Noise only in 6th gear

New member here. I've given my best effort to search to see if my question already exists out there, and I've found a few posts that are close. But I can't find anything that matches exactly what I'm looking for. So I'm posting my question for you guys to help with.

I recently bought a used 2007 V6 4x4 Access Cab TRD Off Road with 6speed tranny. Truck seems well taken care of. 90K miles. Shortly after I got it, I noticed a "noise" that is now making me go crazy trying to figure out what it is, and most importantly how to make it go away!

Gears one through five sound fine. No noise. But once I'm in sixth gear, I get this high pitch whine/resonance that stays there. It sounds like rubbing your fingers around a crystal glass. As long as I keep my foot on the pedal it's there, whether I'm cruising at constant speed or accelerating in 6th gear. But as soon as I take my foot of the pedal, it disappears. And as soon as I reapply "torque" by pressing on the pedal ever so slightly, it's back. Very very repeatable. I can maintain the same speed in 5th gear, and I don't get any noise. But as soon as I drive in 6th, there it is. So I don't think it has anything to do with speed of the tires, wheel bearings, air, windshield, etc. But it has something to do with 6th gear.

The other interesting tidbit is I have firmly convinced myself that it quietens down just a little after about 20minutes of driving -- like it is affected by something "warming up". It's still very noticeable, but just not quite as loud. And it may also be just slightly quieter if it's hot outside.

I honestly can't figure out what it is. Any ideas? I'm just hoping it's not a "you have to rebuild the transmission" kinda thing.

Thanks in advance!

 

Not what you want to hear, but...
Maybe there's a bearing scored in there

 

6th is O/D it takes a beating have you thought about checking the oil level?

 

serious, oil should be number one, and if its full, replace it and all the other gear lubes if your not 100% on their history in the truck. many people neglect gear oil changes.

I would definitely start there, and if your tranny is still noisy, drive it till it pops. hopefully by the time it goes you will have junk spare sitting around

and one last thing, I have faint memories of seeing the fsm for this tranny one medicated evening but it took me forever to find. I DO remember seeing that the shafts are rebuildable, as in replacing gears and synchros is POSSIBLE. the fsm detailed replacements of each gear. good luck I wish the best for your trans

 

Indeed, when you think about it, the truck is in 6th gear 90% of the time so it's going to wear first.

10 to 1 even if you change the gear lube it'll still be noisy. If it's the factory oil it'll even have the break in particulates still in there; since there's no magnet it's no surprise if it's free to cause wear on the gear face causing it to whine. I know I dropped the factory oil on my 5 speed the day after I bought it at 123k miles and it still whines a bit with synthetic at 47-49 mph and 53-55 mph in 5th (oddly enough, silent at every other speed). It'll probably whine forever. Once a helical gearset loses that precision mating it ain't coming back.

It won't whine in 5th on the 6 speed because that just locks the input and output shafts together; no gears are used. Same with my 4th.

 

6th gear whines on these, mine does it, has done it

I know I've read others do it too.

 

Mine didn't have any noise whatsoever in 6th but I think that was sheer dumb luck from what I've read on this forum. Instead the gearsets rattled like a box of rocks idling in neutral and with every shift I heard CLACK!CLACK! bouncing off adjacent buildings. My 5 speed is the exact opposite: whine in 5th, silent when at idle, can't hear the shifting, but the clutch fork squeaks. My Fit whined in 4th straight off the dealer's lot with 8 miles on the odometer. My Civic whined in 4th and made a grrrrsh noise in 5th for over 80k miles (even after bearing replacement). A best friend's Civic whined in 2nd and 4th. A close relative's Jeep sounds like it's straight out of the MASH TV show with its rattles and gear noise, but that could be the 200k+ miles on it.

Now that I think about it, I've never heard a silent one. Manual transmissions just plumb like to talk back.

 

I dunno, mines pretty quiet other than first gear. like it in first though. . . sounds tough.

100k miles

 

OP - does it sound kinda like this?

Speedo is about 4 mph fast up there. 61 needle = 57 actual.

http://youtu.be/MBFrmP3VQ5U

 

Wait. What? It's overdrive? The engine speed is reduced compared to the tranny in a stick shift transmission? We have a separate gearbox for 6th gear? Dang. I thought that was only in autos. Learn something new every day!

 

No magnet on the 6-spd? I thought it had one. I just changed out all the gear lube the other day, I thought only the transfer case was sans magnet, probably wasn't paying attention. I had this idea in my head three out of four had the magnet.

I didn't have a noticeable whine, but I DID notice the whole drive train seemed quite a bit quieter with the synthetic in it, so I guess as said above the first step would be change to a quality synthetic.

 

not sure if being sarcastic.. . . I don't know of the specific ratios on these trucks, but if top gear (5th or 6th, depending on trans) is less than 1:1 ratio, it is overdrive.

 

No, not sarcastic! LEARNING!! Thank you! I honestly didn't know it was over drive. I thought only autos had that. Seriously.

Things like this is why I try to go to mod days. But sometimes being the only girl there sucks.

 

I think it's only slightly below 1:1, but it is OD. Some people would like it to be more of an overdrive, there's barely a difference between 5th and 6th. I don't mind the gear ratios much, they're OK. The truck is so un-aerodynamic that too tall of a ratio in 6th would cause more use of the skinny pedal, and more downshifting, so you have more wear on the clutch and throwout bearing. So it's a compromise between a bunch of factors.

 

I didn't have a magnet on either my 5spd or 6spd. Toyota does crazy things like Aisin vs Luk, NGK vs Denso, so who knows maybe some get magnets.

 

lol, I could imagine. I wouldn't even want to be a female on this forum lol much less meet these a-holes in real life

just kiddin y'all. im the one all desperate for a tw wheeling trip

 

I have a '07 with a 6 speed.
Op with your description it sounds like a bearing for 6th gear is going.
If a tech could advise on this- does #6 gear sit high in the trans?
If fluid got low this could cause early failure?
Op, change your fluid to redline mt full synthetic asap.
Good luck & let us know after change how it works out.
Regardless, drive it until it is completly squealing, the go for a rebuild.

 

Makes me wonder why they don't all have a magnet. How hard is it to put a magnet into each drain plug? I know for sure the transfer case doesn't have it, I believe my '97 was the same.

 

.84 IIRC. Auto's OD is .72 IIRC

or something like that.

 

So my learning here brought me to ask around and it's .84. Someone did the math for me, and a Lexus tech chimed in to help too. Thanks again!