Serious Transmission Jerking/Knocking noise when accelerating

[thatjawncrazy]

Hate to make this thread, because the car has been great otherwise. At 50,000 miles, I noticed a clamp on my front right axle boot had come loose and let grease go everywhere. After tightening the clamp, 25,000 miles later, I see that it came loose again. Grease everywhere. This time, my car drives like crap and is exhibiting symptoms as if the transmission blew up - not the axle.

I'm now getting occasional jerks under light acceleration at lower speeds, almost as if the car is catching itself. I also get a knocking from the front end when under full acceleration merging onto a highway.

I can't move the axle back and forth any more than usual. Each end of the axle doesn't move when i try to move it. I can move each wheel when it's in the air, but pretty sure that's normal.

The "jerks" are coming from the center of the car. The knocking is coming from the front of the car.

wtf could this be?



All the flex joints on the driveshafts are fine. There are distinct lines of dirt around them though, but i think this is dirt that was flung out from when i drive in wet conditions.

 

[thatjawncrazy]

Went to the dealer today.
Well, the knocking sound was a heat shield that a rock had hit and bent to the point where it was hitting some piece in the engine bay. The axle, besides letting all this grease out, is fine. They strongly suggested i flush the fluid at 60k (which i am well beyond) and reset the adaptive transmission learning thing. Gonna get that done next week and see if it fixes the issue. I'm inclined to believe them.

 

[Cashby]

The adaptive value reset on the trans makes a difference. Stingers/G70 are known for harsh downshifting and up shift on some of the lower gears. The reset helps. My 21 G70 had harsh shifts at like 2000 miles and I had them do the reset and it got rid of it.

 

[MichaelJohnson]

Went to the dealer today.
Well, the knocking sound was a heat shield that a rock had hit and bent to the point where it was hitting some piece in the engine bay. The axle, besides letting all this grease out, is fine. They strongly suggested i flush the fluid at 60k (which i am well beyond) and reset the adaptive transmission learning thing. Gonna get that done next week and see if it fixes the issue. I'm inclined to believe them.

I hope that takes care of it.

 

[Andyj]

I read that "flushing" the transmission is not a good idea, and that the transmission fluid should be drained and refilled, possibly even more than once.

 

[Cashby]

If you do a "flush" at home its not really a flush. At home you can basically do 4qts at a time. Drain 4, fill 4. Start car shift through gears and doit again. Ive done it at home and its a little bit of a process.

However, after doing it and flushing until nice clean flud was coming out, the trans temps, shifts etc are sooooo much better. I replaced with Motul.

 

[thatjawncrazy]

So the trans fluid change/adaptive value reset ABSOLUTELY fixed the jerking. The transmission is back to being super smooth and almost unnoticeable. I just need to figure out where the knocking is coming from.

Lesson learned, lifetime trans fluid is not really lifetime. I don't drive this thing hard.

 

[Volfy]

Did you drop the pan and changed out the filter?

 

[ajwklajdskla1]

How much does dealer charge for transmission fluid change?
Did they replace the trans fluid filter as well? Based on googling, filter itself is about 150$ and transmission fluid would cost about 300$?

I have about 52k miles on my 19 3.3t sport RWD and as I accelerate from complete stop to like 20 mph, specially in curby road, i get some kind of vibration with some noise so i thought it was from differential so i replaced differential fluid. For reference, i changed it first time at 34k miles and next one was done around 46k miles. The differential fluid was clean. First fluid i used was KIa oem fluid with lsd.
And when i changed it second time i went with royal purple 75-140 instead of 75-85.after that i dont get that vibration as frequent as before.

 

[Volfy]

I plan on doing it myself. It isn't that complicated. Most shadetrees should be able to do it easily.

I bought the pan/filter for about $110+tax. For ATF, any brand that meet Hyundai/Kia's SP-IV RR spec is good. I'm going with this Valvoline Premium Full Synthetic. Back of the bottle lists SP-IV RR:

https://www.amazon.com/Valvoline-Protection-Synthetic-Automatic-Transmission/dp/B0C1LKVDWR

Dropping pan and refill take 7 litre, so 2 gal should be plenty. That's about $70+tax. To me, DIY is much more than the cost savings, though it is a big advantage. It's first and foremost about knowing exactly what and how it was done, and what exactly goes into my car, and not worrying about having my car damaged by the grease monkeys.

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[ajwklajdskla1]

I was thinking to doing it myself but after watching that video I decided to not too. I just dont feel comfortable working entirely under the car.
Ive done everything myself, like spark plugs, differential fluid, brake pad + brake fluid change but i feel like this one i should get some professional help haha.

I plan on doing it myself. It isn't that complicated. Most shadetrees should be able to do it easily.

I bought the pan/filter for about $110+tax. For ATF, any brand that meet Hyundai/Kia's SP-IV RR spec is good. I'm going with this Valvoline Premium Full Synthetic. Back of the bottle lists SP-IV RR:

https://www.amazon.com/Valvoline-Protection-Synthetic-Automatic-Transmission/dp/B0C1LKVDWR

Dropping pan and refill take 7 litre, so 2 gal should be plenty. That's about $70+tax. To me, DIY is much more than the cost savings, though it is a big advantage. It's first and foremost about knowing exactly what and how it was done, and what exactly goes into my car, and not worrying about having my car damaged by the grease monkeys.

 

[thatjawncrazy]

How much does dealer charge for transmission fluid change?
Did they replace the trans fluid filter as well? Based on googling, filter itself is about 150$ and transmission fluid would cost about 300$?

I have about 52k miles on my 19 3.3t sport RWD and as I accelerate from complete stop to like 20 mph, specially in curby road, i get some kind of vibration with some noise so i thought it was from differential so i replaced differential fluid. For reference, i changed it first time at 34k miles and next one was done around 46k miles. The differential fluid was clean. First fluid i used was KIa oem fluid with lsd.
And when i changed it second time i went with royal purple 75-140 instead of 75-85.after that i dont get that vibration as frequent as before.

I was afraid to touch my transmission lol. Like volfy said, might have been easy, but i'll leave this one to someone else...

They charged $579 for a full flush and resetting the adaptive values. This was $208 for parts and $320 for labor, that's all i know.

 

[Volfy]

Yeah, this one is not exactly beginner friendly. It's a messy job that could potentially get your garage floor or driveway splattered full of ATF. So, a good amount of experience and some comfort level working under your car would help a lot.

That said, I did a similar ATF/filter replacement last year on an LS V8 6sp. GM saved 14 cents by not having a drain plug on the tranny oil pan, so you have to unbolt the pan except 2-3, so the pan can be cracked open and lowered at one end to drain the ATF. Yeah... compared to that, this Hyundai 8sp tranny should be a walk in the park. It's all relative, but this sort of experience has to be built up and accrued over time. Gotta get dirty... and maybe earn a skinned knuckle or two.

 

[Volfy]

BTW, I posted that YT vid because it's a really good guide for this job. However, I don't particularly agree with his plan to flush the tranny 3 times, especially with that rather expensive German Ravenol ATF. That is throwing a lot of fresh fluid away. Understand the concern that the torque converter holds about 2.2L out of the total 9.2L capacity, so I did a bit of math:

After 1st draining and refill of 7L new ATF, there will be 2.2L of old ATF mixed in.
After 2nd draining and refill of 7L new ATF, there will be (2.2/9.2) x 2.2L = 0.53L of old ATF mixed in.
After 3rd draining and refill of 7L new ATF, there will be (0.53/9.2) x 2.2L = 0.13L of old ATF mixed in.

So, 1st flush got rid of 7L of old ATF
2nd flush got rid of (2.2 - 0.53) = 1.67L of old ATF
3rd flush got rid of (0.53 - 0.13) = 0.4L of old ATF

There is definitely diminishing returns here. Personally, I have no problem with a single drain & refill, with 76% of fresh new ATF. I highly doubt the tranny will run any different than with 100% fresh ATF. I'm changing early anyway and will do so again the next time. If anything, getting rid of built-up contaminants and swapping in a brand new filter are just as important, perhaps more so.

But, if you are the OCD type, I can see doing a 2nd flush to boost the fresh ATF up to 94%. Cost would be another 7L of new ATF.

3rd flush is just plain waste of money, throwing away whole 7L of new ATF to get rid of only 0.4L of old ATF.

 

[thatjawncrazy]

Alright well, somehow, it hasn't entirely fixed the issue. It's way smoother, but I'm still occasionally feeling the trans slipping under light acceleration...

Idk what else to have them look for at this point. Have them check/replace the torque converter and spend $1500 in labor doing it? Drive around and floor it from stop sign to stop sign so my trans doesn't slip? Continue to drive it until I get some unfixable transmission error?

The rear diff fluid looked fine the last two times i changed it. The techs said the trans fluid looked fine too.

This is pretty disappointing as I definitely do not drive the car "severely" like the conditions in the manual that tell you to change this fluid 17k miles ago.

 

[lexoman]

I have a 2020 G70 3.3 AWD. I have a similar problem, but in my case it happens on the downshifts. At around 15 mph as I'm breaking to a stop, there is a severe lurching of the car forward as it shifts from 3rd to 2nd gear. The car has 28K miles and this just started about a week ago. Do you think a transmission re-calibration might help?

 

[thatjawncrazy]

I have a 2020 G70 3.3 AWD. I have a similar problem, but in my case it happens on the downshifts. At around 15 mph as I'm breaking to a stop, there is a severe lurching of the car forward as it shifts from 3rd to 2nd gear. The car has 28K miles and this just started about a week ago. Do you think a transmission re-calibration might help?

Yes, but it'll keep happening. Unfortunately the harsh downshifts at lower gears are a well documented issue with the G70s. Just the stock transmission programming....i guess they didn't do enough testing

 

[pulsar]

What a PITA. To build in the trans oil filter screen within the pan is crazy to me. Yes I’m old school and used to GM type vehicles where the screen is separate and you have a dip stick and normal filler hole up top. Most of my cars have been standard transmissions so my G70 is only my second auto trans cars I’ve owned. Aggravating manufacturers want to save $12.00 by deleting the dipstick altogether. Those of us that like to DIY are probably a dying breed and those who keep cars long enough to need to change trans fluid or measure and change out our solid lifters are also probably far and few between. Manufacturers want us to trade cars every 3 years or so or by 50k miles. I don’t fit any of those molds for my Miata is 16 years old with only 55k miles and still looks new and my G37 car before it was hit and totaled was 9 years old with only 47k miles And was still in excellent shape. I expect to keep my G70 10 years and it will have probably 50k miles or so at that time.

 

[thatjawncrazy]

What a PITA. To build in the trans oil filter screen within the pan is crazy to me. Yes I’m old school and used to GM type vehicles where the screen is separate and you have a dip stick and normal filler hole up top. Most of my cars have been standard transmissions so my G70 is only my second auto trans cars I’ve owned. Aggravating manufacturers want to save $12.00 by deleting the dipstick altogether. Those of us that like to DIY are probably a dying breed and those who keep cars long enough to need to change trans fluid or measure and change out our solid lifters are also probably far and few between. Manufacturers want us to trade cars every 3 years or so or by 50k miles. I don’t fit any of those molds for my Miata is 16 years old with only 55k miles and still looks new and my G37 car before it was hit and totaled was 9 years old with only 47k miles And was still in excellent shape. I expect to keep my G70 10 years and it will have probably 50k miles or so at that time.

I want to keep this car until it actually dies (or requires mechanical work exceeding the value of the car) but I cannot drive a car with a transmission like this for another 77k. It's really disappointing. The manual said not to change the fluid, the dealer said i should have, and clearly i should have. Now i possibly messed something up long term, and the only solution i see here is for someone to take apart the trans and see what's wrong in there. Idk what to do.

 

[Volfy]

What a PITA. To build in the trans oil filter screen within the pan is crazy to me. Yes I’m old school and used to GM type vehicles where the screen is separate and you have a dip stick and normal filler hole up top. Most of my cars have been standard transmissions so my G70 is only my second auto trans cars I’ve owned. Aggravating manufacturers want to save $12.00 by deleting the dipstick altogether. Those of us that like to DIY are probably a dying breed and those who keep cars long enough to need to change trans fluid or measure and change out our solid lifters are also probably far and few between. Manufacturers want us to trade cars every 3 years or so or by 50k miles. I don’t fit any of those molds for my Miata is 16 years old with only 55k miles and still looks new and my G37 car before it was hit and totaled was 9 years old with only 47k miles And was still in excellent shape. I expect to keep my G70 10 years and it will have probably 50k miles or so at that time.

Sounds like you might not even need an ATF flush, if that's the case.

I guess I'm used to working on my own cars, I don't mind doing these chores every once in awhile. If I drive the car for 150k, that's probably 2 ATF flushes. Not really that big a deal.

The plastic drain pan is a bit expensive compared to just the filter with the GM, but not that much more considering I had to buy the pan gasket separately. The Kia/Genesis p/n comes all in 1.