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3.90 LSD install and results so far

27K views 54 replies 22 participants last post by  mcm95403 
#1 · (Edited)
A little background first: Mine is a 2019 G/T Plus RWD. Prior to the gear install I had installed Flowmaster 3 chamber mufflers and ended up settling on a Mopar Performance cold air kit, aside from those 2 things the car is all stock but did have a 3.08 open rear end. In cold air one night I was able to get a 6.0 0-60 and 14.6 @ 97 1/4 going by the performance pages but was never able to repeat that. In current air temps (about 60-65 degrees) I was getting 6.3 to 6.4 0-60 times.

I found a 3.90 diff with axles on e-bay from a totaled 2016 Shaker for $789 with free shipping, so I bought it and not wanting to do this on my back in the driveway paid to have the install done - it took the shop about 4 hours on a lift. No computer mods or other work was required beyond the install of those parts. Apparently the computer now gets vehicle speed from the wheel sensors, so there was nothing to do regarding the speedo - speeds are still correct.

My best 0-60 so far in equal temps (it was 61 that evening) is 5.8 seconds - .5 to .6 seconds quicker. I haven't been able to check 1/4 mile times yet. Mileage did drop a little bit, but it's still averaging 30-31 cruising @ 65 and that's not on flat ground. At 55 it will get 36-37. Climbing rolling hills is MUCH easier. Before on rolling hills at a 65-68 mph cruise, the instant mileage would drop to low teens but it's now high teens to 20 mpg instead. I credit the extra toque multiplication of the gears for this. Climbing steeper hills or bridges is also greatly improved and it no longer drops down a gear or two to maintain speed. Punching it at 65 on level road and counting one thousand one, one thousand two gets me to 83-84 mph - passing on the highway is certainly no issue :)

The only problem I've found is that hammering the throttle at low speed - say under 15 mph - gets a drop down to first gear which pegs the tach (not sure but it might be breaking the tires loose), the rev limiter kicks in and it falls on its face, then it upshifts and goes as expected. I think this is a programming problem that can be fixed with a tune. Later down the road I'll do that and also make sure to include tuning for the other mods.

My goal was to get sub 6 second 0-60 times, run at least 100 in the 1/4 and if possible break 13.99. Just going by what I have so far I think this will do that and a tune should certainly put me at or better than my goals.

Oh, and yes, it will now light BOTH tires - time for stickier, wider rubber than the stock 20" Goodyears.

PS, one thing I forgot to mention: When driving like a "normal" car, it goes into 2nd at 5 mph, 3rd at 10, 4th at 15, 5th at 20 and into 6th just past 25. It's pretty funny how many shifts it does at such low mph.
 
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#5 ·
Nice write-up! [emoji106]


Does your car have 18s or 20s?
All GT RWD come with 20's.



Interesting..this is the first confirmed installation of a 230mm LSD ZF differential in a 6 cyl car that I've seen .
You can get it factory installed by ordering a GT with the Performance Handling Group. It will have a 3.09 not a 3.90 but will be LSD and the same 230mm from the Scat Pack.




Sent from my SM-N960U using Tapatalk
 
#31 ·
You selling that 3.90 by any chance? I just got a 2018 challenger t/a 392 and been doing some research about the 3.90 lsd on 6.4s and lots of people have been loving it, my question is, what good does having a 3.90 lsd do to your car, like does it gain any Hp or what? I’m still researching though.
 
#8 ·
Were they RWD GT's?

A Guy
 
#11 ·
I was replying to mcm95403 saying there were GTs on the lot without 20" wheels ;)

A Guy
 
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#18 · (Edited)
Follow the build on ....
instagram : @Project_slow_six and YouTube: Project Slow Six

I never had a chance to test mine N/A. I swapped in a 3.70 manual hellcat diff and 230mm axles Dec 2018 after I was boosted though. Went from a 2.62 open diff....ran a 12.3 in the 1/4 mile with the 2.62 open diff. on the stock 17" Michelin's peddling it off the line.
 
#19 ·
I had a chance to get a good full run on a 50 degree night. I still had about a car length of wheel spin. 0-60 came in at 5.6. 1/4 mile time was 14.2 @ 98 mph, 0-100 was 14.3. At this point I think sticky tires alone would get me at least another 1/10th if not 2/10ths. I may yet go ahead and get a tune to make up for the Flowmasters and Mopar CAI. Pretty sure that would get me to my 1/4 mile goals.

Now if I could just stop thinking about the twin turbo setup.............
 
#20 ·
A tune will definitely put you were you want to be. I can't suggest this enough for the V6s. I recommend Hemifever over Diablosport's canned tunes as Hemifever basically creates a tune specifically for your mods. On a 91 Octane and TCM tune along with my mods, I saw my 0-60 numbers drop significantly running constant 5.2-5.3 with my staggered setup and a 14.0 at the track before I got the wheels and the TCM tune. The car I ran was a de-catted RT with a tune. I'm sure I can finally break into the 13's with the new setup

I'm glad I saw this though. I was always curious to know if it's really worth the money but it seems like it obviously helped your numbers. I'm looking at getting the 3.09 diff though.

985569
 
#23 ·
Mine had the 3.09's factory - I don't know how anyone could say it's too much. The 3.90's "could" be considered too much but it depends on what you're used to I guess. They did drop the mileage and it does turn 2100 or so at cruise, but I pretty much cruise at the speed limit (65 or 70 here) so that doesn't really matter. Sure is responsive though! :)
 
#24 · (Edited)
Well, for what it's worth, My 2015 SXT+ had an open 3.07 differential. I just purchased a used 3.09 LSD and axles to put into my car later this spring/summer. Gearing is almost identical, so it should not be more than what the car is "used to". I do not have a tune, but I do have other bolt-ons (see signature).
I'm hoping that the LSD adds to the grip at launch and I knock some time off my 0-60. Otherwise a fun project to do, I hope.

I went with the 3.09 LSD over the others because I wanted the daily driver aspect to be the same, such as mpg.
 
#27 ·
I know a 3.6 with the 3.90 gears would be a lot of fun to drive. I am planning to do a differential swap in the next few days. I have a 3.90 waiting, just wanted to get to the next maintenance interval so I can do it while I have the car on the lift. My Challenger is a 5.7, so I realize that first gear will run out really fast going from a 3.07 to a 3.90, but I have always enjoyed the way a gear makes a car run.
 
#33 ·
My '14 SXT with open 2.65 axle and NAG1 trans would click off 6.1-6.3 second 0-60 times from day 1. I always wanted to install the 3.06 axle but a lot of research back in 2014 made it seem extremely difficult.
 
#39 ·
Sure, ask away.

These v6 might sound like sh it but with vvt and 4 overhead cams they run pretty good (considering their displacement AND their efficiency)

There are a couple guys currently arguing their ability to withstand boost on HPT in the gas section

How many members here are throwing boost at a 3.6?
I love the way mine sounds with the Borla S-Type system. If I were a little younger I might go with the ATAK instead, but this and the open element T/A fresh air setup sounds great.
 
#38 ·
These v6 might sound like sh it but with vvt and 4 overhead cams they run pretty good (considering their displacement AND their efficiency)

There are a couple guys currently arguing their ability to withstand boost on HPT in the gas section

How many members here are throwing boost at a 3.6?
 
#41 ·
There is at least on member throwing 12psi at one. I've heard of a few others doing really well with it. It seems they hold about as well as the 5.7.

"
TL : DR DYNO DAY 2018 SXT+ 3.6L - Ripp/Vortech V3-Si - 12PSI

There are few tuners around here so it was hard to find a trustworthy one but had heard good things about Pure Fabrication in Panama City, FL so we trekked out there this morning and I put "Renegade" in the capable hands of Joey and he asked me a bunch of questions while looking through the tune and getting it ready to dyno. As a former tech, sometimes it can be a pain to have a customer hovering but he patiently answered all my questions and actually listened to my driveability concerns. When he had enough info to get started I headed out to lunch and let him do his thing.

The end result was a much smoother throttle response and more linear boost throughout the entire RPM range. Now, the numbers!!
First pull - canned Ripp tune: 437whp @ 6600 RPM
Final pull - Pure Fab tune: 449.3whp @ 6600 RPM

For reference, a stock SXT 3.6L puts out approximately 275whp @ 6000RPM
A stock Scat Pack 6.4L puts out approximately 435whp @ 6000 RPM "

DYNO DAY! - (and back-story) - skip to dyno section if you are the tl:dr type | Dodge Challenger Forum (challengertalk.com)
 
#49 ·
Is there a different between the rear diff if its off a manual or auto?
The manual gets a 3.90 LSD rear. This is probably too low for an A8, some report 1st gear on an A8 is worthless with this rear gear. Some like it. I'm on the too low for an A8 side of the opinion, I have an M6. Street use, only on nice days.

Look at the transmission gearing (A8 vs M6) and think about your goals for your car.

On edit: The dumbest question is the one that is not asked, even if others have asked it 100 times before.
 
#53 ·
I personally wouldn't worry about upgrading the head bolts if you are going to keep it 10psi and under.

The stock driveline should handle the power. Especially if it's 2015+ and you don't plan on hard launches with wheel hop.

Brakes are probably fine too but never a bad idea to upgrade those.
 
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