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Originally Posted by tracdogg2
(Post 1588394568)
The pre load springs have nothing to do with tuning the posi. They are more for driving conditions. The clutches need to have torque applied to engage. Guys who are drag racing, autocrossing, or just drive their cars spirited can benefit not using the springs. For guys that use their cars for daily use, especially on snow and ice, need the springs. Also for road courses where they have to feather the gas thru a sweeper and gently accelerate out of a corner. In this case it's Paul's choice if he wants to use them or not. Either way the posi is tuned.
Mike
Originally Posted by 68post
(Post 1588395728)
I'm interested to know which gear oil and in what weight will be used ?
Owner's preference , or builder's recommendation ?
Originally Posted by Solid LT1
(Post 1588396244)
Someone has already asked but, no answer yet.....what did the cryogenic processes run for all those purty shiny parts? Where was it done....turn around time? Thanks!
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Originally Posted by MndShp
(Post 1588395680)
Can you explain the posi tune process in this instance? Thanks
http://www.youtube.com/results?searc...ms+posi+tuning |
Originally Posted by Danish Shark
(Post 1588398646)
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Originally Posted by 68post
(Post 1588395728)
I'm interested to know which gear oil and in what weight will be used ?
Owner's preference , or builder's recommendation ? |
Originally Posted by Solid LT1
(Post 1588396244)
Someone has already asked but, no answer yet.....what did the cryogenic processes run for all those purty shiny parts? Where was it done....turn around time? Thanks!
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I'm far from being any sort of expert on diffs, but after watching those Tom's videos (part 1 & 2) I am quite curious why they haven't adapted a torque wrench to fit into the opposite side gear so as to log some repeatable data. While the video lessons are good, IMHO the typical enthusiast is unlikely to ever set up enough diffs to develop a deft touch for how one should "feel", but pretty much anyone can learn how to "paint by the numbers". Just an observation... Good thread!
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Guys, give me a little time to answer all your questions. They are all good questions. The reply will be long and in depth.
Mike |
Originally Posted by TheSkunkWorks
(Post 1588399661)
I'm far from being any sort of expert on diffs, but after watching those Tom's videos (part 1 & 2) I am quite curious why they haven't adapted a torque wrench to fit into the opposite side gear so as to log some repeatable data. While the video lessons are good, IMHO the typical enthusiast is unlikely to ever set up enough diffs to develop a deft touch for how one should "feel", but pretty much anyone can learn how to "paint by the numbers". Just an observation... Good thread!
Since the clutches are all steel, no fiber, this adds up to quite a bit of metal going into the lube. Pre-seating the clutches eliminates a lot of the metal droppings. The springs are between the side gears pushing them apart, unlike the Dana which uses a Bellville spring behind the clutches pushing the gears together. The dana spider gears are always in constant mess which is a good thing. The disadvantage is the springs compress every time you put a load on it. The eaton springs have no effect on the clutches between loaded and unloaded conditions. They are only there to aid in engagement under very light load acceleration. Synthetic oil is not recommended by eaton because it will reduce engagement under light load. The disadvantage of the eaton design is it opens up the backlash between the spider gears. And in a small amount increases clutch wear. Backlash range is .001 - .005. With a 2 to 1 ratio for every .010 wear in each clutchpack the backlash opens up .005. As the backlash gets wider the hammering effect increases every time let off and step on the gas. When you tune the posi the idea is to reduce backlash to the absolute minimum. If you watch Toms video closely you will see the carrier get "notchy". This is setting backlash at less than 0 and adding some preload without the use of the springs. I prefer to preload the clutches also when setting them up to flatten out any waviness in the discs. Paul will post a pic of a set of preseated clutches and you will see the un-evenness of the discs even though they look perfectly flat when stacked together. The stamping process always creates some amount of distortion. Where Tom does it by feel with unloaded discs, I prefer to set it with them loaded. Either way if you use too thick of a shim it just won't go together. One point Tom did make, never assume that if one side took .050 shims that the other side will also. Especially with original carriers. Another note: new clutches never use the same shim thickness as the factory ones. If you reuse the factory shims, even in the same location, you will have massive spider gear backlash. This is a common procedure for shops doing rebuilds, if they even change the clutches at all. Nearly all of your local garages will not touch the clutches, just bearings and seals and call it a complete rebuild. Since replacement shims come in .005 increments it's hard for the average person to set the clutches ideally. Mike |
I want to touch on something very important since Paul posted pics.
In picture "K" you can see the two passages for the pinion bearing bearing lubrication.In picture "O" you can see the "well" between the pinion bearing race bores more clearly. This well is the garbage collection area. I read all the time on forums about people flushing and washing out their diffs with chemicals with only the rear cover removed or not even that done. The ring gear acts as a scoop. It pulls gear lube off the bottom and throws it into the passage above the carrier. The diff in pic K is upside down so I am referring to the large passage at the bottom. This passage deposits oil in between the pinion bearings. From there the lube travels thru the front bearing rollers into another passage and returns it to the rear of the diff. That passage is the small one above the race bore. The lube also passes rearward thru the rear bearing rollers and dumps under the carrier. The ring picks up the lube by the natural roping effect. This is how lube is recirculated in the diff. Without circulation the pinion bearings overheat. The roping effect also picks up any garbage in the bottom of the housing. Metal shavings, snap rings, etc. The garbage collects in the bottom of the well in pic "O" and gets stuck in the muck. If you use a chemical to clean out the diff you will break loose the garbage and run it thru the bearing rollers. Of course large snap ring pieces won't pass thru the bearings but all the clutch disc shavings will. Unless you are going to remove the pinion, just wipe out the bottom of the housing with rags, not paper towels. Don't spray any chemical into the passages, put it on the rag. The garbage only stays put if the diff is kept flat. If a used diff is stored standing up on the rear cover all these metal shaving will coat the rear pinion bearing. Mike |
Mike you are truly a wizard. I can't thank you enough for all the help you have given me over the years. It has been invaluable!
Steve |
Why would synthetic oil "reduce engagement under light loads" ? Synthetic is superior in almost every metric except price. I'm not questioning that Eaton makes this recommendation, but I would like to hear an oil tribologist explain why they think this is true.
Tracdogg2 is a great resource for us here in the forum and I've learned a lot from him. My dad was a tool and die machinist so I have an appreciation for quality work. Can the setup be adjusted to compensate for synthetic so that it doesn't slip under light loads? I'm using the best synthetic I can buy in my diff after spending several thousand dollars for my custom 12 bolt, unless someone can explain to me why I am wrong. That someone should be able to demonstrate that they know more about lubrication and synthetic oils than I do; possible but not likely. There is a time to be humble, now is not that time.... |
Originally Posted by 632C2
(Post 1588407907)
Mike you are truly a wizard. I can't thank you enough for all the help you have given me over the years. It has been invaluable!
Steve It's always been a true pleasure every time we talk. Your attention and dedication to details has been an inspiration, even to me. Mike |
i dont have all the info, but i have had good luck with Vavoline Syn Power 75W-140
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What do modern posi rear ends use for oil? And what do they call for a standard c3 posi? And if their is a differance, why?
With the REM polishing do I/can i/ should I run a lighter oil? Clutches... Springs.... Haven't got a good answer on this yet... For road race and sported canyon runs, is it better to have or not to have the springs?? And explain why plz |
Originally Posted by lurch59
(Post 1588408336)
Why would synthetic oil "reduce engagement under light loads" ?
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Originally Posted by pauldana
(Post 1588415710)
What do modern posi rear ends use for oil? And what do they call for a standard c3 posi? And if their is a differance, why?
With the REM polishing do I/can i/ should I run a lighter oil? Clutches... Springs.... Haven't got a good answer on this yet... For road race and sported canyon runs, is it better to have or not to have the springs?? And explain why plz Paul, with the REM polishing, I have no idea. In your case I would be more concerned about thermal viscosity breakdown. An oil engineer could probably explain which and why but I'm sticking with real world results. I'd be talking to guys that race and see what they are running and look for a common lube. The biggest killer of these diffs is heat. For long runs a pump and cooler may be needed. I've been working with a company on a billet aluminum rear cover that is already plumped (correctly) for a cooler that the average person can install with simple tools. Hopefully it will available next year. Springs: Paul, leave them in. Drag racers have no need at all for springs. Along with spirited drivers on the street. People driving their car in snow and ice definitely need the springs. In your case you don't need the springs most of the time. BUT, if your are controlling a drift thru a sweeper and are feathering the gas the sudden engagement (as Markus noted) could be enough to break lateral traction. The springs will soften the engagement. |
Originally Posted by gkull
(Post 1588415469)
i dont have all the info, but i have had good luck with Vavoline Syn Power 75W-140
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Interesting!!!Mike built up my super 10 bolt with a tuned differential from Tom. I don't recall seeing any springs in the differential carrier. It's been a couple of years. Is that probably a correct recollection? I won't be driving on snow or ice......NO WAY!
BTW: My 68 has one of the last differentials and half-shaft bearing assemblies built by Kennie of Tom's Differentials. This was in the weeks before Tom left So Cal for Idaho. Kinnie died of a heart attack not much afterward and Tom no longer sells completely manufactured diff's to the public. |
Mike, I very much appreciate the in-depth reply. :cheers:
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