Removal of Sonata under shield ... and maybe leave it off.

I am going to change the transmission oil in my 2006 Sonata with manual transmission. The car has 70,000 miles and I had it changed at the dealership at 60,000 miles as I don't believe in the "lifetime fluid"
approach for "normal" service that many now recommend. Anyway, I went to the dealership just a few weeks before they shut their doors. I thought things looked a little sparse on the lot and in the shop given that it was May. Anyway, since then the car is hard to shift into second gear, especially when cold. I am hoping that they hadn't run out of the correct 75W85 GL-4 and put in a heavier GL-5 fluid and possibly caused damage to the yellow metal parts.
I am going to put in Amsoil synthetic GL-4 as I couldn't find a GL-4 at the local auto parts stores. Apparently, almost nobody uses it anymore.
Anyway, it appears that the only easy way to access the fill plug is to remove the under shield. I thought this only had 4 bolts that held it, but a quick look under makes it appear that there are more than 4 bolts and I was seeing Phillips head screws as well. Can anyone tell me if all of these fasteners are for just the shield or do they hold other parts above the shield that may come loose? Also, leaving the shield off would certainly ease future oil changes and such. Has anyone left their under shield off? Any side effects such as additional air noise or overheating? I can't imagine it has significant functionality other than to smooth the air flow under the car for better mileage and less noise, but if the cooling system depends on it that would be a different story.
Matt
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I've driven a number of cars over 150k without ever changing manual transmission fluid. I don't think it's necessary.
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Mooron wrote:

I am not sure it is necessary either, but I always find a fair bit of metal on the drain plug magnet even after 50K or so and I'd rather not have that stuff circulating through the gears and synchros. And I tend to keep my cars well past 150K unless they get wrecked (which has happened to my last two high mileage vehicles), so I figure it is cheap insurance even if not absolutely necessary.
I got the undershield off and mine had 9 10 mm bolts and two plastic Phillips head screws that got into expandable plug nuts. Of course, one of them was stripped (probably when the dealer changed the tranny oil 10,000 miles ago) and would not come out. I had to break the head off with pliers. And this appears to be a special fastener that I can't find locally. I have an email into Hyundai Parts Online to see if they can get these.
I drove the car for 30 miles today with the shield off and noticed no unusual air noise nor any difference in operating temp, but I will probably put it back on as it does keep things much cleaner up under the front of the engine.
Matt
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I don't know what these thingamabobs are called, but they're pretty standard fasteners. I'd imagine that just about any local dealer (any brand) would have some spare ones lying about (or some in the parts department they could sell you) or some Christmas-tree type fasteners that you could just push in. Realistically, I think these plastic fasteners were simply for assembly at the factory. Considering their position, if you leave them out, I doubt the cover will hang down. Or you could just leave the cover off altogether. Aside from dirt, I think the worst potential side effect is that there's a greater probability for something to come up and damage the engine or transmission.
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hyundaitech wrote:

You may well be right about the purpose. I was just afraid the front might flap in the breeze, but I left the one out and so far haven't noticed any unusual noise.
I decided to put the cover back on for the reasons you mention.
A question for you if you have another minute: Are you aware of any problem with synchros on the Hyundai manual transmission in the 06 Sonata? I had the local dealership change the tranny oil at about the 60K mark and shortly after that the tranny got very hard to shift into second gear, particularly when cold. Now, I own two standard shift vehicles at present and have driven them all my life so I know they all shift harder in the cold, but this is unusually hard and affects only 2nd gear. Shifting into the other gears is still fine.
The dealer went out of business less than a month after I had the work done. My fear is that they were using up supplies at that point and may have used whatever gear oil they had on hand. I know this transmission calls for GL-4 which generally means the tranny has "yellow metal" (brass or bronze) parts, typically the synchro cones. And I know that most GL-5 oils will eat at these yellow metal parts.
The reason I had the cover off was to change the tranny oil. I put in Amsoil Gl-4 synthetic gear oil in 75W-90 viscosity which is close to what Hyundai calls for. It shifts better, but second is still hard to engage when cold and not completely normal even when warm.
Any thoughts as to what might cause this? Do you think it could be oil related? Is this a known failure mode for this transmission? I will probably try to get it back to the dealer (the new one though is nearly 40 miles away) and have them take a look as I at least want to lodge a complaint before the 100K warranty expires. I also saved the oil I removed so that I can have it analyzed should the tranny have to be replaced at some point.
Matt
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I haven't seen enough of these transmissions to know of any common failures. Changing the oil again was my immediate instinct, but you've already done that, so I think it's time to plan a dealer visit.
I hadn't realized I'd been away for so long.
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