Can someone please enlighten me.....

Is there a any sort overdrive for a 6 speed manual, i think i read a thread about it somewhere on DTR but can't remember where i read it, or is it a figment of my imagination, any input would be a help... thanks, Ade..

 

Yes, its an aftermarket overdrive gearbox that you put on the back of your existing transfer case. You remove the tailcone from the transfer case, put this baby on and shorten your rear driveshaft the required amount. Its electrically operated and has a .78 gear ratio. One very important thing is that you cant use it when in 4WD, since it only effects the ratio for the rear driveshaft, not the front. When installing it you wire the overdrive unit's little controller box into your 4WD switches in the transfer case so that it wont let you engage it in 4WD by accident.

The two companies that make them are : Gear Vendors Overdrive and US Gear Overdrive

www.gearvendors.com

www.usgear.com/v2od.html


I will warn you though, these buggers are pricey.... about $2,500...


Cheers ( just had to do that.... I noticed you were from the UK)

Kevin

 

The US gear unit goes between the transfer case and trans and can be used in 4wd. It is also much stronger.

 

Thanks guys, as usual you are a fountain of knowledge, my real reason for wanting an overdrive unit is for fuel ecconomy, or am i barking up the wrong tree.
i don't tow any trailers, but sometimes we are fully loaded up in the back.

I drive from my home in England to southern Spain at least twice a year with the milage topping 10,000 miles for the round trips, and of course fuel here in the UK is about 5 times higher than in the US, at the moment Diesel is about $1.505 per liter, it's about half the UK price on continental Europe

I'm not sure i can afford a new unit, but i may be able to find a good used one over here in the UK, as there are loads of commercial trucks, lorries etc, with Cummins/ NV5600 applications over here, so there will be hopefully some in scrap yards, or better still find one by word of mouth.

Which in your view is the better product, bearing in mind i do some off roading in Spain

 

I have the Gear Vendors unit. It has been 100% perfect and reliable including one instance where it was if fact engaged while in 4WD on the highway at 60 MPH .... DONT ask.... But it works fine even to this day.


It sounds like the US gear model may have some advantages though...


Don think you will find any in the boneyards, since these are not OEM provided devices even in lorries....

I got mine for $600 at an equipment auction



Kevin

 

They are both very strong units, but it will probably come down to if you want to split in 4wd and what the total cost will be. Not sure how much fuel you would have to save to pay for this mod. Most like it for being able to have the perfect gear for a large load and a hill. Also, not sure if it is an issue for you, but I do not believe the gearvendors can be used with a exhaust brake.

One thing you may want to look at is either a larger tank to replace the factory one or an auxiliary tank if you have room to take advantage of the times you can get the really cheap fuel. I also like not haveing to fill up but about 1500 miles or so.

 

I heard that the gearvendors is the one that would not work with an exhaust brake because it needs power input from the drive side and a certain speed to let the overdrive engage, and trying to slow it down from the output side could damage it, is this correct? Also, US Gear has an overdrive unit that hangs off the back like the GV for cars, but for truck its called a dual-range auxillary transmission that goes between the transmission and transfer case, and if it's all gears then an exhaust brake would not be a problem.

 

So your truck came with an overdrive 6spd unit that with a 3.55 ratio which should allow you to run at 1850 at approx 60 mph/100kph. The torque on your engine is peaked at between 1800 and 2100 rpm and you don't pull but run heavy. If you install another overdrive at .78 this will drop your rpm another 200 rpm and result in shifting down more often than now to due a higher torque load on the engine. A more likely solution is an auxiliary fuel tank to take advantage of lower fuel prices along the way- I pack an additional 50 gal tank that is as high as the box, 12" wide and fits in between the p/u box sides= approx 1000miles without fuelling loaded to 8500lb to 10,000lbs all the time. You will not save any fuel but add cost and weight to your truck with an additional overdrive = to 40%. Some have tried this but are almost always empty to show any gain. PK

 

Overdrive was an option on my truck, an O/D light comes on to tell me it's off when all the other idiot lights with ignition key is turned, but unless i'm missing something, the option was not taken up when the truck was purchased in 1999.

The more i think about it the more i agree with you, an aux tank is looking to be a good alternative against a lot of money for an overdrive, it's going to take alot of years to pay for a new overdrive unit.

I have also toyed with the idea of altering the final drive ratios in both axles down to 3.0 or 3.1, and using free wheeling lockable hubs to iliminate some of the drag, though i'm not certain i can use these hubs on my truck.

The truck has oversized tyres on it, so the actual speed is at least 10% over advertised speed on the speedo , ie when the speedo shows 62 mph the actual speed is near enough 70 mph, Which equates to 19,000 rpm.. Ade

 

If ya'll have a dealer on the other side of the pond and if they have a DRBIII, they can correct your speedo. Not sure what it will cost you, but it cost me $25.00.

I am not 100% positive, but I do not think you can go higher (numerically lower) than 3.54. Someone else may know for certain.

I have never noticed an OD idiot light on my '00 six speed, but I will check next time I fire it up. But, I would guess it is for automatics only.

 

One can pretty much guarrantee the NV5600 6 speed in your truck is an overdrive unit and you will have 3.55 gears to be running the speed you are at 1900 rpm. You should also have the front axle disconnect system which means the only parts turning in the front end are the axles not the ring gear. I agree the locking type hubs are better and can be put on but the cost is unbelievable. I am curious as to how this truck got to England and where it originated, can't see it being built any different than the ones in North America. You still did not say as to the weight you carry consistantly causing reduced fuel milage, price of fuel is high but do you need the truck if it is too costly to run. PK

 

If he has 3.55 and oversized tires he is already geared borderline to excessive. Mine runs 1950 at 70 with 32 inch tires. I could not even consider more overdrive.

 

OK guys thanks for your comments they are all noted, and i think upon reflection your right, perhaps it's best left alone, Like you Haulin, i'm running on 32" tyres, i think any higher would make it roll too much when cornering, but i'll ask my local Chrysler dealer if he can set the speedo, i'll let you know how much.

The weight varies sometimes it's virtualy zero, and very occasionally it's it may be at max weight, all i'm intrested in is getting the max per gall, i know there are too many variables in here, but there has to be some middle ground

I'm going to settle for a aux fuel tank, now where did i put that old 50 gall drum

I brought the truck from a joint USAF/RAF Air Force in the east of England, with all taxes paid etc. It was brought new in New Mexico and shipped here, by it's previous owner who is still a serving officer, and wants to buy a MINI. There are alot of Rams here in the UK, mostly brought from specialist dealers, which supply brand new and late second hand models, some are as much as £40,0000. Dodge way out strips the other 2 GM snd F**D in sales, though Chrysler are going to start to sell Rams in the show rooms sometime this or next year.

I have always driven American cars, well at least for the last 25 years, i just like to be diffrent, i do miss that V8 burble that i had with my 383 Challenger( see my pics),but still have a 1977 Caddy Seville which i've had since 1984,

 

Cool, I did not realize that the availability of such vehicles in the UK. I never considered they would be even welcome on those narrow little roads made for mini's. We are just happy to get 7-10 mpg pulling a trailer 20-27,000lbs gross truck, trailer and load. Our truck with the steel deck and fuel tank is never under 8000lbs and can get up to 23mpg (CDN) at 90-100kph on cruise. I have an 80 Gal aluminum truck tank that will be mounted this summer for extra fuel capacity so as to meet the new auxiliary fuel tank regulations. PK

 

PK,

Iwould be greatful for some suggestions with regard to an aux tank and suitable locations, i was uder the truck today as it had it's annual MOT inspection, there is not alot of room under there except where the spare tyre is located, i might end up putting the tyre on an A frame on the back of the truck on a pair of hinges so i can swing it clear of the tail gate. I don't think i can legally carry fuel in bed of the truck well at least not more than a couple of gallons in a can.

The vehicle inspector had great trouble in getting any reading on the emissions test, "boy she runs clean". Obviously you have much stricter regulations on emissions than we do, we always seem to play catch up in that dept. He said it's like inspecting a tractor, and his last comment was "it's a little bit over engineered isn't it". I'm used to such comments, the favourite being "how many gallons does it do to the mile" etc.

Just for your information i think that there are about 2000,000 American cars registered in the UK, and there are bound to be at least the same amount unregistered, but out of a total of 24,000,000 cars in the UK. Yank iron only has a very small %. UK is the bargin basement for US cars, as there seems to be more being exported out abroard especially to the US, than are coming in. Mopar is the King of the Hill, as far as prices go, but obviously they are cheaper than anywhere else.

If you ever visit the UK and are intrested, there are alot of shows, every weekend in the summer months, and the standard is on the hole very high, some of the bigger shows can attract as many as 3,000-4,000 cars, you name it if it was made in the US, no matter how rare, there will be at least. I've been to shows where 6 superbirds, 2 Daytonas, even Cords have been in attendance. Get hold of a copy of Classic American mag, look it up on the internet, it's the best mag in it's field in Europe. Ade