Grinding/rattling when starting from a stop and turning after rear diff work

[Eilermoon]

Hey y'all - I'm relatively new to working on these TJ's and got mine a few months ago. I was swapping all the fluids on it and decided to do the rear diff clutch packs since I was in there on my Dana 35. Long story short, I couldn't get it back together and ended up buying a new, already assembled carrier and popped it in there. Came with new bearings. After re-assembling with friction modifier in the fluid for a while, something's definitely off while driving.

Starting from a stop often produces this grinding/rattling noise, more pronounced when turning at slow speeds. Worst is when I shift from reverse to first so the gears are loaded in the other direction. Usually lasts a few seconds of sounding bad then quiets down and drives straight just fine. Pretty sure I need to open the diff back up but trying to get an idea of what to look for. I checked the lash and paint pattern when reassembling last time and didn't see anything concerning, though it was the first time I'd tried to do that.

I'll also add that my tranny grinds a bit sometimes and I'm worried about that as well, that could be another problem source. Getting into 2nd grinds pretty frequently, especially down-shifting to 2nd. It grinds hard every time and sounds terrible. 3rd can also grind getting into it as well. I'm wondering if those synchros are bad or something, I'm super scared of working on a transmission. I swapped that fluid and was hoping that would help, but it hasn't seemed to.

Manual 1997 5-speed with the AX-15 transmission, 3" lift on 33's. Has ~170k miles on it.

 

[macleanflood]

Got any pics of the pattern you ran?

Did you measure the backlash?

Assuming you put shims in all the sane places?

Pre-assembled carrier? So new ring and pinion? Out of curiosity who sells that?

-Mac

 

[Eilermoon]

Unfortunately I don't have pics of the pattern, really wish I thought to take some.

The carrier came assembled, I just swapped the ring gear onto it, so no new ring or pinion gears. I didn't touch the pinion lol. Because of that, I just placed the original shims back where I thought they went - definitely could have messed this up though.

A bit ashamed to say it, but I grabbed it off Ebay here. Everything looked good and to match my original carrier setup. I figured it might chatter a bit due to coming assembled dry without the modifier lube between the plates, but I'm pretty confident that's not what I'm feeling. It also hasn't gone away or lessened after driving it a while. Gonna see if my partner can help me record some of the noise to share

 

[hear]

my partner

Congrats on making partner. What firm are you at?

 

[Daryl]

That part number 74210X from Dana is over $600. The Chinese copy you bought was $198. Time to remove the rear cover and take a peak.

 

[Eilermoon]

Got any pics of the pattern you ran?

Did you measure the backlash?

Assuming you put shims in all the sane places?

Pre-assembled carrier? So new ring and pinion? Out of curiosity who sells that?

-Mac

Welp friends I got 'er open and found gold. It's gotten much worse recently, and grinds significantly when coasting. Also kind of grinds/rattles after changing gears and turning slowly.

It definitely feels a bit loose, turning the pinion gives a bit more of a lag than I feel like it should. Slapped some prussian blue on it and spun it around a few times, would love your thoughts. It's not super clear to me what needs adjusting...

Also took a video of moving it a bit in case the sound helps someone that knows more than me here. Video linked here

 

[macleanflood]

@hosejockey61 would offer a expert opinion.

Got any gear paint? That's awful hard to read. Looks like the contact is all on the toe.

-Mac

 

[Rickyd]

Carrier replacement 101. Measure backlash before disassembly. Make sure all bearings are good with no wear or play. Install new carrier of whatever flavor to the same backlash and proper preload.oops you didn't follow any rules with the right tools.

Sorry man(or whatever you identify as), you messed up and need to start from scratch or just take it to a good axle shop and pay them a couple thousand.

 

[macleanflood]

Is it me or does this look out of place?

-Mac

 

[Eilermoon]

Carrier replacement 101. Measure backlash before disassembly. Make sure all bearings are good with no wear or play. Install new carrier of whatever flavor to the same backlash and proper preload.oops you didn't follow any rules with the right tools.

Sorry man(or whatever you identify as), you messed up and need to start from scratch or just take it to a good axle shop and pay them a couple thousand.

Sounds like the spec stated on other forums is 5 - 8 thou for Dana 35 backlash. Not sure I understand your full response here - what have I done that's irreversible? Same gears as previous, new bearings.

 

[Eilermoon]

Is it me or does this look out of place?

View attachment 697464

-Mac

I'm thinking that's just the angle of the pic, it looked fine in-person. But will go triple check

 

[Eilermoon]

@hosejockey61 would offer a expert opinion.

Got any gear paint? That's awful hard to read. Looks like the contact is all on the toe.

-Mac

I think you're right about the toe contact, I don't have gear paint on hand. Will grab some and follow up with better pics

 

[macleanflood]

Sounds like the spec stated on other forums is 5 - 8 thou for Dana 35 backlash. Not sure I understand your full response here - what have I done that's irreversible? Same gears as previous, new bearings.

I think he's saying measure your exact backlash as it is now before doing and disassembly.

5-8 thou is on assembly, fresh, not broken in. That number will increase with time.

If you take it apart you need to try and get the gears back to their happy spot... assuming there was a happy spot...and reassembly with the original backlash helps you do that.

Do you have a dial indicator?

-Mac

 

[hosejockey61]

I can't tell anything with those pictures. From your description of everything, I think you need to go back to square one and pull it out and take a good look at everything.

 

[Eilermoon]

I re-shimmed the carrier after measuring the backlash and taking it back out. I basically just adjusted the shims to get the backlash back down to about .011", and it's been much better since then.

I also think there's something else going on here though as I do still have a rattling type sound when turning hard in first gear from a stop. I took a decent video of it if you turn up your volume: https://immich.azulas.dad/share/tLU_AFZLHqDjx1X_ZvTln48riGLHtuinye3TU_2La6ZF-ZQdB6J4qwB_8yPh8CfpZ6o

Honestly this sounds more like a driveshaft or more front end type thing. Maybe driveshaft u joints? My first gear grinds when coqsting in first pretty bad also, but I assumed that was just worn synchros in the AX-15 Trans

 

[hosejockey61]

I re-shimmed the carrier after measuring the backlash and taking it back out. I basically just adjusted the shims to get the backlash back down to about .011", and it's been much better since then.

I also think there's something else going on here though as I do still have a rattling type sound when turning hard in first gear from a stop. I took a decent video of it if you turn up your volume: https://immich.azulas.dad/share/tLU_AFZLHqDjx1X_ZvTln48riGLHtuinye3TU_2La6ZF-ZQdB6J4qwB_8yPh8CfpZ6o

Honestly this sounds more like a driveshaft or more front end type thing. Maybe driveshaft u joints? My first gear grinds when coqsting in first pretty bad also, but I assumed that was just worn synchros in the AX-15 Trans

I think you'll be lucky if that diff survives.

 

[Eilermoon]

I think you'll be lucky if that diff survives.

Why's that? I thought .011" for worn in gears was pretty acceptable. Just hard to get them reassembled accurately? Should be tighter?

 

[KennethS]

Hopefully you kept the original carrier and can get the clutch packs assembled correctly so you have a backup.

 

[Eilermoon]

Hopefully you kept the original carrier and can get the clutch packs assembled correctly so you have a backup.

Oh yeah for sure, I have lots of extra gears and plates now. I figure I'll get it on a proper press at some point and have a backup carrier just lying around

 

[Strizzo]

if its sticking/popping when turning you either don't have the right kind or not the right amount of friction modifier. What gear oil did you use? You might need to run conventional (non-synthetic) lube with those clutch packs.