1. Registration trouble? Please use the "Contact Us" link at the bottom right corner of the page and your issue will be resolved.
    Dismiss Notice

1973-1978 Cj5 Front Axel Swap

Discussion in 'Intermediate CJ-5/6/7/8' started by LarryR, Aug 24, 2022.

  1. Aug 24, 2022
    LarryR

    LarryR New Member

    10595
    Joined:
    May 25, 2022
    Messages:
    2
    Hi everyone,

    This is my first of what I hope, many posts.

    I have a 1973 CJ5 that I got from my neighbor for free, I know...Free jeeps, lol

    I also bought a 78 CJ5 frame with newer front and rear axels in hope of replacing the front drum brake style that came with the 1973 with the the disk style that came with the one I bought with the 1978 frame.

    The question I have is can I just swap out the gears from the old 73 (5350863 41-11 3-73) front axel with the one in the 78 (5356101 3. 54 46) front axel? The numbers are from the tags, one is a 3.73 gear and the other is a 3.54 gear...which is preferred for light off road and highway?

    Both are Dana 30's and I would like to just swap out the whole axel from one frame to the other, its my understanding I will need to maintain the same gear ration in both the front and rear axel, is that correct?

    Am I not asking anything I should be asking here?

    Looking forward to your thoughts and replies.

    Larry
     
    Last edited: Aug 24, 2022
  2. Aug 24, 2022
    dnb5853

    dnb5853 Member 2021 Sponsor

    Grand Mesa, CO
    Joined:
    Aug 13, 2006
    Messages:
    943
    Welcome to the forum. There's an INTRODUCTION thread here: Introductions | ECJ5 (earlycj5.com). Feel free to tell us about yourself. Include pictures of your Jeep!

    While my answers to your questions should be unbiased, I want to 'talk' about your free Jeep.
    Make sure this platform will suffice in your end goal of an off-road vehicle. It's best to know where you are going with any modification keeping the final goal in mind. Don't change directions halfway through your work...it gets too expensive and frustrating.
    For starters, the Intermediates ('72-'75) often have frame cracks behind the front springs, especially those with V8s or those that have been abused. A careful visual inspection is worthwhile...enough of my opinion.

    It appears you have two questions.
    Answer 1: You should be able to swap gears - do some research on "carrier breaks". This break is the difference between carrier deck heights. Here's a good place to start:
    Differential Carrier Breaks | West Coast Differentials
    Setting up a ring & pinion requires precision work. Make sure you understand the effort and have appropriate tools. Just because the bearing shims work in one axle does NOT mean the same shims will work in the other axle.
    Answer 2: Yes - the entire axle may be swapped with relative ease. The spring pads are in the same place. The driveshaft should be a direct fit. Assuming both are drum brake, the brake line interface should be the same. You might have some modification to the drag link or steering gear attachment. A caster check is always in order with an axle swap.
    This advice comes with an ever-present disclaimer: Everything is still stock and NOT modified. So often, frame, spring, steering and brake modifications throw the owner for a 'loop' during such work. Be prepared for surprises.
    As far as gear ratio choice, this is based on individual needs, driving style and tire diameter just to name a few.
    Regardless of how you proceed, the axle ratios MUST match from front to rear.
    Good luck! (y)
     
    Last edited: Aug 24, 2022
    LarryR and Ol Fogie like this.
  3. Aug 24, 2022
    FinoCJ

    FinoCJ 1970 CJ5 Staff Member 2021 Sponsor 2020 Sponsor

    Bozeman, MT
    Joined:
    Jul 18, 2013
    Messages:
    4,867
    What is your purpose with the swap? Is it only to get disc brakes on the front, or is there some other benefit? As you are basically swapping a D30 for a D30, there doesn't seem to be any inherent differences/benefits between them, other than the brakes and the gear ratio. If all you want is the brakes, you can swap the brakes across (or just buy a disc conversion) to the original older axle. Its much easier to swap brakes than to swap the R&P. If you prefer the 3.54 gears, then I'd suggest swapping the axle - and then you'll have to match the old rear axle to the new 3.54 gearing. Gearing is certainly dependent on a number of factors from engine size, transmission, tire size, intended usage etc....but I think I'd be running the 3.73s. The 3.73 with a typical 3-speed of the era, and a decent 31" or bigger tire will still allow for plenty of highway cruising at reasonable rpm, and make it feel a bit more peppy at lower speeds and have better off-road low speed crawl perfomance. If you are planning to keep the tire size small - like 28" - and plan on lots of highway cruising, then the 3.54s would work. I also think whether you have the v8 vs the 258 (or some other swap) will play a big role in gearing.
     
    dnb5853 likes this.
  4. Aug 25, 2022
    dnb5853

    dnb5853 Member 2021 Sponsor

    Grand Mesa, CO
    Joined:
    Aug 13, 2006
    Messages:
    943
    After sleeping on my response...I came to the same conclusion...there's no inherent benefit with the Dana 30s. They're both low pinion and they're both NT. Just swap the brakes, a much easier effort.
    Pay close attention to the spindle & hub dimensions and wheel bearing sizes. Also, take note of any difference with the axle shafts. Some sources say there's a difference in the outer portion for the disk shaft compared to the drum shaft, but I could never confirm that.
     
    Last edited: Aug 25, 2022
  5. Aug 25, 2022
    hudsonhawk

    hudsonhawk Well-Known Member 2020 Sponsor

    North Texas...
    Joined:
    Feb 4, 2005
    Messages:
    1,924
    Should be able to swap the entire knuckle assembly from the disc brake axle including the outer shaft. That way you don't have to modify the drum brake knuckle to work with the disk brakes.
     
    LarryR likes this.
  6. Aug 25, 2022
    TheBeav1955

    TheBeav1955 Member

    Wyoming, Mi
    Joined:
    Apr 14, 2004
    Messages:
    296
    I would agree that swapping out the knuckles is the easiest way to change the front drums to discs but also be aware that you will need to have a master cylinder that is compatible with the disc brakes. The drum brake masters have a residual pressure valve in them the is needed for the drums but will cause issues if you try and run them with the disc setup
     
    LarryR and dnb5853 like this.
  7. Aug 25, 2022
    johneyboy03

    johneyboy03 The green beast

    Quebec, Canada
    Joined:
    Jan 15, 2011
    Messages:
    2,078
    x3 on knuckle swap :p
     
  8. Aug 30, 2022
    nickmil

    nickmil In mothballs.

    Happy Valley, OR
    Joined:
    Sep 23, 2002
    Messages:
    12,262
    I can confirm that. The diameter and type of seal used on the outer axle shaft is different, hence the shaft where the seal goes is different. The disc brake spindle is also machined different from drum to disc brakes as well. Most drum brake 30's (Jeep) used a pressed in seal whereas the disc brake spindles used a V-type seal that fit tight on the outer axle shaft and rode on the inside of the spindle. Years ago I posted up a picture of the differences between the spindles.
     
    dnb5853 likes this.
  9. Aug 30, 2022
    Buildflycrash

    Buildflycrash More or Less in Line. 2022 Sponsor 2020 Sponsor

    Gulf Breeze FL...
    Joined:
    Jun 5, 2007
    Messages:
    3,024
    Before you go any further a quick peek inside all the axles may change your plans. R&P often hold up just fine for 60+ years / but not always. Take the covers off and spin the wheel. It's usually pretty obvious if there are problems.
     
  10. Sep 6, 2022
    LarryR

    LarryR New Member

    10595
    Joined:
    May 25, 2022
    Messages:
    2
    Thanks for the replies and suggestions here, this is a big help! The reason I wanted to swap the axel's is because the front axel on the 78 frame has disk breaks but my goal is to keep this restoration as close to original as possible for the most part. The disk break conversion kit I was looking at is $700. I have to crack the gear cases open this week and take a look, the front wheels dont spin but I think its the hub that is frozen to the breaks. May be something worse that I dont know about but I hope thats it.

    The knuckle swap that everyone is talking about is just the front axel sliding out and back into a new gear case? Sorry for all the newbe questions, I just want to try and maintain or improve what I have keeping it as original as I can but upgrading safety if it can be done, like disk breaks.
     
New Posts