Dirt Driver

My truck is making a weird rear end noise that I'm having trouble diagnosing.

It has started making a mild cyclic clacking/clunking, but it only does it when engine braking on right-hand turns and moderate to lower speeds. Harder turn = louder. Push the clutch and it stops. Apply any throttle and it stops. Turn left or go straight and no noise. I can't duplicate it with the rear jacked up & running and I can't feel anything weird by grabbing/spinning the tires manually. A stethoscope gives the same sounds and loudness at the center and outsides of the axle housing. The pinion doesn't move in the housing, the u-joints have no obvious play, and the driveshaft support bearing isn't suspect.

The only visual abnormality is that the driveshaft has about 3/4-1.0" of rotational slop in the diff. It also looks like the 3rd member has been out at some point. The housing and a backing plate say "Tacoma" in yellow paint pen making me think it's not original.

I changed the older-looking oil last night and there was a pea-sized blob of sludge on the drain magnet and some tiny flakes, but nothing to make me think it's is about to imminently frag. (knock on wood!) I also replaced the passenger axle bearing over the weekend because it was sloppy, but that didn't affect the noise. I'm going to replace the other one too just to establish a baseline. Seems like it could be that bearing anyway based on the symptoms.

Sanity check anyone?

ZUK

iTrader: (1)

The weight has to be on the axle.....only in a turn....I'm leaning towards wheel bearings.

atcfixer

iTrader: (1)

That doesn't seem normal if I'm understanding your description correctly. Most i've seen, eyeballing on the flange is 1/8in to a tiny bit over 1/4in. Sounds like it might need a rebuild, or buy a good used unit.

Now that I looked at your sig, I think we already were talking about a 3rd member =).

Dirt Driver

I misjudged the backlash; it's "only" about 5/8". But still, I rechecked it after changing the remaining axle bearing aaaaaannnnnddd...the noise persists.

Whatever, I'll probably hit the JY tomorrow to see if I can find a decent third member.

ZUK

iTrader: (1)

Gotta be the driveshaft contacting the gastank skid.....or the muffler.

atcfixer

iTrader: (1)

Once I get a chance to check out the rear ends/3rd members I have, I'll mark the slop/backlash in the pic on the flange. Over 1/2in seems quite excessive unless your letting the wheel studs move in the drums, might only make noise while under a load, my dad's T100 is like that, only 4th gear a little, and 5th gear a lot for the grumble noise in the back. He has a spare axle he's "build" up to do a whole axle swap with one with super low miles for the housing / axle bearings, and a Tacoma 3rd member with ~160k miles that was nice and tight.

Never hurts to check the drive shaft path and such though and the output shaft on the transmission for play.

Dirt Driver

The wheels were bolted on and the e-brake locked when I checked. That included the spiders and axle splines, but still kind of a lot. I found a 3.42 carrier at the JY today (probably the only one there) that only has about 1/8" of backlash.

I looked the DS up & down when I was under there last time and there are no rub marks on it anywhere. What I might do anyway before changing the diff is rig up some skateboard wheels on a handle so I can push on the driveshaft and/or tire while it's spinning.

atcfixer

iTrader: (1)

U-joints could make noise too, move them side to side for each pair of bearings. Should move smoothly and no hang up areas or easier then harder areas. If it isn't smooth then changing them could help remove vibrations and such. Really bad ones will be sloppy twisting wise, but generally they don't get that bad before being checked on.

1/8in of movement for the diff sounds a lot more acceptable. Must have came from a lower miles pickup, or well maintained (fluid flushes, quantity fluid etc). Personally I've ran Red Line and it worked well for me but was expensive, just have to be sure to get the correct fluid for application (GL4 vs GL5 and the correct oil weight).

ZUK

iTrader: (1)

auto lockers like the lockrights can make noises......

Dirt Driver

Changed the diff yesterday. The old one feels like there is too much preload on the pinion. The "new" one feels free like I would expect from a used rear end. Filled with synthetic 85w-90 and drove 85mi today. No noises.

Turns out the gears I had were 3.73s, which I was beginning to suspect based on highway RPM and how "punchy" it felt. The 3.42s are nicer on the highway, but the 5th gear pull it had is now noticeably reduced. To be expected, I guess. If only I had a 3RZ swap laying around...

I noticed something curious while underneath: the axle housing bottom has a pointy dent pushed outward below the ring gear. I'm wondering if the original diff grenaded at some point...and WTF they were doing to manage that in a 2WD/4cyl truck.