Engine/Transmission (1998.5 - 2002) Double Over Drive ??? Please

[Mundgyver]

I need input from the forum please. In particular, anyone that has installed a GearVendors Overdrive on their truck. What I have is an 01 H. O. 6 Speed with the 3. 54 gearing. I would like to hear from someone who has installed an aftermarket overdrive and the information I am looking for in a focused way is what the final results were for overall MPG, RPM at 60mph, 65 mph, 70 mph and 75 mph. Thanks for your input in advance.

 

[NIsaacs]

I am not sure if I can help you on this, but I will point out a few negatives for your application,(just my opinion) of the Gear Venders overdrive. It will not work with your exhaust brake. They only come in overdrive, you have a good choice on you rear axle ratio as is. With the 6-speed, the split choice of the aux. trans is not as important as a 5-speed. Unless you are planning on some very high speeds or very low rpm's I don't see any advantage to the overdrive. I also feel that your fuel mileage will not improve to any significant amount, and if you have a 4x4 you must stay in direct. If you had a 2-wheel drive, low ratio rear axle, no jake, and a 5-speed, I would say get one!!





"NICK"

 

[SKneeland]

i doubt you would gain any mpg, lower engine rpm on a diesel doesnt necessarily mean better mileage

 

[RustyJC]

With my truck's 4. 10 rear axle, if I were looking at an overdrive that works with the 6-speed and exhaust brake, I'd go with the U. S. Gear unit. Since you already have a 3. 54 axle according to your signature, unless you regularly cruise at the Bonneville Salt Flats, I can't see where an overdrive would be of that much benefit. At the end of the day, though, it's your money and your truck.



Rusty

 

[wbrown02]

23 MPG at 75 MPH in double overdrive... ... . 1750 RPM ... ... yes a big improvement in fuel mileage . I would have no other overdrive and I have owned both US Gear and the current GearVendor. You can use your exhaust brake with the GearVendor but it must be in the direct drive position..... not a problem at all. I don't shift into overdrive until 65 MPH..... Big advantage for me is no wear on 5th gear while towing... I tow in 4th with GearVendor in OD and the motor turns 2000 RPM at 62 MPH ... ... also big difference in trans oil temp while towing..... 100 degreese cooler towing as stated above verses towing in 5th direct.....

Works great for me... ... Hope this helps!

 

[Mundgyver]

Lots of food for thought here.

 

[Tcolesanti]

With your six speed "I" would get the U. S. Gear underdrive unit so you won't have to shift a full hole when climbing a hill, you could just split the gear and go on your way.

 

[RRFinch]

I agree with wbrown02. I have installed a current version gearvendor on my 5 speed to avoid the 5th gear hard pull with fiver. The unit downshifts very smoothly when I want to use the exhaust brake; the restriction on not using brake when in od is not a big deal. Mileage hasn't change using it.

I found the kit was well made with great fit and finish. It went in as advertised. The instructions were obtuse in a few places, but common sense gets you through most of those. When you are stuck, Gear Vendors has very knowledgeable advisors that are available by phone on short notice. I called them on some things and they were quite helpful.

Fourth over is 100 rpm higher than 5th direct which is really better for pulling. 5th direct is almost too "long" for pulling in my opinion.

I only use double over when above 70 mph here in Nevada, and only when not pulling hard, or maybe going down a hill at slower speeds.

I really wish I could split 2nd more easily. 20 mph is needed to get the hydraulic pump to high enough pressure to shift transmission. Even then, it is hardly enough to split into 2nd over. I usually avoid doing this. Rather, I just rev up higher in 2nd direct.



Great transmission in my opinion.

 

[Hokey]

I installed one on my 04 and love it empty I get an additional 3mpg, I tow in third using the GV overdrive puts me in a good range towing at 60 to 65mph. I have an automatic transmission with 3. 73 gear ratio.

I don't think I would want one with a 3. 54 gear ratio esp. w/ a 5 speed I think the rpms would be too low. but the unit has worked very well for me. Hope this helps.

 

[NIsaacs]

Like I mentioned before, the 6-speed doesn't split as well as the 5-speed. One full gear of the 6-speed is almost identical to the split of the overdrive unit, it doesn't "fit" between the gears like a 5-speed. With the high torque of the Cummins, one hole of the 6-speed works very well.





"NICK"

 

[DOverton]

I really wish I could split 2nd more easily. 20 mph is needed to get the hydraulic pump to high enough pressure to shift transmission. Even then, it is hardly enough to split into 2nd over. I usually avoid doing this. Rather, I just rev up higher in 2nd direct.



Great transmission in my opinion. [/QUOTE]





I have a gear vendors myself and I called about the 2nd gear shifting too high and they sent me a new computer chip to install in the little black box. Just take the cover of the box and pry the old chip out with a tiny screwdriver and push the new one back in. This new chip will allow you to upshift to 2nd over @ 15 MPH! I have really enjoyed it since then.

Dallas...

 

[RonA]

I had a gear vendors behind my getrag and it was great. Mileage was better at 70 mph cruise. Changed to NV5600, great also. Changed to 24valve motor, not as great. Truck didn't like cruising at 65 to 70 in 6 over. If I drove at 80 it was just about right. I took it off and sold it. Had it 3 years no problems. With stock motor and 5 speed, 3rd over was a life saver when towing. Six speed doesn't need it as much, especially if motor is up in the 350+rwhp range.

 

[JFitzgerald]

I recently bought my truck with a GV already installed. It was a selling point for me, even though I thought it might be unnecessary on a 6-speed. It seems to be a very well built unit and I like it. Driving unloaded, it does help mpg, according to the factory fuel computer anyway. If I'm not going over 60 or so, or there's wind, I don't use it, at least until I start BOMBing. I haven't got my gooseneck hitch installed yet, so I haven't towed heavy to see if it would be helpful splitting gears. Seems like it would really help in interstate driving at 70 plus mph. I'm still not sure where the speedo is getting its' signal, and if it compensates for the OD??

 

[Graphic man]

my dad put US GEAR underdrive unit in his 2000 F350 5 speed

he has 3:73 gears and tows a 18,000lb 5 wheel

he loves it ! he now has 10 gears to play with :-laf

he thinks hes a big rig



hope this helps

 

[SHobbs]

Why not go with a Road Ranger 13 spd. I'm wondering if it would be a direct bolt up install. I like the gearing with the Road Ranger. More baby steps to get going faster and easier.