Auto Tranny Problem

[docsplace]

Originally Posted by DieInterim

Hello,

These tranny's use a cable that controls shift pressure. If the cable has broken it will be stuck in "Full Throttle" setting; thus your high rpm shifting. However if your trans feels as if it is slipping... first check your fluid level as per the owners manual.

Blake

Blake! I have the same problem mine will not shift when hot but works good when cold.

So I have a question! if that cable controls pressure and the cable is free working the way it is suppose to, could that cable be to tight or loose and would it not give you the correct fluid level reading when the trany is hot?, otherwise it would not raise the fluid level because there is no pressure to foam up the fluid level when it is hot.

Thanks
Tom
Docsplace

[docsplace]

Originally Posted by hot_sd

Need a better description to suggest something with this problem. Does it remain stuck in third while in "D' or does it loose drive when you attempt a downshift. Is downshift the only problem - does it upshift OK.

Very easy to check whether the computer/sensors are to blame - when you have the problem disconnect the shift solenoid connector, put the car into 'D' and measure the voltage - you should see 12V on both lines (both solenoids should be energized).

I have to say that heat related problem usually tends to be due to things inside the tranny like dirty valves. You can try an transmission additive like lubegard and see if it helps - you may have some debris coating the shift valve(s) or the solenoid vent passages to the shift valves causing it to stick when hot. You can also check the cable from the gas pedal to the tranny's throttle valve - if it is out of alignment you could have problems with downshifts if the cable is becoming too slack due to heat (same thing as what the original poster had).

Ok Checked that voltage on the little white 2-connector from the wire harness that hooks to the top of the trany and I got 1.5vdc on both sides to ground and after a rechecked it a few minutes later there was none, Seems like the warmer it gets the less voltage it produces. that would mean it is in the computer, IS that a seperate control. And just to make sure I checked the right one. Is that the only connector gouing to the trany, I couldn't see any others.

Thanks
Tom

[DieInterim]

Originally Posted by docsplace

No it does not keep slipping, If you down shift to 2nd or 1st while moving down the road and try to pass someone it just will not pickup 2nd or first gear, and then slips instead of staying in 3rd, but as soon as you shift back to drive it works fine. All this happens when the trany or car has warmed up, While it is cold when you take off in the mornings especially since this last cold weather we have had in ohio it works normally. Shifts just like it should up and down. ????

I'm not really clear on the dipstick level check either, If I check that first thing in the morning the level is way high, If I check it hot running in neutral it shows normal level. After I drained and dropped the pan I lost about 2 quarts of fluid and put about the same amount back in it.
What is the procedure for checking fluid level, It has 4 notches first 2 Are cold check add and full and the second is hot add and and full, Should I be checking that while trany is hot in neutral??

Thanks for all your help.
Tom
Docsplace

In Park. I think your transmission requires thatyou check system pressure. Its cheap and simple and can save you cash. If system pressure is low you need to rebuild/replace. If system pressure is with-in the limits, then I would move on to the Controller.

F.W.I.W.,
Blake

[hot_sd]

Originally Posted by docsplace

No it does not keep slipping, If you down shift to 2nd or 1st while moving down the road and try to pass someone it just will not pickup 2nd or first gear, and then slips instead of staying in 3rd, but as soon as you shift back to drive it works fine. All this happens when the trany or car has warmed up, While it is cold when you take off in the mornings especially since this last cold weather we have had in ohio it works normally. Shifts just like it should up and down. ????

I'm not really clear on the dipstick level check either, If I check that first thing in the morning the level is way high, If I check it hot running in neutral it shows normal level. After I drained and dropped the pan I lost about 2 quarts of fluid and put about the same amount back in it.
What is the procedure for checking fluid level, It has 4 notches first 2 Are cold check add and full and the second is hot add and and full, Should I be checking that while trany is hot in neutral??

Thanks for all your help.
Tom
Docsplace

When you say downshift do you mean downshifting automatically by pressing the gas pedal or by moving the shift selector down (or both).

Fluid level should be checked when the tranny is hot (after about 15mins of driving ususally). The correct procedure is to do it while the engine is running. Press the brake pedal and then moving the shift selector thru all the ranges starting at "P". Pause for about 2 secs in each range. Fnally return the shift selector back to "P" and then take a reading. This will make sure all the valve body passges are primed and prevent an excessively high reading.

The cold reading will not be very accurate but is there if you quickly want to check the level before driving the car. Very low or no fluid can damage the torque converter and other parts requiring lubrication.

[hot_sd]

Originally Posted by docsplace

Blake! I have the same problem mine will not shift when hot but works good when cold.

So I have a question! if that cable controls pressure and the cable is free working the way it is suppose to, could that cable be to tight or loose and would it not give you the correct fluid level reading when the trany is hot?, otherwise it would not raise the fluid level because there is no pressure to foam up the fluid level when it is hot.

Thanks
Tom
Docsplace

That cable controls the throttle valve which is used to modify the line pressure under low/high throttle conditions. It is not the primary pressure control - the primary and secondary pressure regulators control the line pressure. The cable tension will not affect your fluid level reading.

[hot_sd]

Originally Posted by docsplace

Ok Checked that voltage on the little white 2-connector from the wire harness that hooks to the top of the trany and I got 1.5vdc on both sides to ground and after a rechecked it a few minutes later there was none, Seems like the warmer it gets the less voltage it produces. that would mean it is in the computer, IS that a seperate control. And just to make sure I checked the right one. Is that the only connector gouing to the trany, I couldn't see any others.

Thanks
Tom

There should be 2 connectors - a circular one and a square one. The square one should have multiple wires and the circular one two. Not sure why you are getting even 1.5V on the live side - it should be 12V. It looks like you did look at the right one. But yes, if the voltage decays as it gets hotter and you also get shifting problems the problem could be in the computer or one of the sensors. Another easy way to check this would be if you could in some way feed 12V to both the solenoids and see if you can get first and second back. That would confirm the problem.

[hot_sd]

Originally Posted by hot_sd

There should be 2 connectors - a circular one and a square one. The square one should have multiple wires and the circular one two. Not sure why you are getting even 1.5V on the live side - it should be 12V. It looks like you did look at the right one. But yes, if the voltage decays as it gets hotter and you also get shifting problems the problem could be in the computer or one of the sensors. Another easy way to check this would be if you could in some way feed 12V to both the solenoids and see if you can get first and second back. That would confirm the problem.

Just double checked this - actually it should be 2V - not 12V - although 12V is normally used to check solenoids in test mode (and which I have usually done in the past). So 1.5V is below normal to start with and if it goes to zero you may have a faulty TCM. I would remove the wiring harness and check both ends for conneciton problems and also see if all wiring to the TCM is OK.

[docsplace]

Originally Posted by hot_sd

Just double checked this - actually it should be 2V - not 12V - although 12V is normally used to check solenoids in test mode (and which I have usually done in the past). So 1.5V is below normal to start with and if it goes to zero you may have a faulty TCM. I would remove the wiring harness and check both ends for conneciton problems and also see if all wiring to the TCM is OK.

OK so that TCM is a single module under the dash that those to wires go to?

Thanks
Tom

[hot_sd]

Originally Posted by docsplace

OK so that TCM is a single module under the dash that those to wires go to?

Thanks
Tom

I guess that should be it. I have a 2000 metro and the control system is different to the older cars. In mine the powertrain control module (PCM) controls both the tranny and the engine. In older cars I believe the 2 are separate. In any event it should be the module that the wiring harness goes from the tranny.

It is very probably that the circuit used to generate the 2V control source may have gone bad. It is probably a voltage reg or a zener type circuit that drops the 12V down to 2V. Sometimes a passive component like a resistor or a cap going bad can start getting worse under changing temperature conditions.

If this is the case the fix should be simple but I'm not sure if the module can be opened and if a circuit diagram of the micro and the support circuity would be available. The more expensive option would be to replace the TCM.

Another thought on how to prove if it is the TCM is to get some freezer spray and chill the module when it is hot and the problem is there and see if the problem goes away. This should prove whether it is the module or something else.

[docsplace]

Originally Posted by hot_sd

I guess that should be it. I have a 2000 metro and the control system is different to the older cars. In mine the powertrain control module (PCM) controls both the tranny and the engine. In older cars I believe the 2 are separate. In any event it should be the module that the wiring harness goes from the tranny.

It is very probably that the circuit used to generate the 2V control source may have gone bad. It is probably a voltage reg or a zener type circuit that drops the 12V down to 2V. Sometimes a passive component like a resistor or a cap going bad can start getting worse under changing temperature conditions.

If this is the case the fix should be simple but I'm not sure if the module can be opened and if a circuit diagram of the micro and the support circuity would be available. The more expensive option would be to replace the TCM.

Another thought on how to prove if it is the TCM is to get some freezer spray and chill the module when it is hot and the problem is there and see if the problem goes away. This should prove whether it is the
module or something else.

I'll wait till the cold weather hits us again this week, that will tell the tale, I have located a used one for 20.00. If it proves to be the problem. I wonder if there is a way or parts referance to see the mudule number and how many differant geo's or Suzuki's had the same part.

Thanks
Tom

[hot_sd]

Originally Posted by docsplace

I'll wait till the cold weather hits us again this week, that will tell the tale, I have located a used one for 20.00. If it proves to be the problem. I wonder if there is a way or parts referance to see the mudule number and how many differant geo's or Suzuki's had the same part.

Thanks
Tom

The cold weather will not definitely prove that it is the TCM - just that the cold makes it work better. You can easily pick up a can of freezer spray at an electronics parts place - we use it all the time to debug problems with with the circuits and ICs we design.

[docsplace]

Originally Posted by hot_sd

The cold weather will not definitely prove that it is the TCM - just that the cold makes it work better. You can easily pick up a can of freezer spray at an electronics parts place - we use it all the time to debug problems with with the circuits and ICs we design.

Looked all over this town for the freeze spray. No one had it, Going to try a can of blowoff, if you turn it upside down it gets cold fast, But i think it is combustable so got to be careful. I'll let you know what the outcome is. Thanks for the help.

Tom
Docsplace

[docsplace]

Well it looks like the TCM may be the problem, I used a can of blow off and held the can upside down and sprayed that TCM and it started working after about 30 seconds. It was intermittent off and on for a couple of minutes but it would pick up first gear in drive. I'm going to get that other TCM and try it and hopefully it cures my problem. I will get back with you on this post after I change this out this week and let you know for sure.

Thanks for all your help.
Tom
Docsplace

[hot_sd]

Hopefully that will fix it and let us know how you get on. $20 is reasonable for a used TCM.