Front Diff Replacement/ 4x4 problems - Infamous Nissan

ThunderChicken · 11-16-2021, 09:24 PM

I was having some problems with the 4wd slipping out and making a clunking noise when under anything other than light throttle. I suspected the hubs, but I found them to be working fine. Dropped the front diff fluid and it's got plenty of metal in it, no large chunks but enough flakes to worry me. How hard is it to change a front diff on these trucks? I suspect that since the cv axle was replaced on this side by someone else that they messed something up, different spline count or something and it shredded the teeth in there.

dvdswan · 11-17-2021, 01:54 AM

I would suspect the t/case more than the diff if it slipping out of gear. Does it do it in 4L or just from 4H to 2H?

cadillacdude1975 · 11-17-2021, 07:50 AM

It is a pain in the ass. It can be done without removing the torsion bars. I took mine out for an engine swap. I removed the driveshaft, unbolted the CV axles, unbolted the two front bushings, then the two rear bushings. Remove vent tube. The driver side of the rear mount pops out easier. Once you wrestle it past the torsion bars, then it has to pull back and rotate down at the same time.

Putting it back in is worse. I dropped the front crossmember. I had to cut one of the bolts off. Cant remove it with the torsion arms in place. Got another one from the junkyard. I had the diff on the ground and reattached the front and rear crossmembers. I then strapped it to a harbor freight transmission jack and raised it back into place. I had to wrestle with it a little, but doing it that way was far easier than the alternative.

cadillacdude1975 · 11-17-2021, 07:53 AM

If the truck has automatic hubs, throw them in the trash. They will fail. They always do as the springs can no longer maintain the pressure needed to lock the hubs and axles together.

Reserector · 11-17-2021, 06:50 PM

Been there. Got the t-shirt. Try this link and see if it sounds like your problem. (I believe dvdswan already guessed it.)
https://mississippi-mud.com/thread-18674.html

ThunderChicken · 11-17-2021, 08:22 PM

Thanks for all the info guys, I really appreciate it. The t case is worth taking a look at given the similarity of the problem. Its not slipping out of gear, more like the connection between two parts of that rotating assembly are slipping. Given that both alternatives sound like a nightmare to replace, I think I'm gonna take a step back and look at the hubs again. Manual hubs are new to me, so I think I could have overlooked something. When I had the hubs off, I checked for chewed up teeth, and verified that the gear in the hub moved up when I turned the dial. Then I put it back on with the hub free, locked it, spun the wheel, and it turned the cv axle. Is it possible that even though the hub was moved up that the weak spring could cause it to move back under load? And is it possible to have bad hubs with the gear teeth intact? Sorry if these are dumb questions, this whole truck is a learning experience.

cadillacdude1975 · 11-17-2021, 09:32 PM

Did you set the snap ring in the correct groove?

Reserector · 11-17-2021, 10:44 PM

Quote:

Originally Posted by ThunderChicken

Is it possible that even though the hub was moved up that the weak spring could cause it to move back under load?

No.

Quote:

Originally Posted by ThunderChicken

And is it possible to have bad hubs with the gear teeth intact?.

Only if they don't engage, which yours do.

Reserector · 11-17-2021, 11:02 PM

Try this:
Theory: If the t-case chain is OK, both driveshafts should rotate the same number of turns in any given distance because both diffs are the same ratio.

1. Find a place to test drive, put it in 4x4 and shut it off. Set the brake.
2. Crawl under and put a piece of tape or something on both driveshafts at the same clock position, such as straight up (12:00)
3. Now drive easy for a few yards, shut it off, look under and make sure they are still clocked the same (aligned, that is). This will prove the theory.
4. Now drive it to intentionally make is skip a few times.
5. Shut it off and check the tapes again.

If they are out of sync, it's your t-case chain.
If they are aligned, it's your diff, CV axles or a hub.

Cost= A bit of time, some tape and some laundry detergent to get your clothes clean after you crawl on the ground. LOL

cadillacdude1975 · 11-17-2021, 11:50 PM

Damn good advice with the tape.

11-16-2021, 09:24 PM	#1
ThunderChicken Join Date: Aug 2021 Location: PA Posts: 13 Vehicle: 1988 d21 hardbody 4x4 Thanks: 3 Thanked 2 Times in 2 Posts	Front Diff Replacement/ 4x4 problems I was having some problems with the 4wd slipping out and making a clunking noise when under anything other than light throttle. I suspected the hubs, but I found them to be working fine. Dropped the front diff fluid and it's got plenty of metal in it, no large chunks but enough flakes to worry me. How hard is it to change a front diff on these trucks? I suspect that since the cv axle was replaced on this side by someone else that they messed something up, different spline count or something and it shredded the teeth in there.

11-17-2021, 01:54 AM	#2
dvdswan Super Moderator Join Date: Mar 2009 Location: Port Orchard, WA Posts: 5,680 Vehicle: 96 HB Thanks: 212 Thanked 906 Times in 791 Posts	I would suspect the t/case more than the diff if it slipping out of gear. Does it do it in 4L or just from 4H to 2H? __________________ Dave 96 HB XE SAS'd D44 3-link on 35s http://www.cardomain.com/ride/2618002

11-17-2021, 06:50 PM	#5
Reserector the Flaming Marshmallow Join Date: Oct 2015 Location: Laurel, MS Posts: 2,095 Vehicle: '86.5 Nissan HB KC 4x4 5.3V8 Thanks: 125 Thanked 588 Times in 461 Posts	Been there. Got the t-shirt. Try this link and see if it sounds like your problem. (I believe dvdswan already guessed it.) https://mississippi-mud.com/thread-18674.html __________________ Becoming the Flaming Marshmallow * SAS * V8 Conversion * The FM "Z71 Conversion" Explained Vid * Ride-Along Vid

11-17-2021, 11:02 PM	#9
Reserector the Flaming Marshmallow Join Date: Oct 2015 Location: Laurel, MS Posts: 2,095 Vehicle: '86.5 Nissan HB KC 4x4 5.3V8 Thanks: 125 Thanked 588 Times in 461 Posts	Try this: Theory: If the t-case chain is OK, both driveshafts should rotate the same number of turns in any given distance because both diffs are the same ratio. 1. Find a place to test drive, put it in 4x4 and shut it off. Set the brake. 2. Crawl under and put a piece of tape or something on both driveshafts at the same clock position, such as straight up (12:00) 3. Now drive easy for a few yards, shut it off, look under and make sure they are still clocked the same (aligned, that is). This will prove the theory. 4. Now drive it to intentionally make is skip a few times. 5. Shut it off and check the tapes again. If they are out of sync, it's your t-case chain. If they are aligned, it's your diff, CV axles or a hub. Cost= A bit of time, some tape and some laundry detergent to get your clothes clean after you crawl on the ground. LOL __________________ Becoming the Flaming Marshmallow * SAS * V8 Conversion * The FM "Z71 Conversion" Explained Vid * Ride-Along Vid Last edited by Reserector; 11-18-2021 at 03:39 PM.

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11-17-2021, 07:50 AM	#3
cadillacdude1975 The Gear Jammer Join Date: Apr 2013 Location: Chattanooga, TN Age: 50 Posts: 10,679 Vehicle: 87 VG33 Pathfinder SE 4x4 & 87 D21 SE Thanks: 457 Thanked 1,400 Times in 1,265 Posts	It is a pain in the ass. It can be done without removing the torsion bars. I took mine out for an engine swap. I removed the driveshaft, unbolted the CV axles, unbolted the two front bushings, then the two rear bushings. Remove vent tube. The driver side of the rear mount pops out easier. Once you wrestle it past the torsion bars, then it has to pull back and rotate down at the same time. Putting it back in is worse. I dropped the front crossmember. I had to cut one of the bolts off. Cant remove it with the torsion arms in place. Got another one from the junkyard. I had the diff on the ground and reattached the front and rear crossmembers. I then strapped it to a harbor freight transmission jack and raised it back into place. I had to wrestle with it a little, but doing it that way was far easier than the alternative.

11-17-2021, 07:53 AM	#4
cadillacdude1975 The Gear Jammer Join Date: Apr 2013 Location: Chattanooga, TN Age: 50 Posts: 10,679 Vehicle: 87 VG33 Pathfinder SE 4x4 & 87 D21 SE Thanks: 457 Thanked 1,400 Times in 1,265 Posts	If the truck has automatic hubs, throw them in the trash. They will fail. They always do as the springs can no longer maintain the pressure needed to lock the hubs and axles together.

11-17-2021, 08:22 PM	#6
ThunderChicken Join Date: Aug 2021 Location: PA Posts: 13 Vehicle: 1988 d21 hardbody 4x4 Thanks: 3 Thanked 2 Times in 2 Posts	Thanks for all the info guys, I really appreciate it. The t case is worth taking a look at given the similarity of the problem. Its not slipping out of gear, more like the connection between two parts of that rotating assembly are slipping. Given that both alternatives sound like a nightmare to replace, I think I'm gonna take a step back and look at the hubs again. Manual hubs are new to me, so I think I could have overlooked something. When I had the hubs off, I checked for chewed up teeth, and verified that the gear in the hub moved up when I turned the dial. Then I put it back on with the hub free, locked it, spun the wheel, and it turned the cv axle. Is it possible that even though the hub was moved up that the weak spring could cause it to move back under load? And is it possible to have bad hubs with the gear teeth intact? Sorry if these are dumb questions, this whole truck is a learning experience.

11-17-2021, 09:32 PM	#7
cadillacdude1975 The Gear Jammer Join Date: Apr 2013 Location: Chattanooga, TN Age: 50 Posts: 10,679 Vehicle: 87 VG33 Pathfinder SE 4x4 & 87 D21 SE Thanks: 457 Thanked 1,400 Times in 1,265 Posts	Did you set the snap ring in the correct groove?

11-17-2021, 11:50 PM	#10
cadillacdude1975 The Gear Jammer Join Date: Apr 2013 Location: Chattanooga, TN Age: 50 Posts: 10,679 Vehicle: 87 VG33 Pathfinder SE 4x4 & 87 D21 SE Thanks: 457 Thanked 1,400 Times in 1,265 Posts	Damn good advice with the tape.