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Gear Vendor O.D. on TH400

Discussion in 'The Garage' started by mtn. burb, Apr 24, 2005.

  1. mtn. burb

    mtn. burb 1/2 ton status

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    Any one run one ?

    Met a guy this morning at Circle K with a built 468BB Dually K3500 runs one. Say's it just bolts on the back of the tranny. Good for minus 800 rpm.
     
  2. sled_dog

    sled_dog 1 ton status

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    I thought they only make them to bolt to the back of the transfer case or back of a 2wd case. Seem to remember someone saying they couldn't use it in 4hi cause it wasn't between the case and the trans.
     
  3. kyser_soze

    kyser_soze 1/2 ton status

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    I've checked out their web site, and it's after the transfer case to the drive shaft or 2wd operation only.
     
  4. gmcjimmy88

    gmcjimmy88 1/2 ton status

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    Anyone have this website? I have a buddy looking for something like that for his (whispering with shame) jeep. Thanks for any help
     
  5. Esteban86K5

    Esteban86K5 1/2 ton status

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  6. Diesel Dan

    Diesel Dan 1/2 ton status

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    I ran one. Had it on a 1988 V30 crewcab, TH400/np205. IIRC the electronics have a wire for 4wd lockout that was wired into the 4wd light. Never had an issue with wanting to use the OD while driving fast enough to require it.

    Why on a jeep? You loose 14-18" of the rear driveshaft, that's like half the wheel base of a jeep right :grin: ?
     
  7. FWP

    FWP CRS

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    Yup, hauled the Blazer on the trailer to the trail and back today actually. What do you want to know?
     
  8. pwrhouss

    pwrhouss Registered Member

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    My dad put a GV on his 1986 Chevy dually. The gas mileage went from 7-8 to 10-12. Percentage wise that is a good increase. The rpms are what really dropped though. Had to cut the driveshaft for it to fit. Real smooth operation. Been on there for about 6 years with no problems pulling tractors and other heavy loads.
     
  9. big_truxx

    big_truxx 1/2 ton status

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    they DAMN!!!!! expensive though!!!! Like $2,800 new IIRC. for that I could by like 1/2 dozen trucks. :haha: I always thought it would be cheaper to do a serious rebuild on a 700 or just buy one from B&M already to haul... for a frand less... :dunno: my $0.02 worth for the morning.
     
  10. Greg72

    Greg72 "Might As Well..." Staff Member Super Moderator

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    But a 700R4 is only a 4-speed....

    A GearVendors unit adds an overdrive to every gear in the tranny, so a TH400 is actually a 6-speed when you're done.


    Given that my 'Burb only gets 7MPG on the highway, I suspect that even a relatively expensive GV setup would pay for itself in fairly short order even with only a modest increase in fuel economy.... like 10MPG. Actually, I'd KILL for 10MPG!!! :D
     
  11. big_truxx

    big_truxx 1/2 ton status

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    So you don't think that swapping from a 400 to a 700 would increase mpg?
     
  12. Greg72

    Greg72 "Might As Well..." Staff Member Super Moderator

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    Sure it would....


    Just saying that having 6-speeds is a pretty cool benefit, and it's really not fair to compare it pricewise to a 700R4 with "only" 4 speeds.

    Ultimately, it comes down to whether you already own the TH400 (makes it cheaper) and whether the vehicle is long enough that you can afford to "throw away" 12 inches of rear driveshaft length to do a GV swap. I'd love to have one in my K5, but there's no way it would work unless I coupled the output of the GV directly to the yoke of the 14BFF!!! :D
     
  13. pwrhouss

    pwrhouss Registered Member

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    Switching to a 4L80E trans would cost around the same thing after the wiring harness and other electronics. And that would probably be a used or rebuilt one. Right now every little bit of fuel mileage helps, but the best thing is you don't go down I-40 @ 75mph in third gear. Really saves the engine.
     
  14. big_truxx

    big_truxx 1/2 ton status

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    I think it is fair since I would expect the end mpg on the highway to be roughly the same between a GV and a 700. I cannot back this by experience since I have never had a GV. If I already had my house/garage built and land situated and had $2,800 sitting around w/ nothing else to buy I might just for kicks see how much mpg the GV would yeild behind a 700 though :D but even at comparing 6 and 4 speeds... some 4 speeds do have an OD in them and usually all OD's (final tranny gears) end up at around the same ratio just the gears in between final and 1st are different spaces apart. ;)
     
  15. rdn2blazer

    rdn2blazer 1 ton status Premium Member

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    I have a buddy thats doing a ground up pro touring street rod build of a 66ss chevelle with a factory 396. it was a factory manual trans car, but it had a th400 in it at the time he picked it up. he put an m21 rock crusher 4 speed manual trans in it and a GV, it will be an 8 speed!. car is not done yet, just needs electrical and interior. ten grand in paint alone and everything is powder coated, hotchkis suspension, you name it, it has best of everything. when its all dialed in he is putting a 572 in it, cant wait to take a ride in it.
     
  16. dyeager535

    dyeager535 1 ton status Premium Member

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    My dads running a GV behind his 465 with 4.10's.

    The GV OD is .78...that's less effective than the 700R4 at .70 (4L80E @ .75?)

    IMO from driving his truck (and his opinion too, with a 10,000lb trailer) the gear vendors unit does not have effective enough gear splits. It helps, sure, but going from, say, 2:1 trans to 1.5:1 trans instead of 1.22:1 (I think I got my math right there) would work better I think. Maybe thats just our terrain, his vehicle setup, and his towing load, but "2nd" OD (3rd if counting all 4 gears in the trans) is still not enough to keep engine RPM and vehicle speed reasonable.

    If you were truly "halfway" between each gear with the unit turned on it would make your vehicle a 6 or 8 speed, in reality it slightly decreases the RPM in each gear. Still not enough to get you out of that "gap" between gears that lugs the engine on a long climb.

    With his setup, OD is pretty much only a 3rd(4th) gear proposition unloaded. You don't stay in the other gears long enough to use the OD when unloaded.

    An auto trans is probably going to give a bit different performance due to converter slip, so I can't really comment on that.

    As to engine wear, GM built trucks with 4.10 or 4.56 and no OD, so obviously they didn't think that engine RPM's were going to be an issue. Of course that doesn't help economy, but with the GV $2800, you can STILL buy a lot of gas before you break even.

    For towing though, I don't think there is probably a better setup than the GV right now, honestly. For solely economy, in an auto, a 700 or 4L80E would be my choice.
     
  17. Greg72

    Greg72 "Might As Well..." Staff Member Super Moderator

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    According my some quick "back of the envelope" calcs an improvement from 7MPG to 10MPG will save me $1200+ in gas the first year (assuming 12000 mi/year)....if I could actually eek out 12MPG from the setup, the savings would be $1700 the first year!!! The breakeven isn't instantaneous on a $2800 upgrade....but it sure doesn't take long.

    There is also something to be said for extending the "cruising range" of a tank of fuel. More psychological than anything, but being able to go a couple of weeks between ($120/tank) fillups would REALLY improve my attitude. :D
     
  18. dyeager535

    dyeager535 1 ton status Premium Member

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    Yeah, thats true. If you don't run the truck very far a year, it will take a lot longer to break even than if you drive it like you mention.

    Psychological factor is there too, I agree about being able to run further on a tank of gas. I like seeing the RPM's drop when you engage it, just wish they would drop more.
     
  19. Desert Rat

    Desert Rat Fetch the comfy chair

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    When I bought my 76 Blazer it came with a GV unit on the back of a 350/TH350/NP205. After I got the 6 inches of lift on, there was no way I could run it. The driveline angle was outrageously steep and short. I ended up selling it and swapping in a built 700r4. I did drive it for a short time at stock height and if you tow, or just want an OD unit and can pick one up used for a stock height vehicle, I would recommend it. But, if you are going up any more than 2 inches, forget it.
     
  20. big_truxx

    big_truxx 1/2 ton status

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    :thinking: I wonder how much better the GV would make a 6.2 700 2wd 1/2 ton burb out :thinking: no towing no nothing but family/grocerie hauling :thinking: Bet it would still be a long time before it saved me enough money to pay for itself. Probably wouldn't really be able to use the last gear effectively anyway. :dunno:
     

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