I had to delay my engine job on my truck due to issues from the city harassing me. But in this time I been thinking about running a Gear Vendors unit on my C6 since I already had planned on getting a built 9" center chunk to swap into my truck to change my gears as well as go with a truetrak.

How ever I cant really find anything online, video nor text based on installation of this unit on a C6 transmission let alone a C6 transmission in a 80-86 year model truck.

Has anyone on here ever installed one of these units before in these trucks?

If so which one did you use? long tail shaft one or the short tail shaft one that looks to come with a output shaft?

Im really trying to decide on this but not sure about what has to be mounted and what modifications I will have to make outside of shortening the driveshaft.

The pictures looks like they have a smallish oblong computer which I could probably ziptie under the dash somewhere but don't know how big it is and I am pretty cluttered behind the dash. Then there is hooking up the OEM speedometer cable to this new setup it looks like you use a speed sensor to make the connection between new and oem but not sure.

In the end I am seriously contemplating doing this as I am thinking of getting one of those Currie 9" chunks with either a 3.25:1 or 3.50-3.55:1 ring and pinion on a trutrak assembly to swap in my truck, that with 31" tires should give me between 2.50:1 to 2.75:1 in overdrive which would put me between where I am now with my stock 2.75:1 with 31" tires to where the truck would be with stock height tires. I think this could go nicely with my engine swap I am doing as well but I just cant decide on if this will be a easy enough swap or if there will be a bunch of modifications that needs to be done. I prefer something that is mostly bolt in just incase I decide to ever go back to the original parts.

 

First I have not done an add on OD unit swap but have looked into this a few times fro my 81 F100 with 300 six & T18.
Do a search in the other truck areas and maybe the drive line area as I know I have seen a post or 2 on this.
Also do a Google search on the GV OD unit as any information you find will most likely be the same for all of them.

It is best to give GV a call to see what they have to say on what unit you would need and what all is needed to install other than the drive shaft being shorten.
I also see GV has changed the site some. I don't remember seeing anything on gear ratios or tire size on the order page. I thought the GV only had 1 ratio think 28% OD?

Now what I have seen they bolt in, a little wiring, shorten the drive shaft and drive.
The bolt in is remove the drive shaft and the stock tail housing, install the adaptor housing, install the GV unit, install shorter drive shaft and use the short adaptor speedo cable (extender) to fit in the GV unit.
I also heard the unit would not go into OD below 30 MPH, that is part of what that box does and the adaptor speedo cable has a sensor that feeds back to the box to let it know you are going faster than 30 MPH and will let the unit shift to OD.
That one reason why I have been looking at the Advance Adaptor's Range Splitter OD unit as you can split every gear but it is only made for a stick trany. It is also the only OD unit made that you can use in 4x4, GV fits on the rear out put shaft of the transfer case.

Now I do like the GV button operation where the AA RS has a shifter you have to move like a 2nd stick trany but its been posted some have used solenoid to shift it.
I would like to see what you can find on this unit.
Dave ----

 

Given the cost of the gear vendors overdrive and the mods required to fit it you may be further ahead with a built AOD or an E4OD with a stand alone controller.

As for the gear vendors.
https://www.gearvendors.com/f2wd3s.html

 

A gear vendors on a C6 is pointless in my OP opinion. I tried twice in the 90's. The inherent problem is the C6 doesn't have a lock up converter. The rpm drop isn't that significant because you have so much slippage in the converter which causes heat and a lot of it. It's a overpriced solution that doesn't deliver in that application. On the other hand the gear vendors behind the ZF5 was a sweet setup and works great.

 

I agree with the last two posts. If you figure the total cost, it 's going to be the same as getting a rebuilt E4OD and a controller box and wiring harness, and your end result will be a much cleaner setup with better fuel mileage than the c6 would ever give you. And you can do some interesting things with the aftermarket transmission controllers, like tow/ haul modes with engine braking and stuff like that.

 

Well my thing is factory overdrive transmissions are supposed to be left in D when towing unless I go with a newer style transmission with computers and everything. I am trying to keep away from something like that as factory setups tend to be on the large size from personal experience doing conversions like this.

The Gear Vendors unit Ive heard good and bad things about it but it supposedly has a smaller controller than oem units. Not to mention C6 transmissions are heavy duty transmissions. I hate to junk a perfectly good heavy duty transmission for some overdrive piece that I cant use overdrive while towing.

The whole point for the overdrive unit would be two fold, one would be splitting the gears and the second would be allowing me to up my axle ratio slightly but be able to have a effective final ratio similar to oem.

These units are listed as being 0.78:1, my truck is currently 2.75:1 but with 31" tires that is more like a 2.55:1 ratio from what all the calculators online tend to say. If I go with say a 3.05:1 gear would put me back to oem spec with my taller tires. Closest I can get how ever is a Currie Third member with a 3.25:1 gear. Even with 31" tires that wouldn't put me back anywhere near my oem axle ratio. Now on paper if I go as high as a 3.70:1 axle ratio with .78:1 overdrive would drop me back down to a 2.88:1 which should be somewhere around 2.60:1 with my 31" tires.

That is the only two reasons why I am looking at it. If its not going to achieve my goal of allowing me to run a lower axle gear to turn my taller tires easier but still provide me with stock like cruising well then I might as well not even get it and just go with the 3.25:1 currie third member with TruTrak and just live with having higher rpm than I would have if I just throw the stock tires back on.

Im not doing it for improving fuel economy, Im doing it for helping my truck pull the taller tires I have as well offset the C6 transmission. The goal was really to improve acceleration but at the same time give me the benefit of lowering gear ratio back down near to stock ratio for highway use.

 

I called them up like two years ago. Asked them if they could do just a overdrive unit without the splitter ability or do something without this on the fly adjusting. The guy I talked to I told him this is for a truck I don't need launch control and all this other hotrod stuff I just wanted a bolt in overdrive unit that will allow me to lower my axle ratio to help turn my bigger than stock tires easier as well as improve acceleration while being able to cruise at the same rpm I was cruising at before roughly. if I can get the final gear ratio back close to where I am at now I would be in the neighborhood of around 2,750 rpm at 75 mph which I am fine with turning that rpm. But if I go with say a 3.25:1 axle ratio without a overdrive unit that would put me lower than what was stock so I theorize I would be spinning closer to 3,200 rpm at 75 mph. In the end I had some questions answered but im left contemplating if its worth spending the $3,000 and if it will even achieve my goal. I don't expect it to improve fuel economy. I just hope it doesn't hurt fuel economy over what I have now.

From the stories I have heard, Ive heard some praise it and ive heard some say what garbage it is and it doesn't work right. Makes me wonder truly if people are not setting something up properly. Ive heard bad things about the fuel command module but when using it with a FI Tech setup it clearly states you have to change the fuel pump setting in the FI Tech interface to work properly with the command module. I always wondered if people are not doing that and blaming the product for their inability to read. I feel that way about gearvendors as well. Are they truly bad like I have heard or are those people that didn't read the instructions and is blaming the product. The product cant be bad if they are still in business and being used in drag cars even.

Math wise it shows 0.78:1 is the overdrive ratio so with a 3.50:1 axle ratio which Currie sells a 3.50:1 third member with TruTrak for $1,500, that 3.50:1 in overdrive would be 2.73:1 which is slightly higher than my stock 2.75:1 which in my mind would put me back to where I am at right now with my taller tires when I am in overdrive. So in my head I would be still turning around 2,750 rpm at 75 mph but will have way better acceleration by running a 3.50:1 axle ratio with 31" tires over running the stock 2.75:1 axle ratio with 31" tires.

I understand lots of people go with overdrives for fuel economy. I am looking at it more for giving me the option of going with a lower gearing to help my acceleration as well as towing but at the same time be selected properly to achieve the same highway driving like I have now once it shifts into overdrive.

It was pointed out years ago to me you cant expect to get great fuel economy out of these trucks due to the flat nose of the truck. I accepted that long ago. Right now with my pending swap to a '96 Explorer 5.0 long block with GT40 heads I am contemplating if I want to do this gearvendors unit as well.

I already plan on buying a Currie third member for the TruTrak but the highest gear I can get is 3.25:1 which isn't that close to my stock 2.75:1. But if I go with a gear vendors unit I can go all the way up to a 3.70:1 and still on paper have a 2.88:1 effective ratio when in over drive. That would really wake my truck up acceleration wise when being powered by a 290ish hp 302 with a C6 behind it.

 

Ok now I see what you are trying to end up with, a lower first gear with a 3.50? 3rd member and end up with a final stock ratio of 2.75 with the 31" tires using the GV OD unit.
This is not what most people do with an OD unit and why I think they said what they did.

Now someone did bring up a good point of the non-lock up converter of the C6 and the slip adding heat but what you want to do I don't think it would be any worst than what you have now.
May be less slip as you end up with the 2.75 ratio with the 31" tires as you are at what 2.50 something with the 31" tires now and with the lower first gear ratio less slip there as well.

What they are talking of is a 2.75 rear gear, 31" tires and then adding the GV OD unit so you end up with a 1.30 (just a number I pulled) final ratio and that would do in the C6 with heat.

Now for the money of the GV unit I would give a look at a built AOD or an E4OD with a stand alone controller. to see what they go for might be close?
I would compare the ratios between them and the C6. The first gear might be a lower ratio. Then look at the OD ratio to see how that compares to the GV unit.
One thing to keep in mind is the lock up converter should also lower the RPM a little as you have less converter slippage and less heat.

I don't know if this is an issue with a built AOD or E4OD but with my 02 Dodge was told something about towing in OD and the lock up the trans does not flow fluid thru it to keep it cool and something had to be done to fix that. I don't remember what that was now. I never did it, I have done a lot of towing in OD and have 225K on the trany with only normal service. Just something to look into if it is an issue.
Dave ----

 

I looked at the AOD few years back as a possible swap but got away from it when I was reading it requires a unique carb with a AOD linkage hook up for controlling the AOD or something like that. But because of the steep overdrive of the AOD I could run a 4.11:1 ring and pinion and in over drive be around 3.00:1 still.

But of course I will go through and look again before I finalize my decision. I know it would be insane to leave a 2.75:1 axle ratio and throw in a gearvendors unit. I do want to run the trutrak differential in any case and since I have to pull the axles and the third member out I have two choices. One is to disassemble my unit and reuse my 2.75:1 ring and pinion gears with the trutrak or take and get one of those prebuilt third members that is ready to go. I think that will be better for me as if I ever decide to revert my changes I can throw in the old unit again.

But yea, its just something I keep throwing around in my head thinking it might would be a good upgrade with a gear swap as well since I will be in the rear axle anyways.

 

I can see the rear gear swap as a whole 3rd member. I would do the same thing so I don't have to set it up did that a few times and it's not fun.

I also have seen posts on the AOD rod with aftermarket carbs and why you would be turned off from them.
How is the EAOD, does it also use a rod or does it use a TPS being it needs to run a control box? Have not seen much on this trany.
Dave ----

 

The E4OD is the heavy duty unit found in f250's and 350's. It was not a very reliable transmission when it first came out, but around 1996 Ford beefed it up and it turned out to be a decent transmission, found behind the powerstrokes and the 460's. Most of the older E4OD trannies are rebuilt to post 96 specs. It is a fully electronic transmission, so it requires a computer box you can buy for around $500 aftermarket.

 

If the EAOD was used with power stroke's & 460's then the bell housing would not bolt to Rusty's 302 or did they make one for the small blocks?
Dave ----

 

E4OD was used with 351W, 460 and diesel. You need to get the correct one to fit on the engine you have.

I don't recall ever hearing about an EAOD.

 

I recently picked up a couple used gv units that were on 86 trucks. Both are the 4x4 adapter model with one being behind a c6 and the other a t19. Have done a fair amount of research before and after the purchase as well as having bought the c6 instruction/installation manual. So I'll be happy to answer any questions I can with those given resources.
Worth noting that my truck is going through a major restore project right now that derailed my plans to install it so I have never actually used one. 😊
Some of this stuff you all may know but I didn't know much about them initially so just putting down the stuff I found interesting.
Earlier I said 4x4 model and what I mean by that is that GV has their own bw1345 case back half that you swap out and the unit (with short adapter) attaches to the t case. All gv units are the same and it's just the adapter /computer that differs. So if going used, you can pick up the pieces from different sources/vehicles. Additionally you dont even have to have the computer if you want to toggle the solenoid on/off yourself (this does incur some definite risks though).

Regarding the cosmetics of it - Mine is an older version so the computers have changed in size some but I don't believe in function. Inside the cab you have the computer (for lockout safety), the dash switch, and the foot switch. One location for the computer is high up on the driver's kick panel. Guessing mine is 4x3x1 so I am planning to mount it on that piece of metal on the firewall to the right of the gas pedal with all the grounding holes in it (I don't have the black box there). If that fails I will velcro it to the firewall up high and out of the way The foot pedal I havent quite decided on the location yet since it's going to require some testing to see what feels natural since the dimmer switch (same hardware) is in the obvious location. The dash switch I am guessing most people with these trucks velcroed it to the bottom of the dash. It is a toggle switch and an indicator light. If one isn't going to toggle the modes than it could be replaced with a simple led indicator light (repurpose the Emissions/Shift light on the dash?) . My plan is to make a plastic piece that snaps into that cubby to the right of the steering column and mount the light/toggle there.
As has been mentioned, the install looks and reads as very straightforward and bolt in. Only real change is shortening the driveshaft or getting a new one to keep the old as a backup.

Again, while my driving usage experience is nonexistent, happy to answer any questions I can from physical unit inspection or the manual.

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Yep Ive done them at work as well, it can be a pain. Something I personally wouldn't want to even do myself on my own Id rather pay someone else to set it up for me lol. As far as the newer style I think they are all computer controlled. Even the newer style AOD that doesn't use said rod is computer controlled as well. I could pick up a later model AOD that is computer controlled but as was said above the computer aftermarket ones which will be easier to source are not cheap themselves. If I got the AOD as a reman ive seen go for around $2,000 - $2,500 with shipping but no core charge included. The place I am getting my long block from they sell the E4OD for $2,000 themselves but doesn't include the $300 for shipping nor the $800 core charge. Either way to go I would have to get a different converter as well as the computer to control the shifting. I will have to sit down and really break down the pricing but I think the pricing will be pretty closely related.

There are a few questions that I keep asking myself that I am trying to answer. One of them is the floor mounted dimmer switch control for manual engage/disengage or what ever that is for. My truck has a floor mounted dimmer switch and I don't want to clutter the floor up with more switches. Im kinda curious if their system has to have a switch wired up or if one could just simply leave it unplugged. If it functions how I understand how it is to function just leaving the wires disconnected from a switch shouldn't effect the operation of the unit.

The other thing is the switch under the dash that illuminates for letting you know when you are in overdrive. What ever that switch is for if its just for simple activation of the unit to be on or off then I would just use a plain old push on/off button and mount it flush on the bottom of the dash as the only reason for me to be switching it off is if the thing is malfunctioning. As far as light goes I don't really need a light as I would know if its engaged in OD or not by feel. If I did put a light in, I would use the 4x4 dash indicator that is empty on my truck, just would have to find out a way to make a new lens for it to just say OverDrive or OD to replace the 4X4 marking.

But from the reading that I did I read somewhere that these units engage at like 30 mph for overdrive. I hate to have a big light on the dash that is on 99% of the time for driving even in the city if that is true.

In any case ideally Id like to just bolt this unit in give it power and ground mount the main switch that activate and deactivates the unit and call it quits. I know the floor mounted switch is to shut off the OD manually for pulling up hills if you need it but I don't think I ever would need that as the truck is only capable of pulling so much weight being a short bed flareside F150. I wouldn't over load the trucks towing capability as it will also over load the trucks braking ability and I cant go wiring in a trailer brake controller, I already have too much stuff mounted under my dash as it is that I have no more room for switches and such.