Bad Diff, what to do guys?
 

So guys, I have been having a thunk when putting in reverse for a long time (about 18 months) in my 2001 Jimmy 4x4 165k miles. I figured it might be rear diff, but also thought maybe the U-joints on the drive shaft. So I drove it.

Well one night it started making a metallic tinking noise around corners, so I parked it immediately and took off the diff cover plate last night. Metallic fluid started spilling out. The videos below show all. The diff ring gear and bearings jump around in there like a jumping bean.

So what do I do? Replace the gears and seals (I can do anything on a car, but I'm in med school, time it limited by hospital rotations), grab a junkyard axle that looks straight? Have it rebuilt?

In addition, I have a $350 worth of front end suspension parts short of the struts/springs that's in my garage that I need to put in, as the front was getting a little loose. It's a TON of work. Plus, the front diff seems loose as the drive shaft turns quite a bit at the front diff before hitting the front gears.

That said, tell me what you guys would do given all the work it needs done.

go with junkyard axles, now is a good time to upgrade to ZR2 diffs and 3.73's

That's kind of what I figured...

Regarding the ZR2 diffs, I've heard about them here and there while reading up, but am not sure what models they are typically in or what the main advantages are. Is it LSD?

In terms of the 3.73 gears, I am actually more interested in gas mileage at this point in my life. That said, can I upgrade differential to a ZR2 without the 3.73? Or is that the standard gear ratio they come in?

Finally, if I do get a ZR2, are there any other parts I need to upgrade in a 2001 GMC Jimmy 4x4?

Sorry, I know I'm asking to be spoon fed a bit here, just limited on time to research all this stuff. I'll trade for spoon-feeding you guys any info on the Datsun Z series or F-body Z28. :P Know all about them.

ZR2's only came with 3.73's, the main advantages were the gears and the rear end is stronger than most non-ZR2's (8.6" vs 7.5" ring gear). It is also wider so it eliminates the need for spacers to make the front and back track widths the same. They also have the G80 locker but it looks like you have one already anyway, so not an upgrade for you there.


You could also try and find a rear end from a 5 speed truck, some of those came with the larger rear end but don't have the extra width and most likely had the more common 3.42 gears.


Of course if you don't care about any of that then just get a straight replacement for what you have.

Thanks Jamaroon, I appreciate it. I guess I will have a decision to make regarding mpg vs heavier duty.

As a final question, if I get a zr2 axle complete with everything, brakes, etc, is there anything else:

1. I absolutely need for the swap, like different u bolts for springs, rims, etc.


Or

2. Anything you would recommend doing at the same time (bushings, spring changes, etc)

you should always count on new u-bolts, and probably the bolt/bushing for the spring to shackle. The rest would be at your discretion.

I am not certain but arent the spring pads wider(further apart) than 2wd or 4x4 axles. Also can anyone give aprox price of this piece?

Did you reply to the right thread? Your comment just doesn't seem to go with the rest of the thread is why I ask..


Anyway,


No, center to center of spring mounts will be the same. But 2wd axles are narrower than 4wd axles so they won't work anyway.


Price of what? A complete used rear diff? $150-$250 around here I think.

Jamaroon, you have been more than helpful.

As far as swapping. Looks like from Google that any 4wd axle from 1994 - 2004 s10, Sonoma, jimmy, or blazer will swap right over, is this correct?

But to clarify, if I do go with a zr2 axle, it will raise the rear 3 inches (so the suv will be stanced front down), and the rear tires will stick out 2 inches further on each side?

Yes any 4wd will swap over, but some have drum brakes and some have disc brakes. Easiest is to get what you have for that. Also, if you're not doing both front and rear at the same time, make sure you get the correct ratio for your truck.


The ZR2 axle will not get you any lift in the rear, the lift is done with the frame on the ZR2's. It will make it 2" wider per side.

make sure you get a correct size and axle for your jimmy

ZR2 axle will NOT FIT into 4x4 or 2wd spring because of ZR2 spring bracket location is different.
also front diff too have to swap front control arms and etc too much headaches...

easier job is put in a correct size axle.
also get from blazers and JIMMY

look at glovebox to get the RPO CODES

BLAZERS/JIMMY never offers DRUM rear brakes.

2001 Jimmy axles offers
4x2, 8-1/2" ring gear (3.42 ratio, GU6)
4x4, ZR2 opt (3.73 ratio GT4)
4x4, w/o ZR2 opt; 7-5/8" ring gear, 3.42 axle ratio (opt GU6)
4x4, w/o ZR2 opt; 7-5/8" ring gear, 3.73 ratio (opt GT4)
4x4, w/o ZR2 opt; 8-1/2" ring gear (3.42 ratio, GU6)
4x2, 7-5/8" ring gear (3.42 ratio, GU6)


Also i added a picture to tell you which ring gear you have.

i OWNED 6 different blazers 88,92,93,98,98,00

Whew, getting two different stories here... I am not intending on doing the ZR2 axle.

That said, Jamaroon and blazerguy, you are both saying slightly different things.

I have a 7 5/8 ring gear rear end 4x4. I am also certain it will be a 3.42 (I will check the glove box code). If I go with a 8 1/2 ring gear 3.42 ratio, will that still be a suitable replacement?

You are 100% wrong on this. There have been lots of people that have swapped in the ZR2 rear end.


The front diffs are exactly the same regardless of if it was a ZR2 or not. Gear ratios are the only variable (other than if it was a bravada front diff, then it had the one piece shaft) ZR2's have longer CV shafts but the control arms are the same lengths.


Spreading wrong information is useless and confusing for others, if you don't know what you're talking about then don't say anything.

Yes, that would be a good replacement, but it will be fairly hard to find. Not many came with that option.

I used to think that also until I measured them all at 38.5 inches pin to pin

you don't want to go through this again im big on pull-a-part but I would suggest a bearing kit and ring and pinion unless you enjoy this kind of work. Just my O-pinion Motive Gear GM10BI-30 Differential Rebuild Kit | Auto Parts Warehouse

My ring gear says 11:41, so it turns out it's a 3.73 G80. Guess I am going for a zr2 or the same stock one. Interestingly enough, the ring gear I swear looks to be stamped 7 7/8. You can see it on the videos I posted. Either way, I would hate to go back to a 3.42, but if I have to I'll pull a 3.42 front as well. I could do that at a different time so long as I DO NOT use 4x4, correct? Sometimes the fronts are taken out of these cars already.

Thanks for all the help guys. I went to pick-a-part today and first blazer I looked at had a GT4 G80 7.65" in the back. Pulled the cover and the diff was clean with minimal metal on the magnet. Locker was working great. What's more is they were having their half off parts sale and today was the last day. Wow!

Took 2 hours to pull and loaded it up in my old 1970 Ford F250 truck. Went to AutoZone and picked up a new 7.65" gasket and some 75w90 (IIRC) for LSD or open diff. Once home I pulled the old diff in a little less than two hours. Took 2.5 hours to clean and install the "new" axle. Another hour for bleeding the brakes and cleanup. All in all not too bad. Pretty quick and fun little project. Drove the Jimmy and drives perfectly smooth. The reverse clunk is 95% gone (new U-joints would prolly help). No clinks or pops around corners.

Really lucked out on this project over and over guys. Going to be sore tomorrow doing it all by myself, but my wife can finally drive her car again and I feel fortunate providence shone in my favor. Next up is the complete front suspension kit I got. Have a new ball joint puller set I am itching to test out. :)

Glad you got it fixed

Thanks for the information in this thread. I just blew out my rear end and this thread has so much information. Thanks guys.

Let me know what solves your noise problem with the reverse.
I have had that noise forever and when I changed differential fluid I didn't find any metal shavings in there just a dark brown fluid..

Just figured I would mention that when I got the new axle in, I opened the diff on the one I blew. The pinion looked and felt like it was meant to be smooth. the ring gear got a few blades damaged, but nothing compared to the pinion. Also to note: my blazer has over 200K miles on it. I did the axle swap with hand tools, although I did but a breaker bar (the kind with ft/lbs on it) for the ubolts on the leaf springs. Getting the old axle out after being disconnected was a lot harder than getting the new one in. I didn't even scratch my American flag painted diff cover. that shocked me. This was a great time to redo brakes as well. However, my parking brakes wont fit in the rotor. weird.

I believe the A-arms are mounted differently to the frame and are a ZR2 item only (different ball joint location for wider track ) like the C/V shafts. The ZR2 front differential came with special factory heat treated gears in a 3:73 ratio only. I will be swapping both after rebuilds, I got a fantastic deal on them I just couldn't pass up !