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Technical Rear end experts, Chrysler 8.75 questions

Discussion in 'Traditional Hot Rods' started by RocktimusPryme, Dec 29, 2019.

  1. RocktimusPryme
    Joined: Sep 22, 2013
    Posts: 198

    RocktimusPryme
    Member

    So Im looking for an axle to swap into my gasser I have had other recent threads about. I found a 8.75 with a 3.91 and a spool already in it. But there is some wierdness. It was setup for a demo derby car. So it has no normal brakes, but has this goofy pinion brake that Ive never seen before. Im assuming I can easily take that off and throw a normal pinion yoke back in right?

    Second and more important question. Its a width I like at under 60", but does the distance from axle flange to face look right to you? Looks like 2 inches. Because I will obviously have to put brakes on there I wanted to make sure they put in shorter axles. I guess if I had to buy axles thats not the worse thing in the world but I want to know what Im going to have to replace before i commit to buy.


    He said he thought it was out of a 68 Newport, which I think should be over 60" wide. Thats what kinda set off my spidey sense.
     

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  2. Blue-Collar-HotRods
    Joined: Nov 21, 2019
    Posts: 76

    Blue-Collar-HotRods
    Member

    You should be able to ditch the home made pinion brake, and replace the yoke. The brakes you need can come off most any Chrysler 8 1/4 OR 8 3/4 with the EXCEPTION of the "A" body units. Even the junkyard Chrysler 5th avenues up to like 88 will work. 10x 2 1/2 is a common as dirt size for that.
     
  3. Flange distance looks right to me .
    I just went downstairs and measured some .
    Just remove that brake rotor and get a good yoke.

    Tommy
     
  4. RocktimusPryme
    Joined: Sep 22, 2013
    Posts: 198

    RocktimusPryme
    Member

    Okay, I think I might guy it if I can get him down on price a little. I was planning on doing a Scarebird brake swap, but if I can go grab junkyard drum brakes for cheap I may do that.
     

  5. Blue-Collar-HotRods
    Joined: Nov 21, 2019
    Posts: 76

    Blue-Collar-HotRods
    Member

    Also, for a race situation, you can buy the slip on rotors, and the GM weld on caliper brackets, and use cheap remanufactured calipers. Dirt cheap, relatively speaking.
     
    Desoto291Hemi likes this.
  6. oldiron 440
    Joined: Dec 12, 2018
    Posts: 3,301

    oldiron 440
    Member

    Jeep liberty rear disk setup bolts right on.
     
    deathrowdave likes this.
  7. RocktimusPryme
    Joined: Sep 22, 2013
    Posts: 198

    RocktimusPryme
    Member

    do you have a reference for that? I tried to do some research but got mixed info. It looks like it’s direct for an 8.25 but maybe not for the 8.75 due to flange thickness? And something about green bearings.
     
  8. studebakerjoe
    Joined: Jul 7, 2015
    Posts: 1,136

    studebakerjoe
    Member

    Rocktimus, there was an article in Mopar Action a while back about the rear disc swap using Jeep parts. If you cant find it I think they'll send you a copy of the article. I may have it myself have to check.
     
  9. oldiron 440
    Joined: Dec 12, 2018
    Posts: 3,301

    oldiron 440
    Member

    One of the mopar forums I'm on it's a popular swap.
    If it fits the 8.25 it fits the 8 3/4 and Dana.
     
  10. studebakerjoe
    Joined: Jul 7, 2015
    Posts: 1,136

    studebakerjoe
    Member

    Did a bit of checking. The A bodies only forum has the whole 2 part series on the liberty brake swap on their. You can download it.
     
  11. thirtytwo
    Joined: Dec 19, 2003
    Posts: 2,639

    thirtytwo
    Member

    Demo cars get beat .. hard... I would be concerned about housing and axle flanges being straight
     
    Deuces, lemondana and town sedan like this.
  12. lemondana
    Joined: Feb 21, 2009
    Posts: 225

    lemondana
    Member
    from Lincoln NE

    If it is a 489 case and you take the yoke off-you MUST put a new crush sleeve on it and torque it down correctly! Several of the rearend companies sell a solid sleeve, then you set it up with shims. IMO green axle bearings suck!
     
  13. deathrowdave
    Joined: May 27, 2014
    Posts: 3,519

    deathrowdave
    ALLIANCE MEMBER
    from NKy

    8 3/4 and Dana 60 are the same flange bolt pattern . I think the issue you may run into with the Jeep stuff is axle flange bolt pattern . Later stuff uses different bolt pattern. This would only require redrilling the rotor or drum if I’m thinking correctly .
     
  14. oldiron 440
    Joined: Dec 12, 2018
    Posts: 3,301

    oldiron 440
    Member

    The Liberty used 5 on 4.5" bolt circle, the axle assm in the Jeep is 8.25 mopar.
     
  15. RocktimusPryme
    Joined: Sep 22, 2013
    Posts: 198

    RocktimusPryme
    Member

    I didn't think about that, a good point.
     
  16. Run like hell away from it, aside from the damage the demolition derby dipshitness may have caused
    I sure proper setup of ring and pinion was not a concern. I wouldn't be shocked if that pinion brake screwed up the pinion per load/depth.

    Remember the H.A.M.B. is about building cars.
    Demolition derby is about destroying them. I don't forget these are people who put the the battery, the gas tank passenger compartment with them, run fuel lines from the tank to the engine inside the car, so if they brake the car fills with gas. Then they crash into other people's cars without firesuites or rollcages.
    If the don't care about their own safety what makes you think they care about proper mechanical techniques.
     
    Last edited: Dec 30, 2019
    lemondana likes this.
  17. b-body-bob
    Joined: Apr 23, 2011
    Posts: 555

    b-body-bob
    Member

    FWIW, there are two different models of green bearings, one that will fall apart and one that will last as long as you need them to. You may still prefer the tapered bearings, and that's OK too.

    http://www.doctordiff.com/blog/tech-info/why-green-bearings/
     
    Desoto291Hemi likes this.
  18. RocktimusPryme
    Joined: Sep 22, 2013
    Posts: 198

    RocktimusPryme
    Member

    Yeah, I hadn't even considered the demolition aspect of it. Its just so damned hard to find a bolt in axle type rear end anywhere near affordable. At least not in a car type width. 8.8s are nice but you eventually have to put 9" ends on them or use C clip eliminators that get mixed reviews for street use.

    The more I think about it I think Im going to pass unless the guy wants to come way down on price. I have access to a couple of OP 9.3s but they have highway gears and parts are so expensive for them.


    Edit: The plot thickens actually. I told him I was going to pass because I just couldn't trust the housing that had been derbyed. He said he had a fresh housing with backign plates that he could swap the chunk and all over too.
     
    Last edited: Dec 30, 2019
  19. oj
    Joined: Jul 27, 2008
    Posts: 6,454

    oj
    Member

    If you're building a 'gasser' you might want to reconsider the pinion brake, depending on your transmission they made for great launch devices.
     
  20. Try hitting oval track swapmeets. More and more classes are allowing Quick Changes and guy are selling some really good 9" Ford parts.

    Just be aware that oval track gears are often very low. 5:00 to 6:50 range and have full spools or mini spools. Limted slips are not legal.
     
  21. RocktimusPryme
    Joined: Sep 22, 2013
    Posts: 198

    RocktimusPryme
    Member

    I am part of the local race car parts for sale group. And yeah I do see them occasionally, but like you said the chunks are almost always nutzo gears.

    And I actually made a deal to buy the 8.75 from this guy. Im getting the fresh housing with backing plates whilst talking him down some on price. Its not a steal @ 500 bucks, but I think its a fair deal and I feel more comfortable without a housing that's been in a wreck, or a lot of them. Im getting a ratio Im looking for, a full spool, the right width and a start at brakes. Considering the prices I usually see for anything else I think its okay.
     

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