Vibration only in fifth gear

Hello everyone! First post. So glad to find you all.

1994 HiAce Custom 4wd 1kz-te + manual transmission (R351F), 2" lift, 235/75/15 tires. I have owned it for only three months.

I have a vibration that occurs only in fifth gear with the clutch out. It is worst from 85-95kph. Part throttle is worst, but high load lessens it. As the van nears 100kph or faster, the vibration lessens. Gears 1-4 are just fine. U-joints checked, tires balanced, steering aligned.

One shop drained the transmission, found shavings, and said I need a new transmission. They filled it with new fluid as the original fluid was very dirty, but refused to take it apart. The next shop said small shavings are normal, they feel the vibration, and that I am just lugging it in fifth. Being only a Custom, it does not have a tachometer, but I have owned countless m/t's before.

Do any of you also have vibrations at these speeds?

Thanks!

If it was caused by lugging the engine then I’d think more throttle would worsen it and that it would also be worse at lower speeds in 5th.
Have you tested in 4th at the exact same speeds? (it’s not clear you’ve tried at 4th at those speeds because you also said it’s fine in 1st, 2nd and 3rd which implies you weren’t testing at the same speeds.)  If it ONLY does it in 5th then it’s hard NOT to conclude that it’s a gearbox fault.
If it does it also in 4th at an indicated 85-95 then it could be a number of things - wheel bearings, transfer box, cv joints, engine or gearbox mounts (especially with the 2” lift), delaminating tyre, diff pinions or output bearings, front driveshaft support bearing (where it goes through the chassis).

That last one can be either the bearing or the bearing carrier. It’ll cause similar symptoms you describe - including the lessening under throttle.

Thanks for the response, Pete. I have the van back from the shop now.

Before I started down this path, I felt like running the van in 4th at +85kph was really racing it, but it seems as though it’s not. A member in a Facebook group told me 3k rpm in 4th gear is 95kph. That said, there is definitely no vibration in any of the first four gears. If I start from a dead stop in third then obviously the engine freaks out, but in normal driving, even lugging it in the lower gears seems fine. The mechanic that told me 5th gear is fine seemed to think that maybe I’m just not noticing it in the lower gears because it comes up in the rpms so much faster due to the lower ratios.

If you have a manual transmission, how does yours feel in 5th at 80kph?

I had the shop change the transmission fluid and both front and rear diff fluids. It does seem somewhat happier now, but then again, I’m not shifting into 5th until 95kph.

I have purchased a diesel tach, and I’m going to install it this weekend.

I don’t have a manual.
I gotta say, a 2” lift will be putting the front halfshafts at quite an extreme angle. Even a little wear on the inner or outer CVs could amplify to a noticeable vibration.

Hello.

I've a 5 speed manual 4x4 but it's a G52 gearbox so probably different. Mine is no noisier in fifth than other gears, but mine is more noisy on overrun, which I think if the transfer box as it's a bit noisy on overrun in all gears. My issue could also be the reaf diff as I've not diagnosed it fully, just saying.

Your problem is not going to be easy to diagnose and in the process you'll probably find a few other issues on the way; you just have to accept this on a 20y+ van.

I don't really know what a garage would do here except put a camera undernesth during a test drive and look and listen for vibrations in several places on the engine and drive train. The torque in fifth gear might be upsetting a weak bush or mount or there could be a resonnance vibration somewhere. Has a weight fallen off the shaft? Are the shocks good and working properly? Is it really the gearbox?

Is it like 'night and day' loud in fifth and absent elsewhere or depends on power through the transmission? Can you remove all the gearbox oil and get an endoscope in the gearbox and look for damaged teeth.

Can you hear noise with the back wheels off the ground and turning the gearbox / shaft by hand while going through the gears (recognising the complexity of the transfer, too).

Is it possible to support the van fully on axle stands or a two post lift and drive it through the gears (and do this safely) while listening with a stethoscope or long tube on the various parts of the gearbox?

Sorry just to post lots of questions but I think you need to eliminate all the alternatives before tearing into the gearbox. It's normal for the oil to darken and for there to be mess on the magnet, but you probably need to drop the oil again quite soon and take a more detailed look and poss get it sampled / test yourself for whether this is synchro, bearing or gear teeth / casing problem if it's definitely the gearbox.

You need to be a detective here otherwise it's a lot of expensive guesswork. At best it'll be a related, small problem that is manifest to the gearbox (such as a mount). Otherwise get your hands dirty.

Oh and watch this:


And this, definitely:


While this doesn't mention fifth gear specifically I think you can work out what could be going wrong, but above still applies.

HTH

Thanks for the thoughts and feedback, friends.

The van did have quite a bit of work done to it before and after I purchased it including new engine mounts and suspension bushing all around. It also has new KYB Monomax shocks front and rear. I even just had the CVs rebooted (though not replaced..)

The vibration is very noticeable in 5th. While I was on some smooth roads today, I tried to drop it down to similar rpms in the other gears to feel for the vibration. While it did seem like there might be more resonance, there’s no gear that comes close to the shake in 5th. I don’t feel any vibration through the shifter, and only a bit through the wheel. I feel it in the floor and my seat. There are times when I put the transmission into 5th at 100kph, and it seems pretty happy (though not perfect), and there are other times when it definitely does not seem happy.

LH119V, I agree with you about not knowing what a shop would do other than a camera. I have been driving it every day in hopes of seeing what might be lurking in the new oil. I’ll drop the oil and report back.

I appreciate you posting all the questions. Alternative viewpoints are always helpful. Also, thanks for the great video links!

There is an App I use on my phone called VibSensor. It uses the phone’s accelerometers to chart oscillation frequencies in the x, y, z axes in kHz. It’s usefulness with a vehicle is it clearly shows the difference between vibration source either before or after the diff. Most diffs are approximately 4 times reduction and 5th is generally 1:1 so an engine/driveshaft turning at 2,500rpm will be a frequency of around 40Hz whereas an axle, bearing or tyre will be around 10Hz.
You turn the App onto record, put the phone on a surface, drive in the sweetspot of the vibration for 10 secs or even a few minutes and it’s pretty clear.
Allows you to narrow down the search.

Well, it took a bit of time to work up the courage to start wrenching on this thing since I just recently got it, but I'm back to my confident old self now.

I decided to change the transmission fluid again. This is 1000km after the shop changed it:



Cosmic, I know!

As suggested, I got in there with my endoscope. Looking aft from the drain plug hole, I found this:


That should put the mass to the right of my finger. So, on the edge of the extension plate?:



Strangely enough, there is no magnet on the drain plug. Shouldn't there be? There is one on the transfer case drain plug. (The oil from the transfer case came out perfect, by the way.)


Looking at the parts fiche from Megazip, it seems as though that mass of shavings is gathered around the Reverse Idler Gear Shaft (33451). Right above that is.......the 5th Gear Counter Shaft bearing (33428B)




How am I doing? Is this making sense? Would this explain why I am only feeling vibrations in 5th since it could be the bearing that 5th gear rides on (looks like a needle-type to me) that is destroying itself? In the other gears, this bearing would be free-spinning and therefore not interfering with operation, I assume.

Also, I couldn't find the VibSensor app that Pete suggested, but I did find something similar. It located the vibration centrally in the van, but I'm not completely sure that the app was working well or if it just sensed vibrations directly around the iphone (which was placed above the engine hump).

Thanks so much for the help and interest so far! I'm happy to be enjoying this type of diagnosis again. It's been a few years...that and I'm still new to the inner workings of transmissions.

Hello.

I think the idea to use a vibration phone app is really excellent. The one I use for the odd task but I've not thought to use them for this sort of thing is called ‘Physics Toolbox Suite’ and I use it on Android and it runs on old phones and new. It’s free and capable of logging all the various sensors on your phone and for the acceleration it records x,y,z(+t) and can save these to *.csv or an Excel doc. It should be straightforward to look at the ratio of the vibrations in relation to speed and if you want to get really fancy a Fast Fourier transform (FFT) will identify the dominant frequency and the app can do that but you’ll probably spot it on an Excel graph as long as you’re sampling is fast enough, you’re not damping the signal and there’s little else going on while logging.

Without a rev counter (?) it might not be that easy to know the engine revs in each gear and therefore the frequency of the vibration(s), but this link should help, especially with GPS speed, rather than the vehicle one as these tend to report lower. It’s another really useful toolbox https://www.blocklayer.com/rpm-gear.aspx but there are other out there and this one is very comprehensive.

Here’s (yet) another YT video that shows the placement of gears and bearings in a 5-speed box and I think your finger in the picture lines up quite nicely with the fifth-gear in relation to the main build plate (in a mirror image).

See:

And head to the fifth gear bit.

While the endoscope image isn’t great (they never are) I think there’s something badly wrong with the mush in the picture and the oil doesn’t look great at all, especially after just a thousand km!

Yes, the drain plug should have a magnet. Looking at the your picture it seems that your drain and fill plugs are the same 24mm hex sockets as mine (I think these are probably much better than the newer hex head arrangement that can be much more difficult to remove).

Based on the ‘service’ records I have for my van the four transmission oils were last changed between 2009-2011, which is ~100k km (~65k miles) ago. It hurts to write these figures and I hope they are wrong but I fear probably not. Here’s a picture of the plugs and the drain magnet from the front diff on mine, but they were all about the same, ie not too bad I think given so much time, but I’m not pleased that my oils are so old.



I've no idea if the magnet could hold more swarf, but I hope so.

Absolutely get a new drain plug with a magnet; they are not at all expensive and I think it’s this part: https://www.amayama.com/en/part/toyota/9034118057. They are widely used.

So, my advice would be to try the vibration app, but you’ll probably need to securely cable-tie your phone to the gearbox rather than just inside the vehicle as I think this will dampen the vibration too much. If you go with inside the vehicle then I think you’ll need to again secure it tightly. Actually though I think your own evidence is saying your fifth gear bearing is toast and speculative research with more driving might do further damage.

HTH

Thanks for another reply! I agree with your assessment. It's time to get the van back to the shop.

Also, thank you for the magnetic drain plug link. I've been trying to figure out which one I needed.

Update:

The mechanic removed the transmission, split the case, and couldn't find any issue. He did notice that the glop of shavings in my photo above was due to an internal magnet that could only be serviced by splitting the case itself.

Despite knowing that I trust him, he was sure that I would not be happy with that answer, so he took it to a transmission-specific shop where they looked over all of the bearings, gears and synchros, removed all of the shavings from the magnet, and resealed it after determining that there was literally nothing wrong.

I guess the build-up on that magnet would have been from possibly never having changed the gear oil after 216,000km. It seems mind boggling.

So, here's the riddle then:

What vibration can be felt in overdrive under light load, but not at off-idle throttle, not in neutral, lessens under full load, and lessens at 100kph+?

I figured I’d update this thread with the last ten months of almost daily driving. The vibration is gone, and I haven’t done a thing except do a couple more trans fluid swaps to really clean everything out. It runs great in any gear now. I’m at a loss for words, but I’ll take it.