Does anyone have any 1st hand experience with this device. I have looked at the numbers that they quote, increase of 40HP, 60 Torque and 20% increase in fuel milage. Is there anything the driver needs to do with a 4 speed automatic, or do you just put it in gear and drive. It seems they put a switch on the floor board to dis-engage the unit. I am considering this as an option.

 

how can an o/d transmission increase hp/tq?

 

its does not increase engine HP or TQ but if u dont take in account the gear reduction or increase on the same gear it make more power to the wheel than a similar truck whitout this device
so they attracts buyers whit this.
but MPG increase i prolly true cuz u will spin the engine slower...
but still whitin the broad power zone

think about a trucks in drag race,the one whit the gear vendor act like a 8speed tranny
low1-1 low2-2 low3-3 low4-4 for underdrive
1-high1 2 high2 3 high3 4 high4 for overdrive
so imagine whit a 6speed... this way ur staying almost always in the desired rpm range....

 

Don't know how they work on an auto as mine is a 6 speend manual but would guess woligator is correct in his conclusions. For instance my 5th over is almost the exact same ratio as 6th under but the 5th over will pull a grade a lot better without having to downshift as soon asI would if I was pulling in 6th under. So it does not really give you any extra hp or mpg but the gear splits do aloow you to pull loads better and optimize your rpms for conditions.On the mpg thing itmaintains consistent mpgs at higher speeds in 6th over. I get 18.5 mpg running 55mph in 6th gear I can flip it into 6th over and maintain that 18.5 mpgup to 83mph at 2000rpmsany faster thanthat it starts to drop off. That drastic mpg dropoff starts at about 64 mph on a6 speed truck without GV OD andif I was running in 6th under (stock 6th) at 83mph my rpms would be about 2500 and I would get about 15 mpg. The 500 rpm drop is worth it I would dothis mod again in a heartbeat to another CTD if I ever bought one. To be able to go with the flow of traffic where I live the speed limit being 70 mph and maintian good economy is awesome. To be able to pass the flow, smoke em, and still maintainit is even better. Also you can mount the switch on your automatic column gear shifter, that's where I would put it if I were you,and there will be a small electronicbox with an on/off switch that is mounted somewheredown in the console too..

 

yeah and im not sure cuz i never played whit one but if u can over-under drive on demande u can go
even farther

low1-1-high1 and so on so its make a 6speeds in a 18spd

 

Wait no you got that one wrong wolly"Underdrive" is just another word forstock and you can't split anything going slower than about 18mph either the GV won't let you for whatever reason. Sothe GV gives me10 forward gears and just1 reverseon my 6 speed. Low, 2nd, 3rd under, 3rd over, 4th under, 4th over, 5th under, 5th over, 6th under, 6th over. It's not really prcatical to split every gear on up shifts all I everdo is just row through the stock "underdrive" gears then flip into overdrive if I need it. The clucth isn't absolutely necessary to shift into overdrive but it's really rough and jerky if you don't use it so I always use mine to keep it smooth and not shock anything. Also there is a slight clunk on the downshift out of overdrive that GV says is normal and everyone else I know that has the unit experiences the same clunking. With time though it seems to be getting less and less maybe it's breaking in I dunno..

The auto is a different animal though I really have no idea how they would work on one and don't know of anyone with an autoon the forums using one. I assume an auto will run stock faster than 25mph in first gear? so you should be able to split 1st gear on one which I can't do in mine so there's 8 forward gears on 48RE. But see I don't split every gear on upshifts because it's not practical. So on a 48RE would the GV always go from 1 to 1over to 2 then 2over so on and so forth on upshiftsor would it just be best to get up to speed normally 1 thru 4 and then flip into 4th over as with my manual??? I don't know this is a question mark for me...

Also note the GV is electronic controlled anytimeyou use 4WD it's wired so the unit will turn off and you can't use it again until you go bak to 2WD turn the truckoff and start it up again. It's a built in saftey feature. The unit is on the tail end of the transmission behind the transfer case so if you were able to go into overdrive while 4WD is engaged it would probablymake some awful noises and tear stuff upbecause the transfer case would still have thefront wheels turing by the stock underdrive ratiowhile the backtires would be in the higher overdrive.

 

How much does it usually cost to do this?

 

Between $2700-$3500 depending on who does the install/

 

It'll cost you $2800 + about $75 shipping for the unit itself. By the time you take the driveshaft to a machine shop to have it shortened you're probably looking at about$3200on a DIY. There's a company called Camping World (google them they have a website with a page that shows all locations) that has stores all over the United States that sells RV's and RV accesories.They also service RV's and do installs of accessories. WhenI called GV asking about the unit that's who they recommended in my area. The one in Nashville, TN did my install had my truck for two days and charged $750 (this is the price GV recommends todealers for install labor) for labor + I had to supply the quart and a half of specialoilfor the unit thenI had to pay 10% TN state sales tax on top of that.By the time it was all said and done just a shade under $4000. Pricey but worth it to me as I didn't have the time to do the install myself. But it's not hard to do if you have the time, tools, and some reasonable wrenching skillsI'd say DIY and save some money.

 

might want to give a call to gv's and ask if you can use the double overdrive on the 48re?