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Discussion Starter #1
Hello there! I’ve just acquired a 2011 Sonata SE with 170k on the transmission. A few days ago, while accelerating onto the highway, it seemed to not want to shift, but after that I noticed no issues. Yesterday, went to get on a highway again, it went from third, seemed to downshift, rpms to redline, and back to third. I stopped, checked for leaks, etc. but nothing.
I’ve taken it to two shops to read codes, nothing at all for the transmission.
i can drive it in manual up to third, shift to fourth and seems to downshift, then rev, lurch forward, then clunk, then back to third. If I run it to third, put in drive, then to neutral as it tries to rev, let the rpms drop below 2k, then back to drive or manual, it does fine in fourth up through sixth, and will downshift smoothly through all the gears.
I’d rather not throw parts at it. I have a transmission for it in the trunk that I don’t really want to put in it.
Any advice??
 

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Discussion Starter #2
Okay, got it to throw a code and go into limp mode. P0735. Now, what to do from there? I’ll be researching...
 

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P0735 is incorrect 5th gear ratio.
It shifts 1-3 fine and when it gets to 4th, it flares and then drops back to 3rd? And if you bump to N and back to D, it will go up to 4-5-6 ok?
On the 3-4 shift, it releases the 3-5-R clutch and applies the overdrive clutch. The OD clutch is used for 4th/5th/6th. If it shifts ok at higher speeds, it sounds like a problem with the solenoid that applies the OD clutch. In other words, "valve body problem".
I would be interested in seeing if you can shift manually 1-2-3, and then accelerate to about 35mph and then manually shift from 3 through 4 to 5 with you foot off the pedal, and then accelerate in 5th and then go to 6th at about 43mph. Try that and see if it slips in 5th gear. In the manual gate ("5" appears instead of "D" on the dash), floor the pedal and see if you get any flare. Then slow to under 40mph, downshift to 4 and floor the pedal again. See if there is any flare (high rpm). If you're not seeing any slipping in any gear, it's a valve body issue. The clutch packs are good if there is no slipping in specific ranges but all heck breaks loose during an upshift.
 

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Discussion Starter #6
P0735 is incorrect 5th gear ratio.
It shifts 1-3 fine and when it gets to 4th, it flares and then drops back to 3rd? And if you bump to N and back to D, it will go up to 4-5-6 ok?
On the 3-4 shift, it releases the 3-5-R clutch and applies the overdrive clutch. The OD clutch is used for 4th/5th/6th. If it shifts ok at higher speeds, it sounds like a problem with the solenoid that applies the OD clutch. In other words, "valve body problem".
I would be interested in seeing if you can shift manually 1-2-3, and then accelerate to about 35mph and then manually shift from 3 through 4 to 5 with you foot off the pedal, and then accelerate in 5th and then go to 6th at about 43mph. Try that and see if it slips in 5th gear. In the manual gate ("5" appears instead of "D" on the dash), floor the pedal and see if you get any flare. Then slow to under 40mph, downshift to 4 and floor the pedal again. See if there is any flare (high rpm). If you're not seeing any slipping in any gear, it's a valve body issue. The clutch packs are good if there is no slipping in specific ranges but all heck breaks loose during an upshift.
I will go try this now! Thank you!
i do have the other transmission, which has less miles on it. I really don’t want to replace the whole thing, pain in the tail, but I also don’t want to have to mess with it later.
 

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Do you have the controller (computer) for that other transmission? If you do not have the other 'computer' you'd need to have the adaptives on yours reset when you install the other transmission.

When shifting to R or D when the engine is cold, does it engage right away or is there a delay before you feel the gear engage? Does it change - for better or worse - when things get to operating temperature?
 

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Discussion Starter #8
I will go try this now! Thank you!
i do have the other transmission, which has less miles on it. I really don’t want to replace the whole thing, pain in the tail, but I also don’t want to have to mess with it later.
So, doing as told, runs flawless. So I decided to just give it a shot without skipping fourth. And it works?? What?? I even tried to drive a bit aggressively, shifted fine. I’m going to drive more and get the transmission good and hot. Then we will see how it acts...
 

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Discussion Starter #9
Do you have the controller (computer) for that other transmission? If you do not have the other 'computer' you'd need to have the adaptives on yours reset when you install the other transmission.

When shifting to R or D when the engine is cold, does it engage right away or is there a delay before you feel the gear engage? Does it change - for better or worse - when things get to operating temperature?
I do have the computer. And the axles!
It doesn’t seem to hesitate or clunk in to gear, that’s the first thing I check on a used car purchase lol.
i have a feeling that if it gets nice and warm, my issue will flare up again. I’ll see soon.
 

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2012 Sonata 2.0t Ltd & 2020 Palisade Ltd
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Incompatible fluid will cause all sorts of shifting problems, but the first signs of trouble are usually with the 2-3 and 5-6, with other shifting being more tolerant of degraded/contaminated/incorrect fluid.

Shift timing is most critical on the 2-3 and 5-6 because there is a component (middle sun gear to be specific) that is clutched to the input shaft in 3rd/5th and locked to the case in 2nd/6th. So on each one of those shifts, any fault in timing can lock the sun gear to the input shaft while it is still locked to the case. To call it a "bind-up" is the understatement of the month.

This is a peek at the solenoid that seems to need attention, based on the symptoms - Oversized Overdrive Pressure Control Valve Kit - 102741-18K
 

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Best advice I can give regarding this: I change my ATF (using OEM method of a simple drain & fill) about every 30K miles or so. I've used the OEM fluid once and Amsoil OE ATF fluid the second time. Big mistake using the Amsoil however (when hot, acts like I have a "hole-shot", high stall torque convertor installed). Either stay with the newer synthetic OEM fluid (SP-4M) or use Valvoline Maxlife Multi-Vehicle synthetic ATF.
 

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Discussion Starter #13
So, it is like I figured, shifts great cold, warms up and it’s the same story, it goes dumb shifting from third.
I’ve been driving it regularly though. using manual, shift up through third, get to above thirty, let off the accelerator, shift over to drive then neutral, give it a second or so, back into manual. At that point it will be in fourth or fifth (sixth if you are really deep in the pedal for third). Shows no issues, just a pain...
the valvoline max life multi vehicle is what’s in it now.
I hate just throwing parts at things, but I’m having the newer used transmission put in Monday. I decided I didn’t want to mess with it myself.
i really just didn’t want to have to be the one to removed the transmission from my trunk lol
 

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So, it is like I figured, shifts great cold, warms up and it’s the same story, it goes dumb shifting from third.
I’ve been driving it regularly though. using manual, shift up through third, get to above thirty, let off the accelerator, shift over to drive then neutral, give it a second or so, back into manual. At that point it will be in fourth or fifth (sixth if you are really deep in the pedal for third). Shows no issues, just a pain...
the valvoline max life multi vehicle is what’s in it now.
The fact that all six gears work as long as you shift manually tells you the hard parts are all ok and the issue is in the valve body. It'd make a good rebuildable core for a transmission shop.
I hate just throwing parts at things, but I’m having the newer used transmission put in Monday. I decided I didn’t want to mess with it myself.
i really just didn’t want to have to be the one to removed the transmission from my trunk lol
Swap the TCM in at the same time and there won't be any oddball behaviors and need for adaptive reset.
Who put the transmission in the trunk initially? It helps to have an extra pair of hands - you don't want to hurt yourself because those orthopedic injuries don't always heal.
 

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Discussion Starter #15
The fact that all six gears work as long as you shift manually tells you the hard parts are all ok and the issue is in the valve body. It'd make a good rebuildable core for a transmission shop.

Swap the TCM in at the same time and there won't be any oddball behaviors and need for adaptive reset.
Who put the transmission in the trunk initially? It helps to have an extra pair of hands - you don't want to hurt yourself because those orthopedic injuries don't always heal.
I planned to either sell or repair the current transmission after removal, as I figure it’s not completely screwed. I do have the tcm and plan to have it installed so it doesn’t go stupid on me.
My friend had the transmission resting on a tire in the back of his truck. We managed to slide it with some attempted lifting into the trunk. I then asked him if he drained the fluid first. No. Sigh. Then I asked who helped him get it into the truck. A forklift. Double sigh. I figure my mechanic will have a cherry picker engine lift that will aid in removal. I might not volunteer to help with that lol
 
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