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Won't shift past 3rd gear. But only some days.

14K views 31 replies 5 participants last post by  g0t0pless 
#1 ·
I drive 44 miles round trip to/from work. Every now and then, and only part of the way, my van won't shift up to overdrive. Before this happened, there were no strange leaks, smoke, or noises. It just decided one day it wasn't going to shift past 3rd.

It will shift in Reverse, Park, 1st and 2nd just fine. Even manually shifting down to 2nd and 1st works just fine.

Any ideas?

It's a stock 95 Astro, with the stock automatic 4L60 (I assume) transmission.
 
#27 ·
Woodweasel said:
I had a similar situation a few month back. It would shift fine, but every once in awhile it would act up and not want to shift. Now the kicker was that my gearshift indicator on the column would flash on and off. No check engine light either and no Code. My trans guy said he didnt think there was any thing wrong with the trans, so he did a little pocking around and found the electronic part of the ignition switch , the square part under the switch itself on the column, was not sending a signal/power to the trans all the time. So the trans wouldnt get any power and it would go into "Limp Home Mode" 3rd only, as he called it. He replaced the switch and it shifts like new.
That sounds like it might be related to the "click" sound below the steering column when I push thebrake to shift out of park.

I'll poke around and see if its a relay or something, because that's what it sounds like is making the noise.
 
#28 ·
Fuse #20 10A, Pink wire, powers all the solenoids in trans. Even if you hook up your meter to read the pink wire at the trans, the open in the circuit could be a bad connection at the passenger side trans pass-through connector or inside the trans on the wiring harness you saw while the pan was off. The clicking from the brake pedal is the brake shift interlock solenoid. Only a problem when you don't hear a click.
 
#29 ·
Astroplane said:
Fuse #20 10A, Pink wire, powers all the solenoids in trans. Even if you hook up your meter to read the pink wire at the trans, the open in the circuit could be a bad connection at the passenger side trans pass-through connector or inside the trans on the wiring harness you saw while the pan was off. The clicking from the brake pedal is the brake shift interlock solenoid. Only a problem when you don't hear a click.
I'll throw a meter on it ASAP. As far as the wiring inside the pan, we did check it over thoroughly when we installed the 2 shift solenoids. So I doubt that's the problem.
 
#30 ·
I stopped at a transmission shop on my way in to work. He put a code scanner on it and told me to replace my coolant temp sensor to see if it clears up. If not, bring it in and he'll have a closer look.

So, my next question is, where is this sensor located? My Hayne's book tells me, but do I access it from the doghouse or the hood? Pretty easy to get to? Whats the part #? And what about do they cost?

Of course I haven't done any research yet, I'm still at work right now.
 
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