Welcome to InfinitiScene.com - Home for Infiniti QX and Q enthusiasts!
You are currently viewing our forum as a guest, which gives you limited access to the forums. Why not register on our forums and gain the extra benefits that our regular members enjoy?

  • Enthusiast Owned and Operated!
  • Registraion is free.
  • You will be able to post, message, and interact with other members.
  • Our forum is full of friendly, knowledgeable members and staff.
  • Plenty of money saving opportunities from write-ups to maintenance help.
  • Create a garage and show off your ride and specs.
  • Opportunity for ad-free viewing.
  • Plus much more!

Registration is fast, free, and easy, so stop being just a guest and become one of our newly registered members today!

FX45 LSD Options

Discussion in 'FX (03-08) - Engine & Drivetrain' started by Dr.2K, Dec 8, 2007.

  1. Dr.2K

    Dr.2K iS Doctor on Duty iS VIP

    Santa Clarita, CA
    2005 FX45
    Ok i need to know if there are any options for the 45 LSD? I did read some stuff on the org a long time ago but nothing really came from it. I know rookie has had work done on his LSD. Need some expert advice, Viet time to chime in and start class :biggrin:.

     *Registered members do not see this ad, register today!

  2. rookie

    rookie Premium Member Premium

    Hardly an expert but I'll provide some explanations which is something that did not happen in the past on this subject.

    Firstly here's the Nismo Diff package that was attempted to be installed.

    Starting from the left you'll the stubby components standing up are the output shafts/axle stubs/side flanges depending on who you talk to. Than you see bearings and seals, some bolts, and than the diff.

    Here are the details posted.
    • Clutch-Type Design with 10 clutches on each side
    • Constructed with four pinion gears for improved strength (stock LSD has two pinion gears)
    • 3-stage initial torque selective adjustable without disassembly
    • Plate-type 1.5-way LSD can be converted to 2-way LSD
    • Compatible on all 350Z & G35 Manual Transmission (with or without stock LSD
    • Compatible on 350Z & G35 Automatic Transmission when upgraded Final Drive gear is used (3.5, 3.7, 3.9)
    • Designed as a multipurpose LSD for city driving
    • Increased power for track or autocross conditions
    • 2 x Output Shafts
    • 2 x Differential Side Oil Seals
    • 2 x Differentail Side Bearings
    • Differential Bolts
    • Instructions
    • Differential Oil
    Note the compatability part. 6MT G/Zs come standard with a 3.5 final drive. 5ATs come standard with a 3.3 final drive. The 3.3 Final drive ring is either thinner or thicker than the other final drive ratio rings. Here's a ring and pinion if you don't know what one looks like.

    One thing not noted in the Nismo LSD kit is what the vehicle came with stock. Either an open diff or a factory viscous LSD. Open diff configurations have axle stubs that are equal length on the inside of the diff. vLSD configurations come with offset axle stubs on the diff inside. The Nismo comes with new axle stubs which are offset length wise. If upgrading an open diff, to any other LSD kit new axle stubs are required.

    More tomorrow. :)
  3. asherchy

    asherchy Premium Member Premium

    im now more confused than i was 2 minutes ago...
  4. rookie

    rookie Premium Member Premium

    It'll all make sense. ;)

    FX RWDs come with a 3.3FD (FD=Final Drive) FX AWDs come with a 3.7FD. AWDs have 2 differentials, 1 front 1 rear.

    Front final drive info.

    Rear final drive info.

    Below are some pics of the FX rear diff, G/Z open rear diff, G/Z vLSD rear diff


    G/Z open diff. Notice part 9 on this cross section vs the FX part 9. The front companion flange that mates to the drive shaft is different between the 2 platforms even though the casing is essentially the same.

    G/Z vLSD diff. Notice part 1 on this cross section vs the last 2 cross sections. The axle stubs/output shafts/side flanges length on the inside of the diff are offset vs equal length on the open diffs.

    Attached Files:

  5. OP

    Dr.2K iS Doctor on Duty iS VIP

    Santa Clarita, CA
    2005 FX45
    Thanks for the explanation Viet, it does hel a bit. So what LSD do you have on now? the vlsd? or some custom one?

    I'm assuming that the 45 comes stock with the open lsd. So is there a way to fit the nismo lsd with on a 45? I know its not a direct bolt on but would there be a lot of custom work needed to make it work? or even the vlsd?

    edit...you beat me to my reply Viet.
    Last edited: Dec 9, 2007
  6. rookie

    rookie Premium Member Premium

    Still got more to explain. Just didn't want the post to be too long. :)

    Below is our rear axle assembly. Notice there is a different side flange for the FX45s, it also specs a bolt instead of a nut and bolt for the VQ35s

    I never was able to quite understand the explanation in the past about what didn't fit until I saw Humberto's exhaust pictures.

    I believe the VK45 bolt pattern on the sideflange is larger than the FX35/G/Z.



    Info from everythinginfiniti on the difference in parts. I don't see a different part for 35 RWD or AWD so we can assume the 35s use the same axles. 45s, have their own parts number.

    Info from everythinginfiniti on the rear hubs (part 7) which is the other end of the rear axles. Would be interesting to know if there is a different part number for the AWD vs RWD. I don't think there really could be a difference in parts at the hubs.

    Attached Files:

  7. rookie

    rookie Premium Member Premium

    Since we've covered most of the components involved we can go over the hurdles.

    For AWDs
    It's not full time AWD so having a full locking diff in the rear probably isn't too big of a deal. I would check with some AWD guys (evos/stis/etc) and get their input on this.

    45 axles being different flanges to the RWD versions poses a problem.
    ~You need the offset axle stubs to fit into the LSD correctly. Making an adapter from the axle stubs to the axles could be a solution but it would need to a very strong design or you could sheer off bolts or whatever was used to mate the 2 together.
    ~Making offset axle stubs that fit the 45 axles could be another solution but again, those custom axle stubs would need to be made very well.
    ~Use 35 axles if the rear hubs are the same. I don't think they'd use 2 different hubs depending on the engine used. The weakest point of the axles seems to be at the hub. I've snapped it there, as well as other boosted G/Zs. All of these failures have been on hard launches at the drag strip so daily use should be more than adequate. These cars that have snapped the axles are either heavily boosted, or running drag radials/slicks at the drag strip and launching hard. They can take the 45 power pretty easily. ;)

    So the next time someone asks if a LSD is doable, here's all the info you need. No blah blah blah they said it wouldn't fit. Explanations of the hurdles help others possibly resolve the issue.
  8. OP

    Dr.2K iS Doctor on Duty iS VIP

    Santa Clarita, CA
    2005 FX45
    Wow, thats alot of info. Thanks for the lesson professor. Now have to take this lesson and apply it to how or if I want this done on the 45. It's seems that option 3 would be the easiest to adapt but will have to check if the 35 rear axle hubs are the same for the 45. But if I want to use this application for the track and go FI at a later date then there is the concern of what happened to your rear axle. Have to do some research. Thanx again Viet.
  9. rookie

    rookie Premium Member Premium

    I don't recall anyone snapping an axle that was not on some drag style tire and launching. Mine could probably be attributed to wheel hop since my driver side rear shock was blown out. Hop hop hop grab with the drag radials is my thinking of what happened. The G and Z guys do it from doing 3-4k launches which is not likely going to happen with a 5AT. :err:

    The good thing about the Nismo kit is it comes with all new bearings and seals as well as the axle stubs needed. I started with a diff I found on my350z. The guy bought an extra 3.5 vLSD pumpkin, upgraded the FD to a 3.7 and replaced all the seals. Having started with a factory vLSD new axles stubs were not required. I eventually changed out the vLSD to the ATS Carbonetics LSD

    Read this http://www.350z-tech.com/zwiki/Limited_Slip_Differential_(FAQ)
    And this http://www.350z-tech.com/zwiki/Limited_Slip_Differentials

    The Nismo is somewhat noisy from what I've witnessed and read about. Some say different fluids and friction modifier can quiet it down.

    For any RWD FXs wanting to change their diff or final drive.

    A 3.7FD is awesome. 3.3 is very very tall when you add in our tire height, some of the heavily boosted G/Zs will use a 3.3FD since they could use taller gears to retain traction, but man it is and is still one of my favorite upgrades to daily driving.

    Getting a hold of a 3.5 vLSD equipped pumpkin would be ideal. From this point you can either replace the FD or keep it 3.5, upgrade it to a full locking diff without the need to get new axle stubs if you want to use something besides a Nismo.

    It's fairly expensive when you add everything up. But your final drive ratio is constant, it will be a shorter gear in every gear meaning you accelerate through each gear faster at all rpms. It does not make more power, it just changes the drive ratio much like using shorter tires.
  10. OP

    Dr.2K iS Doctor on Duty iS VIP

    Santa Clarita, CA
    2005 FX45
    Just curious and this is probably too easy but is there not a way to replace the flanges on the nismo or other vlsd's with the 45 lsd flanges?

    Also, the 45 has a 3.7 final drive as the faq's state but a 3.5 would be better, correct? Would I need to replace both the front and rear diff's? or just the rear? More i read the more questions i have.
  11. HumbertoCALI

    HumbertoCALI Premium Member Premium

    South Gate, CA
    2003 FX45 AWD

    Just learned something new today....

    There is a Steel and Aluminum Manfg. in Los Angeles that I know of that can probably make the Piece that is need to join the Flange. It's just a matter of how confident you will feel to have this specialty part made for your FX..

    The benefits would be great. But the down side of having something break is not worth it in my opinion..
  12. OP

    Dr.2K iS Doctor on Duty iS VIP

    Santa Clarita, CA
    2005 FX45
    :LOL: Bert, a bit timid are we? ....You'll probably get over this once you have more confident driving with your 'now' completely fixed fx!;)

    Gonna try and get this done by spring if possible.
  13. rookie

    rookie Premium Member Premium

    Remember the hurdles I said.

    Any of the full locking diffs require the offset axle stubs. Open diff axle stubs are not offset so you can not reuse the stock 45 axle stubs. Using vLSD axle stubs which are essentially the nismo axle stubs will not mate correctly to your stock axles.

    The lower the number 3.3 3.5 3.7 3.9 4.0 the taller the gear. Tall is higher mph per gear but also a bit slower in the acceleration. For boosted vehicles the taller gears help by not overpowering the tires in the low rpms, and you can stay in boost longer since the mph per gear goes up with taller gears. It's reverse for shorter gears.

    I don't think it would be a good idea to run a different final drive ratio in the rear vs the front. I have not looked up the other AWD vehicles in the Nissan family but I think most if not all the AWDs are going to be 3.7

    For custom axle stubs. They really need to be made correctly or I can see expensive repairs happening. The diffs are all in the 1k range. Removal and reinstallation of the pumpkin itself is labor intensive as is the diff install. Usually in the 5-750 range.

    Not a great pic but this is what the offset axle stubs look like. Manufacturing that in a custom diameter for the 45 axles would be expensive in my head.

    Attached Files:

    • 3-2.jpg
      File size:
      156.3 KB
  14. Old Blue

    Old Blue Member

    Spring TX
    FX 37 rwd
    Ten years later, I'm trying to do this on my FX37.

    Same song, second verse. August 2017.