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Old 07-12-2005, 12:32 PM   #1
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Default Strange Trans Problem

Happened for the first time today. On the highway when shifting from drive to OD I completely lose my trans, theres nothing there. Pull over, put it back into drive, everything ok drives like normal and shifts great. Ok so I try using OD from the start, runs fine, shifts ok. Ok so I again try starting out in D and going to OD, I lose it again. Its like its in N however you can feel it trying to shift. Heres the kicker, It shift great when left in D or OD without switching. Runs great. However switching from D to OD is the only time I lose it. Makes no sense to me . This thing shifts great, like a new trans until you try to put it in OD from D. Anyone have any clues. I would like to fix this problem.
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Old 07-12-2005, 02:06 PM   #2
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I am almost at a loss... Would be nice to see if the PCM is confused or getting a bad signal somewhere...

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Old 07-12-2005, 02:18 PM   #3
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Do you think it is possible that when changing you are not engaging the shifter into position fully, whereas when you start off there you are using more pressure.

The lockout on these trans (I think) are cable controlled, not electronic. But the actual shifiting from gear to gear is electronic and therefore could be influenced to shift or not shift by the PCM/ECM. This doesn't account for the slippage you are mentioning. That I would assume to be more gear selector cable related.

Try being a little rougher on your shifter. Might be hopeful thinking, but it just might work.
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Old 07-12-2005, 02:27 PM   #4
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Quote:
Originally Posted by BillBost37
Do you think it is possible that when changing you are not engaging the shifter into position fully, whereas when you start off there you are using more pressure.

The lockout on these trans (I think) are cable controlled, not electronic. But the actual shifiting from gear to gear is electronic and therefore could be influenced to shift or not shift by the PCM/ECM. This doesn't account for the slippage you are mentioning. That I would assume to be more gear selector cable related.

Try being a little rougher on your shifter. Might be hopeful thinking, but it just might work.
I agree.

Also, are you using the gear indicator to indicate that you're in OD? Over time those indicators tend to loose calibration and end up not being accurate. The indicator might say you're in OD, but you might actually be one gear higher...in Neutral. That would perfectly explain your issue.

When you manually shift from D to OD count the number of "clicks". You should only have one.
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Old 07-12-2005, 03:25 PM   #5
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Quote:
Originally Posted by BillBost37
Do you think it is possible that when changing you are not engaging the shifter into position fully, whereas when you start off there you are using more pressure.

The lockout on these trans (I think) are cable controlled, not electronic. But the actual shifiting from gear to gear is electronic and therefore could be influenced to shift or not shift by the PCM/ECM. This doesn't account for the slippage you are mentioning. That I would assume to be more gear selector cable related.

Try being a little rougher on your shifter. Might be hopeful thinking, but it just might work.
I was thinking maybe somthing is sticking??? I checked the shifter and it was fully in the OD position. It was not really a slip but nothing there at all, as if it was in N. I had to pull over and put it in D for it to move again, (putting it in D while going did nothing). As I said it shifts great, Perfect almost. I just drove it to work and ran fine. I did not shift from D to OD however, I was too scared to do that. I can no figure out what it could be? I have been searching the net with not luck.
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Old 07-12-2005, 04:05 PM   #6
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Low fluid, perhaps?

Also, pull your vacuum line for your vacuum modulator to make sure there is no ATF in the line. I had the same problem, but it was for both 3rd and OD. They require much more fluid and fluid pressure than 1st and 2nd gear.


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Old 07-12-2005, 04:14 PM   #7
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that doesn't sound like a fluid issue... or a cable issue. sounds like an electrical gremlin. i don't have my manual handy, but I'll see what I can find later... see what changes on a d-OD shift versus being in the OD range the entire time.

I don't think it'* a cable issue, because if you know it'* in OD just fine, I don't imagine you're going to be that far off when you shift in to OD from D...
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Old 07-12-2005, 05:26 PM   #8
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Quote:
Originally Posted by opensourceguy
Low fluid, perhaps?

Also, pull your vacuum line for your vacuum modulator to make sure there is no ATF in the line. I had the same problem, but it was for both 3rd and OD. They require much more fluid and fluid pressure than 1st and 2nd gear.


-justin
Nothing to do with low fluid or vac modulator. You can ignore the information in the quote above.

I agree with the electrical gremlin theory. Do you have any access to a scan tool? Most of them will show you the soleniods working as the transmission shifts. Doubtful it shows any shifting, since it isn't happening. However it would possibly tell you what gear it thinks you have selected D, OD or N. That'* where I would be looking. Sounds like it thought N, the part that gets me is you went back to D and it still didn't respond.

Take a look at the connectors going to the transmission for any signs of rubbing (coating missing) and grounding (bare wires touching metal).

It wasn't overly hot that day was it? Or you hadn't been driving hard that would heat up the transmission? Sounds like you weren't stopped long enough to have let it cool if it was doing this from an overheat, but just want to rule it out.
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Old 07-12-2005, 08:17 PM   #9
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Quote:
Originally Posted by BillBost37
Quote:
Originally Posted by opensourceguy
Low fluid, perhaps?

Also, pull your vacuum line for your vacuum modulator to make sure there is no ATF in the line. I had the same problem, but it was for both 3rd and OD. They require much more fluid and fluid pressure than 1st and 2nd gear.


-justin
Nothing to do with low fluid or vac modulator. You can ignore the information in the quote above.

I agree with the electrical gremlin theory. Do you have any access to a scan tool? Most of them will show you the soleniods working as the transmission shifts. Doubtful it shows any shifting, since it isn't happening. However it would possibly tell you what gear it thinks you have selected D, OD or N. That'* where I would be looking. Sounds like it thought N, the part that gets me is you went back to D and it still didn't respond.

Take a look at the connectors going to the transmission for any signs of rubbing (coating missing) and grounding (bare wires touching metal).

It wasn't overly hot that day was it? Or you hadn't been driving hard that would heat up the transmission? Sounds like you weren't stopped long enough to have let it cool if it was doing this from an overheat, but just want to rule it out.
I have dual B&M Trans Coolers, so it wouldn't be over heating. I dont currently have access to a scan tool. Would it be a solenoid? It does shift perfectly, only not when you switch from D to OD, or today it screwed up going from D to OD and from OD to D. I am an idiot when it comes to these complicated trannys.
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Old 07-12-2005, 09:52 PM   #10
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stupid kinda off topic question of the day..

WHY DO YOU HAVE 2 AUXILARY TRANNY COOLERS??? are you towing tanks??????
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