1st-2nd shift problem

C

chilie349

New member
Joined
Jun 1, 2011
Messages
2
Reaction score
0
Points
0
I have a 2003 gmc sierra 1500 v8 w/automatic transmission. acouple months ago it all of a sudden would not shift from 1st too 2nd. I have to bring the rpms up to 3,000 then let off the gas when the rpms drop to about 2,200 i can feel 2nd gear engage and there is no problems with it shifting after that (untill i come to a stop again and have to go from 1st too 2nd). i brought it to a transmission shop. they took it for a test drive, and said i needed a new transmission. they said no codes were found. when i pressed for more info the clerk said the test driver said it wouldn'd shift into 2nd. i had explained the trick to getting it to shift before his mechanic test drove it(bring rpm upto 3,00 then let off gas) but i don't think he told the driver. he said the trans. is 7 years old and it would be more cost effective to just replace it. the transmission clerk seemed too nonchalant about the diagnosis, i just wanted to get some more advice/information before i commit to this costly repair. i thought about just replacing the shift solenoid, and hope that fixes the problem, but again i would like some more info before i start anything. thanks for your time.
John
 
it has 101,000 miles on it. the fluid is a brownish pink. fluid level is good.
 
chilie349 said:
I have a 2003 gmc sierra 1500 v8 w/automatic transmission. acouple months ago it all of a sudden would not shift from 1st too 2nd. I have to bring the rpms up to 3,000 then let off the gas when the rpms drop to about 2,200 i can feel 2nd gear engage and there is no problems with it shifting after that (untill i come to a stop again and have to go from 1st too 2nd). i brought it to a transmission shop. they took it for a test drive, and said i needed a new transmission. they said no codes were found. when i pressed for more info the clerk said the test driver said it wouldn'd shift into 2nd. i had explained the trick to getting it to shift before his mechanic test drove it(bring rpm upto 3,00 then let off gas) but i don't think he told the driver. he said the trans. is 7 years old and it would be more cost effective to just replace it. the transmission clerk seemed too nonchalant about the diagnosis, i just wanted to get some more advice/information before i commit to this costly repair. i thought about just replacing the shift solenoid, and hope that fixes the problem, but again i would like some more info before i start anything. thanks for your time.
John
Click to expand...

1-2 shift does not happen at WOT until you let off the gas. Best case, try replacing the TPS. The Middle case leak in the 2nd gear apply circuit (servo assembly or 1-2 accumulator). Doublecheck by using the pressure gauge and watch for a big drop when the PCM commands 2nd gear and at worst case is poor line pressure rise from a bad EPC valve.

If there's a problem ONLY on the 1-2 shift, 1-2 accumulator piston cracked or stuck cocked in the bore. Check the yellow spring inside the accum housing for breakage. Also, if the accumulator housing walls are scored, the housing must be replaced. Easy fix in the pan.

And my advice is to take it to another transmission shop, they will put a line pressure gauge on the pressure test port and go for a drive to verify proper line pressure. Base pressure at idle in P,N,OD should be around 70psi and around 140psi in R. Max line pressure should be at least 190psi at WOT in 1st or 2nd, 225psi is optimum. If base pressure is low, trans or pump is worn out. If max pressure is low, check EPC solenoid. If reverse is slow to engage, and line pressure does not come up to at least 130psi in reverse, replace the boost valve with a Transgo 0.490" or 0.500" boost valve which is a easy fix in pan also.

Good luck and keep us posted an no worries about the mileage if you have been servicing your transmission, i have over 365,000 miles on mine and still going strong with the right service. ;) Since your transmission fluid is brown, it indicates your transmission has been slipping and you need to get it serviced and have them replace the boost valve and sleeve and also have them swap out the Servo's with Corvette Servo's to give you a more positive shift.
 
Last edited:
well i will tell you to save your money DON"T replace your tps:rolleyes:

With a 100 k and brownish fluid i would drop the pan and look in side to see how much medel is there. If you see a lot (more than a few pices) replace the trans if your going to keep it. If not much medal put new filter in and take it to a trans shop and ask them to check your valve body .

Good luck
 
03 SIERRA wont shift 1st to 2nd unless I let off gas!!

Hi I just posted this same thing as a comment on another thread. I will try this and get back to you. Thanks Molson
 
Hey, I’m facing the exact same issue suddenly and they also told me to change my transmission,
I have 03 sierra truck.
I also have the speedometer playing crazy with abs and e-brake light popes up, I changed all the speed sensors and still facibg these problems

Please tell me your updates about the problem so I know what to do
 
what would happen if you did not change your engine oil for 100,000 miles or more? the price of an oil change is cheaper than a new engine. you should drain and add fresh ATF every 30,000 miles. the price of tranny fluid is cheaper than a new transmission.
 
You must log in or register to reply here.

Share this page



Back
Top