'96 Metro Trans Problem

[Chacheska]

Just bought a '96 Metro 4 cyl 3 speed auto with 118,000 miles. Trans was slipping and down a qt of fluid. I filled the trans but it didn't help. The trans fluid was light brown so I dropped the pan and screen. Magnet looked like a furry Chia pet. Cleaned pan, magnet and screen and replaced close to a gallon of fluid. Didn't help. and after awhile the fluid was again light brown. Problem: Car always shifts fine when cold for the 1st 15 minutes. After it gets fully warm it bypasses 2nd gear and shifts into 3rd at 20 mh. If I manually shift into first from a dead stop it starts out in second and will shift into 3rd when I manually shift back into drive at 20 mph. If I start out in drive and manually shift into 1st gear at 13 mph it will shift into second and I can manually shift back into drive at 20 mph which will again put it into 3rd. If I try to manually shift into 2nd at any time it goes out of gear completely. If I disconnect the round connector near the VSS under the hood it stays in 3rd gear all the time in the drive position. DTC's are 753, 758 and 780 (shift solenoid A electrical, shift solenoid B electrical and shift malfunction). ALSO ...... something is draiing my battery. With a healthy battery I start out with the battery light off or very dim but as the car warms up over time the battery light gets brighter as the voltage drops. I had the chargig system checked at Autozone but they said the battery and alternator were both fine but I only drove a mile and a half to Autozone when it was cold when I got it checked so it wasn't fully warmed up. I suspect that whatever is draining the battery drains it to the point that one or both of the shift solenoids isn't getting the voltage to them that they need to shift the gears after awhile which causes the shift problems. Does that make sense? When I hooked up a multimeter to the battery and started the car the voltage dropped a little with the running lights on. When I turned on the marker ights the voltage dropped a little more. When I turned on the headlights it dropped a little more. When I stepped on the brake it dropped 1/2 volt and when I put it in drive it dropped another 1/2 volt. It seems like the problem is the alternator even though Autozone said it wasn't. No codes relating to the electrical problem other than the shift solenoid codes. When I shut the car down the battery slowly goes back up close to full charge about half an hour after the test using the lights, brake, etc. I was also wondering if the shift solenoids may be shorting out and overheating the trans fluid which would be making it turn light brown. Does any of this make sense? Any other possibilities or tests? How do I check the shift solenoids? Could it be the TCM? Thanks in advance! Happy new year!!

[spy1309]

To get a diagnostic of transmision with home tools is pretty hard why not get a used transmission from the junkyard and save yourself some headaches or get the solenoids from a used transmision.

[hot_sd]

I presume the slipping was fixed with fluid change. If you disconnect the shift solenoid connector and if the tranny is placed in the “D” position it will stay in third – that is normal behavior. If you can manually shift into second and first with the connector disconnected then the problem is either in the solenoids or the control system/sensors. Have you checked the manual shifting with connector removed.

You can test the electrical functionality of the solenoids by removing them and either checking continuity with a multimeter or by applying 12V to the terminals – you should hear a click. Testing mechanical functionality is harder – if you have an air compressor you need to rig up a tube into the solenoid opening and force compressed air at about 40PSI and see if the solenoids vents the air when energized. If so the solenoid is fine.

Skipping second due to a control system fault means both solenoids are turning off simultaneously which is a bit odd. Second is generated by turning off the second brake solenoid – this closes the 1-2 shift valve which in turn activates the intermediate servo and the clamps the second brake band to the sun gear drum which locks the sun gear in place so only the planet carrier and ring gear(s) rotate.

The first test to do would be the manual shift test. If the solenoids short out I suspect that the ECU should automatically current limit – if not the circuit generating the control voltage may overheat and burn out. The brown fluid is most likely due to either burnt fluid or clutch material from the clutches or band.

As for the electrical problem – it could possibly affect the ECM and cause side effects like this.

[Chacheska]

Thanks for the great tips. That's the sort of info I was looking for. To answer 2 questions, the fluid is still light brown even after putting in 3/4 of a gallon of fresh fluid. As I recall, the 2nd gear problem persisted even after I manually shifted through the gears with the solenoids disconnected. NEW INFO. Today I went to where the car is stored and noticed I left the ignition o which drained the battery. I put in a fully charged battery. Before I drove it I took out fuses #1 and #2 which control the headlights. I didn't want the battery to drain too fast. Lo and behold, I drove the car for 45 minutes without the tranny slipping! It went right through the gears. I took it to a second Autozone where they did another alternator test with the car fully warmed up. No problem with the alternator or battery. The whole time I drove the car no codes or battery light came on. The dash was clear. Now the bad news. I drove it another 10 minutes and the trans started slipping again! At the same time I heard a loud buzzing under the dash. I reached under and felt a connector mounted on the steering column vibrating. I don't know what it is because I don't have a '96 shop manual. I decided to turn the headlight switch on (I was trying anything) and the buzzing stopped. If I put the marker lights on only it started buzzing again. I kept the switch turned on and drove a few more miles with the trans acting up like it did before. I then plugged the 2 fuses back in. Fuse #2 sparked when I put it back. Fuse #1 didn't. The buzzing was now gone in all modes. I drove 15 miles home and no codes or warning lights lit on the dash. When I was 2 miles from home the trans was really acting up. I had a hard time keeping it in ANY gear from a dead stop. Once I got it to 3rd and stayed over 20 mph I didn't have any slipping problems. When I got home I checked the battery and it was fully charged ater driving 35 miles so whatever was draining the battery stopped. I will repeat the manual shift test with the connector seperated tomorrow. I have a feeling it's an internal trans problem and that the thinning out of the tranny fluid after it gets hot is causing the shifting problem. Possibly not enough internal pressure for the weak seals. Just guessing. One important question, please. Is it best to disconnect the solenoids and leave it in the 3rd gear default mode while I try to solve this problem? I was told that tranny slipping is what burns up the trans. I'm guessing the 3rd gear only mode will cause less damage than the constant slipping even though the car has to start from a complete stop in 3rd gear. Thanks very much!

[hot_sd]

If the problem is there when the connector is disconnected then, yes the problem is internal to the trans. Once the connector is out the gears are manually selected by the manual valve and the car electrics do not play a part in the tranny's operation.

Slipping is usually one of two things that come to my mind. Firstly the line pressure may be too low. This could be due to a failing oil pump or a faulty primary/secondary pressure regulator inside the valve body. The other is that the friction material on the clutch plates and possibly the band has worn out and as a result is not gripping correctly. Unfortunately if this is the case the tranny will have to be rebuilt.

Slipping can distroy the friction metarial on the clutches and bands and render them useless but also the slipping can be caused by clutch discs and bands that are nearing the end of their life. Overheating is another leading cause of trannies burning up - you may want to consider an oil cooler flush. Has the tranny been serviced regularly.

I would measure the line pressure first. This should be done at both idle and stall (WOT) conditions. You can do it yourself or have a mechanic do it for you. You shoud read 28-56PSI - idle and 71 - 99PSI at stall in forward. In reverse 78-113PSI at idle and 150 - 200PSI at stall.

There is a more comprehensive test involving line pressure and engine rpm to actually pinpont which assembly is responsible (forward clutch, direct clutch, one way clutch etc). If you want to start getting into all this I would suggest buying the service manual for the trans. ATSG does a good rebuild manual that has all this info - the website is www.atsgmiami.com

[Chacheska]

I just want to thank you very much for taking time to try to help me with this problem. I'll try some of your suggestions and take it from here. I just bought the car from a third party so I don't know any history. I guess the electrical problems have nothing to do with the trans problem like I thought they did. I only paid $150 for the car. Once again, thank you very much!

[Chacheska]

I did think of two more questions. Why does the trans always shift normally when cold for the first 15 minutes and get worse once it's warm/hot? This last time it ran 45 minutes before slipping with fuses #1 and #2 removed. I need to understand that. Second, what is the connector on the steering wheel column that was buzzing and why did it start buzzing as soon as the trans started slipping after 45 minutes of no slipping? There must be some correlation there.

[hot_sd]

It is not uncommon for transmissions to work when cold and then malfunction when hot - in fact this applies to many things. The fact is things change in size/expand when hot. In the case of the slipping for example the forward or direct clutch drums can expand when hot. If the clutch disc thickness is below spec the clearance between the piston and the discs would be sufficient to prevent slipping when cold. When hot the drum could expand to the point the clutch discs can no longer engage fully.

No idea about the buzzing - the only thing in the steering column that I'm aware of related to the tranny is the shift lock and the simply controls shifting out of park. Nothing controlling the insides of the tranny there as far as I'm aware.

Another thing to double check although I doubt if it is the problem is the tension on the cable from the gas pedal to the thottle valve in the tranny. You can find this on the top of the tranny. If it too slack you can get shifting problems.

[Chacheska]

I really appreciate all your help. I like to try to understand the underlying cause and related issues. The one thing that I need to know that you didn't answer is if it's a better idea to unplug the shift solenoids for the time being and leave it in default 3rd gear mode until I fix the problem by swapping trannies or fixing any related electrical problems. That's kind of important to me so if you could answer that last question I'd be very grateful. Thanks again for sharing your knowledge with me.

[hot_sd]

Yes, you cannot do any damage to the tranny by keeping it in third - it's more the fact that it may not be good for the engine as it will cause the engine to labor moving from a dead stop.

Glad to help and hope you get this resolved.

[Chacheska]

Yeah, I was a ittle concerned about the engine rpm's at a dead stop in 3rd. The short time I did drive it in 3rd I was surprised that the engine seemed to accelerate fairly well with no lugging from a stop but I'm sure it's not doing the engine any good. I haven't driven it the last couple of days to test the manual shift with the solenoid connector disconnected yet. By the way, thanks for the ATSG URL. Great site! I can't thank you enough for all your time. I have a unique probem with my '94 that I'll post in a few minutes.

[hot_sd]

Yes, the ATSG book for the MX17 is quite good and I used it when I rebuilt my tranny last year. It is not so good for the newer cars as it does not cover the OBD2 control system too well (mine is a 2000 Metro) but I also have the chevrolet factory manual which has a good deal on the newer trannies and the shift control system/solenoids and together they have all the info you need for diagnosing and rebuilding the MX17 tranny.

[Chacheska]

Like most people, I can work on a lot of mechanical things but trannies are alien to me. They seem very complicated. It's probably easier for me to swap it out for a good one. Just posted my rather unique problem with the '94 I have. I hate to tell you this but I have 7 of the little suckers. Two 92's, three '94's, a '96 and a 2000. One '92 is a parts car. The other '92 and the '96 are automatics. The rest are standards. I keep finding them dirt cheap and just can't resist. This is worse than having a gambling problem!

[hot_sd]

Well, they are really not that complicated - main thing is understanding how planetary gearsets operate. Everything else in the tranny is there to make this gearset work by locking and unlocking different sections of the gearset. Some newer trannies have more fancy features like using a pulse train to gently engage the solenoids etc but the basic principes remain the same.

As for collecting metros - I know of someone locally who buys them cheap and non - working, fixes them and then sells them on. I think he does good business since the gas prices went up.

[Chacheska]

Mine all run, most of them very well, except for that parts car. Most of them need a little work. I don't know if different topics are assigned to different people but if not, and you get a chance, please read my other post with the '94 problem. That's a wacky one. Who am I conversing with?

Karl