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-   -   "Anti spin differential" - Why do I need one? (http://www.ramforumz.com/showthread.php?t=82945)

Frank Drebin 05-19-2011 09:48 AM

"Anti spin differential" - Why do I need one?
 
So I had a couple of deals fall through on me yesterday, so I am still in the market for a 2011 Ram.

My 03' had the posi rear end...now 8 years later it is an option?

Why is something like this good to have? I know it sounds like a dumb question but help me out here. To me its a non issue but the father in law who is a mechanic says its a must have.

Thanks

RedDodge 05-19-2011 09:58 AM

In my opinion it's a must have as well...and you'll know it the first time you have to step down when the roads are damp.....With the power of the Hemi and only a one legger, that rear tire is going to spin, you'll have no grip and won't be able to merge into traffic....with my 08 I always had to put it in 4x4 for those situations.

Now granted, you can't pounded it even with the posi because then you'll spin both tires but you certianly have 90% better traction with it.

And of course if your ever going to go 4 wheelin, without a posi you won't be able to do half as much.

Turbovsix 05-19-2011 10:18 AM

If I had it to do all over again, I would have DEFINITELY picked a Ram with the limited slip gearset. I didn't realize that my 3.55's didn't have limited slip until well after I bought the trunk (I made an ASSumption there that it had limited slip).

I personally don't care for the intervention of traction systems as I find they are too intrusive and hamper driving in certain situations. Not saying they're bad all around, but I'd prefer to have the LSP kick in and then have the traction control engage at a higher threshold.

Basically, you're running around with two open diffs on these if you buy the 3.55's, and I personally think it's stupid that Dodge didn't include the lsp on the 3.55's - I guess it's a cost-savings opportunity for them, and they figure that most folks nowadays are happy with the electronic traction control.

Just my opinion natch -

Frank Drebin 05-19-2011 10:32 AM

Quote:

Originally Posted by RedDodge (Post 528874)
In my opinion it's a must have as well...and you'll know it the first time you have to step down when the roads are damp.....With the power of the Hemi and only a one legger, that rear tire is going to spin, you'll have no grip and won't be able to merge into traffic....with my 08 I always had to put it in 4x4 for those situations.

Now granted, you can't pounded it even with the posi because then you'll spin both tires but you certianly have 90% better traction with it.

And of course if your ever going to go 4 wheelin, without a posi you won't be able to do half as much.

So in 4X4 without the limited slip I'll only have 2 opposite corners grabbing? With limited slip I'd have both rear wheels working for me as well as 1/2 front ones?

I had absolutely 0 traction problems with my 03, I mean 0. I couldn't spin the wheels without a brake torque. Not as much fun to drive. I don't mind the rear end breaking loose once in a while, know what I mean?

wannab 05-19-2011 10:35 AM

I did a little test with my 2011 Sport, 3.55 rear, did a power brake and left two black marks on my drive way. Others who have taken there 3.55 rear trucks to the track are stating smoking both back wheels.

RamMan27 05-19-2011 10:50 AM

I really wish I joined this forum a month BEFORE i purchased my Ram. Some very good information on here that would have been nice to know before hand.

FireWire 05-19-2011 12:00 PM

My 3:55s haven't caused me any problems as far as getting around even though we've had lots of snow this winter. I didn't join the forum untill after getting the truck either.I would have made sure I had LS if I knew my truck didn't have it.
You'de think it would be standard on a 390 HP vehicle.

Jeff

herc 05-19-2011 01:41 PM

It's a misconception to think of an open diff as only powering one side. No one directly said that here, but I know lots of folks think that from conversations I've had.

In an open diff, each side gets exactly the same amount of torque, no more or no less (not including a tiny fraction caused by the gearing geometry itself). Also, for a given input (drive-shaft) speed, the COMBINED speed of the two sides will be the same. So, during normal driving down the highway, both wheels are equally powered, at the same speed.

The problem is that since neither wheel can get MORE torque than the other, and since a free-spinning wheel can't accept any torque, the non-spinning wheel doesn't get any either. The free-spinner's speed just increases to twice the speed as would be if both could turn. With the LS, the spinning side uses some technique to grab onto the other side and pull it along, thus transferring EXTRA torque to the side that actually has more traction. For anyone that's into learning about stuff like this, the howstuffworks.com website has TONs of info.

I don't have any scientific testing evidence, but I would think that without an LS, if you could punch hard enough to break both wheels loose at the same time, they would both continue to spin. As one gets more traction than the other, it would start to slow down, speeding the other up. As long as the vehicle started moving enough while both were still spinning, you might be able to lay a good double patch. I'd suspect though that one stripe would be longer than the other.

I too am in the camp of "wish I had it", but I couldn't resist everything else about the 2011 I found on my dealer's lot, but it has the 3:55s. I'm not TOO worried about it though. My '98 didn't have it either, and I even plowed with that. The only real issues I had were when starting on wet or slippery pavement in 2WD. I figure all of the problem cases I had with the old one will be dealt with fine on the new one with the traction control.

For me, it's way better to have it, but certainly not a deal-killer.

wannab 05-19-2011 02:33 PM

My last truck 2004 Nissan Titan had a open rear. That thing only would spin one wheel. Ended up putting in a tru trac.

916Timmy 05-19-2011 02:39 PM

Let's just say this...My hemi truck has 3.21 gears. I spun the right wheel getting on the freeway the other day...uphill ramp on totally dry road. I wish mine had one!!!


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