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  #1  
Old 01-17-2005, 11:42 PM
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Difference between open, limited slip, and locked differentials

I hear people talking about these different setups and I have little idea what they are. I hear people throw names around like ARB air lockers and I would like to know what all the fuss is about!
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Old 01-18-2005, 12:08 AM
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An open diff is whats most common in vehicles. That setup is the ring gear with a carrier and spider gears. Only 1 wheel is powered with this type of diff and its the one with the least amount of resistance. This means that if you have one wheel on gravel and one on ice, the one on ice will get all the power and the other wheel won't spin at all. It also gives the smoothes performance while turning, but not good for snow/ice/mud.


A LS (limited slip) is a carrier, typically with no spider gears, that contains a series of clutches. These clutchs engage when one wheel starts spinning more than the other. These clutchs then transfer power to the other wheel. They don't have quite as good a road manners as an open, but most times aren't bad. They are also known to fail at bad times like when you're stuck in mud, there is too much resistance to overcome and instead of getting the power to the other wheel the clutchs just spin. Its good for mostly onroad driving and some light offroad.


A locker is any kind of a positive locking device. There are many different kinds from a drop in (replaces the spider gears) to a full spool, or a spool. The drop in (commonly called a lunch box locker) are the cheapest but have unpredicatable nature on the street when turning. They are also the most prone to failure. The full spool are the most expensive but have better onroad manners and are more reliable usually than the lunch box style. The spools either replace the spider gears (mini spool) or the entire carrier (full spool). These are solid pieces of metal that lock the 2 axle shafts together and they can't turn independantly of each other at all. They have the worst street manners, but are great for offroad. The spools are relatively cheap though, my mini spool for my 9" cost me $16. I do have a Lincoln locker in my Ranger axles currently, which is where you weld the spider gears together and then weld them to the carrier. Its definetly NOT a real good way to do it, but my Ranger never sees the street. Besides that the axles that are in it aren't in the greatest condition anyhow and I have a D44/9" combo waiting to go in.


Unless you're doing alot of offroading I would stick with a LS or open diff.
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Old 01-18-2005, 10:59 AM
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I like the idea of limited slip. I do mostly street driving but I use 4 wheel drive quite often. How hard/expensive is it to turn my open rear end into LS?
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Old 01-18-2005, 06:09 PM
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Limited slip: You are MUCH more likely to spin out entirely in the snow and ice (everyone SAYS that they'll ease off the gas but no one does hence the invention of ABS). If you're talking off road the OEM is not that good-it won't mean the difference between getting stuck or not -particularly if you have 4 wheel drive). All that being said, I would get it with a 4X2 as a "poor man's 4X4" but I'd put the money toward a better sound system or something unless I did SERIOUS off-road in which case I'd get a on demand locker. IMHO. Unless you did it yourself, I believe it would cost close to a grand to get LS now.
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Old 01-18-2005, 10:36 PM
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so an open differential is actually better in snow/ice/mud than a LS?
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Old 01-18-2005, 11:07 PM
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The limited slip diff is a good compromise between a full blown locker and the open. I've had trucks with open diffs and my current truck is factory LS, and it is a vast improvement over the open. I rarely need to engage the t-case now whereas with my other rigs it was a common occurance b/c of the open diff. They are infinitely better on ice and snow/mud than the open unit. Just don't have the cruise on when you're on an icy highway, or it will swap ends on you. As far as getting one installed, it should be less than a grand, but there are others on this site that could probably pinpoint cost for you better than I. And from what I've read over the years, the aftermarket units seem to hold up better than the factory ones.
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Old 01-19-2005, 02:09 AM
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Quote:
Originally posted by kbldawg
so an open differential is actually better in snow/ice/mud than a LS?


As stated its easier to get sideways going down the road or when making corners when on wet or icy roads. Its better when you need to try and go through snow or mud, but slippery surfaces can get dicy at times. The cost (depending on what LS unit you go with) will run around $600/axle. Thats usually about the ballpark for parts and labor, but obviously this is just a range to look at.
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Old 01-23-2005, 01:25 PM
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Post Traction Management System

When will FOMOCO get off their duff and offer the Traction Management System that is available to class 8 vehicles by Meritor/Wabco?

The TMS utilizes communication between the ABS/Brake Computer and would use the present open differential and eliminate headaches and expense of maintanining mechinical differential devices for improved traction.

This would be great for 4WD applications and further propel Ford, once again as an industry leader in light trucks and sport utility vehicles.

Any FOMOCO design/engineering people listening?
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Old 01-24-2005, 11:59 AM
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I really don't like the idea of a traction control system on a 4x4 truck. It is really just something else to break. I just fought that battle with a GMC pickup I had. It had that stupid Autotrac on demand 4x4 system and it was a real piece of crap. If you want that stuff on the high end SUV's and such that's fine because if you are driving one of those you probably have the money to just take it to the dealer when it dies. I grew up driving pickups and the reason I have stayed with them is that I like having control over what the thing is doing. I went back to the ford I have now because it at least had a lever for the 4x4 even if the front diff is auto locking.

Oh well I have ranted long enough on this one... well one more thing.


The real joke here going back to GM for a moment are those people who bought H2's and actually tried to take them off road. They are spending a lot of money having front diffs and tcases rebuilt because they had the same crap in them my GMC did.
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Old 01-24-2005, 11:59 AM


 
 
 
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