Mechanics

STUCK IN 2ND GEAR

1995 GMC Sierra

Transmission problem
1995 GMC Sierra V8 Four Wheel Drive Automatic 213000 miles

I have a GMC 2500 that I just purchased 3 months ago. Motor is 454 with heavy duty trans. After about a month, my truck starts to die when I take it out of park. Sometimes it also happens when I go into park. Turning the key on and off 3 or 4 times let's it start again every single time, but that's the only way to do it. I assumed there was a problem with my ignition and put it on the back burner. Recently, my truck has been stuck in 2nd gear. I can move the shifter into all gears, but I only have 2nd, Neutral, Reverse, and Park. Tranny takes off in 2nd, will not shift up or down. Randomly though, it works perfectly. Has never slipped or stuttered. I took my truck to a transmission shop, they pulled the pan and did a service. Said solenoids A and B were bad, replaced them but didn't fix the problem. Aslo, the mechanic said my tranny is " cherry" and there is absolutely nothing else wrong with it. He advised I look into the ignition problem. I took it to a dealership for diagnostic, they said the ignition works fine, but I'm pretty sure they got lazy on me and didn't run a computer scan. A well respected mechanic in town says he's 100% sure I need to replace the ECM. Looking for another opinion and reassurance before I buy the part. Thanks.
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ShouldaBoughtaChevy
December 26, 2008.



The guy that mentioned the ECM has not looked at my truck, have only spoken with him and gave him a run down of the problems.

Tiny
ShouldaBoughtaChevy
Dec 26, 2008.
I have seen the ignition switches do some strange things when they begin to short internally. It will effect the trans as well since it is comp contolled. Do all other accessories work ok when the trans is messing up or when it dies when put in gear or park? When it dies, use a test light to see if all fuses have power into them in the panel under the dash, if not it could very well be the ign switch is bad and not feeding everything all of thetime or cant hold any real draw through it

Tiny
Jack42
Dec 26, 2008.
The only obvious thing that happens when the truck dies is that the fuel pump doesn't turn on. All accessories, gauges work and motor cranks. Like I said, turning the ignition on and off 3 or 4 times fixes it every single time. One other notable thing is that sometimes when I turn the truck off, the fuel pump sometimes runs for a long period of time after shutting off (once it ran for 45 minutes). But the motor dieing and the fuel pump acting weird only happens 2 or 3 times a week, and doesn't seem to die more often when the trans isn't shifting.

I haven't noticed anything that doesn't work when the trans won't shift. My biggest problem is, I work in the oil field and am away from home for weeks at a time so the repairs have to be done in a shop and I can't do much to my truck. I'm mostly trying to avoid unneeded labor costs. (Fixing the ECM, but then I have to fix the ignition instead or vice versa)

Also forgot to mention, when the trans shop ran the codes, three faults came up: Solenoids(replaced), Ignition, and ECM.

Any further insight would be greatly appreciated.

EDIT: One more thing, would like to give Jack some feedback, but I don't have any points to give. : \ How do I go about showing my appreciation?

Tiny
ShouldaBoughtaChevy
Dec 26, 2008.
No feedback necessary, lets just see if we can get to the bottom of this. Do you haopen to know the exact codes so I can look them up to see where we are at with this? Does the speedometer work properly when the trans isnt shifting?

Tiny
Jack42
Dec 27, 2008.
No, I don't know the codes. I've decided to just wait on fixing it until I get home this coming Friday. Decided I'll probbaly just replace the ignition switch myself (only $11 part) and then go from there.

The speedometer works. It does jump when the key is first turnned over though (sometimes as high as 40mph, and whether the trans is shifting or not) and falls right back to 0.

And I lied to you. I heard the mechanic wrong when he said ECM, he actually said TCM (trans control module) which is about $200. So I plan to just throw parts at it starting with the cheapest until something fixes it. And after some research It seems that the 95 Chevy/GMC has SERIOUS issues with the ignition, which is also why I'll just start by replacing that.

Tiny
ShouldaBoughtaChevy
Dec 28, 2008.
Good call, since there are no solid leads to start with, ignition switch is a good place to begin

Tiny
Jack42
Dec 28, 2008.
My GMC also has just stopped and is staying in gear, we didn't get any specific codes because we didn't have the computer on the truck when it was acting up but it did point with the codes we seen toward a computer problem. But when I pull the positive off of the battery and reset the computer it will start if it wasn't starting or it will shift properly, I am planning on swapping out the ECM.

Tiny
Mav16
Jan 6, 2009.
UPDATE: Replaced the ignition switch, truck shifts great. It wasn't as cheap as I originally thought though, NAPA misquoted me when I talked to them on the phone. $183.95 for the part from NAPA, $149.99 from Autozone.

Thanks again for the help.