Thick transmission fluid for trouble shooting transmission?

Joined
Feb 24, 2005
Messages
3,078
Location
eastern NewMexico
On our old 3.3L Hyundai sonata, backup car I have it narrowed down to worn lockup solenoid valve body, which I think it is or a worn torque converter clutch.
The car is 2008 with 270,000 miles on the transmission, nearly all highway miles.
I'm thinking if I dump out some of the transmission fluid and replace it with say some AW iso46 hydraulic fluid and it is a leaky solenoid; could the thicker fluid keep the transmission line pressure up assuming it's a solenoid/valve body enabling the converter lockup to stay locked up or at least locked up longer?
And if it's a worn torque converter clutch thicker fluid won't matter.
I'm not saying this is or could be a fix. Either the p0781 code goes away and I install a new or rebuild valve body, flush the fluid, ect or it doesn't. Even then I say it's a 50/50 chance I part it out or junk it from there.
The dealer is absolutely useless, all they'll do is replace the torque converter for like a thousand bucks and they can't get a valve body.
The local transmission shop reached the same conclusion as the dealer and as I did for a diagnostic fee of $100, it's probably the valve body which they can't get or it's the torque converter.
I have a place that might be able to get a valve body or rebuild mine with steel sleeves. Either way I would like to know for sure one way or the other before I go all in.
 
On our old 3.3L Hyundai sonata, backup car I have it narrowed down to worn lockup solenoid valve body, which I think it is or a worn torque converter clutch.
The car is 2008 with 270,000 miles on the transmission, nearly all highway miles.
I'm thinking if I dump out some of the transmission fluid and replace it with say some AW iso46 hydraulic fluid and it is a leaky solenoid; could the thicker fluid keep the transmission line pressure up assuming it's a solenoid/valve body enabling the converter lockup to stay locked up or at least locked up longer?
And if it's a worn torque converter clutch thicker fluid won't matter.
I'm not saying this is or could be a fix. Either the p0781 code goes away and I install a new or rebuild valve body, flush the fluid, ect or it doesn't. Even then I say it's a 50/50 chance I part it out or junk it from there.
The dealer is absolutely useless, all they'll do is replace the torque converter for like a thousand bucks and they can't get a valve body.
The local transmission shop reached the same conclusion as the dealer and as I did for a diagnostic fee of $100, it's probably the valve body which they can't get or it's the torque converter.
I have a place that might be able to get a valve body or rebuild mine with steel sleeves. Either way I would like to know for sure one way or the other before I go all in.
You may find some interesting info in this thread:
I always want to try it, but never have a dying automatic transmission in the stable to try it with.
 
Have you thought about just Flushing the Trans Fluid 1st and get new fluid in there and see what happens?
Another question, how often did you change your Trans Fluid and does this car have an External Trans Cooler on it?
What trans fluid is this car specked for and what trans fluid have you used?
How much trans fluid does your Transmission hold?
Have you ever taken a trans temp reading, meaning with an infrared gun aimed at the Pan, or plug into your OB whatever Port to get a Temp Reading, if that is possible?
 
Are the symptoms worse when hot (thin) vs cold (thicker)? That might be an indicator.
Does this transmission have a replaceable oil filter (in the pan)? If your lockup clutch is wearing significantly, that's where the spalling off material will wind up and possibly restrict pump flow when it gets severe enough.
 
Are the symptoms worse when hot (thin) vs cold (thicker)? That might be an indicator.
Does this transmission have a replaceable oil filter (in the pan)? If your lockup clutch is wearing significantly, that's where the spalling off material will wind up and possibly restrict pump flow when it gets severe enough.
Yeah that's exactly why I'm thinking it's a worn valve body. It starts unlocking the torque converter when it's warmed up. When it's cold it usually doesn't do it.
 
I patched my BILs Cutlass Ciera with a "honey" that looked like Cherry Grenadine. Forget the brand now but it was front & center in the auto parts stores.

I'd do a fluid exchange as well and the filter if you can get to it.
 
Used transmissions for your car, in my area, average 400-700. That's what I would do because even if you fix the valve body you almost have 300k on the car.
 
it is an incredibly thick additive. instead of spending money on new fluid.

@oil pan 4 , I concur. It’s a quart of the stuff like molasses. Glob it in there and it will thicken up the fluid you’ve already got.

I had a very ill Chrysler FWD trans and botched a change of the externally-mounted solenoids; pretty sure some debris fell in which I couldn’t suction out. In one way, the transmission ran better, and in another it got worse. I added Lucas to thicken the fluid for more pressure and lubegaurd to reduce a nasty slam-shift habit … got the ratios right, and then continued driving it another year and a half. It lost a couple of quarts per year, and I had to get good at adding in the right replacement ratio of ATF, Lucas and lubegaurd. Such a hack, but a good hack.
 
If you don't mind spending money for fluids, trying a different viscosity may provide valuable insight. Racers try synthetic motor oils in auto transmissions from time to time. Especially when more pressure is needed. It sometimes works. But remember, these guys need 12 seconds of trans operation, not thousands of miles.
 
Yeah that's exactly why I'm thinking it's a worn valve body. It starts unlocking the torque converter when it's warmed up. When it's cold it usually doesn't do it.
In theory that seems true... however I drove a few years with no lockup on my 2004R in my 84 olds because it started with those symptoms until it eventually never locked up. I even found. Gm TSB explaining what worn part would cause this.....not sure what triggered me to figure it out but one day I replaced the vacuum switch on the inner fender with one from a parts car and then it locked up perfectly fine. Still going with over 300k miles.
So it's always possible it's something else even if wear makes the most sense.
 
Back
Top