Sticky second gear

Hi,
I just test drove a 1995 GMC Suburban and the owner told me that on some occasions, the car wouldn't shift from second to third gear. He then had to
put the car in neutral, switch off the contact, switch it back on and it would then shift from second to third gear. This would only happen once while driving it and then the problem would not occur anymore. Sometimes this wouldn't occur for weeks or months. Can this be a problem? What would be the problem and how can it be fixed?
Thanks,
Geert
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<<Hi, I just test drove a 1995 GMC Suburban and the owner told me that on some occasions, the car wouldn't shift from second to third gear. He then had to put the car in neutral, switch off the contact, switch it back on and it would then shift from second to third gear. This would only happen once while driving it and then the problem would not occur anymore. Sometimes this wouldn't occur for weeks or months. Can this be a problem? What would be the problem and how can it be fixed? Thanks, Geert>>
Of course this is a problem, although it seems to be intermittent -- at least for the time being. From what you have said, when the transmission fails to shift from second to third gear, you must stop the vehicle and then go through a work-around procedure which, so far, has restored the transmission back to a normal shifting pattern.
When the transmission is in the "2" position, it starts out in second gear and stays in second gear. Perhaps the selector is defective and is locking the transmission into this setting.
I am assuming that you are having the shift problem when the transmission is in the "D" position. If the transmission shifts properly after fiddling around with the gear selector, then the gear selector is likely the source of the problem.
Take the vehicle to a transmission specialist and see what he recommends.
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Hi,
The tranny gets stuck in second while it's in "D". It starts in first, goes to second and stays there. I know that there's something called "limp mode" that lets you drive the car in second with a faulty tranny but then there's an indicator light telling you that it's in limp mode. This is not the case. From a Hummer-site there's an article about this problem with the 4L80. There can be a number of reasons for this problem : -corroded battery terminals -bad grounding - can be solved by installing a heavy-duty braided grounding wire to tranny and engine. - clogged shaft-speed sensor. Since this is a magnetic device, it can gather iron-particles and this can distort the signal. I was just wondering if anybody has ever come across this problem. If it's none of the above, it can be a faulty B-solenoid and then I'm looking at a tranny rebuilt.
Geert

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>Snipped for brevity<
TranSurgeon wrote: ..... where-as some of us FIX them.........
Thanks God you do, the rest of us would not be able to drive them if you did not.                                     Remo
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Ok Transurgeon,
what do you think is wrong with the tranny? BTW, on the Hummer-site, the article was actually from a tech who has repaired numerous army Hummers. I would really appreciate some help as good tranny techs are hard to find here in Belgium.
Geert

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4L60E or 4L80E ?

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4L80E I guess.
I'm not sure. The owner said it was the heavy duty. It's a 1995 K2500 Suburban.
Geert

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if its an 80E, fail-safing to second gear, the most obvious cause is lack of power to the shift solenoids
start with the transmission fuse, in the small fuse panel on the end of the dash, accessible when the driver's door is open

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Hi TranSurgeon,
I don't think it's the transmission fuse, since this only happens once in a while. The owner said that when this happened, he had to cut the power and start the truck again. The this wouldn't happen anymore for the rest of the day or even a few days or weeks. When I testdrve the car, this is exactly what happened. The car didn't shift from second to third. I cut the power and restarted. Then the car shifted just fine.
Can this also be caused by one of the causes I described : - bad negative connection - corroded battery terminals or perhaps a bad connection to the solenoids? This is what the Hummertech also described : since the solenoids draw a high current, they are very susceptible to bad connections.
Thanks for the help.
Geert

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Could still be a bad fuse or fuse holder. All it takes is a bit of corrosion to cause the fuse to have a poor connection. Pull it and see if the fuse is actually in good shape. THEN think about other bad connections. OH and FYI TranSurgeon knows his stuff, he OWNS and OPERATES a Transmission Shop FULL TIME, not just fixed a few in the army....
--
Steve Williams



"Geert Annys" < snipped-for-privacy@pandora.be> wrote in message
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pull the connector on the transmission and check for corrosion on the pins
also look for any evidence of ATF inside the connector, some of them would 'wick' fluid around the pins
also watch for any evidence that the 'PRN4321' in the dash is dimming when it does this, which would indicate a bad ignition switch

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Thanks for the info TranSurgeon (and for the reassurance Steve)
It's sure a great help to have people like you around. I'll look into it as soon as I get the car. One last question. As I was used to driving a '84 Burb (I've been a fan of American cars from day one I drove one), I'm not used to dealing with a lot of electronics in a car. I also feel that electronics have no place in a car. They're too much prone to defects. But, as it is inevitable to get a car without the electronic stuff, what can I do to protect the connectors and wiring?
a grateful Geert

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I had similar problem with my '91 K2500HD 6.2L Dsl.
It would shift fine, then occasionally would not go past 3rd.
I would shift to N while driving, stop then restart the engine and usually the fault would be cured. Eventually this "fix" stopped working.
When the transmission encounters certain errors, (some will be tolerated with no apparent effect) it will store them until the engine is shut down. Others will be stored longer. Stopping and restarting the engine is like rebooting your PC to clear an error.
Step 1 is to dump the error codes.
Step 2 is to find a list of the error code meanings
Step 3 is to find a troubleshooting procedure and wiring diagram.
It turned out that the TPS had an intermittent open circuit which my $150 GM visit failed to diagnose. I found it by unplugging it then measuring the ohms at the plug while rotating & jiggling the TPS "Wheel"
After I replaced the TPS, everything was fine for a while, then the transmission would not shift back to 1st after stopping until the vehicle started moving again only when hot. More troubleshooting revealed that the engine speed sensor, whose case was slightly cracked, would go open circuit when it got hot. Replaced that. Tranny's been great since (touch wood).
These are by no means the only possible causes, but probably the easiest and cheapest to fix. However I have bought good used TH350's including torque converters for less than what the two sensors cost me.
Good luck!
One-Shot Scot wrote:

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