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Discussion Starter #1
Hey all;

I've got a 15 5.7 Challenger with the 230mm axles...I think 3.09 open diff (8 speed).

I'd like to upgrade to the 3.90 LSD diff, but not sure what all I'd need. I know I must swap entire diff on 15+, but would I need SRT axles as well?
 

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2015 RT 5.7 M6
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Hey all;

I've got a 15 5.7 Challenger with the 230mm axles...I think 3.09 open diff (8 speed).

I'd like to upgrade to the 3.90 LSD diff, but not sure what all I'd need. I know I must swap entire diff on 15+, but would I need SRT axles as well?
Check your build sheet to confirm which rear end you actually have. I have the 3.9 with limited slip (have a 6spd manual) and I was under the impression that the 3.09 limited slip is a direct replacement? I bought a new 3.9 (similar to the 3.7 which I believe is stock on the A8) for ~$700 shipped from wholesale mopar parts and it is the cheapest one of the cheapest diffs you can get. The 3.09 are almost double that. The reason I want to go with a 3.09 as it is impossible to prevent the rear tires from spinning with the 3.9 which on the A8 makes 1st gear useless.


Actually the best person to answer this question would be Luke from Steve White.

Looks like I was wrong about the 3.7
http://www.challengertalk.com/forums/6616698-post18.html
 

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I thought all 15s were LSD. If that's the case then it is a straight swap between the 3.09 and 3.90. I just swapped mine from 3.90 to 3.09.

Sent from my SM-S975L using Tapatalk
 

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all the 5.7 + A8 are open diffs with 3.09 - FCA isn't offering the option like it was for '14 and earlier for LSD.
-same for the V6 models


Any 6.4 or SRT 6.2 SC are LSD with either transmission. [3.09 / 3.90 / 2.62 / 3.70 are ratios offered in LSD]
-the last two ratios are the A8 / M6 for Hellcat
 
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Hey all;

I've got a 15 5.7 Challenger with the 230mm axles...I think 3.09 open diff (8 speed).

I'd like to upgrade to the 3.90 LSD diff, but not sure what all I'd need. I know I must swap entire diff on 15+, but would I need SRT axles as well?
Just a question on what your end goal is as well. Eventually I'll be "downgrading" to a 3.09 LSD because if you go the s/c route your first gear will be worthless.
 

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Discussion Starter #7
I guess 3.09 LSD would be my best option, but dam its like 1400 bucks lol
 

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Discussion Starter #8
Now being a 15 with ZF tranny, I will try to find a 15+ 8spd rear diff. What all would I need, just the entire diff, or axles too?
 
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