Rear Differential Identifiers??? Manual vs Automatic

Posted by robertbaxley03, May 24, 2012
Drivetrain Tech - 4G63 transmission, clutch, flywheel, driveshaft, gears, differentials, transfer case, shifter, etc.

  1. robertbaxley03

    robertbaxley03 Moderator

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    Prince George, Virginia
    I have been shopping for a four bolt, and will be picking it up Saturday. I do trust the gentleman that I am picking it up from, but I must check the rear myself. I am wondering the means and ways of identifying the difference from the auto 4 bolt rears to the manual rears. Also a quick way to determine 1g or 2g. Here is what I have come up with so far.

    1G cars have cups that are held to the axles by bolts.

    2G cars have a rear axle that is held in by a nut. The axle slides into the diff, the wheel side of the axle is slid through the knuckle assembly and held in by a nut. This is much like the front axle design.

    1g 90-91 rear service info.

    [​IMG]

    2g 97-99 rear service info.

    [​IMG]

    One sure fire way to check the rear is to count the ring and pinion gear teeth. By doing this you will verify and have no doubt of what rear you are getting. You can see above that all years (90-99) use the same gear reduction type. All manuals use a 3.545 reduction ratio while all automatics use a 3.307 reduction ratio. Drive gear teeth and pinion gear teeth vary based on AT or MT and viscous LSD or conventional diff. Use the chart above to find out what diff is in front of you.

    I do not know any of the codes on the rear diff covers. I know that the combination on the rear diff cover is not a sure fire way to check the diff, but it would be a good fast check. If you know the codes (B1G, B1H, B1J) and which vehicle they belong to, that would be great. Any additional info would be great. Hope this information helps others and I know it helps me.

    Robert
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  2. robertbaxley03

    robertbaxley03 Moderator

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    Prince George, Virginia
    Thanks for the replys and checking the parts that you had. From the info that I have gathered all the above information is correct. There are some above that I would like to find out what they belong too. Once we can verify this, I will update the origional post.
    Thanks again.

    So far I have come up with the following info. This information was compiled by talking to other DSM'ers and getting them to look at their diff.

    Another way to tell the difference between a 1G and 2G differential when it is out of the car is.....

    "The 2G bolts up with three bolts on each side of the nose cone and two on the rear cover. The 1G bolts up with two on top and one on each side of the housing. Then it has two on the cover just like the 2G." (1gkfwd link forums)

    If you are lucky enough, the diff will still have a sticker. This sticker will state the reduction ratio. This is a good Identifier of what car it belongs to. Keep in mind that covers can be changed. Look at this link for a picture from WES_393 on Tuners

    http://www.dsmtuners.com/forums/152988201-post3.html

    1G AWD Auto - 3 bolt LSD - J1G

    1G AWD Auto - 4 bolt LSD - J1H (2highpsi and 1gkfwd link forums)

    1G AWD Manual - 3 bolt LSD - B1G

    1G AWD Manual - 4 bolt LSD - B1H

    2G AWD LSD Auto - JFH (1gkfwd Link Forums) BFB (WES_393 Tuners)

    2G AWD LSD Manual - BFH

    Diffs that we still need to identify are

    All Conventional diff models. (There are two types of diffs. One is the LSD's which seem to be the most common and conventional diffs which I have yet to see)

    All 2G models

    Please verify that the numbers you post are correct by either counting the ring and pinion teeth or by using the diff in your car for a period of time with no ill effects. I am not asking people to open their rear diffs if they are in use on the car, just rear the numbers and post them up.

    Robert
    Last edited: May 25, 2012
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  3. WES_393

    WES_393 DSM Wiseman

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    Black Forest, Colorado
    For 2g's this is what I have gathered.

    2g LSD Manual: BFH

    2g LSD Auto: BFB

    Not sure about 2g Non-LSD.

    The rear diff cover will state the reduction ratio right after the Japanese characters. That should make identification much easier.

    Attached Files:

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  4. robertbaxley03

    robertbaxley03 Moderator

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    Prince George, Virginia
    Can you verify the BFB number for the Auto LSD???? Just asking because there is another member with a 2G Auto LSD diff with the number code JFH???

    If you did post the correct numbers, what year model car did this diff come out of if you know????

    Thanks for your input.

    Robert
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  5. i3oi3c78

    i3oi3c78 Proven Member

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    What if the diff. has a different cover on it? How can you identify what diff. you have?
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  6. GRAVEDIGGER

    GRAVEDIGGER Proven Member

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    Uniontown, Ohio
    Pull the diff cover and count the teeth on the ring and/or pinion.
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  7. i3oi3c78

    i3oi3c78 Proven Member

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    Holyoke, Massachusetts
    I was thinking that was the only way. Thank you for the help.
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  8. robertbaxley03

    robertbaxley03 Moderator

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    Prince George, Virginia
    This is a good question!!! The covers can be changed over and/or swapped, so just the number on the case is not always a sure fire identifier. If the case has grey sealant, there is a good chance it is the factory sealant. If there is any doubt, you will have to pull the 8 bolts and count the teeth like mentioned above. Use the service manual (or images above) to find out which diff you have after counting the teeth.

    Robert
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  9. ARFWD

    ARFWD Supporting Member

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    I also added the 1G 3 bolt non lsd on link. The one I have here is B11.

    To varifiy that the cover is correct counting the teeth is a for sure way of knowing. Also youll be able to see the Vicious in there to know if its LSD or not. Other way of checking that is the non lsd axle will fit in both sides.
    #9
  10. NHerron

    NHerron Proven Member

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    I want to contribute as much as I can to this since this subject seems very confusing.

    In the first post, second picture, it says Conventional Diff A/T - 3.545 and Conventional Diff M/T - 3.307. This MUST be a misprint because every other DSM FSM/TECH manual contradicts it. I searched around and could not find anyone with a 3.307 rear end coupled to a manual trans -and vice versa, no 3.545 diffs coupled to auto transmissions. So basically, auto is 3.307 and manual is 3.545. Nothing else.

    I also wanted to note I have a 97' GSX M/T with a NON-lsd rear end. It is labeled BFB 3.545. I have found 2G's are rare for LSD type differentials since they were only an option. And I'm not happy about it, by the way.

    SO, what we have here is a good bit of confirmation, enjoy!


    2G Viscous-type LSD differential coupled to a M/T is labeled:

    "Viscous LSD
    BFH
    ***3.545"


    Post No. 1, + Pictured

    2G conventional-type differential coupled to a M/T is labeled:

    "BFB
    ***3.545"


    Post No. 5, + Pictured
    Post No. 5, + Pictured

    2G Viscous-type LSD differential coupled to an A/T is labeled:

    "Viscous LSD
    JFH
    ***3.307"


    Post No. 1, 5, + Pictured
    Post No. 145, + Pictured
    Post No. 2

    2G conventional-type differential coupled to an A/T is labeled:

    "JFB
    ***3.307"


    Post No. 1, + Pictured
    Post No. 127

    *** = The Japanese characters
    Last edited: Nov 6, 2012
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  11. Sinister96

    Sinister96 Proven Member

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    Saint Clair Sho, Michigan
    Figured this is a good thread to post in. I have a 96 gsx auto, it has a vicious LSD, its labled JFH and it is 3.307 ratio. My problem is where do i get axles for it because graveyard says the 2g race axle they make areny the same ones i have. Mine have a tri-ball-bearing cv joint that goes into the diff. One of you guys that knows about these diffs help me out pls.
    #11
  12. UrbanSmoker

    UrbanSmoker Proven Member

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    Damnit i was sold a BFB And thought it was a LSD, as a spare, oh well
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