Are there any add on overdrive units available for my 73 F250 4x4 ? It's a four speed , I'm thinking one that would mount between the transmission and transfer case.

 

go online to gearvender.com it is an overdrive that bolts to the tailshaft my are c6 auto but i have seen them there for that app wont be cheap mind you with buying,shipping,drive shaft work ect but i have 2 of them in my trucks and i love them no problems in the 5 years drops the rpm about 600, very good reliable unit you can check my gallery "class of 79" i have a pic of the unit installed there hope this helps regurds

 

I believe this is the correct website: Gear Vendors under/overdrive transmissions the most awarded auxiliary transmissions.

 

great product,

my father in law has one on his 1988 (or 89) supercab Diesel (with Banks turbo kit)
he's got the 4sp (3+granny low) and 4.10 rear end

that truck has almost 300K on it, and still gets about 20mpg @70mph
yet still pulls like a ****

 

Ive seen them that mount between the trans and transfer, I just dont remember who made them. I know they are not near as common as the Gear Vendors that mount on the rear of the transfer. The trouble with one that goes between the two is you will have to fab up some new transfer case linkage or your shifter will end up under the seat. Ive got a buddy who has a Gear Vendors in his Dodge and loves it. And how many times are you really going to need OD when youre in four wheel drive??????????

 

peb there is some sort of 4 wheel "lock out switch that only alows unit in 2 wd not sure how it works as my trucks are 2 wd but like i said not cheap but a good reliable od trans these guys did their home work and would put it in my other 2 if i could afford it

 

Yeah there is a lock out on them to prevent them from engaging while youre in 4WD. I think I remember my buddy saying that there is also a lockout in 1st, 2nd and maybe 3rd gears in his 5 speed Dodge. My buddy set his up in his Dodge utilizing a 2 speed axle switch from a medium duty truck mounted on the shifter. You know........the red button............... He uses it to split gears just like a 2 speed axle. Works slick..............

 

you can also "split" the gears on the gear vender works good for my truck/camper/boat combo in the hills but my 78 reg cab/501 is way to fast to do that as you only have time to hang on and thats about it but if i ease up on the throttle it sounds neat "going through all 6" and the "6 speed emblem" is a real consversation starter at the car shows i have had guys crawl underneith to see how its installed

 

yep, they are called a dual range by u.s. gear. they are available in under/direct and direct/over (there might have been an under/over but im not completely sure anymore) they are gear driven rather than planetary (like an aux. box in a semi) and they can be shifted at lower speeds. if i remember right it is only about an inch longer than the adapter that it replaces.

I never did understand how the gear vendor could work behind the transfer with its under/over gears. it would be like having different gears in the front axle.

I would let you know how they do, but I don't have my bronco together yet

mine is an under/direct so I can start off in 2-LO and run 33's with 3.55's. in the low side it will like swapping to 4.10s but in high it should be quiet and efficient, plus i will be able to split gears to keep the little 6 in its powerband! I need to get back home and get back to work on it...

 

Yeah the one in my buddies Dodge is a Gear Vendors direct/overdrive. It has a switch that prevents it from shifting when it is in 4x4, I beleive it's operated off of the transfer case linkage. It also has a switch that prevents it from shifting when in 1st, 2nd and I beleive 3rd gears. I'm not sure how that swich works....The gear box is behind the transfer case in his 12 valve Cummins 5 speed 4x4 3/4 ton. He pulls heavy horse trailers a lot with it and it has been brick reliable. Like I mentioned before, How many times would you really need to use overdrive when you are in 4 wheel drive? Now if a guy went with an underdrive/ direct unit that would be a different story. I could see how you would want underdrive for lower gears when 4 wheeling............ then you would want a unit that mounts betweeen the transmission and the transfer case, so it would be usable in all gears whether you were in 2wd or 4wd. But just for an overdrive to help keep the RPM down at higway speeds, I think the Gear Vendors would be the way to go. I am in the process of swapping in a ZF 5 speed behind a 4BT Cummins in my 78 F150 4x4 and may consider a Gear Vendors at some point, just to keep the RPM down even further out on the highway for better fuel mileage. Meaning I'd end up running a double overdrive, the same as my buddies Dodge which he swears by.............

 

The US Gear unit is no longer being manufactured and parts for them are getting quite scarce.

 

Consider a "ranger" overdrive half the cost of the Gear vendors and it mounts in front of the 4 speed. Ranger Overdrive

 

all the good stuff is getting scarce, I just forked out 4 digits for a doug nash (now by richmond) 4+1 for my capri

not a big fan of overdrives (can you tell?)

tex, I recall hearing that, but the dual range is simple enough i'm not that worried about it

the ranger overdrive is neat, and gives you yet another lever on the floor! then you just need a doubler and twin stick for the x-case!

 

As I recall, the US Gear unit was originally designed and manufactured by Doug Nash.

 

yeah, ironic huh? i didn't know until i already owned both of them.

there is a new aux tranny out that takes place of the extension housing, unfortunately its just a jeep thing so far.

also to consider is that you will still have the divorced transfer case, so the ranger unit would probably be easiest.