2001 Grand Am Transmission Slip in 3rd and 4th

[TireDoctor]

All of a sudden my 01 Grand Am seems to slip in 3rd and 4th (D) gear. When manually shifted, it pulls hard in 1st and 2nd without any slippage. However, once shifted in 3rd, when depressing the gas pedal, the engine with rev very high and the car does not go any faster. If you remove your foot from the gas pedal, the revs drop, and you can feel a slight "lock up" but as soon as you get back into it, it seems to slip again.

Does anyone have an idea?

Thanks

[xeroinfinity]

Get the fluid level checked, and check all the corresponding fuses for the trans axle.
If thats ok get it scanned with a scan tool capable of reading trans codes.

Not good to make it slip, this could damage your clutches and that can get expensive to replace/repair.

Good Luck

[TireDoctor]

Originally Posted by xeroinfinity

Get the fluid level checked, and check all the corresponding fuses for the trans axle.
If thats ok get it scanned with a scan tool capable of reading trans codes.

Not good to make it slip, this could damage your clutches and that can get expensive to replace/repair.

Good Luck

Fluid level,

1) No leaks are present.
2) We raised car on level, pulled lower plug and fluid dribbed out, although not running at the time. Does running have a major effect on level testing?

Fuses? - Humm, how many are there and are they in one location?

When attempting to drive, you can feel it shift into 3rd and 4th, but it is like there is not enough hyd. pressure to fully engage clutches, any idea on that?

Thanks

[xeroinfinity]

Ok what engine and how many miles ???

Yes it should be running to check the level.
The fuses are under the hood fuse box.

If those are good you might try a fluid and filter change, not a flush!

[TireDoctor]

Quad 4, 145K miles

[xeroinfinity]

You are way over due for a fluid & filter change if it hasnt been done before.
Its recommended you change it every 40-50k miles.

Did you ever check the fluid while it was running ??

[TireDoctor]

XI

Yeah, this is my son-in-law's car, change is due, but I don't think this is the problem. I haven't jacked up and checked the level running, but there is no signs of any leaks, so I'm thinking its full considering it dribbled out when tested not running, and this problem happened suddenly.

I'm not trying to discount your ideas, I just hate to shot gun things and like to investigate before doing, too much.

I've been doing a bit of searching, found that:
1) 4t40e's in chevy's may experience similar problems due to MAF build up. So, I checked the MAP sensor, found that it was replaced, put in upside down, and the vacuum hose was jammed against air cleaner body. Put it in correctly, and test drove. The car seemed to run fine, and did so until this afternoon, same problem.
2) I scanned for codes, none.
3) I found an article about cracking pressure tubes on 4t40e's.
4) Since we swapped cars, I was driving this for the day today and noticed more than on the original quick drive. Here's what I've noticed.
Car starts and idles very high 2.5K, and comes down slowly until idling about 800 in N. When accelerating normally, shifts from 1-2 come at 3.5K RPM, and it seems like it should shift sooner, then it really doesn't shift from 2-3 until you back off the peddle, and then you can feel a slight shift, tack drops, and then when pressing peddle tack comes back up to 4K with no effort, almost like it when into N or instantly back into 2nd.
5) Also talked to an old bud, and another tranny shop tech who indicates that these units are really reliable who have both been in the biz 20+ years and indicate that they do very, very few of these. I didn't think to ask, but does the 01 4t40e have a vac modulator?

6) This car apparently has now had 4 MAP sensors gone bad...orignal GM + 3 aftermarket units. If this is going again, I'm thinking that maybe the PCM is getting mixed signals.

If need be, I'm prepared to pull the unit, but not until I've got a better indication that this is the problem, and not an external sensor on tranny or engine.

Any of this change your opinion of fluid is the problem or make you point to something else?

[xeroinfinity]

Yes the lack of maintenance is the cause of 95% of transmission troubles, which causes them to over heat and crap out.

Thier are numberous TSB's for these transmissions and many updates were done in 2003-04 with the 4T40-45e's.

Your best bet is to change the fluid & filter. DO NOT get it flushed with those kinda high miles!! It'll just make matters worse.
Also your scan tool may not read trans codes even if thier were any.

On the high idle could be a vacum leak or the IAC needs cleaned along with the TB.

Were the MAP senors realy bad, were they tested ??

If its not shifting right, agian it could be due to inadequate fluid pressure from a clogged filter or low fluid level. Its the cheapest thing to try an is WAY overdue. And a scan from a trans shop would also tell you if the shift solenoids are working properly, and how the fluid pressure is doing. Low fluid pressure is a major problem with the 99-02 4t40e-45e's IMO.

These as with most tranys are reliable . But as soon as you neglect them(from improper maintenance) or abusing them by driving them like its a race car(constant manual shifting) you will have problems !

I know personaly these are not great transmissions by no means! I tore a couple out several months ago and rebuilt one in my 99 SE to try and fix several problem areas, beafed it up as much as possible.

Here is my thread on the 4t45e....
Beafing up your 4T40-45E transmission- Tips & Tricks