Heres a chuga chuga, thunk thunk question which is driving me nuts because I can only hear in while accelerating.

I get a high pitch ringing/whine from the back end under load. Cruising ok, but when I floor it just a bit the ringing begins.

Could this be an angle problem of my rear diff caused by my 4'' lift, rear seal binding, out of balance drive shaft, or something else you have come across which I have not?

Thanks for any replies, ideas in advance, as I don't think anyone would volunter to lean over the back gate for me while i motor up a hill..urhm, any takers?

With 4" of lift and a stock two-piece driveshaft.... I'd say your carrier bearing is a good culprit. Have you noticed any vibration when taking off from a stop? That is usually a sure sign the carrier bearing is on its way out.

Do any 98s have carrier bearings? Mine doesn't and I have the same problem I think. Mine whines on acceleration too, I think it's when my rpm is over 3500 or 4000 but not sure about those numbers.

Couldn't tell you. Well, if there is no carrier bearing; lets look at what else would be under stress from the lift and whine. Pinion bearing perhaps?

There is not a carrier bearing on his rodeo.
4" of lift is not excessive,have you checked your rearend fluid?

While under load could it be an exhaust heat sheild vibrating?The Turtles sheilds came loose and caused a weird vibrating whiney type of noise......a couple hose clamps around the front two sheilds cured that.It did it real bad while excellerating from a stop.....bad harmonics I guess.

That was a leap towards the cheap side of possiblilities. <img src="/forums/images/graemlins/smile.gif" alt="" />

Hope that helps before you dive into the rearend and start checking bearings for flat spot's.
Goodluck

Bansil

Thanks guys...got those already...

Did the hoseclamps trick on the heatshields quite while ago hmm, thanks...will need to recheck them, changed the gear oil (and additive) this morning and managed a different frequency with the (suspected) gear ringing, cool.

Not cool. The cover was so RTV'd that the bolts came out red and crusted with RTV rubber. <img src="/forums/images/graemlins/scared.gif" alt="" /> This rear cover really fought me for about one foot from the case when taking it off because the rubber was so thick on the inside until I pulled my pocket knife and cut it away. ARG. The guy who had this one before me wasn't so keen on buying <$5 gaskets I guess. The most time was spent removing rtv...wire brush on the case cover and bolts, friggen tweezers to get the rtv out of the bolt holes, and repreping the bolts/holes. <img src="/forums/images/graemlins/barf.gif" alt="" />

Obviously this one has been opened before, not a good sign.

I'll need to check the backlash and look around again underneath for other possibles, next week sometime, and am soo hoping that it is the pinion and have to take the time to rebuild it... <img src="/forums/images/graemlins/lol.gif" alt="" /> You all know what that means. <img src="/forums/images/graemlins/wink.gif" alt="" />

Will keep you informed.

OKok, I fogot to mention a few things.

No wobble at start or anything. It all runs smooth cept for the whine. Have a nice quote for you from the 1998 Isuzu Rodeo/Amigo factory workshop manual:

Bearing Noise -
Bad bearings generally produce a rough growl or grating sound, rather than the whine typical of gear noise. Bearing noise frequently "wow-wows" at bearing rpm, indicating a bad pinion or rear axle side bearing. This sound can be confused with rear wheel bearing noise.

true?

Gear Noise -
Gear noise (whine) is audible from 20 to 55 mph under four driving conditions:

1. In drive under acceleration or heavy pull.
2. Driving under load or under constant speed.
3. When using enough throttle to keep the vehicle from driving the engine while the vehicle slows down gradually (engine still pulls slightly)
4. When coasting with the vehicle in gear and the throttle closed. The gear noise is usually more noticeable between 30 and 40 mph and 50 and 55 mph.

The second exactly describes my whine, even though I sure wish it was growling, grating and wow-wowing. <img src="/forums/images/graemlins/lol.gif" alt="" /> The book also does a step through of what to check, adjust and replace. Let me know if anyone wants me to type it in.

Thanks again.

I'd be interested in hearing what's wrong with yours, then I can fix mine. lol

pinion shaft bearing. My gf 99 amigo had a whine under load in the rear, so i changed the fluid, milky coffee looking fluid. Changed it, whine still there and got worse. Pinion seal then broke, changed that and noticed the bearings were really loose. So, loose bad bearsing could be the noise itself or now that the bearsing are loose, the gears arent meshing like they should.

check the fluid

kevan

QUOTE:

pinion shaft bearing. My gf 99 amigo had a whine under load in the rear, so i changed the fluid, milky coffee looking fluid. Changed it, whine still there and got worse. Pinion seal then broke, changed that and noticed the bearings were really loose. So, loose bad bearsing could be the noise itself or now that the bearsing are loose, the gears arent meshing like they should.

---
fluid was clear but not new, just changed it (above), whine still there and getting worse... <img src="/forums/images/graemlins/cyclops.gif" alt="" />

This is highly highly likely. Replaced a broken pinion seal about 6 months ago, but didn't replace the bearing. Did your whines go away once you replaced the pinion bearing?

Many thanks...for this...even though I would like to simply ignore it to justify the locker rebuild. <img src="/forums/images/graemlins/lol.gif" alt="" />