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4.88 Gears Vs 3.73

Discussion in 'Early CJ5 and CJ6 Tech' started by Dauntless1971, Jul 1, 2017.

  1. Sep 27, 2019
    shaun

    shaun Member

    ohio, Beavercreek
    Joined:
    Oct 15, 2015
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    248
    1000.00 for OD with 5.38 or 4.27 and NO OD? Or 4.56, 4.88
     
  2. Sep 27, 2019
    shaun

    shaun Member

    ohio, Beavercreek
    Joined:
    Oct 15, 2015
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    248
    Love to get an OD and can install it myself but 1000.00 I may not have right now..
     
  3. Sep 28, 2019
    Renegade ll

    Renegade ll Member

    Thayne Wyoming
    Joined:
    Feb 17, 2013
    Messages:
    374
    I have a 71 cj5 with a sm465 (6.55) tranny, d18 tc (2.46) and 4:88 gears with overdrive. final crawl ratio is 79:1. If I put a Teraflex gear kit in the tc I would go to a 100:1 crawl ratio.
     
  4. Oct 1, 2019
    jpflat2a

    jpflat2a what's that noise?

    Riverside CA
    Joined:
    Jul 30, 2003
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    7,835
    I haven't heard too many folks complaining about their V6 and wanting to go faster.
    I have heard a lot of folks wanting to go slower with their V6 off road.
    Especially the 3.73 guys.
     
  5. Oct 1, 2019
    wheelie

    wheelie beeg dummy Sponsor 2019 Sponsor

    York, PA
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    Mar 6, 2004
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    I went from 3.73 to 4.88 in my '71 (231 OF, 3 spd, 33 tires) and I do want an OD. Just feels like it could use it, to me. Not that I want to go that fast because it probably won't see the highway but, it has been on the highway with the 3.73 and seemed okay. I think the 4.88 would have the engine wound up a bit more than I like so, an OD would seem logical. Just my .02.

    As the previous post suggests, I wanted lower gearing off road EVERY time I was off road with the 3.73 and 33" tires. Every time.

    I really like the 4.88s but would also really like to add an OD.

    4.27s and no OD might be good for a JEEP that sees limited trail duty and runs 31-33 tires.
     
  6. Oct 2, 2019
    oldtime

    oldtime oldtime

    St. Charles,...
    Joined:
    Aug 14, 2006
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    I think 4.27 with O.D. is too high for a jeep.
    The compound FDR would be same as 3.20 differential ratio.
    That said it may work well for a Cadillac.

    The Warn O.D. became a "Jeep Special Equipment Approved Option" in 9/1964.
    Kaiser Jeep Corporation specifically stated that it was only approved for jeeps with 4.88 and slower differential ratios.
     
    Buildflycrash likes this.
  7. Oct 2, 2019
    Buildflycrash

    Buildflycrash Member Sponsor

    Gulf Breeze FL...
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    Jun 5, 2007
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    Me.
     
  8. Oct 2, 2019
    Tom_Hartz

    Tom_Hartz Member Sponsor 2019 Sponsor

    North Carolina
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    Apr 9, 2014
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    331
    I have a V6, 4.88 gears, 33" tires and OD. I would not change a thing.
     
    Last edited: Oct 7, 2019
  9. Oct 7, 2019
    Ns0mniac

    Ns0mniac New Member

    San Clemente, CA
    Joined:
    Aug 7, 2019
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    Had 4.27's with 33's and no overdrive and I found it to be a good compromise of highway and off-road performance, but I run an SM420. The other option is to switch to a lower transfer case gearing like Tera Lows or an entire transfer case swap so you can run longer gearing in the axles and still have a good ratio in low but then you're talking a decent investment. Shorter axle gearing with an overdrive is probably the more economical option.
     
  10. Oct 7, 2019
    Buildflycrash

    Buildflycrash Member Sponsor

    Gulf Breeze FL...
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    So for us with V6 and 3.73 axles wouldn't the TeraLow make the most sense (cost and ease of upgrade) to get a slower off road ratio? Who supplies those? I guess a TC rebuild would be in order as well? (the more I type the more this is costing me:banghead:)
     
    ITLKSEZ likes this.
  11. Oct 7, 2019
    ITLKSEZ

    ITLKSEZ Volvophilic

    Post Falls, ID
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    Aug 13, 2015
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    3,453
    Someone really needs to make/market an underdrive that works/fits the same as the overdrive. I’ve seen homebuilt units using the low range unit from a Quadratrac. It’s a killer idea.
     
    Jrobz23, Buildflycrash and Ns0mniac like this.
  12. Oct 7, 2019
    Ns0mniac

    Ns0mniac New Member

    San Clemente, CA
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    Aug 7, 2019
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    Herm offers complete Tera Low transfer cases as well as compatible overdrives, his prices are listed on his website. You can purchase a pre-built case or send yours in to be built.

    You can also use this website to calculate your final drive ratio as well as crawl rate in MPH and feet per minute and then check what kind of difference you'd have with different differential gearing, transmissions, transfer case gearing, etc.

    http://www.grimmjeeper.com/gears.html

    Editing to avoid double posting:
    On the T86 equipped Jeeps the best option to slow you down offroad is definitely a transmission swap. If you can find an SM420 locally and don't mind the old-school clunkiness of it that's the route I'd take. A transfer case regear or axle regear will only change your crawl ratio by around 10 points (35ish from 25ish, can't remember exacts). An SM420 swap would net you a crawl ratio closer to 65.
     
    Last edited: Oct 7, 2019
  13. Oct 10, 2019
    Jrobz23

    Jrobz23 Member

    Northern, WI
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    Oct 3, 2016
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    626
    This. I spoke with Herm about it and he wasn't put off by the idea. With the Roxor out, in 3.73 gears, this is a seriously good idea that the eCJ5 crew can benefit from as well.
     
    ITLKSEZ likes this.
  14. Oct 10, 2019
    colojeepguy

    colojeepguy Colorado Springs Sponsor 2019 Sponsor

    At the foot of...
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    The Roxor tcase doesn't have a pto port in the back.
     
  15. Oct 10, 2019
    Jrobz23

    Jrobz23 Member

    Northern, WI
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    Last edited: Oct 10, 2019
  16. Oct 10, 2019
    colojeepguy

    colojeepguy Colorado Springs Sponsor 2019 Sponsor

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  17. Oct 10, 2019
    Jrobz23

    Jrobz23 Member

    Northern, WI
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    The plate has an indent for the shaft to have a carrier-bearing on the other side. Nicer setup, but still compatible with Spicer18 attachments, so sayeth the interwebs. I saw an article about a MM Engineer saying he had a Spicer18 OD unit on his Roxor tcase (T18 they call it).
     
  18. Oct 11, 2019
    shaun

    shaun Member

    ohio, Beavercreek
    Joined:
    Oct 15, 2015
    Messages:
    248
    I have a 420 tranny I need to rebuild so I’m also looking into the future. I got that for 50.00 so I want to rebuild it or send it in to get synco gears. Just can’t put 1000 down at moment before I even get to enjoy it. Still wiring it all up. Thanks for the info I may use your info. What setup do you have..
     
  19. Oct 11, 2019
    Ns0mniac

    Ns0mniac New Member

    San Clemente, CA
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    Aug 7, 2019
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    Replied to your PM (y)
     

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