Gear Vendor's Overdrive

Discussion in 'General IH Tech' started by nightwingdrb, Apr 1, 2014.


  1. nightwingdrb

    nightwingdrb Farmall Cub

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    Alright, so I'm the standard IH owner (read "cheap" and "moderately resourceful") and I have been looking for a divorced or remote mount Gear Vendors OD unit for my '61 C100 Travelette for several years now with no luck. I have found several, but they are all way out of my price range.

    I finally found one out of an older GM RV with a Turbo-400 transmission at a pretty decent price. I had been told that Gear Vendors didn't make an adaptor for the T-98 trans (true) but that they would sell me "everything that I needed" for a divorced mount kit (also true) for like $600-700 (not so true.) I called them the other day and the adaptor alone is $850. They are wanting $1200-1400 plus a $250 core charge for my TH400 tailshaft for everything that I need.

    So with that in mind:
    1. Does anyone have any ideas where I could find a good divorced adaptor at a better price? I have not called the gentleman at maximum-overdrive to see if he would sell me just the adaptor. That is on my list of things to do today.

    2. Do you think that I could have a driveshaft shop build me a yoke that would slide into the GV input to turn the TH400 adaptor into a divorced mount setup? I'm already going to have a yoke built for the rear shaft to replace the carrier bearing setup. I'm thinking that if you put a mounting plate on the front of the adaptor with a bearing in it and then slid the yoke through there and mated it with the splines on the GV it would basically do the same thing as their adaptor. (See picture.) I may have drawn it backwards. To be honest, I'm not super familiar with the unit. Mine is still attached to the OD and I'm doing it from memory because I forgot to bring my camera to work today!

    3. I understand that the easiest/fastest "right" way to do it is to just pony up at gear vendors and be done. And if I do, I'm still well ahead of what GV wants for the whole ball of wax.

    4. GV wants $250 for their "universal mounting kit." I own a drill, a vise, and a sawzall. I would think that for less than $50 I could go to the hardware store and get some strap steel and cut that out of the mix, getting me down to $1000 or so, which sounds like a good deal to me and gets me well below the maximum-overdrive price.

    5. I have the BD240 I-6 with a BW T-98 4 speed. I don't want to change the drivetrain. I'm trying to keep the truck as close to stock as possible while still being able to drive it daily. I've looked into swapping another 5 spd manual but nothing I've found so far has a long enough input shaft. By the time that I buy a tranny, lengthen the input shaft, and machine an adaptor for the I-6, the cost becomes prohibative. ($2K range)

    If anyone has any ideas, please let me know. Thanks!
     

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  2. TBAKPhi22

    TBAKPhi22 Binder Driver

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    Yes, GV is quite expensive. I bought a unit from my friends dad years ago and had to get an adapter for the 727 trans. You might be able to find something on Ebay, I dont know. I kept the furd adapter i got with mine to hopefully sell. They kept calling me for months after to get me to send it in for the core!
    As for a mounting kit, I dont know what you need to mount (to the frame at least) mine is just hanging off the back of the trans with no cross member.
     
  3. Scavenger Scout

    Scavenger Scout Binder Driver

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    Is the price too fabulous to pass up, or high enough to justify holding out for a divorce mounted unit? That's the real question. You'll save the most money buying it all together, used.

    You could also buy it, then get on some GM muscle forums and start offering the TH400 adapter in trade for divorce mount parts. Somewhere there's a chevelle owner with a divorce mount GV pulled out of a motorhome.

    Is this part of building the most fun, or the most frustrating? I never know til it's over. Good luck!
     
  4. nightwingdrb

    nightwingdrb Farmall Cub

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    TBAKPhi22 -- Yeah, with the regular kit, it mounts to the back of the tranny like you're saying. Since they don't make an adaptor for the T-98, I have to use a short jack shaft between the end of the tranny and the input of the OD. So I have to mount it like a divorced xfer case. I'll need some sort of mount to support its weight.

    Scavenger Scout--I already bought it because the price was just too good to pass up. Even if I do shell out the $1400 for the full on GV kit, I'll be money ahead. It's just more than I wanted to spend. Since I bought it, there has only been one listed on eBay that would have been a better deal, but that's the way things go sometimes.

    I do like the idea of haunting a Chevelle forum for IH parts though!

    Thanks for the help.
     
  5. R290

    R290 High Wheeler

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    Can you get by with just some bigger tires.:beer:
     
  6. Darrell Tuxworth

    Darrell Tuxworth Binder Driver

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    For that amount of coin I would look into an aftermarket tranny/t-case. At least this way you would have modern equipment.

    One of the vendors offers a NV4500 adapter/kit I heard works really well.

    Darrell
     
  7. Darrell Tuxworth

    Darrell Tuxworth Binder Driver

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    For that amount of coin I would look into an aftermarket tranny/t-case. At least this way you would have modern equipment.

    One of the vendors offers a NV4500 adapter I heard works really well.

    Darrell
     
  8. justinhw

    justinhw Farmall Cub

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    you mentioned a divorced overdrive unit - can you mount a divorced tcase backwards? or swap the gears?
     
  9. R290

    R290 High Wheeler

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    In a pickup sure, but a 2:1 overdrive is a bit high. 30% would be more reasonable.

    http://www.shopih.com/AA-508602-p-MT.html
    found the nv4500 adapter about 5 bills.
     
  10. nightwingdrb

    nightwingdrb Farmall Cub

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    The bigger tires are definitely on the list down the road. The ones on there now are brand new from December, so they're going to have to do for now. I also have new gears for the rear end to swap but that isn't going to get me all the way to where I want to be.

    The nv4500 adaptor was my first choice. But it was going to be $500 for the shaft, plus another $500 for anyone to make me an adaptor to mount the trans to my I-6. All told, I was looking at well over $2k to do the swap. Apparently I'm the only person in the world who wants to keep the 6cyl.

    My brother-in-law has done the backwards xfer case in a Chevy and he said that if you don't have a super high performance motor, it won't work. Since the xfer case is non synchro, you have to decide if you're driving in hi or low while you're stopped. You have to make up for that lack of gearing with motor power and a granny gear. He didn't think it'd work well with the 6.

    I found out that my idea of making the TH400 adaptor into a divorce mount won't work either. The input shaft is slightly different between the two models and by the time that I have one machined and hardened I'd be in it deeper than the GV prices. I talked to Glen from Maximum-overdrive and he said that if I want the adaptor immediately, he only wants $650. But if I'm willing to wait another month or two, he's working on a new design that won't require replacing the input shaft that will be even cheaper. He also said that he will buy my GV adaptor from me if I were to buy from him. He seemed like a really nice guy and so I will probably buy it all from him. If the GV unit hadn't been such a great deal, I probably would have bought the whole shooting match from him.
     
  11. justinhw

    justinhw Farmall Cub

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    Those are great points I didn't consider, thanks!
     
  12. Peter Albrecht

    Peter Albrecht Farmall Cub

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    I have been considering a gearvendors unit for my Travelall. I was thinking of using the divorced unit and mounting it where the center support bearing is. This would allow the jackshaft to be left alone and shortening the driveshaft and possibly changing the yoke at the OD end of the shaft. I'm not sure if the unit would be in the way of the e-brake cables. I have the Borg Warner model 11 auto tranny ( T-38 ? ) with its gear ratios and the % of overdrive, it looks like 1st gear w/od would give me a gear right between 1st & 2nd. Same deal with 2nd gear w/od. That would certainly help with towing where 2nd would be over revving and 3rd would be bogging. I have a 3:54 rear axle, so 3rd w/od would allow some faster freeway speeds when not towing. I have a line on a used divorced unit for about $1500. Fabbing a mounting bracket using the mounting surface for the center support bearing and driveshaft work will cost a good bit. Gearvendors recommends their electronics to operate the unit which is $250+. So, I'm thinking " do I want to put that much dineros into my Travelall ?" It is certainly cheaper to go the route of gearing than adding muscle to your motor. It would make towing up steep grades a little easier as well. Lots of pros, I guess the only con is the cost. Let us know what you decide to do and how it works out.
     
  13. nightwingdrb

    nightwingdrb Farmall Cub

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    This is exactly what I'm planning on doing except I plan on shortening the jack shaft and leaving the main shaft alone. I think that will be the cheaper option.

    and
    The thing about the GV system is that if it operates below about 25 mph, the oil pump doesn't develop enough pressure to keep the system properly lubricated. So, depending on how fast you can go before you shift into 2nd, you may not get the 1st OD. Both GVs and Glen at max-od have said that generally, you don't get a true doubling of your gears--it's usually like 1, 2, 2OD, 3, 3OD.

    So, do you NEED the wiring harness? Nope. You just have to remember to shut your OD off anytime you put it into reverse or go under 25 mph.

    You can find the wiring harnesses on eBay cheaper than that, but I see it as cheap insurance against forgetting to shut it off and grenading my OD.

    The mounting brackets that GV offers are nothing more than some steel plates with holes drilled in them at regular intervals. They want $250 for their mounting kit, but if you're at least familiar with regular hand tools, I just can't see there being that much material involved or it costing all that much to make. I could be wrong though. The GV kit is definately the easiest route to take.

    I definately will!
     
  14. nightwingdrb

    nightwingdrb Farmall Cub

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    Alright, it's been a while, but I finally have an outcome on my Gear Vendor's project.

    What happened was I went ahead and bought the adaptor from Maximum--overdrive. Then I found a set of instructions on one of the other forums that said you could mount the OD directly to the transmission with a single U-joint. I figured that I'd give it a try, so that I could save a little money and only have one driveshaft built. After I mounted everything up, I got a grand total of 500 feet away from the garage before the driveline vibrations nearly knocked out all my teeth.

    I tried adjusting the mounts. I tried adding bigger rubber mounts to isolate the vibrations. I tried just about every different idea I could think about and could never get it to work without vibration. The system worked fine and I was getting good results from the OD, it just shook like a paint mixer!

    Finally, I found this manual from Dana/Spicer: http://www2.dana.com/pdf/J3311-1-DSSP.pdf. The meat and potatoes of the book is that u-joints rotate in an elliptical pattern, not a true circle. So, when you've got 2 properly aligned u-joints (within 3* of parallel to each other) the acceleration of the first will cancel the decelaration of the other, and will cancel the vibrations. If you've only got 1 u-joint, you have to have everything PERFECTY aligned IN ALL DIRECTIONS to make it work without any vibrations. And then, it's never going to be absolutely smooth. I was getting things within 1* and it was still very noticeable and very bad.

    But I needed to use the truck, so I pulled everything out and decided to go ahead and do the axle swap I've been putting off. The new axle would take me from 4.56 gears to 3.73s. And it has been AMAZING. I am able to cruise at 65-70 MPH under 3000 RPM on 235/75 R 15 tires (28.8 in. tall.) According to the gear calculator I found at http://www.grimmjeeper.com/gears.html, if I upgrade to a 31" tall tire on the rear, I'll be able to do 75. Before the swap, 55 was top speed.

    So based on all of that, I have decided that I'm not really interested in trying to make the Gear Vendors stuff work. Unfortunately, my wife isn't too happy about me dropping all that money on a part that I'm not going to be able to use. Like one step above "Go sleep on the couch" not happy. Hopefully over the next week, I can get some good photos and post everything for sale and my tale of woe will save someone else from making the same mistakes I have.
     
  15. walkersscout

    walkersscout High Wheeler

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    Yeah, need to use a double cardone u-joint to avoid that problem.
     

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