01 Gmc 2500 Transmission Problem

kurt1993 · January 19, 2011

I have a 2001 Gmc Sierra 2500HD 4x4 w/ the 8.1L and Allison tranny it just rolled 50K miles and as i was plowing today i shifted as usual from forward to reverse when i was at a complete stop i herd a loud clunk (considering the transmission is silent when it usually shifts) and the truck jerked as it locked into reverse where it would usually just lock smoothly into reverse i finished up the plowing job taking it real easy but the truck would still clunk and jerk forward when shifted into drive and backward when shifted into reverse. I also noticed on the dash the little gear indicator would blink and not lock into a solid state unless it was in Park or 3 and my Service Engine Soon Light came on too.

I would like to know if i have any serious transmission issue or if its something more simple like a solenoid? do i need a complete rebuild or just something simple?

Thanks i would really appreciate any sort of helpful advise or answer

-Kurt

Mike G · January 19, 2011

I'm no expert on the Ally, but it sounds like a reverse pack or solenoid went. Stop by a parts store and have them pull the SES code.

djmercer1 · January 19, 2011

I have a 2001 Gmc Sierra 2500HD 4x4 w/ the 8.1L and Allison tranny it just rolled 50K miles and as i was plowing today i shifted as usual from forward to reverse when i was at a complete stop i herd a loud clunk (considering the transmission is silent when it usually shifts) and the truck jerked as it locked into reverse where it would usually just lock smoothly into reverse i finished up the plowing job taking it real easy but the truck would still clunk and jerk forward when shifted into drive and backward when shifted into reverse. I also noticed on the dash the little gear indicator would blink and not lock into a solid state unless it was in Park or 3 and my Service Engine Soon Light came on too.

I would like to know if i have any serious transmission issue or if its something more simple like a solenoid? do i need a complete rebuild or just something simple?

Thanks i would really appreciate any sort of helpful advise or answer

-Kurt

First thing to check is the neutral safety backup switch.

dewfpo · January 19, 2011

First thing to check is the neutral safety backup switch.

X2.

DEWFPO

kurt1993 · January 20, 2011

First thing to check is the neutral safety backup switch.

X2.

DEWFPO

weird i didnt do anything and the day after i tried to drive it again but nothing went wrong... my dad said he went to advance auto and had the guy clear the codes and its been fine.... but is it really fine?

Mike G · January 20, 2011

What was the code they cleared?

djmercer1 · January 20, 2011

First thing to check is the neutral safety backup switch.

X2.

DEWFPO

weird i didnt do anything and the day after i tried to drive it again but nothing went wrong... my dad said he went to advance auto and had the guy clear the codes and its been fine.... but is it really fine?

thats typical nsbu behavior when it starts geting bad. any chance the underside of the truck was wet when it acted up?

very common failure and a cheap fix...

kurt1993 · January 21, 2011

First thing to check is the neutral safety backup switch.

X2.

DEWFPO

weird i didnt do anything and the day after i tried to drive it again but nothing went wrong... my dad said he went to advance auto and had the guy clear the codes and its been fine.... but is it really fine?

thats typical nsbu behavior when it starts geting bad. any chance the underside of the truck was wet when it acted up?

very common failure and a cheap fix...

yeah i was plowing so it was real wet! lol thanks this is the kinda info i wanted to hear somthing that doesnt just have to do with codes... people never useto have codes to diagnose a problem anyway the codes are

P0700

P1713

P0700

the code PO700 appeared twice idk why?

txab · January 21, 2011

...... people never use to have codes to diagnose a problem anyway the codes are

P0700

P1713

P0700

the code PO700 appeared twice idk why?

Because vehicles didn't have all the electronic sensors and hardware like they do now....

Now you can think you have a trans problem when it is really related to a MAF sensor

djmercer1 · January 21, 2011

...... people never use to have codes to diagnose a problem anyway the codes are

P0700

P1713

P0700

the code PO700 appeared twice idk why?

Because vehicles didn't have all the electronic sensors and hardware like they do now....

Now you can think you have a trans problem when it is really related to a MAF sensor

dont know why the p0700 appeared twice, possibly 2 codes in the tcm(someone else will know)?? there are more codes to be read though, the p0700 is a generic code set as a result of a request of the tcm, need a different code reader to get the tcm codes, i dont know which readers read individual modules....

if memory serves, i think some trucks also had issues while plowing of getting snow/ice/water into the air intake and that set maf codes...

ChevyTech77 · January 21, 2011

Didn't know there were two posts in two different forums for the same truck with the same concern.

I replied in your other thread.

kurt1993 · January 23, 2011

http://www.gm-trucks.com/forums/index.php?...p;#entry1123385

most likely the best answer to my question....

gmtech4 · January 23, 2011

we already fixed this for him in 2 other threads

kurt1993 · January 23, 2011

we already fixed this for him in 2 other threads

actually to be fair Rob your post was equally as good his just included the "wetness factor" and that the trucks left tire can kick stuff up right onto the censor which probably happened and im guessing thats why i had the problem i had cause all i needed was the codes cleared so far.... but i do still think im going to have a professional take a quick looksee