12-Bolt Popping and Binding - Update w/Dyno sheet & Video - LS1TECH



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12-Bolt Popping and Binding - Update w/Dyno sheet & Video

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Old 02-08-2017, 02:03 PM   #1
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Default 12-Bolt Popping and Binding - Update w/Dyno sheet & Video

So in December I had my 12-Bolts bearings replaced and new set of 3.73 put in by a new shop due to another shops error and ruining the bearings. Well drove it home seemed ok and so it's sat till a couple weeks ago it was upper 50s clear roads took for a spin. Seems like the more I drive the car the worst it starts popping from the rear end and really feels like it's binding up.


It has an Eaton Posi with Moser 30 spline axles (passenger side was replaced due to bend) and am thinking that my Eaton is screwed up now. The rear pops when turning especially going in roundabouts and starts popping hard randomly when going straight, coasting, or very light cruise speed.


Thanks everyone



Update:

Well got the car tuned by The Shop Inc. here in Lincoln, NE a couple days ago and they did a great job straightening out the old Mail Order tune. The Shop told me when I stopped by to see how things were going it made 466 at the wheels on his Mustang Dyno with a really long flat torque curve. So I think this 408 likes the 102mm setup. But he got the rear end popping issue straightened out, and it was a fluid issue. Chad thought I was crazy when he test drove it as the rear made zero pops but then out of the blue it did it to him luckily. But after changing the fluid out all is well so far .



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12-Bolt Popping and Binding - Update w/Dyno sheet & Video-mustang-dyno.jpg  

Last edited by neblackshirts; 03-14-2017 at 04:45 PM. Reason: Adding words
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Old 02-08-2017, 04:00 PM   #2
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Is the Eaton posi the clutch plate type ? sounds as if the 'additive' wasn't added.
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Old 02-08-2017, 04:16 PM   #3
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Is the Eaton posi the clutch plate type ? sounds as if the 'additive' wasn't added.
Yeah it has the carbon disc clutch packs, I also thought this and could be the problem but that would really disappoint me in that I'm 0 for 3 in work done by shops in my area.


Would a pinion angle way out of alignment cause these symptoms I've described?
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Old 02-08-2017, 06:57 PM   #4
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An Eaton posi(clutch plates) and Auburn posi(cone clutch) are very sensitive to NOT having the additive in them. Without the additive,they grab-slip-grab-slip-grab,sounding like popping/knocking. The sound/noise is very audible inside the vehicle but barely audible outside.
A pinion angle WAY OUT OF PROPER ANGLE because the driveshafts' front u-joint and rear u-joint are not synchronizing.

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Old 02-08-2017, 08:28 PM   #5
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Are you sure the torque arm isn't loose at the rear end? It will make those popping sounds when turning if it is. Bob
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Old 02-08-2017, 09:12 PM   #6
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I have had Eaton style posi's chatter and buck as they got hot without enough additive. It may not be the issue but if it's a new gear it wouldn't be the end of the world to drain and refill with the correct type and amount of additive.
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Old 02-08-2017, 11:03 PM   #7
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Are you sure the torque arm isn't loose at the rear end? It will make those popping sounds when turning if it is. Bob
That's a good place to start hopefully it is something simple as this. It does have a Spohn crossmember mounted adjustable torque arm.
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Old 02-08-2017, 11:07 PM   #8
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Does anyone have a recommended fluid to use for the Eaton Posi over what Eaton recommends the GM Dexron LS? This Camaro will see much more street/highway time over track time if that matters.

Thanks again everyone
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Old 02-09-2017, 08:38 AM   #9
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I bought a 12 bolt used from someone and had the same issue. I assumed they did not add diff lube so I changed the gear oil and used 2 bottles of diff lube. The rear still popped so I added 2 more for the hell of it, assuming I'd be tearing the rear end down anyway. Within 10 miles of adding the extra diff additive the popping subsided. I would honestly drain the fluid, replace with some non synthetic gear oil of your choice and toss in more than the recommended amount of additive.
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Old 02-09-2017, 10:01 AM   #10
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I had a alburn in my S-10 for 15 better yrs and out of the blue its tarted doing that. I couldn't think of why,I pulled it down and really found nothing. It was old so I thought i'd replace it. Bought the same (cone) type and redid the rear.I installed all new bearings set it up and it worked ok. I had an on/off noise so I opened it up made a few shim adjustments and put it back together. it started popping jerking and all kinds of **** just like the first posi,I was pissed. I put in some more additive and it went away,that was last summer .
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Old 02-09-2017, 12:17 PM   #11
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referring back to post #9,the effects of the additive don't become immediately apparent,takes a while(driving) to totally mix in with the existing fluid.
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Old 02-11-2017, 08:28 AM   #12
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That's a good place to start hopefully it is something simple as this. It does have a Spohn crossmember mounted adjustable torque arm.
Thats gonna make everything worse. But I agree, it sounds posi related. Some harshness should be considered normal as your suspension gets more aggressive.
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Old 02-12-2017, 12:20 AM   #13
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Thats gonna make everything worse. But I agree, it sounds posi related. Some harshness should be considered normal as your suspension gets more aggressive.
I agree with you on the suspension seeming harsh especially with everything changed. I'm not sure there nothing stock except for the k-member. The harshness is something I need to get used to for sure.

But not sure what you mean exactly on "thats gonna make everything worse". Are you meaning this due to is being a crossmember mounted torque arm? Also do you think I can hurt anything driving a bit with the rear popping? I have to drive it about 15 miles to the shop to have it looked at but definitely don't want to break the Eaton Posi.

Thanks for chiming in I know you defiantly know your suspension setups.
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Old 02-12-2017, 08:11 AM   #14
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I agree with you on the suspension seeming harsh especially with everything changed. I'm not sure there nothing stock except for the k-member. The harshness is something I need to get used to for sure.

But not sure what you mean exactly on "thats gonna make everything worse". Are you meaning this due to is being a crossmember mounted torque arm? Also do you think I can hurt anything driving a bit with the rear popping? I have to drive it about 15 miles to the shop to have it looked at but definitely don't want to break the Eaton Posi.

Thanks for chiming in I know you defiantly know your suspension setups.
Yes, they are very harsh. Anything happening in your rear end gets magnified 300% with a chassis mounted arm. They are annoying as **** if you ask me, but a necessary evil
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Old 02-24-2017, 07:06 PM   #15
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Rear popping issue solved hopefully in my above update.
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Old 03-14-2017, 04:52 PM   #16
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OK so while bored at work I stumbled upon a video that has the exact 100% same popping and sound as from my 12-Bolt rear-end as I was experiencing but would even pop randomly while going straight. Since the tune being done and having the shop add some friction modifier it has improved drastically but is still there just not to the degree as it was before.


Yes it's a Ford sorry and hope owner doesn't mind but it's about 2 minutes into the video:
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Old 03-14-2017, 09:25 PM   #17
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Nice car, thanks for the ride! Your axle sounds exactly like the Detroit locker in my Mav. All I can think of on a 12 bolt is the clutches are setup tight. In fact, I can feel my '98 Dakota R/T (with the big 9.25" posi) chunking like that on tight turns. No sound, just the feel...
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Old 03-14-2017, 09:51 PM   #18
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Nice car, thanks for the ride! Your axle sounds exactly like the Detroit locker in my Mav. All I can think of on a 12 bolt is the clutches are setup tight. In fact, I can feel my '98 Dakota R/T (with the big 9.25" posi) chunking like that on tight turns. No sound, just the feel...
Not my video or mustang but I agree for a Mustang that is a pretty cool car and always good to see others enjoying this hobby/lifestyle.

My 12-bolt didn't make that popping sound until a local shop replaced the bearings. But after I took it in for a tune and they added some friction modifier it helped out a lot. I would just be driving in a straight line and random pops would start. Turning I got but the going in a straight line spooked me, but I think this is a case of it being just the nature of the beast. The previous owner told me it was an Eaton Posi but others that have rode in my Camaro say that it reminds them a lot of a detroit locker. Maybe previous owner was mistaken on it being an Eaton but any how I came across that video and posted it to maybe give everyone an idea of what my Camaro was doing.

By the way nice Maverick, I bet that it surprises a lot of people. Ford always was able to make some pretty light weight packages that are great for todays modern tech.
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