Help with auto transmission problem

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  #1  
Old 02-19-05, 09:59 AM
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Help with auto transmission problem

I wonder if anyone could provide some insight into a problem with my automatic transmission. The car is a 2000 Chevy metro with around 77K miles. A few days ago it suddenly stopped shifting into second and would go directly into third when 20mph was reached with low acceleration. Apart from this problem there has been no visible signs of any other problems fluid looks fine. Checked TV cable looks OK. The check engine light came on for a while (has gone off now) and my OBD 2 scan tool reads an error code of P0756 shift solenoid B performance or stuck off. I also have the service manuals for the car including some info on servicing the trans and it says that this is more likely to be a mechanical problem with the solenoid than an electrical one.

So I took it into a transmission repair place who said they would initially replace the solenoid and see what happens. Well, they replaced the solenoid (or they claim they did anyway) and the car still has the problem. They are now suggesting either rebuilding or replacing the trans as the clutch packs may have burnt out. Does this sound correct. My service manual says a simple cleaning of the hydraulics and the valves may fix the problem.

Id be grateful for any suggestions.
 
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Old 02-19-05, 03:37 PM
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suggest taking to dealer for diagnossis to see what they find, it could be as simple as a sensor that is bad to needing more major work the dealership are more up to date and will know of any updated parts that has came out to fix possible problems if any for your transmission.
 
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Old 02-19-05, 04:58 PM
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It's more likely the valve body is causing the P0756, sticky valves in valve body keeps the fluid flowing to certain port, when the A or B shift solenoid does not see pressure increase/decrease due to sticky valves, it'll turns the engine light on, try to remove the valve body and take it apart(overhaul), clean all the spool valves and see if the code return.
 
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Old 02-19-05, 08:04 PM
andyfort
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buy a bottle of lube guard from auto zone and it should take care of it. If not we at "AAMCO" will put an updated valve by a company called sonnax that will fix it but you have to pull the tranny to service the valve body.
 
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Old 02-19-05, 10:35 PM
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Thanks for the info. I was planning to remove the solenoid first and confirm whether it is working using compressed air and 12V as per the fault finding guide in the service manual. If it passes the test I was planning to remove the valve body for cleaning.

According to my tranny service manual you can remove the valve body without removing the tranny from the verhicle. It says you have to remove the pan first, remove the accumulator pipes and then unbolt the valve body from below and then remove.

Can the valve break?
 
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Old 02-21-05, 05:13 PM
wagonman76
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If you are going to remove the valve body, make sure you know exactly where the check balls go. Ive heard that when you remove the body, the balls fall out and if you dont know where they go, youre SOL.
 
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Old 02-21-05, 09:05 PM
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Yep - thanks for the tip. Based on what I read in the service manual yes, there are 4 check balls in the upper valve body so you have to place the upper body face up when separating the upper and lower sections. The locations are marked on the service manual but if they fall and roll out of sight then yes, big problem.

I will clear space on my workbench when working on the valve body to make sure none of the parts get lost. I am also thinking of replacing the 1-2 shift valve just in case the old one is damaged.

Based on what I have read, the only causes for this problem could be a stuck solenoid, stuck valve or I guess a broken band although I'm not sure how likely broken bands are in an automatic. Maybe an expert can answer this one.
 
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Old 03-05-05, 11:04 PM
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Well, eventually I got around to tracking down the problem. It looks like the second brake band has broken I bought the appropriate service manual by ATSG and it is excellent - shows all the valves and hydrolic circuits in all the gears. I immidiately realized that the shift solenoid and 1-2 shift valve failure would also cause the reverse gear to fail. Also the transaxle has a small viewing window which allows inspection of the servo at the point in connects the band. I removed it with difficulty as it is meant to be removed with the transaxle outside the vehicle and the band has broken off near the pin. So unfortunately I will have to remove the assembly and install a new band.

I understand that there are special tools for pulling off the oil pump which is behind the torque converter. My ATSG book quotes a part number but I have no idea who the manufacturer is. Any pointers to where I can find such a tool would be welcome. I guess it is called an oil pump remover. It is a pulling tools with 2 arms.
 
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Old 03-06-05, 01:25 PM
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According to my info you need 2 (j 6125-1b) and 2 (j 35495) kent-moore is the company that sells them.I call them spent more lol.I would just take the trans to a shop and give them a couple bucks to pull the pump for you.It will be much cheaper than buying tools you will never use again.
 
  #10  
Old 03-06-05, 01:42 PM
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Thanks - I'll check this out. Yeah, kent moore tools - expensive for sure (at least the transmission ones). I did manage to pick up a couple I need for the job on ebay at a fraction of the cost (one sells for around $250 and I picked it up plus some others which looks like for working on the trans for $5 so maybe I might get lucky again). Failing that taking it to a shop is a good idea.
 
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