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Discussion Starter #1
Does anyone know if a srt 3.06 can be put in to an RT ? Can I use all the same axles, will it all match up if I just bolt it in, drive shaft, ect.? Are the srt diff LSD, or open? Or are there other things to consider? Also I was just thinking of switching the rear end I found one for cheap off a srt charger. Do you think it will work? Also with a 3.91 what kinda RPMS you running around 100mph? I am afraid if going to a 3.91 it would be screaming with no more umph? I saw that they make a 3.23 I don't know if that would work? I would like some advise, or any comments would be helpful.
 

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Discussion Starter #2
Also what about the stock torque converter? No problems? Can I just upgrade the rear diff and do that later. I was thinking of going to a 3200 stall a long,long,long time down the road.
 

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2009 SRT-8 Getrag LSD Differential Swap Kits MPK09SRTDIFF the 3.91 is more drag friendly and a gas killer for the street...the 3.73 is more street and drag friendly so ull have the best of both worlds .. And the 3.06 is street friendly LSD ..bill sent me the info to this link a long time ago ..maybe he'll come on and explain it better then I can
 

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3.91 you wont notice 1st gear LOL
 

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Thanks for the intro Larry......

You can install a 3.06 differential into your car. You will need the differential, axles and the rear section (4 bolt) of an SRT driveshaft. The hubs are the same. All SRT differentials prior to '09 are "open" and after '09, the 6 speed differentials are Getrag limited slip.

If you opt for the Getrag, you can go with a 3.06, 3.73 or 3.91. I assume you are aware that higher ratios (210mm 2.82 R/T & 215mm 3.06 SRT) are high end gears or "freeway", while lower ratios (226mm 3.73, 3.91) are low end gears or "acceleration".....Remember, higher #s are lower ratios. The 210mm, 215mm & 226mm are the diameters of the ring gears. bigger differentials are stronger.

If you want a Gretrag, you'll need the differential, axles, hubs, pinion bolt and the 3 bolt driveshaft with the Getrag LSD coupler.
The Getrag coupler is thicker than the R/T coupler and can be added to the R/T driveshaft in place of the R/T coupler. I also recommend getting the "pink bolt" replacements for the rear coupler/driveshaft. They are stronger and are made for the increased torque of the lower gear ratio. The Getrag 3.91 LSD, axles, hubs and pinion bolt can be had brand new for about $1500. Add $500 or so if you decide to get a new Getrag rear section driveshaft. That's what I did or you can opt to get the Getrag coupler instead and mate it too the stock R/T rear section driveshaft.

As far as speed goes, with a 3.06 ratio, you won't notice a lot of difference from the stock 2.82 R/T ratio. All other things being the same, you'll notice a slight benefit in low end acceleration. Mileage difference here is negligable. The 3.06 limited slip Getrag version will allow for better grip as it's driving both wheels. Note that the Getrag 3.06 will be about twice the cost of the Getrag 3.91

At the other end is the 3.91 Getrag limited slip. This is what I have in my car now. All I can say is WOW! The added low end acceleration and grip (with good tires) is amazing. Combined with my mods makes it a beast on the streets. I run 500 rpms higher at freeway speeds with my 3.91 ratio than I did with the 3.06 I had in my car prior. I run 3k rpm @ 80 mph. IMO, the performance increase and fun factor is well worth the drop in mileage. If you spend a lot of time on the freeways and are concerned with mileage, the 3.91 might be too low. Per my EVIC, I get 20+ mpg at 70 mph all day with the 3.91 and 400 rwhp.

Get a hold of me if you have questions. I did the 3.06 SRT "open" diff. upgrade years ago, then I went with my current set up....3.91 Getrag. Having done both, I can help you with either.


Edit ....... Almost forgot, you can get 3.23 or even 3.55 gear ratios if you want. To do this, you would need to have a differential built or assembled. The gears are available through Richmond and there are several manufacturers of limited slip differentials. I believe some have installed these gears into Getrags but most rebuild the "open" 215mm SRT differentials.


Edit again......As far as the torque converter goes.....Typically, people go to a higher stall converter to improve take off or launch when mods (cam for example) change the powerband of the engine. A limited slip differential will help with that and a limited slip with a lower gear ratio will help even more. No problems running a differential gear change with the stock converter. I run a 3200 stall in my car now (Paramount Dominator) and it drives just like a stock converter on the street.

I think that covers it. Let me know if I forgot anything.
 

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Discussion Starter #6
Thanks for all the info. I'm thinking I might go to the 3.91 now. I will let you know when I do.
Bill I will pm you when I'm ready to pull the trigger.

Thx,

Rob
 

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Thanks for the intro Larry......

You can install a 3.06 differential into your car. You will need the differential, axles and the rear section (4 bolt) of an SRT driveshaft. The hubs are the same. All SRT differentials prior to '09 are "open" and after '09, the 6 speed differentials are Getrag limited slip.

If you opt for the Getrag, you can go with a 3.06, 3.73 or 3.91. I assume you are aware that higher ratios (210mm 2.82 R/T & 215mm 3.06 SRT) are high end gears or "freeway", while lower ratios (226mm 3.73, 3.91) are low end gears or "acceleration".....Remember, higher #s are lower ratios. The 210mm, 215mm & 226mm are the diameters of the ring gears. bigger differentials are stronger.

If you want a Gretrag, you'll need the differential, axles, hubs, pinion bolt and the 3 bolt driveshaft with the Getrag LSD coupler.
The Getrag coupler is thicker than the R/T coupler and can be added to the R/T driveshaft in place of the R/T coupler. I also recommend getting the "pink bolt" replacements for the rear coupler/driveshaft. They are stronger and are made for the increased torque of the lower gear ratio. The Getrag 3.91 LSD, axles, hubs and pinion bolt can be had brand new for about $1500. Add $500 or so if you decide to get a new Getrag rear section driveshaft. That's what I did or you can opt to get the Getrag coupler instead and mate it too the stock R/T rear section driveshaft.

As far as speed goes, with a 3.06 ratio, you won't notice a lot of difference from the stock 2.82 R/T ratio. All other things being the same, you'll notice a slight benefit in low end acceleration. Mileage difference here is negligable. The 3.06 limited slip Getrag version will allow for better grip as it's driving both wheels. Note that the Getrag 3.06 will be about twice the cost of the Getrag 3.91

At the other end is the 3.91 Getrag limited slip. This is what I have in my car now. All I can say is WOW! The added low end acceleration and grip (with good tires) is amazing. Combined with my mods makes it a beast on the streets. I run 500 rpms higher at freeway speeds with my 3.91 ratio than I did with the 3.06 I had in my car prior. I run 3k rpm @ 80 mph. IMO, the performance increase and fun factor is well worth the drop in mileage. If you spend a lot of time on the freeways and are concerned with mileage, the 3.91 might be too low. Per my EVIC, I get 20+ mpg at 70 mph all day with the 3.91 and 400 rwhp.

Get a hold of me if you have questions. I did the 3.06 SRT "open" diff. upgrade years ago, then I went with my current set up....3.91 Getrag. Having done both, I can help you with either.


Edit ....... Almost forgot, you can get 3.23 or even 3.55 gear ratios if you want. To do this, you would need to have a differential built or assembled. The gears are available through Richmond and there are several manufacturers of limited slip differentials. I believe some have installed these gears into Getrags but most rebuild the "open" 215mm SRT differentials.


Edit again......As far as the torque converter goes.....Typically, people go to a higher stall converter to improve take off or launch when mods (cam for example) change the powerband of the engine. A limited slip differential will help with that and a limited slip with a lower gear ratio will help even more. No problems running a differential gear change with the stock converter. I run a 3200 stall in my car now (Paramount Dominator) and it drives just like a stock converter on the street.

I think that covers it. Let me know if I forgot anything.
Where would be a good spot to get the 3.73 gears... What do I need to get if I already have the getrag 3.06 in my SRT8
 
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