Rear Differential Question.

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  1. Hodgee

    Hodgee Member

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    Lately i have been working on a 69 Road Runner for my brother and we recently pulled the engine to freshen it up ... it has i believe an 8.25 rear in it but i look in the 69 service manual for the b body cars and their is nothing mentioned about the 8.25 ... would this have come factory and are their any stampings that might tell me what gear ratio is in it... Please be kind as this is my first Mopar car rebuild.
     
  2. Russ69Runner

    Russ69Runner Well-Known Member

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    Post a picture would help. Think you should look at the 8and 3quarter. If you look for roadrunner rear end and rebuild. Found three different rear end's for that year. What size is the motor and that will tell a lot. Find on the web will show how to rebuild it. Dose the pig or chunk have an X on it if so it is the lightest one made. Not a four 26 motor rear end. So take some pic's please. They made these 741-742-489. I have the 741 and putting a set of 3.55 gears in it. So look up 8.75 roadrunner rear end and you will see a lot of info. Got my gear and rebuild set form doctor Diff. He helped me get the rite stuff to completely rebuild mine even axel bearing's.
     
    Last edited: Jul 9, 2018
  3. Hodgee

    Hodgee Member

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    Ill go and take a pic but i can tell you it has an 10 bolt cober on the back and not a front loader
     
  4. Hodgee

    Hodgee Member

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    Its a 383 motor
     
  5. Hodgee

    Hodgee Member

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    Here is an image.

    20180709_195600.jpg
     
  6. 69hemibeep

    69hemibeep Sponge Bob Square Wheels

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    Either the rear has been changed or you might have a recreation, tribute, clone. What are the first 5 digits of the VIN
     
  7. Hodgee

    Hodgee Member

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    RM23H
     
  8. 69hemibeep

    69hemibeep Sponge Bob Square Wheels

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    Yep the VIN says its a runner
     
  9. Russ69Runner

    Russ69Runner Well-Known Member

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    Hodgee this one for the book's. Don't know what it is out of. Some where on the pinion shaft in put their should be a number casted. You will have to do a search with that number and see what comes up. Back in the day we put a nine bolt rear end in a duster out of a Chevy pick up truck. It was a positive rear end and heavy duty so that is what we did. you may find some number's on the ring gear. That could be traced also. Good luck my friend. Russ.
     
    Last edited: Jul 11, 2018
  10. Hodgee

    Hodgee Member

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    Thank you.
     
  11. Hodgee

    Hodgee Member

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    Here's some better pics.

    20180711_195343.jpg

    20180711_195458.jpg
     
  12. dmartin

    dmartin Well-Known Member

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    Yeah I think mopar pumpkins bolt from the front at least my 8 3/4 does you may have a doosey there good luck
     
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  13. Hodgee

    Hodgee Member

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    Thanks!
     
  14. Russ69Runner

    Russ69Runner Well-Known Member

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    You will have to pull the inspection plate and look on the ring gear. If every thing is original then should be some number's their. Possible manufactory stamp. Could be a dodge rear end. Look up dodge charger rear end's on Ebay and see if some thing look's the same. Did you look around the frame bumper attached to the rear end. Well just trying to help ya out bud. The only other place may be on the brake shoe backing plate. Can't think of any other places for numbers. Russ.
     
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  15. Russ69Runner

    Russ69Runner Well-Known Member

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    Hey Hodgee. Did you figure out what the rear end is. It is too bad that someone did not put paper work some where on the rear end swap.
     
  16. RonLiv

    RonLiv Well-Known Member

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    Not sure if this helps or not. chrysler differential.jpg
     
  17. Hodgee

    Hodgee Member

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    Looks to me like a 68 8.25
     
  18. RonLiv

    RonLiv Well-Known Member

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    I'm certainly no expert, but from all the research I did on my 69, Chrysler introduced the 8 3/4 "banjo" rear diff in 68 and was used on the Roadrunner. They were not date stamped, but did have a casting code "489".
     
  19. RonLiv

    RonLiv Well-Known Member

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    Again, I'm no expert and I don't know if parts are interchangeable by different manufacturer's but Chevrolet made a 10-bolt(and a 12-bolt) pattern rear differential in 1968 that is circular like the picture shown here. I'm doubting this is a Chrysler rear, but again I don't know much.
     
  20. 69hemibeep

    69hemibeep Sponge Bob Square Wheels

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    differential-identification-chart.jpg
     

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