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Can a bad alternator cause transmission problems?
Topic Started: Jan 10 2010, 10:17 PM (7,124 Views)
StevieC
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Ok. Unrelated to my metro, but thought it'd be an interesting discussion for those who have auto boxes.

My 96 plymouth voyager van recently started failing to switch to 3rd or overdrive. I had an idea the alternator would fail after the power steering hose blew and drenched it in fluid.

Upon testing it failed without trace of doubt. The van actually stalled!

My question is can a bad alternator cause confusion in the sensors to the point that the computer will activate limp mode?
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mwebb
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FOG

StevieC
Jan 10 2010, 10:17 PM
Ok. Unrelated to my metro, but thought it'd be an interesting discussion for those who have auto boxes.

My 96 plymouth voyager van recently started failing to switch to 3rd or overdrive. I had an idea the alternator would fail after the power steering hose blew and drenched it in fluid.

Upon testing it failed without trace of doubt. The van actually stalled!

My question is can a bad alternator cause confusion in the sensors to the point that the computer will activate limp mode?
a definate maybe .
depends on the conditions of the alternator failure

did it fail hi
fail low
is it bursting
is it rippling .........


and that application has a famously weak transmission as well
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StevieC
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mwebb
Jan 11 2010, 12:40 AM
StevieC
Jan 10 2010, 10:17 PM
Ok. Unrelated to my metro, but thought it'd be an interesting discussion for those who have auto boxes.

My 96 plymouth voyager van recently started failing to switch to 3rd or overdrive. I had an idea the alternator would fail after the power steering hose blew and drenched it in fluid.

Upon testing it failed without trace of doubt. The van actually stalled!

My question is can a bad alternator cause confusion in the sensors to the point that the computer will activate limp mode?
a definate maybe .
depends on the conditions of the alternator failure

did it fail hi
fail low
is it bursting
is it rippling .........


and that application has a famously weak transmission as well
I will have more info when I get it off the van. It makes the lights flicker, I know that much!
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StevieC
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Thinking about... I don't think it even gets out of first gear. It's either first or neutral.
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billy508
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billy508

@StevieC Check out this link. http://www.allpar.com/fix/trans.html :banana :banana :banana Note the reference to Trans computer retaining
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Johnny Mullet
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Hi-Tech Redneck

............ Moved to "General Tech"

The Trans in those models are notorious for having issues.
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mwebb
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FOG

..." I will have more info when I get it off the van.
It makes the lights flicker, I know that much! "....


i must disagree
you need to test the charging system WITH the suspect alternator installed
if you wish to find the problem

it may not be the alternator
=================================
a simple test would be to replace or charge the battery
then disconnect the alternator - and run the car

if the symptoms are no longer present
the alternator is SUSPECT , but actual testing under load will be needed to confirm that

if the symptoms are the same with the battery fully charged and alternator disconnected
then the alternator is probably not related to the transmission problem

see the voltage drop testing thread
in the
"how to , guides" area in this forum
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rstenicc
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[ *  *  *  * ]
I have rebuilt replaced several of those trannys for being bad. VERY notorious for going south.
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StevieC
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I'm going to try disconnecting the alternator to see if it makes a difference.
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StevieC
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Billy,

Thanks for the link. I am going to take re-assurance in the following text:

"Losing overdrive and third gear
Believe it or not, this is a sign of good design. Rather than having the engine shut down completely, Chrysler designed a "limp home mode" which causes the transmission to only use first and second, as a very visible sign that something is wrong. The immediate reaction should be checking the computer for error codes and changing the transmission fluid. If that fails, it could be a sensor problem or an internal problem. Suggestion is usually to chnage the fluid and filter (maybe flush the fluid too) and make sure that you use the correct amount of the appropriate chrysler fluid - DO NOT USE ANYONE ELSE'S FLUID!"

Fingers crossed it isn't anything serious!
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StevieC
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OK,

1. Transmission is not leaking fluid. The power steering rack is leaking.

2. Transmission only goes into limp mode AFTER it tries to switch to third gear. Before that, it will happily switch between gears 1 and 2.

3. If I drive along in 1, then 2, and then drop the accelerator, it selects overdrive as the lowest gear and does not go into limp mode. However, if at any point it tries to enter the third gear while accelerating it produces a DTC and goes into limp mode.

4. The DTC says that the 3rd gear ratio is incorrect. Assuming that it uses the input speed sensor against the output speed sensor to check the gear ratio, a bad sensor could cause this code.

We tested the alternator, it won't put out more than 33 amps.
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StevieC
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An update, late as it is.

Note: Transmission is A604.

I took the solenoid pack off, and tested resistance between the 12v supply and the switch grounds. There was no resistance in any of the four paths. Supposedly I can conclude from this that the solenoid pack has had it.

It gave in when I got off the highway, I suppose the faulty alternator might have fried it?

Mwebb, where are you when I need you?!
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StevieC
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Also - I tested the input sensor and the output sensor, both function.

And disconnecting the alternator had no impact, besides dimming my lights!
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mwebb
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FOG

a 1996 chrysler mini van will have scan data available
an MT2500 or a genisys or better still
AutoEnginuity will get into the transaxle computer and give up any DTCs

then you can test the circuits it gives up.
a generic tool will not do it

there are PIDs that show the adaptive s for each set of clutch discs, from those adaptives you can take a pretty good swag at remaining life in the transaxle
assuming no hard part failure s

if you have a DTC that refers to
incorrect or NOT plasible relationship of the input and output speed sensors
the trans-axle is Ka-Ka.

if you have a DTC the refers to any solenoid CIRCUIT , you probably have an open shift solenoid
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StevieC
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I had a buddy read it with his machine, he said the third and overdrive solenoid(s) have had it. Woooooooooo. Thanks Mwebb.
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