Gear Vendors overdrive

Transmission and Drivetrain Tech

  1. marksmopar1

    marksmopar1 Well-Known Member

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    AJ Question for ya....
    Do you have a picture of your 4 speed trans attached to the GV?
    Also, I am thinking of a GV behind a 4 speed in my 69 Dart. Can I use the A body trans or do I need to have the E-B Body main-shaft to attach the GV? I am a bit confused when looking at the GV site,,, lengths of tail-shafts etc. and what will I need.
    Appreciated! Also in Wpg :)
     
  2. AJ/FormS

    AJ/FormS 68 B'cuda fb, Form S clone ... 367/A833/3.55s

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    I haven't been to the site since 2004, so I cannot answer your questions.
    I used the A-body trans I had. In fact I had 3 different ones and the only one I didn't bolt the GV to was the close ratio T/A one.
    But GV only had the B/E tail in 2004, so I had to buy a long mainshaft to make it work. Yeah so that sucked cuz I had to take the whole trans apart to swap in that mainshaft. Ok well it wasn't that bad cuz to install the GV adapter the trans has to come apart anyway..
    But I gotta say, that the 3.09 in the Commando box is awesome. It allows running 3.55s which take off like 4.10s, but leaves the other gears alone. And as you probably already know; that 1.92 second gear with the 3.55s makes an awesome 6.82 roadgear; good from 30mph@2550 to 60@5100, when running a small cam hi-torque 360. So most of the time, my trans is in second gear.
    Unfortunately, there is only one gear in the Commando box that can be swapped into the regular A833 and that is MS-first. So I had to buy another complete gearset lol. I got my set from Jamie at Passon; he had it, I wanted it, the price was good, and on inspection; the used parts were in excellent condition. I also got one of his lightweight aluminum cases and matching sidecovers.
    I'm an hour from the South perimeter. I'm semi-retired. You should come over. I have lots of free time.No beer; just pop. You might like to take some of my junk home.
     
  3. marksmopar1

    marksmopar1 Well-Known Member

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  4. marksmopar1

    marksmopar1 Well-Known Member

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    AJ ,
    I should drop over. I am retired as well.. playing with my cars mostly.
    I’m in Wpg, southwest area near perimeter. A meet up is a great idea, I’m sure we could do some trading!
    I need some expertise on this GV to 833 swap, just some of the finer points and your opinion on what works best etc.
    I’ll send you a PM
     
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    • AJ/FormS

      AJ/FormS 68 B'cuda fb, Form S clone ... 367/A833/3.55s

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      waiting, lol.
       
    • mopardude318

      mopardude318 Well-Known Member

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      I think I could benefit greatly from a GV OD in my '02 Cummins 2500 quad cab long bed. when going up a steep grade, the 3 to 4 shift really sucks ass and lugs the truck down. same for when the TC lockup occurs. I think it would be really beneficial to be able to split the 2-3 and 3-4 gears esp. while towing...I think Del has one, doesn't he? (67dart273)
       
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      • AJ/FormS

        AJ/FormS 68 B'cuda fb, Form S clone ... 367/A833/3.55s

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        IDK about diesels but it sounds to me like yours is either working too hard or not up to the task. The GV unit has a .78 split. meaning that if you shift at 3000, the Rs will fall to .78 of that or to 2340rpm, on the upshift or 2340 will rise to 3000 on the backshift........ but you cannot outshift the GV under power. So if climbing a hill, in say 3rd/over, and you wanted to go to 3rd, you would have to figure out a way to disconnect the engine momentarily to outshift the GV.
        I'm thinking that will not be very useful to you.
        Better I think is to just stay in whatever gear it takes to climb your grade
         
      • mbaird

        mbaird mbaird FABO Gold Member

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        I bet you have 4.11s.
        When I sold Dodge I had a hard time convincing customers to get 3.55s vs 4.11s.
        A Cummins will rev past its powerband with too steep of gear . I remember towing my car to the track with a 5 sp manual and losing mph when I dropped to 4th on a big climb.
         
      • Dragnut

        Dragnut Well-Known Member

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        So I have a buddy who has a 4x4 business and he has been doing drivelines for a long time, I ran this GV stuff by him and ask what he though, He told me to stay away from stuff like this and his reason is if the company ever goes out of business you are screwed for parts...
         
      • AJ/FormS

        AJ/FormS 68 B'cuda fb, Form S clone ... 367/A833/3.55s

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        I wonder tho if that's a valid argument in this case because that unit is about as basic as it gets. All it is , is a planetary reduction unit with a hydraulic clutch.
        On your truck, gearing is everything.
        A closer ratio trans would be nice, but you can overcome that with gearing.
         
      • roccodart440

        roccodart440 Well-Known Member

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        That gear reduction in a diesel would be very optimal and rarely would you ever have your foot buried while climbing with a cummins, unless passing. but it take less than a second to lift, shift the OD and get back on the throttle. You can, and should disengage at light throttle. If you disengage under full decal it's a bit harsh. Keep in mind im talking automatics here. Manual transmissions with the OD need to be clutched from what I've been told. I run an auto.
         
      • AJ/FormS

        AJ/FormS 68 B'cuda fb, Form S clone ... 367/A833/3.55s

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        From what GV told me; more power, or no power, has to be going in than is going out during the shift; either upshifting or down-shifting. And the driveshaft always has to be turning in the "Forward"direction when the GV is engaged.
        So when downshifting, the wheels are powering the driveshaft which is powering the pump inside the unit, and the planetary. With no power going into the front, the GV is happy. With more power in, the GV-clutch has to also brake the engine. If there is a fluid coupling in between there then you may get away with it. But with a Hi-Po clutch, and 11/1 Scr and 185psi cranking pressure , the GV has a nasty time backshifting cuz the direction of the torque is the same as when in reverse.... which I can tell you from personal experience, kills the GV unit almost instantly. That cost me 50% of retail to rebuild plus shipping,both ways I think, back in about 2005. And, I was without the GV for most of the summer.
        But in the forward direction, under full power, the shift from second to 2-od always breaks the tires loose. With 3.55s that can be as high as 80 mph.

        For you guys with clutches, and having bypassed the GV-computer for split shifting; there can be a shift lag from the moment you press the button to the moment it shifts. The slower your driveshaft speed, the more pronounced the lag.When I spoke to GV about what I was wanting to do, they said I would need ~4.56s to get the pump pressure up fast enough to not slip the GV clutch to death, at low engine rpm, in first gear. By the time the 2-od shift comes there is plenty of pressure.
        At the time I was running a 2.66low gear and with 4.56s that makes a minimum starter gear of 12.13. I did the math to get the driveshaft rpm per 1000 engine rpm, and then did the testing with the 3.55s that I had in it, to find the driveshaft rpm where the GVclutch lagged seriously.
        Next I got me an ODbox with the 3.09 low, for a starter gear of 3.09x3.55=10.97, and did the testing with that; and found that after about 3000engine rpm, it was a non issue; 3000 in 10.97 starter gear is 22mph so it's not a big deal. That's how I solved the shift lag.
        Further more, when the unit is new, it will hold it's pressure for at least a minute. So if you roll to a stoplite with the unit still engaged, chances are very good that it will remain engaged, and you can motor away. I exploited this one summer by installing 4.88s, and starting in 1-od, after having charged the pump. This gave me a starter gear of 4.88x3.09x.78=11.76 around town, and a starter of 3.09x4.88=15.08 for; 550rpm=2.9 mph for idling around, and parading.
        But I gotta tell you guys, getting your engine to idle at 550 with a 230/235 cam, and make enough torque to pull itself... is a bit of a trick. And to do it in a parade for a couple of hours is a different trick,lol. You shoulda had a automatic,lol.
        The following summer I tried it with 4.30s, but by the end of the summer, that od box was proving to be a pita. The gears were just too far apart for city driving. And timing the backshifts was getting to be real aggravating.
        So by next summer I had a Commando 3.09 box in it, and that has been working very well for me ever since....... with 3.55s, which make a starter gear of 10.97, and a parade speed of 4mph@550rpm. I later sold the 4.30s.
        Now I can splitshift the first two ceares ... If I want yo.... but no longer have to. The splits in the main box are sufficient.
        For you guys with 5speeds
        Your gear splits are progressively shorter having splits as large as .5 or .55 on the bottom, and as close as .80 up top. The GV has a split of .78, about the same as from 4th to 5th, and only a little closer than from 3rd to 4th. The GVod works best with splits in your trans of .78x.78=.60. Like what is usually found between first and second.or occasionally between second and third. Like the Mopar 4spdod. It has ratios of 3.09-1.67-1.00-.73od so the splits are .54/.60/.73
        But the AX15 5speed for instance,has ratios of 3.83-2.33-1.44-1.00-.79od so the splits are .61/.62/.69/.79 and splitting these produces ratios of 2.99-1.82-1.12-.78. Combining these gets you
        3.83-2.99-2.33-1.82-1.44-1.12-1.00-.78-.79;yes 9 usable ratios, and splits of
        .78-.78-.78-.79-.89-.78-1.01; notice how nicely things work out in the first three gear, but going into 1.00/Fourth from the 1.12/3-od split, the split is down to .89.... which at 3500shift is just 385 rpm. And .79fifth is the same as .78-4th-od.
        But ask yourself; what is the likely hood that you will be able to split first and second... because the driveshaft speed will be so slow. and what is the likelihood you will need to split second and third. The split from third-od to fourth produces an rpm drop of just 385rpm so means about nothing. and double od puts your rpm at 65~1900 with 4.11s and 30s; can your engine pull that? and to what end?
        So what would the GV actually get you?
        Well if you had a diesel with similar ratios, you'd get a nice 2-2od-3-od run and then the 315 rpm-drop into fourth from 3500rpm in 3od. Is that worth the approximate $4000 buy-in? only you can decide.
        But I have no idea what your diesel ratios actually are; the above is only a study.
         
        Last edited: Dec 9, 2019
      • Nat

        Nat Well-Known Member

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        i have one in my car with 355 gears and 235-60-15 tires at 70 mph i'm at 2300 -2400 rpm so far it's been good lots of higway driving . It was in the car when bought. it shifts very quickly and hard . If I were to buy another old 3 speed auto car I would put in a GV overderive unless someone made an 8 speed conversion kit
         
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        • AJ/FormS

          AJ/FormS 68 B'cuda fb, Form S clone ... 367/A833/3.55s

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          I see from Amsterdam it is only about 100 KM in any direction to a border and less to the ocean. So it seems to me a GV is kindof a luxury investment. It's a good thing yours came with the the car.
          Yes I enjoy mine too, but Canada is a huge country; even my home province is huge. I also run 3.55s, but with a 4-speed manual gearbox.
          PS: on the Google map, it looks like you have some very strange borders,lol.
           
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