Transmission issues
05-23-2012, 03:45 PM
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Transmission issues
Bear with me as I "attempt" to explain my issue. An issue I'm pretty sure I am going to need someone with some "in-depth" knowledge of Tacoma transmissions!
I own a 1995.5 Tacoma - V6 - 4-Wheel Drive - with an automatic transmission. This past winter, I noticed what I thought was the transmission slipping in first gear and my heart sank thinking the worst! It's also a fix that's WAY out of my comfort zone! I added a bit of transmission fluid - thinking the fluid was a bit low - and it was, which seemed to fix the problem for a short while. But then it started again and I noticed the O/D (overdrive) light flashing on the dash. I knew then something was certainly - not right. My first thought was complete transmission failure, as I let myself think the worst! However I didn't hear that tale-tale sound of the planetary gears screaming when they've gone bad as i drove it. In fact, once I got the truck rolling it would shift into the upper gears with no problem - like there was no problem at all?! Only when I first start off does it feel like the transmission is slipping.
My first stop was the local auto part store to have the flashing O/D light code read. The code was PO753 stating that the #1 shift solenoid needed replacement. Simple enough as my tranny doesn't have a throttle body, so it should be an easy swap. Unfortunately my "pro" wasn't available to help me and I just simply did not feel comfortable working on a transmission! So I contacted an old friend of mine who lives half way across the US from me to get his opinion, since he works as a master service tech (25 years) for a Toyota dealership, but will tell you quickly he doesn't like working on transmissions. He seemed to think it was nothing more than the shift solenoid from my description. He got the part for me and shipped it to me. Now I had to find someone to work on the truck!
After doing a search here at yotatech.com, I realized that the problem I've just describe "seemed" to be an easy fix. So until I found someone to work on the truck I chose to park it - as a precaution.
After remembering a guy from many years ago (by chance) who had experience with Toyota's, I dropped by his shop to see if he would work on my truck. He offered to work on the truck using the supplied part from my buddy with Toyota.
After replacing the shift solenoid he said that didn't fix the problem. According to him the transmission wasn't actually slipping, but would not drop down into first gear?! And the slipping I was experiencing, was the truck starting off in second gear! He did say however, that he could manually drop the transmission down into first gear by placing the shift lever in "L", but it would not drop down into first gear with the shift lever in "DRIVE"?! He carried the truck to "his" local transmission guy - still with no success. He "said" he was getting some kind of code stating there was an electrical problem, which he thinks is the root of the problem. He seems to think there is a short somewhere that is causing the problem?! He's had the truck now for almost 3 MONTHS and still cannot find the issue or the "short" in question. Anyone ever heard of this?
According to him there's nothing wrong with the transmission and the gears seem to be fine. He also says he did not find any serious metal trash in the transmission oil pan when he dropped it for the first time to replace the shift solenoid.
All this said - he is now ready to give up. He says he cannot find the wiring short that's causing the transmission to not drop down into first gear and basically says I can drive it by "manually" placing the transmission in first gear and once rolling, place the truck in "DRIVE"?!
I now humbly place my plea for help on these boards PRAYING that someone can help me figure this out! This little truck is my bread and butter - and I MISS IT - to say the very least! Especially with the price of gas! If ANYONE has experienced this issue with a Tacoma or knows what, or where I need to look - PLEASE HELP!
Please allow me to thank you in advance! And accept my apology for writing a book here!
I own a 1995.5 Tacoma - V6 - 4-Wheel Drive - with an automatic transmission. This past winter, I noticed what I thought was the transmission slipping in first gear and my heart sank thinking the worst! It's also a fix that's WAY out of my comfort zone! I added a bit of transmission fluid - thinking the fluid was a bit low - and it was, which seemed to fix the problem for a short while. But then it started again and I noticed the O/D (overdrive) light flashing on the dash. I knew then something was certainly - not right. My first thought was complete transmission failure, as I let myself think the worst! However I didn't hear that tale-tale sound of the planetary gears screaming when they've gone bad as i drove it. In fact, once I got the truck rolling it would shift into the upper gears with no problem - like there was no problem at all?! Only when I first start off does it feel like the transmission is slipping.
My first stop was the local auto part store to have the flashing O/D light code read. The code was PO753 stating that the #1 shift solenoid needed replacement. Simple enough as my tranny doesn't have a throttle body, so it should be an easy swap. Unfortunately my "pro" wasn't available to help me and I just simply did not feel comfortable working on a transmission! So I contacted an old friend of mine who lives half way across the US from me to get his opinion, since he works as a master service tech (25 years) for a Toyota dealership, but will tell you quickly he doesn't like working on transmissions. He seemed to think it was nothing more than the shift solenoid from my description. He got the part for me and shipped it to me. Now I had to find someone to work on the truck!
After doing a search here at yotatech.com, I realized that the problem I've just describe "seemed" to be an easy fix. So until I found someone to work on the truck I chose to park it - as a precaution.
After remembering a guy from many years ago (by chance) who had experience with Toyota's, I dropped by his shop to see if he would work on my truck. He offered to work on the truck using the supplied part from my buddy with Toyota.
After replacing the shift solenoid he said that didn't fix the problem. According to him the transmission wasn't actually slipping, but would not drop down into first gear?! And the slipping I was experiencing, was the truck starting off in second gear! He did say however, that he could manually drop the transmission down into first gear by placing the shift lever in "L", but it would not drop down into first gear with the shift lever in "DRIVE"?! He carried the truck to "his" local transmission guy - still with no success. He "said" he was getting some kind of code stating there was an electrical problem, which he thinks is the root of the problem. He seems to think there is a short somewhere that is causing the problem?! He's had the truck now for almost 3 MONTHS and still cannot find the issue or the "short" in question. Anyone ever heard of this?
According to him there's nothing wrong with the transmission and the gears seem to be fine. He also says he did not find any serious metal trash in the transmission oil pan when he dropped it for the first time to replace the shift solenoid.
All this said - he is now ready to give up. He says he cannot find the wiring short that's causing the transmission to not drop down into first gear and basically says I can drive it by "manually" placing the transmission in first gear and once rolling, place the truck in "DRIVE"?!
I now humbly place my plea for help on these boards PRAYING that someone can help me figure this out! This little truck is my bread and butter - and I MISS IT - to say the very least! Especially with the price of gas! If ANYONE has experienced this issue with a Tacoma or knows what, or where I need to look - PLEASE HELP!
Please allow me to thank you in advance! And accept my apology for writing a book here!
05-24-2012, 05:26 AM
#2
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Well, it does sound like a short, it may not be in the transmission, it very well could be on the truck side of things. Even the ECU could be at fault.
These kind of issues are not easy or fun to track down at all. No real easy fix sadly.
These kind of issues are not easy or fun to track down at all. No real easy fix sadly.
05-24-2012, 06:33 AM
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I'll assume by ECU - you mean the "brain" of the entire truck - right?
Thanks again!
05-24-2012, 06:41 AM
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That is possible although I think that the transmission has a separate ECU but I might be thinking of one of my other cars.
05-24-2012, 08:27 AM
#5
The easiest way to see if this is an electrical short involves a leap of faith.
Cut the wires to your solenoids with a few inches to spare. Cut them at the ecu with a few inches to spare. Run new wires. Solder and heat shrink each connection.
Its drastic but will 100% eliminate the stock wiring.
The engine ecu is also the transmission ecu.
EDIT: Also, you could buy a cheap multimeter and test to see if there is a short yourself. Place the probes on each of the wires to the solenoid and see what the reading is. You could disconnect the connector from the solenoid and the ecu to just test the wiring. That will also allow you to test the ecu on its own buy probing the pins and the solenoid on its own by probing its pins.
Cut the wires to your solenoids with a few inches to spare. Cut them at the ecu with a few inches to spare. Run new wires. Solder and heat shrink each connection.
Its drastic but will 100% eliminate the stock wiring.
The engine ecu is also the transmission ecu.
EDIT: Also, you could buy a cheap multimeter and test to see if there is a short yourself. Place the probes on each of the wires to the solenoid and see what the reading is. You could disconnect the connector from the solenoid and the ecu to just test the wiring. That will also allow you to test the ecu on its own buy probing the pins and the solenoid on its own by probing its pins.
Last edited by UKrunner; 05-24-2012 at 08:30 AM.
05-24-2012, 10:22 AM
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Sounds to me like a similar problem I had - turned out to be the first gear shift sprag. Do a search, I think something will come up. Basically, you may need either an overhaul or a donor transmission installed (which is what I had done). This won't throw any codes, and it may not be evident from the condition of the fluid.
05-24-2012, 11:14 AM
#7
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I have a 96 4wd 4runner transmission for sale right now if you decide to swap transmissions, I am pretty sure it is the same thing as the Taco.
It has the IPT valve body mod as well which improves the shifting drastically.
It has the IPT valve body mod as well which improves the shifting drastically.
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05-29-2012, 08:00 AM
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Sounds to me like a similar problem I had - turned out to be the first gear shift sprag. Do a search, I think something will come up. Basically, you may need either an overhaul or a donor transmission installed (which is what I had done). This won't throw any codes, and it may not be evident from the condition of the fluid.
06-01-2012, 11:01 AM
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Mine normally would go into first if I manually selected it. So, I was never really "stranded", but it was annoying enough for me to do something about it. If you have checked out the shift solenoids, and the fluid level and condition is good, there isn't much else you can do but have it overhauled or replaced. When dealing with this issue, that is.
06-01-2012, 12:09 PM
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Have u checked the fsm yet? Look here http://ncttora.com/fsm/1996/SIL/tech.../di/at/pst.pdf
From what I can see, looks like the ecm is bad, or, u have a short, somewhere in the 50,000 miles of wire in that rig... I would get a multi meter and start testing all the connectors from ecm, to tranny, that should tell ya where/if the short is... If no short, try to borrow a known good ecm to test with, or bite the bullet and buy one. If the ecm dosent fix the issue... Idk?? I hate working on auto tranny's... tooo many parts in there for my head to wrap around....
From what I can see, looks like the ecm is bad, or, u have a short, somewhere in the 50,000 miles of wire in that rig... I would get a multi meter and start testing all the connectors from ecm, to tranny, that should tell ya where/if the short is... If no short, try to borrow a known good ecm to test with, or bite the bullet and buy one. If the ecm dosent fix the issue... Idk?? I hate working on auto tranny's... tooo many parts in there for my head to wrap around....
06-18-2012, 02:52 PM
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Update
First and foremost... Thanks to all those who've taken the time to offer me advice.
Here's the latest UPDATE...
After almost 4 months of having a mechanic with some experience with Toyotas look at the truck, he's down to believing its an electrical short somewhere in the wiring from the the fuse box "under" the hood to the transmission. He replaced the #1 shift solenoid in accordance with the "code" (PO753), - which was read more than one time - and then the rest of the time, he spent "looking" for the short! As stated previously - I can "manually" place the transmission in "L" and the truck does fine. I barely even have to get it moving and then switch to "D" and the truck does fine. No harsh gear changes from one gear to the next. For whatever reason the transmission is in "fail-safe" mode?!
So today I decided to drive the truck and it wasn't long before I realized the "O/D light" on the dash was flashing again. I stopped by the same local auto parts store and had them read the "code" again. And ONCE AGAIN the EXACT SAME "code" showed up telling me I needed to replace the #1 shift solenoid!!!
So I'm almost 90% sure now that it's some kind of *@%#^ electrical short that may end up costing me as much to get resolved as what a replacement transmission would cost!!! The maddening thing is - EVERYTHING seems to point to the fact that there isn't a problem with the transmission itself - and replacing it won't fix anything!
So I guess the next stop - some local auto electrical place to "see" if they can find the damn short!
Here's the latest UPDATE...
After almost 4 months of having a mechanic with some experience with Toyotas look at the truck, he's down to believing its an electrical short somewhere in the wiring from the the fuse box "under" the hood to the transmission. He replaced the #1 shift solenoid in accordance with the "code" (PO753), - which was read more than one time - and then the rest of the time, he spent "looking" for the short! As stated previously - I can "manually" place the transmission in "L" and the truck does fine. I barely even have to get it moving and then switch to "D" and the truck does fine. No harsh gear changes from one gear to the next. For whatever reason the transmission is in "fail-safe" mode?!
So today I decided to drive the truck and it wasn't long before I realized the "O/D light" on the dash was flashing again. I stopped by the same local auto parts store and had them read the "code" again. And ONCE AGAIN the EXACT SAME "code" showed up telling me I needed to replace the #1 shift solenoid!!!
So I'm almost 90% sure now that it's some kind of *@%#^ electrical short that may end up costing me as much to get resolved as what a replacement transmission would cost!!! The maddening thing is - EVERYTHING seems to point to the fact that there isn't a problem with the transmission itself - and replacing it won't fix anything!
So I guess the next stop - some local auto electrical place to "see" if they can find the damn short!
06-19-2012, 03:05 PM
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This freaking nuts!!!!
Just when I thought I had this kind of figured out - or at least as close as I could come to a conclusion - I notice ANOTHER "quark"! 
When I'm at speed (60 -70) I'm starting to notice a little variance in the tachometer. At 70 the RPM's are around 2200, but I've watched it jump a few times to around 2500 and then back again?!
And I'm noticing a little "bump" when this happens. Not every time, but it's just further adding to the stress over this truck!
I guess I should just stop driving the freaking thing until I can get it to someone who can (hopefully) fix it without talking me to the damn cleaners - AGAIN!
This is literally making me physically ill!!
When I'm at speed (60 -70) I'm starting to notice a little variance in the tachometer. At 70 the RPM's are around 2200, but I've watched it jump a few times to around 2500 and then back again?!
And I'm noticing a little "bump" when this happens. Not every time, but it's just further adding to the stress over this truck!I guess I should just stop driving the freaking thing until I can get it to someone who can (hopefully) fix it without talking me to the damn cleaners - AGAIN!
This is literally making me physically ill!!
06-20-2012, 07:31 AM
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06-20-2012, 07:50 AM
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Depends on when it is happening. It is unlock when over a throttle input threshold or a lot of other driving scenarios.
If just driving along mine will lock and unlock in time with the blinkers for some reason. Besides that, an electrical short could do it as well.
If just driving along mine will lock and unlock in time with the blinkers for some reason. Besides that, an electrical short could do it as well.
06-20-2012, 08:01 AM
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I'd drive the blessed thing as is for a while (i.e. having to manually place the transmission into "L" to start off from a stop and then once movnig shift up to "D"), if I didn't live in constant fear of causing damage to the transmission! I'm honestly about as frustrated with this as I have been with anything!!!!
06-20-2012, 08:02 AM
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Your speed should not change when the converter locks or unlocks, just the RPM's. The cruise will adjust the throttle and it is normal for the converter to unlock from time to time, particularly when going up a hill or accelerating.
06-20-2012, 08:07 AM
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I guess I'm just a bit more "aware" of it because of all the "continuing" transmission troubles I'm having with the truck! That and the fact I can see the tach fluctuating by about 2-3K RPM's. I can also "feel" it every once it a while.
06-20-2012, 08:11 AM
#19
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2-3k? That is not the converter then, the converter should only change ~500rpm's or so give or take depending on speed/gear.
If it is changing that much then it is downshifting to 3rd gear. This will also happen if enough load is put on the truck but generally not as common as the converter lockup in cruise mode. It does still happen with the cruise control from time to time though.
If it is changing that much then it is downshifting to 3rd gear. This will also happen if enough load is put on the truck but generally not as common as the converter lockup in cruise mode. It does still happen with the cruise control from time to time though.
06-20-2012, 08:14 AM
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2-3k? That is not the converter then, the converter should only change ~500rpm's or so give or take depending on speed/gear.
If it is changing that much then it is downshifting to 3rd gear. This will also happen if enough load is put on the truck but generally not as common as the converter lockup in cruise mode. It does still happen with the cruise control from time to time though.
If it is changing that much then it is downshifting to 3rd gear. This will also happen if enough load is put on the truck but generally not as common as the converter lockup in cruise mode. It does still happen with the cruise control from time to time though.
