12 bolt Moser / Eaton Posi - Lateral-g Forums

RBuhr69 · #1 11-03-2013, 08:14 AM

No way bashing Moser or Eaton.....

Just curious if people are experiencing an issue when backing up in tight spots that it sounds like the rear end is fighting itself or sounds like it is tearing parts up, but its not as it all works fine. This is on a brand new 12 bolt Moser/Eaton Posi unit.

No issues going forward, no issues hard cornering forward left/right, backs up in straight line no noise, just when I back up out of my garage after car has sat. Doesn't appear to do it as bad after driving car all day when I pull into garage, and then back out again.

I did do some searches on google and sounds like it is common but didn't see much in the way of if there is a resolution to fixing it. Some comments were this is normal, some stated they added another bottle of limited slip lube beyond the required 1 bottle.

I have not called Eaton or Moser yet as I wanted to hear some conversation with people who have already experienced this issue. Did it go away with time, did adding another bottle help, did you have to have someone open up the rear and see what was wrong? Is there something that can be done to help, etc..
Thoughts?

**glassman** · #2 11-03-2013, 10:46 AM

Thoughts:
I have a freshly rebuilt 12 bolt in my 70 Cam, built by a very reputable "rear end only" shop here locally. I am having issues coming off the freeway or a highspeed comedown and when turning right or left, like say after a stop sign or red light, the rearend "clicks" or "sticks" but then its fine.

I had it double checked (and they gladly replaced an axle seal and inspected and retoleraned the inside).

Basically what i've learned is the 12 bolt design is rather antiquated and the gear oil stays "up top" after a rapid slow down, then the clutches sort of bind/stick, both from older design and from lack of weight in the rear, but only turning though. Going straight, no problems.

I've been recommended by quite a few people with experience, rebuild it, sell it, and go 9 inch. These 12 bolt rear ends are great for going straight.

Let us know what you find out on yours, this is just the 2cents on mine. GL

Mike

RBuhr69 · #3 11-03-2013, 02:25 PM

What is on the inside of the Moser is what I would think that makes a difference in how the rear end works/behaves....But i'm not a rear end expert either. I did hear the Moser a more straight line rear end, but they are used in all forms of racing so I don't know.

I have an Eaton Posi in mine, I hear people like their Wavetrac or Tru-Trac's better...

Vince@Meanstreets · #4 11-03-2013, 02:42 PM

What fluid and what slip additive are you using?

I have had to use 2 bottles on a few units. Also no synthetics.

RBuhr69 · #5 11-03-2013, 03:19 PM

Lucas 80-90 Non synthetic with 1 bottle of KEN-LSA KENDALL LIMITED SLIP ADDITIVE from Moser when I ordered the rear end.

Guess it would hurt to try another bottle?

**glassman** · #6 11-04-2013, 08:56 AM

from what i understand it may as some friction is required.

chr2002ca · #7 11-04-2013, 09:37 AM

I purchased a new Moser 12-bolt unit(69 Camaro) with an Eaton posi a few years ago and put about 3500 miles on it and never had any issues like you describe. It had a little bit of a whine to it that you could hear at lower cruising speeds but a lot of gear sets do that and it's not related to the posi unit or the housing. I remember adding some GM posi fluid from a small bottle, but it didn't require the whole bottle. I would be careful adding too much. Did Moser have any suggestions?

Vince@Meanstreets · #8 11-04-2013, 03:45 PM

I wanted to throw this out too but are you sure it's a clutch posi and not a worm gear tru track type? They don't like friction modifier at all and will do what you a describing.

RBuhr69 · #9 11-04-2013, 06:04 PM

I ordered Eaton Posi, and the packing slip just says ETN. I will call tomorrow to verify and ask questions on what is happening. Thanks..

RBuhr69 · #10 11-05-2013, 01:40 PM

Moser said to call Eaton, they have never heard of this issue atleast the gentleman i talked with...lol

However, Eaton said more than liklely it is the oil I am using (Lucas). He stopped me mid sentence and said to switch and that should take care of it....

Go with Mobile1 or Shell mineral/petroleum based gear oil and a four ounce bottle of GM friction additive/modifier is also necessary for optimum performance.

with that said.......any advice of exactly what I need? I assume this is not the synthetic version of Mobile1 Gear oil and plain straight oil.......