Need help identifying my axle

Discussion in 'Got gears?' started by LAKOTA, Sep 14, 2004.


    LAKOTA Sungakan yankahaypi mita

    Below is the actual location of the letters/numbers I have found on my axle. The bottom picture is from Steve Dove's book. I cannot find the part number code or the manufacturer code (see Doves diagram below). Is it in a different location from the letters/numbers I have located? What do the letters/numbers B268/9792977 identify? The car is a 68 GS. The letters/numbers on the tube are 67? WD

    Thanks for your help,



  2. GStage1

    GStage1 Always looking for parts!

    Maybe you had a light stamping so all the letter(s) and/or number(s) don't show up. I have seen this many times. Some rears did not have any numbers at all on the tubes.
  3. monzaz

    monzaz Jim

    number stamp on tube

    If that drawing is correct you are looking in the wrong area according to the picture it should be on the other side on the front of the tube (passenger side front tube between the cast center and the spring perch unless buick puts them in a different spot... ??? Jim

    LAKOTA Sungakan yankahaypi mita

    Thanks George/Jim.
    Jim you are not reading the diagram wrong. That is the general location where I found the stampings. With the W stamping I assume it is a posi, but when I lay down a patch of rubber the passenger wheel is consistent while the drivers side lays down for a short (very short) distance and then stops. It could be the unit needs repair but at this point I do not even know what it is. Any further help will be appreciated.

    My questions;
    1. How do you determine a posi unit without the stamping?

    2. How can you determine the gear ratio without the code?

  5. monzaz

    monzaz Jim


    Well you can open the rear and that will tell you everything from the posi to the size to the gear ratio. Jim
  6. rod61727

    rod61727 Member

    please explain in further would be great...posi vs non posi...what to measure or count, etc.(for the novice)...thanks
  7. monzaz

    monzaz Jim

    rearend ID

    First take the cover off and drain fluid... Probably needs to be changed . The fist thing that should be evident is some sort of spring system in the spider gear area(center hole/ window where the cross shaft goes through with the smaller gears(we call them side gears and even smaller spider gears 2 each)) if there is then it is most likely a posi of some form. clutch, cone or other. If it does not and both wheels spin same direstion look for a weld job on the spider gears that is bad. poor mans posi we call that. as for id ing the gears ...most of the time the side/edge of the ring gear has numbers on it try to find them by turn and wiping with a rag until you find them. if you do not find them they are probably on the back of the gear that is mounted to the posi ring gear carrier and would need to be disasembled to see. (most are on the outer edge diameter of the gear though) (12 bolt put them on the back GM earlier years) you should find some numbers like a part number 6-7 digits maybe and a couple of 2 digit numbers these are the ones you want example 41 10 (4.10 gear) take the larger number 41(ring gear teeth) and divide by the smaller number 10 (pinion teeth) and you will get your ratio. hope this helps. let me know if you run into any probs. :TU:
  8. Mike Trom

    Mike Trom Blah, Blah, Blah

    The standard gear ratio for a '68 GS400 with auto tran is 2.93 with a performance option of 3.42.

    If you jack your car up with the rear wheels off of the ground you can spin your rear tire by hand and count how many times the drive shaft goes around with one complete rotation of the tire. A 2.93 ratio would have the drive shft turn almost three times for one complete turn of the rear wheel. This should give a ball part estimate.

    As for checking for posi I thought that if you rotated one rear tire, the tire on the opposite side would turn in the opposite direction. This would indicate a posi rear. (I may be wrong with the posi check trick). From your post it sounds like you have the standard non posi 2.93 axle.

    I have attached a chart from the '68 Chassis service manual.

    Attached Files:

    • ax.jpg
      File size:
      41.3 KB
  9. GStage1

    GStage1 Always looking for parts!

    Here is the way to review your rear axle, sure fire way, no mistakes!

    1. Remove the pumpkin inspection cover and drain all fluid.
    2. Look at the center area of the carrier as stated by someone else.
    3. If you have some springs in the center section, 4 coil springs indicate
    an Eaton posi carrier. If you see an "S" spring, that is a GM posi carrier.
    4. Since your car is a 68 GS, you can not assume you have a posi. It was optional.
    5. If you do not have a posi carrier, you have an 8.2" rear which uses U-bolts to hold the rear u-joint in place. Also, the 68 GS uses very rare/hard to find axle bearings.
    6. If you are going to install a posi set-up, I would strongly suggest you install the corporate 71-2 Skylark/Cutlass 8.5" rear. It is much cheaper and easier to get parts. The coporate 8.5" rears use 4 screws and 2 straps to hold the rear U-joint in place.
    7. You can not assume the axle codes stamped on the tube indicates what the rear has since it could have been changed.
    8. Jacking up the car and spinning the wheels can sometimes work. For a posi unit, both wheels should spin in the same direction. This test does not always work since one brake drum could be hanging up and the other tire does not rotate. I have had this happen about 3-4 times in cars in the local salvage yard. Also, if the posi clutches are in poor condition, your tires may not spin in the same direction.
    9. The reason for the going to the 71-2 Skylark/Cutlass 8.5" rear is you can find good posi units and gears from any GM car/van/truck from 71-89 with the same 8.5" center section. I usually have the best luck finding them in the 80-89 full size GM station wagons.
    10. See this for more info
  10. LAKOTA

    LAKOTA Sungakan yankahaypi mita

    Thank you for the information. This is what I have been searching for. George I took a look at the information you have made available...great service and I would like to help support its further use. I will be in touch. I am beginning to think my aviator should have a stamp that says[size=+1]apprentice reply at your own risk. [/size]

  11. GStage1

    GStage1 Always looking for parts!

    Most welcome! We all have to start somewhere and hopefully this info will help save you money and prevent costly mistakes. :beer :TU:
  12. rod61727

    rod61727 Member

    Have a rear end(# on housing is 1373437) out of a 68 Electra225 which had a 430 with TH400 (Aluminum tag has #215332 and B1 followed by 68...(maybe for FEB 1, 1968?) and also the number 507...can you tell from these if it is a Posi? Was the 430/TH400 combination in an Electra always a posi rear end? Any info would be appreciated...Thanks
  13. monzaz

    monzaz Jim


    I know alot of you guys what to now if a certain rear is posi or not and number will tell you if that particular HOUSING had one from the factory but over 30 some years thing break and people mess with rearends so if you really want to know what is in the rear you must check the insides for absoluteness... GStage1 can give you all the numbers he wants but that still will not tell you if it is a positraction you have ONLY that it is supposeto with that housing... Good luck with all these rears remember its suppose to be fun. Knowing how to physically figure a posi rear from the outside will help you in the long run NOT to get taken by someone who says it is a posi (CHECK IT OUT) be sure, Jim
  14. LAKOTA

    LAKOTA Sungakan yankahaypi mita

    I appreciate your help. I am in a learning process and ask questions that are elementary to a educated person. I believe those that posted a response (to my question) in this thread responded correctly. One can interpret my questions in different ways. It is difficult to answer a general question in specific terms. And I appreciate all the help I can get. What I have determined (from the generous people who responded) my unit is a non posi. I cannot find the numbers to determine the ratio, and do not want to take it apart. But, I can count the teeth on the gear. So I have one remaining question.

    Which is the pinion gear, and where is it located in the housing?

    I can assume this answer just by the configuration. But, my assumptions in the past have put me in hot water to many times.

    Thanks for the assistance.

  15. Mike Trom

    Mike Trom Blah, Blah, Blah


    If you do not want to take it apart and count the teeth just jack it up, spin one rear wheel (1 rotation) and count the number of times the drive shaft turns. This will give you a ball park figure on your gear ratio. If you want to find out exactly what your ratio is, count the teeth.

  16. LAKOTA

    LAKOTA Sungakan yankahaypi mita

    Thanks...I have finally determined the rear is the standard 2.93 peg leg. And I can now identify similar axels. I truly appreciate all those who responded.


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