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Tansmission Shifting.

krazycold

By krazycold
in Ask A GM Technician

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krazycold Enthusiast

krazycold

Posted
Posted

Hi i have a 2004 gmc savana 2500 van with a shifting issue.. when i pull the shifter from park to reverse nothing. but if i continue going through the gears.. ie.neutral it goes forward, Drive it goes forward and so on till i go to number one.. all seems fine have correct oil amount, no smell. is it possible that the park/neutral position switch has failed. any and all help is appreciated thanks guy's /girls

gmtech4 Senior Enthusiast

gmtech4

Posted
Posted

youre clear as mud bud,makes no sence at ALL

 

get it scanned

 

if no reverse ,it means no reverse and trans is done!

 

clarify please!!!!

krazycold Enthusiast

krazycold

Posted
  • Author
Posted
youre clear as mud bud,makes no sence at ALL

 

get it scanned

 

if no reverse ,it means no reverse and trans is done!

 

clarify please!!!!

 

 

hard to scan no power to data port...

 

if trans is no good, should i be able to put selector or gear shift into neutral and have the vehicle drive away this trany has the park/neutral position switch and i wonder if the pin on the shaft that detects the reverse gear is broken.. if you need more info please reply i will do the best that i can to provide info.. For the data port can i run power temporarily to the plug or thats not an option.. would an aftermarket remote start derate trans checking all option before replacing the transmission. thanks again

txab Senior Enthusiast

txab

Posted
Posted
youre clear as mud bud,makes no sence at ALL

 

get it scanned

 

if no reverse ,it means no reverse and trans is done!

 

clarify please!!!!

 

 

hard to scan no power to data port...

if trans is no good, should i be able to put selector or gear shift into neutral and have the vehicle drive away this trany has the park/neutral position switch and i wonder if the pin on the shaft that detects the reverse gear is broken.. if you need more info please reply i will do the best that i can to provide info.. For the data port can i run power temporarily to the plug or thats not an option.. would an aftermarket remote start derate trans checking all option before replacing the transmission. thanks again

 

Check your cigarette outlet fuse, it's on the same circuit as port.

krazycold Enthusiast

krazycold

Posted
  • Author
Posted
youre clear as mud bud,makes no sence at ALL

 

get it scanned

 

if no reverse ,it means no reverse and trans is done!

 

clarify please!!!!

 

 

hard to scan no power to data port...

if trans is no good, should i be able to put selector or gear shift into neutral and have the vehicle drive away this trany has the park/neutral position switch and i wonder if the pin on the shaft that detects the reverse gear is broken.. if you need more info please reply i will do the best that i can to provide info.. For the data port can i run power temporarily to the plug or thats not an option.. would an aftermarket remote start derate trans checking all option before replacing the transmission. thanks again

 

Check your cigarette outlet fuse, it's on the same circuit as port.

 

 

 

 

 

Checked it out you are correct sir no power to the cig lighter plug. repaired put scan tool on vehichle and no trans codes found... leaning towards the tranny shot thanks guy's you all have been a great help..just wondering if the band have stuck together or something else has failed novice wanting to know how this all takes place is there a place to get online breakdowns of transmissions for the do it you selfer!!!!

Shu Enthusiast

Shu

Posted
Posted

If you have it in neutral and it acts like drive, then I'd lean toward a guess it is in fact your PN switch. Can you start it in neutral now? Have you tried to remove the shift rod from the transmission lever and then shift the lever manually (on well supported jack stands) to see if you have all gears working in the transmission? If a stuck band, maybe throw a bottle of Lucas Transmission Fix in it and see if that frees up whatever is stuck. How many miles are on the transmission? Have regular fluid changes been done?

krazycold Enthusiast

krazycold

Posted
  • Author
Posted
If you have it in neutral and it acts like drive, then I'd lean toward a guess it is in fact your PN switch. Can you start it in neutral now? Have you tried to remove the shift rod from the transmission lever and then shift the lever manually (on well supported jack stands) to see if you have all gears working in the transmission? If a stuck band, maybe throw a bottle of Lucas Transmission Fix in it and see if that frees up whatever is stuck. How many miles are on the transmission? Have regular fluid changes been done?

 

 

I have not tried to do the shifting manualy... the vehicle starts in park put selector in reverse i have nothing no whinning no lurching nothing move selector again to neutral spot and the vehicle drives away just like it is in a drive gear thats what has led me to the pn position switch. in the first place.. thanks hope this will help me determining if it is a pn switch.. and not a trans.... thanks again guy's

Doug_Scott Senior Enthusiast

Doug_Scott

Posted
Posted

Unless they have really changed things up, the park neutral switch is for starting the engine. It is to prevent you from starting in gear. Nothing to do with selecting reverse.

If you have drive in neutral, chances are you will find you also have drive in Park, but the park pawl is stopping you from moving. Try to rev the engine in park and see if it feels like it does if you press hard on the brake while in gear and rev the engine up. If that is the case, I would think you either have a solenoid gone bad, or a clutch pack seized up. If it is a solenoid, you may be able to recover the trans, if it is a clutch pack, trans is toast.

 

I used to rebuild transmissions at a Chrysler dealership many, many moons ago, way before electric enabled transmissions (904 and 727, right about the time Chrysler started with lock up converters 30 years ago). If the park neutral switch still works like it used to, you would be wise to not try to rebuild on your own.

Shu Enthusiast

Shu

Posted
Posted
If you have it in neutral and it acts like drive, then I'd lean toward a guess it is in fact your PN switch. Can you start it in neutral now? Have you tried to remove the shift rod from the transmission lever and then shift the lever manually (on well supported jack stands) to see if you have all gears working in the transmission? If a stuck band, maybe throw a bottle of Lucas Transmission Fix in it and see if that frees up whatever is stuck. How many miles are on the transmission? Have regular fluid changes been done?

 

 

I have not tried to do the shifting manualy... the vehicle starts in park put selector in reverse i have nothing no whinning no lurching nothing move selector again to neutral spot and the vehicle drives away just like it is in a drive gear thats what has led me to the pn position switch. in the first place.. thanks hope this will help me determining if it is a pn switch.. and not a trans.... thanks again guy's

 

The reason I asked if you had taken the linkage off and checked it manually on the transmission was to eliminate the linkage from being an issue. Sometimes things wear in the linkage and then it doesn't engage the shift lever on the transmission correctly or fully. This also allows you to 'feel' what is happening in the transmission shift mechanism while moving the lever. You should feel distinct clicks as you rotate the lever from one gear to the next. If you do not, then you are going to have to take the pan off and figure out what is broken. The fact that it will start in gear is definately a problem with the P/N switch but could also be related to a lever problem.

 

As far as just taking your vehicle to a transmission shop for repair because as someone else put it "transmissions are not a DIY" I strongly disagree. Transmissions are greek to many shade tree mechanics and most owners and I know of several shops who take advantage of that. My recommendation is to eliminate the simple things that most people can figure out with a few minutes and some simple tools so then you knwo for sure if the shop is blowing smoke up your $%^& when they immediately tell you you need a new or rebuilt transmission.

 

FWIW a buddy had a 85 Monte SS which was "acting funny shifting" so he took it to a trans shop. Immediately they said he needed a new trans. My buddy couldn't afford it at the time and had no other means of transport. So I decided to take a look at it for him. Fluid was clean. On jack stands it shifted just fine through the gears. On the ground it struggle. It wasn't the trans at all but rather a plugged Cat Conv. We replaced that and all was good as new. I wonder to this day what that shop would have said when they put a new trans in it and it still ran the same. Diagnose as much as you are able to before risking being bent over at some shop.

krazycold Enthusiast

krazycold

Posted
  • Author
Posted
If you have it in neutral and it acts like drive, then I'd lean toward a guess it is in fact your PN switch. Can you start it in neutral now? Have you tried to remove the shift rod from the transmission lever and then shift the lever manually (on well supported jack stands) to see if you have all gears working in the transmission? If a stuck band, maybe throw a bottle of Lucas Transmission Fix in it and see if that frees up whatever is stuck. How many miles are on the transmission? Have regular fluid changes been done?

 

 

I have not tried to do the shifting manualy... the vehicle starts in park put selector in reverse i have nothing no whinning no lurching nothing move selector again to neutral spot and the vehicle drives away just like it is in a drive gear thats what has led me to the pn position switch. in the first place.. thanks hope this will help me determining if it is a pn switch.. and not a trans.... thanks again guy's

 

The reason I asked if you had taken the linkage off and checked it manually on the transmission was to eliminate the linkage from being an issue. Sometimes things wear in the linkage and then it doesn't engage the shift lever on the transmission correctly or fully. This also allows you to 'feel' what is happening in the transmission shift mechanism while moving the lever. You should feel distinct clicks as you rotate the lever from one gear to the next. If you do not, then you are going to have to take the pan off and figure out what is broken. The fact that it will start in gear is definately a problem with the P/N switch but could also be related to a lever problem.

 

As far as just taking your vehicle to a transmission shop for repair because as someone else put it "transmissions are not a DIY" I strongly disagree. Transmissions are greek to many shade tree mechanics and most owners and I know of several shops who take advantage of that. My recommendation is to eliminate the simple things that most people can figure out with a few minutes and some simple tools so then you knwo for sure if the shop is blowing smoke up your $%^& when they immediately tell you you need a new or rebuilt transmission.

 

FWIW a buddy had a 85 Monte SS which was "acting funny shifting" so he took it to a trans shop. Immediately they said he needed a new trans. My buddy couldn't afford it at the time and had no other means of transport. So I decided to take a look at it for him. Fluid was clean. On jack stands it shifted just fine through the gears. On the ground it struggle. It wasn't the trans at all but rather a plugged Cat Conv. We replaced that and all was good as new. I wonder to this day what that shop would have said when they put a new trans in it and it still ran the same. Diagnose as much as you are able to before risking being bent over at some shop.

 

 

 

 

 

 

lets back up.... I start the van in park not neutral... however i put the selector to neutral and the trans goes into forward gear... i have tried to put in reverse and rev the van but to no avail it will not move... I am with you shu to many people get taken avantage of by certain company's becuase thier diagnostic skills is change it out and the problem went away... i believe in checking out all possible angels before calling trans... i am not a dyI'er.... however i am not an automotive mechanic... but i am a heavy duty mechanic with no automotive experience guess everyone starts somewhere EH!!!

krazycold Enthusiast

krazycold

Posted
  • Author
Posted
Unless they have really changed things up, the park neutral switch is for starting the engine. It is to prevent you from starting in gear. Nothing to do with selecting reverse.

If you have drive in neutral, chances are you will find you also have drive in Park, but the park pawl is stopping you from moving. Try to rev the engine in park and see if it feels like it does if you press hard on the brake while in gear and rev the engine up. If that is the case, I would think you either have a solenoid gone bad, or a clutch pack seized up. If it is a solenoid, you may be able to recover the trans, if it is a clutch pack, trans is toast.

 

I used to rebuild transmissions at a Chrysler dealership many, many moons ago, way before electric enabled transmissions (904 and 727, right about the time Chrysler started with lock up converters 30 years ago). If the park neutral switch still works like it used to, you would be wise to not try to rebuild on your own.

 

 

Hey doug thanks for joining in. In the great debate would the van start in park. would it be possible i'am not sure what to say i dont have the van at my disposale at all times have to go to the yard and run the thing its out doors and cold where i live so getting into the shop is the first step.. i will continue with the progress today and get back to you.. thanks again guy's your becoming a great help in the should i or should not put new trans in.. vehichle has less than 83,000km on it.. lack of use and old trans fluid.

Shu Enthusiast

Shu

Posted
Posted

Doug makes valid points. It could be a bad solenoid or broken clutch pack and I am not discouting either of those as both could cause your problems. The P/N switch is placed on the shift lever to keep you from starting the vehichle in any gear other than Park or Neurtal. It will not cause it to not go into reverse or have drive where neutral should be. That is the shift lever. If you have a linkage issue it may casue the lever to not move precisely and cause this to some extent. I do question why no reverse at all though as even with bad linkage you should be able to play with the shifter enough to find reverse. This is where what Doug suggests makes sense. In many automatics reverse is the first gear to stop working when fluid levels are low. Are you sure it has the right amount of fluid?

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