[lloydt2442]

I bought my son a 95 gmc sonoma and the transmission wouldnt shift. well the guy says "ever since that happened the speedometer quit working and the brake lights stayed on." well I've had the same thing happen to me before and I drove myself crazy trying to figure out what it was. So I call a good friend of mine who is a mechanic and he said oh that happens all the time! its the speed sensor! so I replaced the speed sensor and it didnt fix it. Any ideas!? I've checked all the fuses as well and they were all good.

 

[YankeeRodder]

You have problems my friend! I don't think they are related. The Tranny sounds gone. I suspect the speedo cable is cabbaged due to the tranny problem or super high miles and it just gave up. The brake lights I am betting are hanging up because of the master cylinder is gone too? Does the pedal go to the floor? Take em one at a time and pretty soon all of the problems will just be a bad memory. Best to you on this, nice little truck for a guy to get started with, lots of ez to find cheap parts.

 

[lloydt2442]

yeah i don't know.. the pedal goes to the floor. and the thing thats throwing me off is it doesn't do it all the time just every once in awhile.

 

[lloydt2442]

any other ideas?

 

[Importtech]

You sure you got the correct part replaced? I have to agree with your mechanic is likely the speed sensor and or wiring problem to it. Transmission uses the speed sensor for shifting, cruise operation and ABS operation... Most times when the speed sensor goes out you loose shift quality , cruise operation and brake and ABS light come on. This holds pretty much true regardless of what car line you are dealing with... On Ford trucks the sensor is in the rear end housing... Not sure where it is on chevys... havent looked at one in a while...

 

[lloydt2442]

it was near the rear of the transmission! i'm positive we replaced the right thing! I havent messed with the wiring to it but it looks like that may be where my problem is.

 

[Importtech]

If I can remember I'll look at a wiring diagram this eve and maybe point you in the right direction on how to check it out.... I suppose you could have multiple problems that are actually not related since you say the pedal goes to the floor but the symptoms you describe are typical with a failing speed sensor... ABS light on too?

 

[lloydt2442]

I'm sorry i read what he said wrong. the brake pedal doesn't go to the floor. the brakes work just fine its just on the dash it says brake lights when the transmission isn't shifting. someone else told me to turn the key on and put it in neutral and try to start it. I'm not real sure what that is checking but I'll try it. He also said my solenoid may be bad. And another guy told me the ignition switch.. I don't know but I don't think either of those could be my problem.

 

[Importtech]

Okay I'm allittle confused... You mean it doesn't shift Like 1-2nd or it doesnt want to come out of park or and or wont crank?

 

[Dean]

Sounds about the same one of our trucks - 99 GMC - 350 box van was doing when a shift solenoid had to be replaced.

 

[lloydt2442]

Okay I'm allittle confused... You mean it doesn't shift Like 1-2nd or it doesnt want to come out of park or and or wont crank?

it doesnt shift 1-2nd. it comes out of park just fine and cranks over after wiggling the key a little bit.

 

[wills65]

the guy that told you to put it in neutral and try to start it was showing you how to check for a bad park/neutral safety switch. which, if bad, will keep the brake lights on all the time.
as for the trans not shifting, a buddies, T/A just had the same problem and he replaced the shift solenoids and bada-bing, problem solved. most likely the speedo not working is directly related to your transmission issue because the speed sensor is located on the rear of the transmission.
do you have any codes?

you having to wiggle the key a little bit may not have anything to do with your problem, then again I could be wrong

 

[Importtech]

the guy that told you to put it in neutral and try to start it was showing you how to check for a bad park/neutral safety switch. which, if bad, will keep the brake lights on all the time.

Dont think the brake light will stay on with a bad range switch but it could cause the occasional hard to start.

If the shifting problem is only in one gear then maybe a shift solenoid could be the problem, however if the cruise is inop, brake light on, speedo inop all occured at the same time I'd be leaning towards something with the speed sensor. Often when the speed sensor fails the car will still shift but very rough. Sometimes ecm/tcms have a preprogrammed limp home mode where the vehicle will stay in one gear (usually 2nd) when there is an problem with the tranny. I do know some of the Gm trucks had a problem with an electric plate inside the tranny but can't remember exactly what years it affected. I'll try to send a wiring diagram your way this eve..

IIRC the plate is a pressure sensor plate.

 

[lloydt2442]

the guy that told you to put it in neutral and try to start it was showing you how to check for a bad park/neutral safety switch. which, if bad, will keep the brake lights on all the time.
as for the trans not shifting, a buddies, T/A just had the same problem and he replaced the shift solenoids and bada-bing, problem solved. most likely the speedo not working is directly related to your transmission issue because the speed sensor is located on the rear of the transmission.
do you have any codes?

you having to wiggle the key a little bit may not have anything to do with your problem, then again I could be wrong

no codes yet. A friend of mine is coming over tonight and he has the little computer thing that you plug into the ecm and it will tell you whats wrong with it.

 

[lloydt2442]

well we got it scanned. It showed one thing and one thing only. the speed sensor. so autozone either sold me a faulty part or its the wiring. It has worked all day today except for about 5 minutes or so and then I parked it and got back in and it was working. maybe a short in that wiring is the only thing I can figure out. I guess I'm gonna call a dealership and see what the wiring will run me. maybe a junkyard would have it as well!? anyways thanks guys on helping me out!:beers:

Thanks,
Lloyd

 

[Importtech]

Do I get the prize You may be able to get a repair kit (connector end) from the dealer... I know that there are several gm repair ends out there for various sensors...