Hey guys - FNG here with a question about my T100 (I did a search first and found a couple threads describing the same problem, but no answers).

1995 T100 4WD, 5-speed: everything works just fine but a few months ago I noticed it making a humming/whirring noise and small vibration when I would let off the gas in 4th or 5th gear. Seemed to be worst right around 50 mph. Doesn't happen at all under acceleration, less noticeable at constant speed. In gear, out of gear, clutch in or out, brakes on or off makes no difference - it's still there. There was a ton of ice/slush/snow frozen to the bottom of the truck from driving through the drifts in my driveway, so I figured that had something to do with it and the sound actually went away after I ran it through the car wash (with the special underbody wash, of course).

Well, the sound came back (I don't think it ever really went away), the snow has been gone awhile, and the car wash doesn't make any difference anymore (I think that was probably a fluke anyway). Any suggestions on where to start? As soon as the snow melted I got under it and hit all the grease points on the shafts and such. CV joints look good. Don't notice anything out of the ordinary when I look around under it. Thanks in advance...

By the way, this is my 6th Toyota (3 2wd pickups, 2 4Runners, and now the T100). I bought it used off my Dad last summer - 275k+ miles on it but he's a maintenance nazi and it was always garage-kept in North Carolina. It's run like a top for me since last June (still does), but I know the noise is something that needs fixed.

 

Crap - just realized I put this in the wrong forum - Sorry!

 

start with checking the rear differential fluid level...

The CV's are a waste of time (for future reference) b/c there is no load on them... In H2 anyway...

 

Don't know how in the world that could have happened

 

Put match marks on your driveshaft and flanges, then drop the driveshaft and drive around in 4Hi (front wheel drive). If the sound goes away, it's more than likely U-joints. They might look good and have very little play, but at speed and without load, could be vibrating.

 

Update - Drained and replaced the rear dif oil - initial level was good, old oil was clean (color of maple syrup), some fine very metal particles on the magnetic plug but no chunks or shavings, replaced with new oil and the sound is still there.

There is a support bearing that looks like it's molded in a rubber doughnut for the rear driveshaft. The rubber has a crack in one side, maybe that could be an indicator of a problem? Anybody experience a failure with that part before? It is adjustable (to keep it perpendicular with the driveshaft), so I moved it a little to do that and while the sound is still there the volume/amount of vibration seemed to change a little. I have to drop the shaft to change that, but I think that is the next thing I'll check.

 

replace "rubber support bearing" with "mid-shaft bearing"... When they go out you notice vibrations.

Mines been out since I've bought the truck...meh...


I had a T one time... Had to give it up when the rear went... Toyota wanted for one gear what I could buy a whole set for. But I couldnt set them up so it had to go...

Miss that truck...

 

SOLUTION FOUND: While the mid-shaft bearing was a little worn and had some play, the rear universal joint was the culprit. The u-joint would rotate freely on one bearing set but the other was so bad I could barely rotate it by hand even with the shaft attached. I replaced both pieces and it's good as new.

That mid-shaft bearing is a pricy bit ($115 from Autozone). I am a little worried because the new u-joint is the lifetime-warranty, no-grease fitting type. I would rather have the grease fitting and the responsibility for using it, but we'll see how this one lasts. It was not a difficult job to take apart.

 

Glad that its squared away, don't ya just hate mysterious noises.I have a rattle thats buggin me,prob the tailgate guts

 

I'm with you - I hated driving the truck because of the noise.

 

I wish I'd seen your thread earlier . I had the same problem last summer and I ended up finding it when I was tightening my lug nuts and saw the u-joint flex out of alignment. If the Autozone u-joint doesn't last Napa sells one that is made in Japan and is servicable.

Btw mine went with only 110k

 

Autozone had two u-joints available. I bought the more expensive one with the sealed bearings and synthetic grease. Turns out the cheaper one has a grease fitting on it. I could've saved five bucks and had a servicable piece. With almost 300k on the truck, I'm sure I'll be replacing the front ones before too long.

 

Thanks for the tip. I know this is a little old but I've been having exactly the same vibration and I was afraid my rear diff was going. Do you have a part # for your fix?

 

1-1612DG from AutoZone is what I used. 1-1612DL is the one with the grease fitting on it.

 

Bummer! I finally crawled underneath and by pure luck managed to find the 2 14mm closed end wrenches. Don't try removing those drive shaft flanges with a half inch socket... Easy access wasn't in the design.

Unfortunately both of my u-joints and even my center bearing were like butter. I remember greasing it all 3 years ago when I bought her. So I just re-greased what I have and will go back to the drawing board or just get used to it. Hopefully it's not my diff. I hear stories about weights falling off your drive shaft and leaving it unbalanced as it turns. Does anybody know of a test for that? Or a test for the differential? Maybe jack it up and turn it with a stethoscope?

A lot of people say it could be tires as well. I have some chop on my Dueler A/T set, but not that would create this 2nd/3rd order oscillation whirring. It feels like a bad wheel bearing sounds, but all my wheel bearings are < 10,000 miles old. At that time, I also replaced a CV and installed the WARN manual hubs, so CV joints are not the problem.

Thanks for the suggestions. As you say, little noises can just make a guy worry.

 

Did you check the hanger bearing too?. I have the same problem. I already replaced the front and rear. I flexed mine the other day and the hanger bearing almost locked up. Gotta replace it now...

 

The bearing itself was smooth as snot. I'd give it a slight flick and it would spin over 8 or 10 times. Oddly enough, when I crawled under there I noticed a pair of 2" ice cycles hanging off the shaft pointing straight up. I assume if the shaft were vibrating at a 60-50 MPH coast, those buggers wouldn't have been able to hang on? Just a theory anyhow.

 

Is it safe to drive full speed with driveshaft removed in 4-Hi? That would be a nice test to see if the vibration disappears with shaft removed, but that sounds unhealthy...

 

pinion bearings in rear diff! change fluid asap. if noise doesnt go away, then take it to a diff specialist or your mechanic. i recently had the same thing happen. very loud WHINE when decelerating. front pinion bearing (the one farthest from the oil) was the one that went.

 

Thanks cordray. I just changed it 2 months ago fully synthetic. It's not so much a whine as it is a constant feel like a set of small rumble strips every 2-3 wheel revolutions. I wonder if driving without the shaft would relieve enough load on the diff flange to notice a difference. So it was just the bearing and not gears themselves in the diff? Maybe worth a look this summer.