Calling All Mechanics on GLP......I need some gawt-dayum guidance

Ok, I'll come back later.

Any help is GREATLY appreciated

The problem is obviously with your battery


Your battery needs a new car

Chattering then maybe your gears too. But the Pinion and Carrier may be fried..... You also may have a trans problem.

In either case it's really not home mechanic stuff.

Any metal in the old oil?

I asked Chat GPT for you. Here is it's response:


Rear Differential Whine Diagnostics


97 Tahoe 2 door Z71 Sport with all the off-road goodies offered by GM

Now, the rear-end/differential is making a whine/hum that starts around 20-25mph and is constant all the way up to 70-75mph.

If I let off the gas it disappears.

The rear end is a 10-bolt 8.6" gear. It has 30 spline axles, it has the factory G80 locker and 3.42 gear ratio.

I replaced the axle bearings/seals and changed out the differential oil and added some reaally good friction modifier for the locker.

So, this is my question. Is this pinion bearings, carrier bearings?

Is this the backlash on my gesr and pinion becoming too sloppy?

Based on the symptoms you described, it is likely that the problem is related to the pinion or carrier bearings in the rear differential. The whine/hum that starts around 20-25mph and is constant up to 70-75mph, and disappears when you let off the gas, is a common symptom of bearing wear. The fact that the problem persists even after you have replaced the axle bearings/seals and changed the differential oil suggests that the issue is not with those components.

It is also possible that the backlash on your gears and pinion is becoming too sloppy, which could be causing the whine/hum. To determine the root cause of the problem, you may want to consult a mechanic or a differential specialist to have the rear-end inspected and diagnose the issue more accurately.

Is there a loose nut behind the wheel?

usually backlash causes that.

your tires are out of spec

one of them on the same axle has a smaller outer diameter.

Gear worn out.

Or it is “dry”, which I doubt since you just serviced it.

Get a run out gauge and measure the backlash. These rears are easy to work on, watch some youtube on it.

Don't listen to me but.. My buddy had similar on gmc..pop the differential case open and you'll probably see a broken gear tooth. That'd be yer problem. If not idk. The shop said 600 for my buddy. Diy method it's cheaper to had a matching gear ratio and pull the entire rear axle diff assembly and bolt the used one back on.


But i recall buying new gears etc and installing didn't look that bad. But kinda prides. Prices change a lot though.



Drain the fluid and pop it open. See what's going on.



Not mechanical advice though. At all. Wait till a real glper mechanic chimes in.


Goodluck

Nm that post above. Lol. Goodluck though.

This is from GM...



***Important: Installing any friction modifier causes the clutch pack in the locking differential to slip and miss engagement. A fluid flush can often remove debris that is a contributor to clutch chatter. Adding friction modifier additive can cause a loss of locking differential functionality***

Too tight would make a whine/hum rather than too loose.
Plasti gauge when installed to check mesh/back lash.

Sounds like pinion bearing is going south waiting too long to repair will cause too much water on pinion and ring gear and causing them ton need to be replaced as well. Getting a rear end rebuilt is not cheap. It requires very precise setup and not easy for a novice with limited tools.

Start by putting it in park and then see how much slack is there when you try to move the drive shaft back and forth.
Zero? Like absolutely no slack either way?
Or a quarter turn?
I wouldn't like either answer.

rear axle

replace it, drain and see if any metal pieces.

I used to have a book that showed the wear pattern when the gears were too loose and too tight.
Basically, the wear should be in the middle of the surface of the gear wear surface.

Gearbox with worn gear maybe? Check the gearbox oil for metal contamination and you know if its in there or not.

Make sure it's not worn u joints.

Drive it like you stole it, till the rearend goes out, then buy a replacement from O'Reilly for about $1700, with a 3 year warranty.

The pinion depth is set wrong.

Did you use a new crush sleeve or did you count threads? If you slapped it back together and tightened the nut, there's your problem.

Stop driving it until a professional sets it up properly. Or just buy another rear axle.

You need to raise the vehicle off the ground, with the wheels hanging and in neutral...Parking brake off, and check it manually.

If the noise is inside the differential, then remove the inspection plate. Rotate the wheels to determine if the spider gears are worn...If so, get a Jasper rebuilt for probably $1500-2000 I'd guess.

Don't rebuild it yourself unless you're a machinist and know what you're doing...A rebuilt is the way to go.

Or you can buy a used differential for $100.

I'm pretty competent with this stuff. I have all the goodies too in my garage.


However.......

Time is a very important thing for me so it may just be easier like you said and just buy a rebuilt rear end and just swap it out.

In fact, I think I'll do that now.

You like Jasper?

I was on Rigid Axle and they have A1 Cardone.

I guess I'll compare what internals are in each and go from there.

Thank you