Overdrive questions

Discussion in 'Early CJ-5 and CJ-6 Tech' started by Otis rocks, Mar 19, 2013.

  1. Mar 19, 2013
    Otis rocks

    Otis rocks Sponsor Sponsor

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    So I'm 17 and me and my dad have been fixing up my 68 CJ5 with the 225 and it's going to be my daily driver and I wanted to know if an overdrive would be something I should look into or not. I also wanted to know what exactly they do..Thanks!
     
  2. Mar 19, 2013
    John151

    John151 Sponsor Sponsor

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  3. Mar 19, 2013
    duffer

    duffer Rodent Power Sponsor

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    IMO, short of a sbc, a 225 in a CJ is the absolute best application of an OD. Do it. Check classified but may be better to just get a rebuilt one from Herm-you know what you are getting there.
     
  4. Mar 19, 2013
    colojeepguy

    colojeepguy Colorado Springs Sponsor

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    V6 Jeeps came stock with 3.73 or 4.88 gears. Don't bother to put an overdrive with the 3.73's-it'll simply be geared too high. The 4.88 gear with overdrive combo is an excellent all around choice for a CJ.
    Also, with a little practice, you can amaze your friends by going through 6 forward gears! :D
     
  5. Mar 19, 2013
    baljoint

    baljoint Member

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    ...and 2 reverse gears!
     
  6. Mar 19, 2013
    Abnredleg

    Abnredleg New Member

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    My Wagon had 4.09 gears with a 6 cylinder and the overdrive I installed made a nice difference as it was my daily driver especially at the upper end. And as baljoint pointed out there was nothing more fun than backing up the street and shifting the overdrive while in reverse and watching the heads turn and question marks come out of their ears!
     
  7. Mar 19, 2013
    duffer

    duffer Rodent Power Sponsor

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    Right on the 3.73's. Mine has the 4.88's and I tend to forget those tall gears were the normal offering. I have 4.09's in the 3B and the OD is perfect in there behind a small block. About 2300 rpm at 75 mph.
     
  8. Mar 19, 2013
    John151

    John151 Sponsor Sponsor

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    Since the OP is asking about the purpose of overdrives, we should point out that the typical usage is to switch into overdrive once you have reached cruising speed for the purpose of fuel efficiency (vs. turning a 3 speed into a 6 speed).
     
  9. Mar 20, 2013
    colojeepguy

    colojeepguy Colorado Springs Sponsor

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    ^That's true, but it's also very useful for splitting gears, especially off road.
    Example-headed down a hill, 1st gear too slow, but 2nd gear you're riding the brakes.
    Put in 1st gear OD! I use mine like this often.
     
  10. Mar 20, 2013
    duffer

    duffer Rodent Power Sponsor

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    An OD in a Jeep is a little different than a typical OD in a car as Doug points out above. If the OD is used with either of the 134 engines, the top speed is only marginally increased because neither of those power houses have enough poop to increase the top end notably and with the OD engaged, you are usually no longer at the peak of the torque curve. IMO, gear splitting becomes at least as important (probably more important) as cutting the rpms at 1:1 with the 4 cylinders.

    The 225 does have enough power to substantially increase the top speed with the 4.88 optional gears but with the 3.73's you would be effectively running 2.80's with the OD engaged and be right back in the same situation as the 4 bangers-although 20 to 25 mph faster. However, the gear splitting advantage would still be there. Whether it would be worth the cost for just that is debatable.

    Do you know what gears are in the 68? After 45 years, they could have been swaped more than once.
     
  11. Mar 20, 2013
    Otis rocks

    Otis rocks Sponsor Sponsor

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    well we were told the back axle is an AMC quadatrack so I'm not sure on the gears I'll check that tonight or tomorrow depending on when I have the time to do it!
     
  12. Mar 20, 2013
    timgr

    timgr Jeepin' Nerd Sponsor

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    You need to post some pictures of this axle. The only axle that fits your description comes from a '76-79 CJ-7 with an automatic transmission. This axle does not fit without modification, and the gear ratio will not match your original front axle. The front and rear axle ratios must match. If they do not, something will break if you try to use 4WD.

    A Quadratrac axle is possible, but unlikely IMO. Often POs are clueless and jump to conclusions based on incomplete knowledge and understanding. So don't assume.

    Let us help you. Post pictures.
     
  13. Mar 20, 2013
    Otis rocks

    Otis rocks Sponsor Sponsor

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    it has been modified it has been offset and I will post some pics tonight of it but I had another thread and I wanted to know what axle I had that's what they told me..but I will post pics
     
  14. Mar 20, 2013
    colojeepguy

    colojeepguy Colorado Springs Sponsor

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    The stock rear axles in early CJs are offset, to line up with the offset output on the transfer case.
    AMC 20 rear axles for quadratrac applications were offset for the same reason. So, as Tim pointed
    out, its possible but unlikely that's what you have.
    X2 on the pics!
     
  15. Mar 20, 2013
    Otis rocks

    Otis rocks Sponsor Sponsor

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    [​IMG][/IMG][​IMG][/IMG]
     
  16. Mar 20, 2013
    duffer

    duffer Rodent Power Sponsor

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    Well, bummer. That does indeed appear to be an AMC 20 rear axle. I am not sure why someone would replace a 44 with one of those as you really do not gain anything. We still need to know what the gears are. If you aren't going to wheel it hard or put big tires on it, may as well just use it. I would be looking for a flanged D44 rear axle for a replacement in the mean time.
     
  17. Mar 20, 2013
    Warloch

    Warloch Did you say Flattie??? Staff Member Sponsor

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    Notice the shock mounted to the diff cover???

    Lower gears are great for the OD. I put my first one in when I was 16. Made a huge difference, mine was a 225/T90/D18 with 5.38s in a '49. I run them in all of my rigs and they are 5.38s or 4.88s all of them.
     
  18. Mar 20, 2013
    Otis rocks

    Otis rocks Sponsor Sponsor

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    So why is the Dana 44 better than the quad? like I said i am new to the jeep thing...and I won't be doing anything hard off road since it is my daily driver I don't want to risk putting it out of service for too long.
     
  19. Mar 21, 2013
    Posimoto

    Posimoto Hopeless JEEP Addict Sponsor

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    That rig already looks like it has some big meats on it. Spring over and a different method of dealing with the steering, but should be fine as a DD. The steering box must be mounted pretty low on the frame. It would be good to have a brace for the box from the snout across to the pass. side frame. Something like this:

    [​IMG]

    Foothill Offroad used to carry the clamp and you could fabricate from there. I'm guessing those tires are 33's or bigger and that puts a lot of strain on the end of the steering box at the pitman arm. If you fabricate a brace it needs to attach to the frame with a bolt parallel to the length of the frame. When I made my first one I welded it to the frame and it eventually cracked. You can kinda see what I mean for the mount in this pic.

    [​IMG]
     
  20. Mar 21, 2013
    timgr

    timgr Jeepin' Nerd Sponsor

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    It's a Dana 30 front too. It's not a "Quadratrac" axle per se, but an AMC Corporate 20 (M20) that was used in Jeeps a lot in the '70s and '80s. The axle used with the automatic transmission and Quadratrac '76-79 has the offset to the passenger side you need for your Dana 18 transfer case.

    Likely the PO took both axles from a CJ-7 and put them under your CJ-5. This would save having to regear the rear axle to match the front axle. The CJ-7s had 3.54 axles standard and 4.09s optional - neither of these ratios needs an overdrive IMO.

    There's no other reason to keep the M20, really. It has a terrible reputation for weak axle tubes and breaking the hubs-to-axle connection. The original Dana 44 that came with your Jeep is a better axle. The M20 can be fixed up by trussing the carrier and adding aftermarket one-piece axles, at some expense.

    Why is the Dana 44 better? (This is about the Dana 44 from your Jeep, not the later flanged Dana 44). Well, first it does not have the weak axle tubes that the M20 has. So you don't need to truss the axle to beef up the weak housing. Second, the M20 only came open or with the TracLoc limited slip differential. Since these axles originally were used with the Quadratrac, they were only open differentials. A limited slip or locker could have been swapped in, but it's likely open. If the Dana 44 had limited slip, it would have been the excellent Dana PowerLock. Limited slip was a popular option, so it's very possible you lost limited slip going to the M20. Both the M20 and the Dana 44 have two-piece axles, where the wheel hub is separate from the axle shaft, and they are joined with a big nut on the end and a key. My impression is that the M20 hubs loosen up pretty often, and the axle end and keyway self-destructs. This is why one-piece axle shafts (with the hub and axle one unit) are a popular upgrade for the M20 axles. One-piece shafts may not be easily sourced for your offset axle ... it's something of an oddball. The Dana 44 also could have problems with the hub spinning on the shaft, but I think it's much less common. Regardless, if you don't have 1-piece aftermarket shafts, check the tightness of the hub nut regularly - it has to be wicked tight.

    Also notice that this Jeep is now spring-over (ie the springs are on top of the axles, as opposed to the original condition with the springs passing under the axles). A lot has been done to this Jeep. The spring-over is tricky ... sometimes owners will try to save money on a lift kit by using factory springs in a spring-over configuration to get more lift. It often turns out badly ... as mentioned, doing it right is tricky. Looks like you got the CJ-7 springs too, except the CJ-7 was not spring-over.

    The rear shock mounted on the differential cover is goofy ... never seen that before, and hope not to see it again.

    Does it drive ok? Have you driven it much? It might be fine ... just depends on the PO's quality of work.
     
    Last edited: Mar 21, 2013

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