mild bang shifting

[wisdav1]

hi, i have a 2001 1/2 ton chev , that has 125000 on it. i got it 3 mo. ago with 122000,first thing i did,was drop the pan and change the filter,then auto-rx for 1100 mi,then had the trans flushed,and put in schaffers 204s.now its still has mild bang shifts from 1st to 2nd. is there anything i can do to fix this
thank you

 

[MolaKule]

Explain "bang shift," that's a new one to me.

In what condition are the universal joints.

 

[Bluj40]

Thats the same bang im having in 02 Accord dx,with 61k miles, after putting the magnefine filter and SF-Z1, 1st-2nd would occassionally give me a mild bang, but after that everything else is smooth.

 

[caremd99]

The 4L60E in the GM 1/2 ton is known for the 1-2 bang shift under light throttle. Mine (2004 CC K1500) does it too sometimes and has since Day 1 (which was Jan 1 2005). Even changing the fluid to AMSOIL ATF doesn't seem help this one. I have heard there is a PCM update to eliminte this bang but I haven't had this done so it may be nothing more than rumor. You can search www.gm-trucks.com for more info.

 

[wisdav1]

hi molakule'
u joints are ok,it kinda jolts going from 1st to 2nd,not a smooth shift.

 

[MolaKule]

Assume you have the 700R4 or its electronic equivalent such as the 4L60E?

Does the tranny seem to "hang" or delay the shift and then upshift hard.

Was the original fluid really dark?

I would recommend changing fluid every 5k for the next 10k and use maintenance doses of ARX or LC.

If that doesn't do it, you may have some worn hydraulic actuators, clutches, or severe valve body varnishing.

If the shifting inproves with each OC, then I would be optimistic.

 

[Ramblin Fever]

So is light throttle actually a bit more harmful, then moderate throttle?

My sister's 4L60E does this too.

 

[caremd99]

There is a PCM update to eliminate the 2-3 and 3-2 clank in the 4L60E. I had this installed last week. The 1-2 bang is much better now but still there slightly.

 

[lewk]

try this link http://www.usatransdoctor.com/DomesticCHEVYSELECandAnswers.htm this is a common problem with this transmission tha GM wont acknowledge. I have the same problem. you can temporarily cure this ill buy turning the car off and restarting after a brief pause. understand that the possibility exist for frying your tranny since the system defaults to a full-line pressure limp home mode.I have 221k on my 97 astro and I can find no one to do the upgrade w/o also wanting to do a rebuild. 200 vs 2000 big ones.mtbf to me means failure, I wouldn't rebuild my engine just because it has high miles.maybe its me!

 

[99]

The computer calibration for the trans is probably the problem. These transmissions have shifts controlled by the computer, so this is the first place I'd look assuming you are running the proper fluid and it's at the proper level. Like caremd99 said, you can go to the dealer to have the PCM reflashed to a newer release level...usually these updates fix prior release problems.