Transmission bucking

D

digital fx

Member
Location
connecticut
Car
2012 m56x
Name
john
Hey guys I'm having what seems like a problem with my transmission.I was driving about 35mph when suddenly my transmission seemed to jerk hard to where it slowed the car down a little hard to explain the feeling, like I hit a hard bump .then my check AT and check engine light came on and the transmission would not shift into 4 or downshift smoothly. After shutting the car off briefly it began to drive normally all lights went off.any ideas what I'm dealing with guys.I haven't had a chance to get codes read or anything any help would be great thanks
 
Viperi said:
low on fluid?
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That's another thing I don't know where to check the fluid I've done some searching and I came up with two possibilities of where to check fluid under the car and under the hood after removing engine cover and unscrewing a 10 mm bolt .it would be great if someone can clear that up for me and a link to a thread with instructions would make my day so much simpler. Thanks
 
Under the hood near the passenger side by the firewall. Remove 10mm bolt, start up the engine while parked and go through each gear selection, turn off the car and check the stick.
 
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Car actually needs to be running when you check fluid level and the fluid does have to be warm as it expands. But if you check the fluid level with the car off, it will read slightly high. I actually tested this out - checked fluid level with car off and then checked with it running and I had to add a half quart.

The service manual also says to check fluid with car idling, it's pretty much the same for any car. But if you checked it right after shutting off the car, it's probably close enough.

And OP, if your transmission fluid level is good, your valve body might be failing. That's where all the solenoids are that control shifting. The bump you felt was the transmission going into limp mode where it locks into 4th gear and won't shift anymore to prevent further damage. If it happens again, check the codes and I'll be you'll have a code for a solenoid failure. I had this happen about a year ago, was driving along and transmission thumped and CEL came on. Shut car off and restarted and it was fine for a few days. Then it happened again and again with greater frequency. Checked the codes and it was one of the solenoids. Replaced the VB and all is well.
 
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Ok I got the codes read and checked fluid .as for the fluid it was at a perfect level checked on even surface while warm and shifted through all gears.the code I got was 1730 A/T interlock condition. With a bunch of electrical probable causes. Anyone familiar with this situation. I'm looking to take care of this ASAP don't want to end up doing a rebuild. Thanks for the feedback so quickly everyone!
 
See if it comes back, if it doesn't, no worries. Sometimes there are weird hiccups when voltages drop for whatever reason. Since you have an '03, I believe your TCM is in the passenger cabin and separate from the VB so I'd check the connections and harness. If that doesn't solve it, it's probably your VB that needs replacement. Rebuilt ones aren't cheap, but it's not absurd and labor isn't that bad. It's right inside the tranny pan so you can do it yourself (I've done it several times now) or take it to a shop.

I don't think anything actually needs to be rebuilt inside your transmission. It's going to be either your TCM or VB.
 
shadow191 said:
See if it comes back, if it doesn't, no worries. Sometimes there are weird hiccups when voltages drop for whatever reason. Since you have an '03, I believe your TCM is in the passenger cabin and separate from the VB so I'd check the connections and harness. If that doesn't solve it, it's probably your VB that needs replacement. Rebuilt ones aren't cheap, but it's not absurd and labor isn't that bad. It's right inside the tranny pan so you can do it yourself (I've done it several times now) or take it to a shop.

I don't think anything actually needs to be rebuilt inside your transmission. It's going to be either your TCM or VB.
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Do you know where about inside the cab the tcm might be so I can check connections .I googled tcm failure symptoms and I found basically what I've tried to explain what was happening with my car
 

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Even the '03 has the TCM on the valve body? I know that my TCM is in the VB and on the G/Z, they swapped in like the 04.5 model year and then made another change in '06. But the FX has always had the TCM in the VB?
 
Yep. that's the VB from a 03.

---------- Post added at 08:09 AM ---------- Previous post was at 08:07 AM ----------

Another picture (pic #4) of the 03 VB with the TCM is on the DIY thread.

---------- Post added at 08:16 AM ---------- Previous post was at 08:09 AM ----------

Those pictures are from two different 03 FX35. As matter of fact it on an 05 FX45 VB also.
 
That's interesting, learn something new every day. I always thought the VB's matched the G/Z, I guess the years are off a little. Mine '07 is compatible with the last model of the 5 speed auto with the low resistance solenoid (I think). The 3 versions on the G were external TCM, then in 04.5 they integrated the TCM onto the VB, then in late '05 or early '06, they changed the resistance on the low coast solenoid and something else. The 2 versions with integrated TCMs aren't supposed to be interchangeable. I wonder when they switched the FX VB from high to low resistance.
 
Man you guys are good,once again thanks for all the knowledge and timely feed back.I'm gonna contemplate if I want to give this a try or leave it to a pro I'll let you guys know.in the mean time im gonna try and figure out how to hand out some forum thanks
 
Good luck. Pulling the valve body isn't that hard, it's just very tedious and messy. There aren't any frozen or stuck bolts to worry about and everything is pretty easily accessible. But it's a long time under the car just taking out bolts and once you get the pan off, things get messy. Shops do tend to charge a lot for stuff like this though so it may be worthwhile to do yourself since no special tools are required.

The problem will be if you don't find anything obviously wrong with the TCM or harness. You'll then need to take it to a transmission shop for diagnosis so maybe it makes sense to just have a pro do the whole thing. If you just plan to swap to a new VB, they're maybe $800 or so and you could do the swap yourself. But that price doesn't include the TCM and those are ~$400 on their own. I'm still leaning toward solenoid issue though as those fail much more often than the TCM will since they have actual moving parts. It used to be very hard to get individual parts like solenoids, but I believe Sonnax makes/carries all of the individual stuff now so a shop could get them.
 
Hey guys.so I took my fx in to a pro and was told it is indeed just as shadow said a valve body issue .I have decided not to tackle this myself but to have a pro do the work.what I heard from the guy I took the car into is that these transmissions have a history failing valve bodies. Are you guys aware of that? And any advice in which way to proceed in fixing this,should I just replace the Valve Body the transmission does still shift smoothly, or should I replace the entire transmission with a low mileage one my fx has 120000 on it or the most expensive option complete rebuild.and I think I may be looking to step up to the jx in the near future still haven't made up my mind thanks for the help
 
Check the fluid - if the fluid isn't burnt and there aren't any metal shavings your transmission is likely fine. Was there ever any slipping or other issues besides the one you're having? A replacement valve body is cheaper than a replacement transmission and throwing in a used transmission of unknown history to replace a good condition transmission isn't something I'd recommend. And I wouldn't rebuild the entire transmission over a valve body issue, it doesn't make sense.

If you're considering replacing the FX, then I'd go with the cheapest option to fix your current situation which is a simple VB replacement. I wouldn't swap the entire tranny or rebuild unless you know there is an issue with the rest of the transmission. The only person who wins in that scenario is the shop since they make a lot more in labor.

And I don't know if a failing VB is that common, but I did have one fail. Not my OEM one but a modified Stillen one so I can't say if there was a defect, or if the upgrade wasn't done properly.
 
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