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Discussion Starter #1
hey everyone,

I tried searching around the forums for my issue. The closest I found was not shifting at WOT. I figured I would ask just in case.

I have a 95 Z28 auto with about 125,000 miles on it. Out of no where the car shifts fine from 1st to 2nd, but does not go any higher than 2nd gear.

This is under normal driving conditions.

Would this be the 3/4 clutch going bad?? or speed sensor???

Thanks in adance!!

Jesse
 

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Have you hooked your car up to a scanner and scanned for codes. Most of the transmission codes do not turn on the ses. Being that you own a 95 with the 16 pin dlc that is like a obd2 car, but is really an obd1 car, you will need a scanner that reads obd1 and obd2 cars. Using a paper clip across the dlc terminals won't do it, neither will a cheap obd1 code scanner like the Actron CP9001 that simulates a paper clip.

There are also engine codes that mess with the transmission also.

No shift past 2nd could be 3-4 clutch pack, but also torque converter, oil pump, valve body faults, Input housing faults including the 3-4 clutch, vss.
 

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Have you hooked your car up to a scanner and scanned for codes. Most of the transmission codes do not turn on the ses. Being that you own a 95 with the 16 pin dlc that is like a obd2 car, but is really an obd1 car, you will need a scanner that reads obd1 and obd2 cars. Using a paper clip across the dlc terminals won't do it, neither will a cheap obd1 code scanner like the Actron CP9001 that simulates a paper clip.

There are also engine codes that mess with the transmission also.

No shift past 2nd could be 3-4 clutch pack, but also torque converter, oil pump, valve body faults, Input housing faults including the 3-4 clutch, vss.
The torque converter won't cause a trans to not shift past 2nd. It's not likely it's a VSS either.

Frank
 

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3-4 clutch failure is common in 4L60E's. Especially those with the kind of milage you have. A bad 3-2 downshift solenoid will also cause this, but it will kick a code. Have you checked the fluid in it? What condition is it in? If it's discolored or has a burnt smell, chances are it's the 3-4 clutches. Does it attempt to make the 2-3 shift but just seems to go into neutral or does it just not attempt the shift?

Frank
 

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This morning I took it to Aamco for free testing, they said it is the 3-4 clutch packs. They didnt hook it up to check for any codes, just drove it around the block. he said it was $550 just to remove the trans and would have to quote me how much to replace everything they found wrong with it. So I'm guessing around $1,000 or more with labor and parts. sucks

it shifts into 2nd and does not attempt to go into 3rd. The engine will continue to rev higher but it will not even try to go into 3rd. downshifts from 2nd to 1st have been normal. This issue happened out of the blue. There were no signs of bad shifting before this.
I haven't been able to check the fluid, its been 40s/30s here in Chicago. I'll check it this weekend.

thanks
 

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I would avoid having it built at Aamco..

Frank
 

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Don't want to second guess the pros out there but according to the GM service manual, you know, the people who built the car and the 4l60e for the car, they say it plainly that a converter or the vss can cause a no shift up from second condition.

Plus the fact that if trans is rebuilt the torque converter will be replaced anyway.
 

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I'm all ears. Please explain to us HOW a converter will cause a no 3rd or 4th? Then, please explain HOW a VSS will cause it? A converter doesn't know what gear the trans is in. It's simply a fluid coupling with a lock up clutch. A converter can cause many issues, but causing the transmission to lose any specific gear is not one of them. A bad VSS will cause a no upshift condition, but it won't specifically disable 3rd or 4th.
This is where actually knowing about the 4L60E helps. You look through the GM diagnosis list and repost without any facts to back it up. Sure a converter will cause a no 3rd or 4th because it won't allow any movement...LOL Sure a VSS will cause a no 3rd or 4th, because it will cause a NO upshift condition. The car has 1st and 2nd, which eliminates either possibility.
Why am I stressing this point? Very simple. Foruns are great for sharing information. The problem is, sometimes there is bad information shared. I've been building transmissions for a living for 23 years. I specialize in this particular transmission. So, why is it so impartant that I point out that you gave bad info? What happens if the original poster takes your advice and only swaps a converter? Anyone who actually builds transmissions knows this won't fix his problem. To me, that seems like alot of wasted time and money...Just because he took bad advice from a forum.

Frank
 

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This morning I took it to Aamco for free testing, they said it is the 3-4 clutch packs. They didnt hook it up to check for any codes, just drove it around the block. he said it was $550 just to remove the trans and would have to quote me how much to replace everything they found wrong with it. So I'm guessing around $1,000 or more with labor and parts. sucks

it shifts into 2nd and does not attempt to go into 3rd. The engine will continue to rev higher but it will not even try to go into 3rd. downshifts from 2nd to 1st have been normal. This issue happened out of the blue. There were no signs of bad shifting before this.
I haven't been able to check the fluid, its been 40s/30s here in Chicago. I'll check it this weekend.

thanks
If you want i live in Chicago i have a snap on scanner and i could hook it up if you want just let me know

Sent from my SPH-D710 using AutoGuide.Com Free App
 

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Cahall you should be directing your how would questions to the GM techinical department. I have simply reported what the factory manual said about no shift past 2nd. I generally believe GM puts info into their manuals for a reason. If they say the 4l60e may have a problem in an area, I believe them. I do not have the years of transmission repair & trouble shooting you have, but I can read the trouble shooting chart GM puts out and was reporting what they said might be the cause.
 

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Cahall you should be directing your how would questions to the GM techinical department. I have simply reported what the factory manual said about no shift past 2nd. I generally believe GM puts info into their manuals for a reason. If they say the 4l60e may have a problem in an area, I believe them. I do not have the years of transmission repair & trouble shooting you have, but I can read the trouble shooting chart GM puts out and was reporting what they said might be the cause.
And I explained why it's written that way in their manual. You have to actually be able to decifer what they're saying. If you put that much faith in what you read, try replacing a converter if your 4L60E loses 3rd and 4th.

Frank
 

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Here's the thing, I wouldn't have just changed the torque converter and called it a day. Would have torn down my trans, as I only do my own and a few close friends, replaced the usual parts I replace, found any bad parts I don't usually replace, tested the electronic devices and replaced any bad ones, then put trans back together.
 

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Here's the thing, I wouldn't have just changed the torque converter and called it a day. Would have torn down my trans, as I only do my own and a few close friends, replaced the usual parts I replace, found any bad parts I don't usually replace, tested the electronic devices and replaced any bad ones, then put trans back together.
And when you tore the trans down, you would have found burnt 3-4 clutches...Which would have been the cause...NOT the torque converter.

Frank
 

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Just went through the whole trouble shooting section and it's funny that GM only listed the torque converter as a suspect in the no shift from second category.Only other converter faults was for no drive at all, and of course torque converter problems. Why would that be Frank, you think they just included it for poops and giggles, or maybe they had a reason.
 

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Just went through the whole trouble shooting section and it's funny that GM only listed the torque converter as a suspect in the no shift from second category.Only other converter faults was for no drive at all, and of course torque converter problems. Why would that be Frank, you think they just included it for poops and giggles, or maybe they had a reason.
I don't care how they listed it. If YOU think a converter will cause a no 2-3 shift, you should never be near an automatic transmission...

Frank
 

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Just went through the whole trouble shooting section and it's funny that GM only listed the torque converter as a suspect in the no shift from second category.Only other converter faults was for no drive at all, and of course torque converter problems. Why would that be Frank, you think they just included it for poops and giggles, or maybe they had a reason.
You tell us what you're reading. Now tell us exactly HOW a converter will cause a no upshift past 2nd? What can fail in the converter to cause this?

Frank
 

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Yeah, you'll want to take the GM service manual and its associated information with a grain of salt... They are written by technical writers, not engineers. Even experienced dealer techs (which I was one for 12 years) disregard the manual on a regular basis because of information like this. I use them for reference only (wiring diagrams, hydraulic diagrams, torque specs, etc.). I've seen some "green" techs run some pretty wild goose chases because of faulty manual information.

Either way, a bad VSS can (and likely would...) be responsible for a no-upshift condition, but not a situation where it shifts 1-2 and then no higher. A torque converter falls in the same category. It either works or it doesn't. There is no way it can work in 1st and 2nd, but not allow 3rd or 4th. Both scenarios are, quite literally, physically impossible...

Of the 200 or so 4L60E's I build every year, "I lost 3rd and 4th gear" is, by far, the most common failure - at least 75% of them... It's simply a burned up 3-4 clutch.
 

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I will take it I'm wrong about the converter, but saying I should never go near an automatic, is calling me an idiot. As a moderator of this forum, I have it within my power to ban members who disrespect the moderator, namely me. You get 1 warning only, if we can't have a friendly disagreement without you getting the personal insult playbook out, then changes can be made. Because of your wealth of knowledge, I am letting this one slide, next time it will be different.
 

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Wow... I wasn't trying to disrespect anyone. And I certainly didn't intend to infer that anyone was an idiot! I apologize if I did...

I was simply agreeing with the dispute of some incorrect facts in the GM service information.
 

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Jon, we have no problem. You can say what ever is in your mind and I know there won't be any disrespect from either of us. It was Cahall that I have the beef with. He can't seem to have a friendly disagreement without opening the insult play book. After you explained about the manual and it not being always right on, I was ready to concede the point, which I did. But there is never a good enough reason to treat each other poorly, as Cahall did. Saying I shouldn't be allowed to go near an automatic, is saying I'm an idiot. While not being a 700r4/4l60 expert, I have successfully rebuilt enough of them, with 0 failures, to at least give an answer to a question. My answers are not always correct. I will engage in argument, sometimes a false idea, like thinking GM manual is correct. He is also a knowledgeable member and I would hate to lose him as a member, but there will be no disrespect allowed on my watch.
 
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