Results 1 to 13 of 13

Thread: 3.90 gears

  1. #1
    Join Date
    Jan 2020
    Posts
    2
    Post Thanks / Like

    3.90 gears

    Hi guys,

    First post ever, I have done some research and wanted to get some additional insight on this potential gear swap I’m thinking about. I have an A8 scat, thinking about swapping to 3.90 gears to increase the fun factor. Not worried about 1/4 mile time or anything, I just have the occasional street fun when I ride with my mopar buddies. Now you guys are way more informed than me so I wanted to ask for opinions.. is the gear swap a worthy swap? Any pros/cons that come to mind? I do have a tuned PCM/TCM, would I need to get that retuned if I do the swap? What type of differences can I look forward to with the swap?

    Many Thanks!



    Sent from my iPhone using Scat Pack Forums

  2. #2
    Join Date
    Jun 2018
    Posts
    768
    Post Thanks / Like
    Quote Originally Posted by billet_6.4 View Post
    Hi guys,

    First post ever, I have done some research and wanted to get some additional insight on this potential gear swap I’m thinking about. I have an A8 scat, thinking about swapping to 3.90 gears to increase the fun factor. Not worried about 1/4 mile time or anything, I just have the occasional street fun when I ride with my mopar buddies. Now you guys are way more informed than me so I wanted to ask for opinions.. is the gear swap a worthy swap? Any pros/cons that come to mind? I do have a tuned PCM/TCM, would I need to get that retuned if I do the swap? What type of differences can I look forward to with the swap?

    Many Thanks!



    Sent from my iPhone using Scat Pack Forums
    No tuning necessary at all. Down side is gonna be say good bye to your traction. 3.90 is big jump imo.


    Sent from my iPhone using Tapatalk

  3. #3
    Join Date
    Aug 2016
    Location
    LINY
    Posts
    3,418
    Post Thanks / Like
    It's an easy direct swap. No changes need at all. If you're not chasing times, its a very rewarding mod. Traction will be become an issue. I run a 3.70 on mine with a 315/50/17 ET r. Fun factor is increased tenfold

    Sent from my SM-G988U using Tapatalk
    16’ charger Scatpack
    Forged 392 based 426 stroker, Arrington phase four Apache heads, custom grind cam , ported and matched 6.1 manifold, long tube headers , solo performance cutback ,ati pulley and pinned crank , custom cai , Tba diff brace with 3.70’s out back and 30” et r’s

  4. #4
    Join Date
    Jan 2020
    Posts
    2
    Post Thanks / Like
    Awesome, thanks for you guys' opinions!

  5. #5
    Join Date
    Jun 2019
    Posts
    218
    Post Thanks / Like
    What does the car come with stock?


    Sent from my iPhone using Tapatalk

  6. #6
    Join Date
    May 2015
    Location
    Louisiana
    Posts
    2,627
    Post Thanks / Like
    Quote Originally Posted by Grand_hustle17 View Post
    What does the car come with stock?


    Sent from my iPhone using Tapatalk
    A8 Scat Pack has 3.09, the M6 Challenger Scat has 3.90.




    Sent from my SM-N960U using Tapatalk
    2016 Challenger SRT 392, A8, Technology Group

  7. #7
    Join Date
    Jun 2013
    Posts
    1,594
    Post Thanks / Like
    I regret my 391 but then again I'm a 5speed. If I had one more gear I bet that would make me change my mind. Doesn't really apply to you but you will love it. Best mod I've installed

  8. #8
    Join Date
    May 2015
    Location
    Louisiana
    Posts
    2,627
    Post Thanks / Like
    For Scat Pack or any A8 with 3.0X gears, if you want to know what it will be like on the highway going to a 3.90, just get out there in 7th gear instead of 8th and it will be almost exactly the same. Yes, 7th with a 3.09 is the same as 8th with a 3.90. Gives you an idea what the rpms will be like and if that will work for you.


    Sent from my SM-N960U using Tapatalk

  9. #9
    Join Date
    Aug 2016
    Posts
    535
    Post Thanks / Like
    A8 changing from 3.09 to 3.90 will increase 500 RPM in 8th gear.

  10. #10
    Join Date
    Jun 2019
    Posts
    218
    Post Thanks / Like
    Im assuming this kills 1/4 to help top end?


    Sent from my iPhone using Tapatalk

  11. #11
    Join Date
    Aug 2016
    Posts
    535
    Post Thanks / Like
    No, 3.90 will gain .2 in the 1/8. back half will not change
    Likes Jay Z, Grand_hustle17 liked this post

  12. #12
    Join Date
    Jun 2019
    Posts
    218
    Post Thanks / Like
    Quote Originally Posted by MXS67454 View Post
    No, 3.90 will gain .2 in the 1/8. back half will not change
    Gotcha.. seen one vid, guy ran [email protected] I was a tad intrigued. I currently run 7.4 in the 8th but at 92-93mph. Made me raise my brows lmao. Any full 1/4 testing lurking around?


    Sent from my iPhone using Tapatalk

  13. #13
    Join Date
    Feb 2017
    Posts
    37
    Post Thanks / Like
    I also run the 3.70 gears in my Scat and according to the in car timer I went from 12 0s to 11 7s in the quarter mile, now I haven't been to a track, I am going by the in car timer



Tags for this Thread

Share This Thread

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •