FUBARED Third Member

[Sparkplug]

I think my rear end is toast. If I push in my clutch, or let off the gas, I hear a grinding that I am pretty sure is coming from the rear end. I had a friend ride in the bed at speed, and so did I and, the sound is almost definetly from the rear. But it seems a lil more pronounced on the drivers side. But that may have been due to the wind. I have an aussie in the rear, with 31's. I drive my truck pretty hard, stupid hard really, I dun care too much about fixing it, Ive pretty much replaced everything. This is the first problem with the rear end. If I get a rear end, it will be 4.10, instead of stupid 3.9 in 81, so that will be good. I just wanted everyones input on how to tell if the rear is bad, and some common symptoms. Thank you.

[joey0712]

Pull the third and look at it.... 

[93tonkatoy]

Either remove your DS, or park on a level surface, and take the tranny out of gear. Turn the diff flange both directions. If the flange pushes out and pulls back in, then the pinion bearings are worn out. If this is the case, when you remove the third member, you will see carvings in the carrier from the pinion hitting the carrier.

[Joey88RUNR]

Jack the rear end up, and put it in gear go to the back and listen for the noise

[93tonkatoy]

In the shoutbox, you were talking about swapping the 3rd gen axle housing into your truck. It will directly swap in, and the brakes should not be an issue, because they are still drum brakes. The spring perches are the same width, but I believe you will need the late model's u-bolts and bottom plate (3rd gen axle tube is larger diameter. Not totally sure about the u-bolts, but check. Also, you may need to swap the flange on the new one to mate to your DS yoke (different bolt patterns). And remember, if you don't re-gear the front to match the rear, you won't have 4WD (it'll bind up the drivetrain).

[Sparkplug]

im getting an ifs v6 rear, im sure the guy will let me take spring plates, and ubolts. Im gunna take all he will let me get. 81 came with 3.90, I have already swapped front axles previously, so my front is 4.10, and rear is 3.90. I was always told this was so close of a ratio that it didnt matter. Im hopin for a lil more pep with 4.10 in rear tho, u guys think it will be noticeable? Thanks.

[84xcab]

Possibly, you wont be able to use that aussie in the v6 though

[Sparkplug]

aussie is gettin moved to the front, ill get a selevtable for the rear eventually

[84t0y]

if its louder on one side it mighht be just a wheel bearing

[Dingman.]

x2

[Sparkplug]

i was thinking possibly a wheel bearing also. How do i tellif they are bad?? My rear end will bang when shifting sometimes, like there is too much slack. So naturally i assumed rear end.

[Dingman.]

It could be either, what led me to believe it was a wheel bearing is cbecause you said you heard it from one side more than the other.

Jack up the rear end and spin the wheels i don't know if that will help, also spin the diff flange.  etc..

[Rocksurfer]

If the 3rd is on the coast side and is making the grinding noise it could be a loose pinion. The pinion will drop down and rub against the carrier.

[Sparkplug]

so possibly just tighten the pinion nut? I realized last night also, that the axle id be getting comes from a 90's runner. And they had coils in the rear, lol, dunno how I forgot about that for so long. Found a v6 axle out of an 87 i think, but its an auto, what gears wud it have?

[84xcab]

Probably 4.30 unless it came stock with 31" tires then it would be 4.88

[germ]

I think you'd be saving yourself some work if you just dig into your existing setup. Set it up on jackstands, grab the tire, and try lifting it up and down, and pulling it in and out. If there is any play, it could be just as easy as a wheel bearing. Then drop the shaft, and check the pinion like was discussed above. If that doesn't point you in the right direction, drain the gear oil, and look for metal shavings. it's not that hard to drop out the 3rd, so that would be the next step. Could also be the Aussie has given up the ghost and is just whining at you. They don't die often, but they certainly can.

I think your asking for a whole bunch of fab work to replace the axle housing, which may create more problems for you later. Of course, this is a good excuse to upgrade.

Erik

[boggerunner]

sounds likle the pinion nut backed off, its happened to me a few times, and did the same thing when i let off the gas, it grinded, so i kept my foot in it all the way home to fix it.

[93tonkatoy]

If you find that it is the nut backing off, do yourself a favor and go ahead and replace the nut. I tried retightening the nut (and restaking it) several times before I rebuilt and regeared the diffs. For some reason, The nut would no longer stay tight (maybe internal threads stripping out?). I just pitched the old one without looking at it very close.