might be starting in 2nd gear because your quadrant isn't reporting the gear position correctly.
▲ That's a big problem and you have to fix that problem FIRST.

After you solve that quadrant-reporting problem, then more info would be needed.

I don't like what you said about "slipping" because the clutches or bands inside your transmission will NOT survive more than a few moments of that - and maybe just one time.

Clutches and bands do NOT slip in an automatic transmission. That's a rule.

About driving in DIRECT/3rd gear at highway speeds ....

You can get to maybe 40 in 1st, 65 or so in 2nd and maybe 90 in 3rd.

That would be pushing the engine to red line --- not really recommended.
 

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Have you verified proper fluid level with the engine fully warmed-up, running in Park or Neutral? Is the fluid discolored (should be bright red.)

As said, you need to get the adjustment correct so the dash indicator is correct.
 

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Here's the part that makes it a little scary ......

" ....... it’s my understanding that in this type of transmission the gears are like pairs that work together. If one works then two should work. if two is bad then one is bad. Same for three and four. So in my simplistic thinking, since I have third gear then my 4th/OD is there and should work right? It is extremely difficult to get it to shift into third gear and I’ve got to get the RPMs up pretty high after the truck is warmed up for a little while, but it does finally go."

Those are all very bad assumptions and not very logical with a little Voodoo Logic tossed in for balance.

There are special elements inside the unit for each gear --- and although it's true that some depend on others to be correct - it's not as simple as you are suggesting.

There is a 2/4 band that is needed for both 2nd and 4th.

2nd needs the 2/4 band to apply, but it has a planetary set for the gear reduction and uses a sprag and then .......

........ 4th (OD) uses a sprag, another clutchpack, a planetary set,

But I digress.

This won't easily correct your statement unless I show you the power flow through a 4L60E.


Here's a chart of the parts inside a 4L60E and their applications for the 4 forward and 1 reverse gear sets:

Slope Font Line Parallel Map
 

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Discussion Starter · #5 ·
Have you verified proper fluid level with the engine fully warmed-up, running in Park or Neutral? Is the fluid discolored (should be bright red.)

As said, you need to get the adjustment correct so the dash indicator is correct.
This is the easiest one to answer so I'll start here first. Yes, the fluid level is spot on and bright red. I checked it after it had warmed up, on a flat surface while running in Park.
 

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This is the easiest one to answer so I'll start here first. Yes, the fluid level is spot on and bright red. I checked it after it had warmed up, on a flat surface while running in Park.
I automatically assumed that would have been done by anyone experiencing transmission problems, right upfront.

That's why I didn't bother asking it. But thanks anyway because it's always good to have more information than necessary.

Did you see in that chart how many different elements are really in your transmission?

........... and those parts have multiple parts inside of them that couldn't be enumerated because it would be MORE totally intimidating.

Mememorize this chart because it will be on your final exam ... for fifty percent of your final grade ...... and I don't mark on a curve!
 

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70mph in 3rd is no problem at all. You'll get like 8mpg though.

Going up to 90mph to pass someone is cool too, just don't stay up there for more than a few seconds as it's stressful over long periods.
 
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