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Discussion Starter #1
Had transmission serviced (rebuilt) recently. trans works pretty good now. problem is a strange hesitation or fluctuation in the engine when sitting at a stop. this appears to happen only when sitting, say at a light, with the brake applied and in gear. does not appear to do it when just idling. was NOT doing this before the transmission work. transmission guy says it is an engine issue.

Also noticed that when i accellerate and let off the gas a couple of times close together for short bursts, the transmission will sometimes hang in the lower gear for a moment or so, then drop (with a noticeable clunk) in to the higher gear. could not replicate for trans guy so no word from him on this.

any ideas? wife is constantly complaining about it....
 

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hmmm, definitely sounds like mr transmission guy did something wrong, otherwise it would do it in neutral as well. check the fluid level, hows that doing? and does this happen at all times? only cold? only warm? (in terms of engine/trans temp)

As for the holding a low gear it's my understanding that the transmission is programed like that from the factory. It's to help with freeway merging and if you have a heavy foot it will actually learn that you like power and will hold gears for longer
 

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Discussion Starter #3
As for the hesitation, it seems to do it in and under all conditions, but only at a stop with brake on - not while on the move. I was thinking it was something that might have been handled while the trans work was being done. Maybe the solenoid pack or perhaps the MAP sensor or something. I just do not want to start replacing stuff just to see if it stops happening. I would like troubleshooting guidance...


The 'hang shift' is an issue because it was not happenig before the rebuild. I understand about the way the trans 'learns' how you drive. What I would say here is that it is learning too quick; it is formulating a plan based on insufficient samples....
 

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ok, then in all honesty what I would do is go do a good, detailed search on shops in your area. I personally preffer mom and pop shops, look at their BBB ratings and what not and find the best one and go talk to them. express your concern that you dont want to through money and parts at the problem and hope it gets fixed. I'm sure they'll have some very experienced mechanics who can help you out :)
 

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Starting with a clean throttle body, watch the TPS (throttle position sensor) signal voltage at idle in gear.
With the throttle sitting at idle, the TPS voltage should sit rock-steady. If the voltage jumps around, even by a few hundredths of a volt with a corresponding change in idle speed, replace the sensor.
Another thing to watch for is A/C compressor engagement causing the idle fluctuation. Watch the A/C clutch when in gear for a corresponding change in idle speed when the clutch engages or disengages.
The intermittent late shift may cause a TCM fault code, but the 'ck eng' light will only come on with a PCM (engine) fault code. There is no way you would know if the trans stored a fault code or event data.
You can try an instrument cluster self-test to see if a fault code shows up in the odometer display (be prepared to write it down), otherwise you would need a more advanced scan tool/code reader.
This same symptom happened on the wife's '02 Caravan and it turned out to be corroded wires where the harness rubbed on the sharp front edge of the metal transaxle pan (ground). Examine the harness routing at the front of the transaxle to make sure that it hasn't rubbed through anywhere. After splicing and shrink wrapping the wires, I taped and tie-wrapped the harness away from the sharp edge.
 

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You need to find out what type transmission fluid the shop put in there. If they used Dexron with an additive, like so many do around here, then it needs to be flushed and refilled with ATF+4. I know that's a long shot, but I've seen it happen all to often at these shops. I think the ATF costs them a little more and they get a better deal on the Dexron and additives.
 

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Not to mention that most transmission fluids labelled as "universal" are Dexron in disguise. "Dexron w/additive" is not a viable substitute.

#1 Rule with Chysler electronically controlled transmissions (which is pretty 99% of them since the late 80's) - ATF+4 only. DO NOT USE DEXRON! EVER! Unless, of course, you feel like spending money on a reman transmission.

The only exception would be the older 3 speed hydraulic transmissions (A413 & A670) - they can use Dexron, but even then ATF+4 will work fine in them.

In short, the basic rule is ATF+4 only. You can't go wrong with it.
 

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Wambus, did you ever get the problem rectified?
 

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Discussion Starter #9
I have not fixed it as of yet. I just now saw the recent posts here and I have not had a chance to contact the shop and see what he used. If he used dextron, can I just drain it and refill or do I need to do somnething more involved?

I removed and cleaned the throttle body last year.

I will check TPS - that is easy; I even think I have the correct cover sheet.... Yuk Yuk

I do not think it is the AC engaging for no reason, 'cause I don't hear or feel the other associated sounds that accompony that - but I will certainly have a look.

The mainharness that passes around in front of the engine is fine (I think). I has it twist-tied to the front crossmenber for many years before the trans work. the trans guy actually zip-tied it up there when he was done.

Could it just be the MAP sensor?
 

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Virginia Gentleman
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wambus said:
I have not fixed it as of yet. I just now saw the recent posts here and I have not had a chance to contact the shop and see what he used. If he used dextron, can I just drain it and refill or do I need to do somnething more involved?
If you're lucky and if the Dexron hasn't been in there too long, a change to ATF+4 might save it. It would be worth trying.
 

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Draining will leave some old fluid behind because the torque converter cannot be drained. Flushing would be better.
 

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I agree with Mark about flushing. If you discover that the shop used Dexron, you should insist that they do a flush with ATF+4. Word of mouth can be your best or worst advertising, if you catch my drift.
 

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Discussion Starter #13
So, the two choices are bad TPS or wrong trans fluid. This happens ONLY when stopped in gear. Never when driving and never when idling in park. I plan on going back to the transmission guy about this so I want to be sure....
 

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Discussion Starter #14
Hey everyone,

I was planning on replacing the existing fluid in this thing tomorrow. How critical is it that I flush and fill? I was hoping to try this and see if the 'hesitation', which now seems more like some kind of transmission slippage, went away or was diminished.

I am not sure how to go about forcing this guy (independent mechanic) to do the flush and fill. My transmission job is under warranty until June. should I take it to another shop and get a report or will they defer so they wont tick off another mechanic?
 

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Discussion Starter #15
OK,

I may not change fluid. May just take it to an engine shop then a transmission shop and ask them to just figure it out. I am going to try some of the trouble shoots mentioned earlier in this thread. Why are there no codes?
 

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You may have fault codes stored in your TCM and not know it.
An engine code reader won't display TCM codes and a TCM code won't light the 'ck eng' light in a '99 vehicle.
You may need an advanced code reader to access the TCM fault codes, if any. Not everything sets a code.
It is important to find out if this shop used the correct ATF or you could be looking at another overhaul in the future. He may even have the scan tool necessary to interrogate the TCM and perform a quicklearn.
If you drain the pan and replace the filter, you have roughly half of the old ATF still in the transaxle. A transfusion can get almost all of it out.
If this symptom wasn't there before the rebuild, you need to verify that it really is not in the transaxle. This guy should take a little more interest in your concerns than just blaming the engine. He should prove it one way or the other.
 

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Discussion Starter #17
What do any of you think about using Lucasoil transmission fluid additive? Will this harm a mopar Caravan) transmission? Not really on topic, I know...
 

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Chrysler does not recommend any ATF additives. The ATF must meet Chrysler MS-9602 for ATF+4 (Google it). Verify what is in your transaxle first with the rebuilder.
 

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Lucas can help IF the issue is hardened internal seals, but that problem was worse on earlier cars (I had a 1994 LeBaron with the bad seals and slow cold engagement and Lucas helped). And a rebuilt transmission should have new seals anyway, so Lucas won't help you. It could also void the rebuilder's warranty.

I assume there's no tach to verify if it's hesitation (RPMs would not build fast) or slipping (RPMs build fast but forward motion doesn't happen).
An overlooked item is possibly that they damaged or did not properly set the crank position sensor when installing the transmission if the issue isn't slipping.
 

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Discussion Starter #20
There is a tach, but I will need to really pay attention next time I drive it.

Where is the crank position sensor on this engine? How do I check for this?
 
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