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Discussion Starter #1
our 03 mdx has developed a strange problem,it wont upshift from 1st gear.it will cycle from park,neutral and drive but it never upshifts when driving.even if I manually go from 1st,2nd,3rd and fourth it stays in 1st gear with high revs.the transmission was rebuilt just over 2 years ago and I did a 3 liter drain and fiil a few months ago.fluid is nice and clean but I did notice that It was a bit overfull on the dip stick.what would cause this problem?

thanks
 

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Have the 3rd/4th gear and 5th gear pressure switches been checked? If they can catch it "in time" before damage is done it might save a big expense.
 

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It sure couldn't hurt to return the fluid to the right level (which should be measured with the transmission warmed up - hard to do in 1st gear - and within 60 seconds (IIRC) of turning the engine off, with the vehicle parked level.

I'm betting that it is indeed a problem with the pressure switches or shift solenoids... pretty common in any automatic transmission. A dealer will tell you that you need a new transmission, as will more than a few shops... but in my experience it's almost "fixable" as long as no individual gears are truly slipping (as opposed to "flaring", which feels like the tranny shifts to neutral in between gears, but then engages).
 

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Discussion Starter #4
Thanks for the reply guys,i have not had anything checked yet.the trans has not been slipping in any way since it was rebuilt.i better find some way to test the solenoids,transmissions are something i know zip all about

Thanks again
 

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Discussion Starter #6
heres the info I found in the service manual for a transmission that wont shift into 2nd

shift solenoid valve A defective- check the D5 indicatorand check for loose connections

shift valve A defective- inspect the o-ring and check the shift valve for seizure

where the heck are these guys located on the trans?cant seem to find a picture.thanks
 

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The best thing (by far) for troubleshooting a Honda tranny is the HDS (Honda Diagnostic System). I won't go into detail here, but there are a lot of threads on the subject. With one of those, you can turn shift solenoids on and off, listening for the click (no click, you have your culprit).

I just looked up the "control matrix" for the transmission, and it looks like none of the shift solenoids change state when shifting from 1st to 2nd, so maybe you can eliminate the shift solenoid A as the problem...


113503


The "shift valve A" is a little more challenging, both because of the location, and the fact that Honda calls two different components the same thing...

113504


113505
 

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I know nothing about that scanner. Hard to imagine that it would have the "depth" of the Honda HDS tool though. The HDS burrows down into pretty much anything you'd ever want to twiddle or monitor in your Honda / Acura. For example, I could pull up a screen showing the status of all the shift solenoids and valves, which was priceless for troubleshooting a transmission. You could tell (for example) if the solenoid was being activated late, or the tranny was just reacting to the solenoid activation late. I can't believe that generic scan tool could do that, but it's likely simpler and almost certainly more versatile (does more than Hondas / Acuras).

FWIW, the tool I bought looks a lot like this one: US Amazon HDS Tool

I pasted in the US tool because it was about half the price of the Canadian Amazon HDS systems (partially US$ vs. CA$, partially because you guys pay more for everything up there). ;-)
 

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Discussion Starter #10
thanks again habbyguy,that tool is unavailable here in Ontario.so I swapped out the pedal position sensor with a used one now it seems to go through the gears.but now theres a real nasty whine and vibration coming from the car somewhere.i hope its just a hub bearing.gonna put it back in the garage and see if I can find the source.
 

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When you say "whine", the first thing that pops to mind is the all-too-common torque converter whine. If the whine essentially disappears when you shift to D4, that's what's causing it.

Otherwise, you can usually work out which wheel bearing is causing the problem by the way the sound changes going around corners (lots of threads on that out there).

Good work on swapping out the pedal position sensor - the tranny does take a LOT of input from that (its shifting "map" uses that sensor to determine which gear it should be in at a given speed - I only wish that map was customizable - my MDX used to like to downshift when I drove over a paint stripe). ;-)
 

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Discussion Starter #12
so after another test drive tonight I think the rear left wheel bearing is the culprit.when swerving on the road we could make the sound and vibration come and go.
 

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Sounds likely, though sometimes any kind of metal-to-metal contact (usually due to a bad bushing) can create the same kind of noises (which are always there, but generally prevented from reaching the chassis by the bushings). You can always jack up that corner and spin the wheel and listen with a mechanic's stethoscope.

FWIW, I'm experimenting with a "real time audio diagnosis system" - basically a clip-on contact microphone feeding an FM modulator (battery powered, of course). My plan is to clip it on near the suspect component and tune my radio to listen in on what the component is doing. In the case of a rear bearing, it would mean clipping it to one knuckle, then the other (if the sound is radically different, you've found the source). Don't know exactly when I'll have time to test it, but it should be fun, might be worthwhile.
 
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