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Discussion Starter · #1 ·
Dropped my '06 mag SRT8 off at the shop today and sure enough they said some diff bearings are likely the cause of the noise I've been hearing. They said that they would have to tear it down to find out exactly what needs to be replaced and that it would cost a couple hours of labor.

Now comes the tough decision...

Should I pay about $800 for them to rebuild it with new bearings, should I try and find a used replacement, or should I upgrade to the new LSD?

I don't really know where to look for a used replacement diff. Anyone know of a good website? I found 1 on ebay, but it didn't say how many miles it has on it:

300C Charger Magnum SRT-8 SRT8 Differential Axle Shafts | eBay

Then there's a "Wavetrac" LSD differential, but I'm not quite sure what it is or if it fits:
Wavetrac Differential 2008 Dodge Challenger SRT-8 LSD | eBay


As for the new Getrag LSD, what all would I need? From reading through a few websites, it looks like I will need the diff, new halfshafts, new wheel hubs and a new driveshaft. Has anyone upgraded to the new SRT LSD? If so, were there any problems with computer/abs? I have a diablo predator, so I'd be able to change the rear ratio if neccessary.

Any thoughts?
 

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I wouldn't buy a used diff, as it is liable to have bad bearings too! You never know with used mechanical parts.... I would for sure pay for the rebuild, and if you have the cash throw in a LSD!
My .02$
 

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What noise are you hearing?


I'm getting the new Getrag 3.92 LSD put in my car. If you want to go Getrag, this is what you need.

The Getrag 3.92 LSD differential brand new is a little more than what they want to charge you for your repair. ($892.00)
The 3.06 and the 3.73 are more expensive.

http://www.allusasupercenter.com/2009_SRT_8_Getrag_LSD_Differential_Swap_Kits_p/mpk09srtdiff.htm

differential - Optional gearsets are 3.06, 3.73, 3.92
hubs (2)
left axle & right axles
differential bolt


You'll need the 2009 Challenger SRT driveshaft which is the same as the R/T driveshaft (3 bolt couplers) because the new Getrag
LSDs have 3 bolt couplers.
Below - There's 2 different driveshafts. 1 for Challengers (shorter) and 1 for Magnum, Charger and 300's.
If you do thid, you need this one - Part # 5038864AB

http://www.allusasupercenter.com/SRT8_Differential_Swap_Driveshaft_Kit_p/srtdrvshft.htm?1=1&CartID=0

driveline (rear section with Getrag 3 bolt coupler)
 

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Discussion Starter · #4 ·
I wouldn't buy a used diff, as it is liable to have bad bearings too! You never know with used mechanical parts.... I would for sure pay for the rebuild, and if you have the cash throw in a LSD!
My .02$
Yeah I am pretty wary of buying a used diff too. You never know what you're getting.




Fireman, the noise I'm hearing is a humming noise that varies with vehicle speed. It also gets a little louder when under load like when driving uphill or getting on the gas a little bit. I thought it might have been a wheel bearing but it doesn't really match the symptoms. The noise doesn't get louder when turning.


So if I decide to go with the Getrag 3.92 here is what it will cost me:

Getrag 3.92 Differential -- $892.08
Pair of rear hubs -- $194.66
LH half shaft -- $224.95
RH half shaft -- $195.30
New 4 to 3 bolt driveshaft -- $568
Driveshaft hardware -- $11.60
Differential bolt -- $1.95
Shipping -- $191.12
------------------------------------------
Total -- $2279.66


That's a lot of money to spend just because 1 friggin bearing starts to go bad.
 

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That's a lot of money to spend just because 1 friggin bearing starts to go bad.
Yes it is....But it would be so much fun.....Don't forget the money spent on roasting tires....LOL!


So if I decide to go with the Getrag 3.92 here is what it will cost me:

Getrag 3.92 Differential -- $892.08
Pair of rear hubs -- $194.66
LH half shaft -- $224.95
RH half shaft -- $195.30
New 4 to 3 bolt driveshaft -- $568
Driveshaft hardware -- $11.60
Differential bolt -- $1.95
Shipping -- $191.12
------------------------------------------
Total -- $2279.66
That's what I paid. Your acceleration and traction will be AMAZING! Look at it this way........If you don't want to buy used, anything else you buy will cost at least as much if not more.

One thing....Did you check the hubs? It's possible that your noise is hub bearing related. If you can get your car on jackstands or a lift, you can run the rear wheels at low speed and see if you can determine where the noise is coming from. It may end up being a lot cheaper in the long run.
 

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Discussion Starter · #6 ·
That's what I paid. Your acceleration and traction will be AMAZING!

I know acceleration will be a lot better, but how is cruising down the interstate at 75 mph? Is the engine revving high? How's gas mileage when cruising at 75? 3.06 to 3.92 is a pretty drastic change....
 

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The gear ratio calculator has 75 mph at 2700 rpm with the 3.92. You could get a 3.06 LSD if you wanted. They're more expensive though.

Mileage? From what I hear it's better around town and a little worse on the freeway. I don't have the exact numbers yet. My diff will go in on the 14th along with the new motor upgrades.
 

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Discussion Starter · #8 ·
So I took my car into another highly respected driveline shop here in Atlanta, and they said my differential needed to be replaced. They said the diff oil had slowly leaked out of it and ruined it. I got my diff serviced at Jiffy Lube about 10,000 miles ago, even though I knew it was a gamble. Bottom line, don't go there!

I was on the fence about upgrading to the new Getrag 3.91 LSD, or just replacing with stock parts (3.06 open diff). I chose to have the stock unit replaced because it was about $1000 cheaper. The shop ordered the diff and put it in. When I was on my way to pick it up, the shop called me and told me that the new diff has a 3 bolt coupler, and the old driveshaft has a 4 bolt coupler. They said I would have to order a new driveshaft which is $700 + shipping. WHAT THE F?????????!!!!!! The whole reason I went with stock parts is because it was $1000 cheaper.

Right now, my car is sitting in the shop with then new diff installed, with a driveshaft that doesn't fit. What should I do? Should I have them take off the diff and return it? At this point, I would rather spend the extra for the 3.92 LSD. Shouldn't the shop have noticed that it wouldn't fit before they went through the trouble of installing it? Ahhhhh!!! Hopefully they will work it out with me and I won't be the one who gets screwed.
 

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IIRC, the 3 bolt rear end of a SRT drive shaft will slip right onto the R/T front section. The spline line up is tricky, as it only goes in at one indent and is a booger to hit. Patience required.
I had a Chally built tranny and front drive shaft section installed and drove home with the stock rear end.
Later had the Chally 3.06 diff installed with the rear section of a SRT drive shaft.
 

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Discussion Starter · #10 ·
Well, I picked my car up from the shop today. They were able to take the 3 bolt yoke off of the new differential and replace it with the old 4 bolt yoke from my old differential. This is awesome, because I thought I was going to have to buy a new $600 dirveshaft that I really didn't need.
 
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