Anyone on here put a Gear Vendors Overdrive on their gas powered SD yet? If so, i'd like some testimony... thinking about making the purchase and not sure if they are all they're cracked up to be for increasing fuel economy

 

I am quite interested in this topic

 

I've always heard that it worked, but just wasn't worth the money. Of course this was when gas was $2 a gallon......

 

I have one, but its not in my truck. Its in my big block Monte Carlo. I will vouch for its strength and durability. It made my animal a lot more tame to drive, it made the 4:56 gears streetable. I would say that it definitely would make a difference if you did alot of highway traveling. You have to weigh the cost of the installation vs. the potential fuel savings to see if it would make financial sense. If your not worried about the money, go for it, I dont think you will be dissapointed. I thought about doing it myself. Just think then you would have a 10 speed transmission!!

 

I would think that it would be more suited to the diesels as they have all that low torque to move a heavy SD at low RPM. You might be undergearing the gas engines too much, but maybe not the V10.

I couldn't imagine it being any good at all with a 2V 5.4 in a SD. The stock gearing on my 2V 5.4 in my F150 feels extremely weak on the highway.

Mike

 

Do you have the 3.73? my truck, despite its size screams on the expressway until about 99mph when it cuts out. Mine is only a dog thru first gear, other than that, I had a GV OD on my 86 with a 460 and my 89 7.3 IDI. It made a huge difference, I think that it shouldn't be on the verge of over/ under gearing the 5.4 simply because the 5.4-2V has more power and torque than both those engines (according to factory ratings and dyno slips).

My 5.4 is putting roughly 235 horse on the ground and if my memory serves me right it was right around 330 lb-ft of torque. With a relatively flat torque curve

My old 460 dyno at 220hp and 300 lb-ft AFTER an edelbrock performer manifold, holley carb, and dual exhaust. It had a VERY flat torque curve.

Not to get side tracked, but from a power aspect i don't see why the GV OD would be an issue, just because it has 8 small holes don't mean it's too anemic to turn another gear

Also, if I did put the GV on there would't it turn into a 12 speed (4 std gears +underdrive on all 4+ overdrive on all 4)

 

No. You either get the under drive or the overdrive, not both. You'll end up with 8 (or maybe 7 if they don't split first).

 

Hello 5.4l to freedom,
The gear vendors is not an over/under drive. it just adds 1 overdrive gear. It operates as a 1 to 1 coupler until it is engaged then it adds the .68 (I think) to 1 overdrive gear. So you can have 1st, 1high, 2nd, 2high, etc.It has an internal pump similar to that in any automatic transmission, so it needs to have the vehicle moving to be able to shift into the overdrive gear. They reccomend 30 MPH before engaging it. You cant use it in 4 wheel drive because you would have different gear ratios front to rear. (it attaches to the rear of the trans or tranfer case, but does not affect the transfer case.)If you buy one new it has all the components and speed sensing equipment to ensure that it engages and disengages as designed. I have it on a simple switch on my shifter, I just have to remember to make sure to disengage it when coming to a stop or slowing down. As a side note, it really hits hard when going in and out of gear, I love it because I can chirp the tires going into the high ranges on my 6 speed TH 400!

 

This sounds different than the GV i have on the 89, the one on there has a on/off switch, and a switch to choose between over and under drive. If it's in underdrive it goes lots slower, and in over drive it goes a lot faster... and if it's off it drives normally.

Is the UD/OD an option? I was aware of the lack of 4x4 when it's engaged, but I only need it for my highway cruising so no issues there.

On the electronic transmissions, does it move the shift points to compensate for the OD or does it just engage thru every gear with standard shift points?

 

What speed do you cruise at?

The modular motors are good for a sweet spot right at the normal cruise of 2000-2400RPMs... I don't think you're going to get better mileage by halving the rpms down to 1000-1200... The reason I say this is that it's pretty well known that a lower gear hardly effects MPGs on the modulars - going from a 3.73 to a 4.30 doesn't change the MPG numbers much, and if anything makes it better under a load.

But if you do it, please, let us know how it works out.

 

I'm going to have to disagree with you there, granted that may hold true for a 3 valve or a 4.6 (or maybe a V10?) but I've noticed my 'optimal' RPM is around 1500-1700, and it's downhill from there. At expressway speeds (70-80) I average 12.5 mpg, but this weekend on my 4th of July trip I took back roads at a flat 60mph and avg 16.6 the entire trip! that is what got me thinking about doing the gear vendors...

I got 410 miles to 3/4 of a tank on the longbed, and on the expressway it takes me a third of the tank to go 140 miles, but a GV is a chunk of change I don't want to spend unless I can theoretically 'prove' there is a 75% probability i will get a return on the investment.

So tips, ideas, anyhting is appreciated, thanks for the good discussion!

 

OK, I looked it up. The confusion I think is that Gear Vendors is advertising it as an over/underdrive unit. The fact of the matter is that it just has 2 gears, a 1 to 1 ratio and a .78 to 1 ratio.(I was wrong earlier I thought it was .68 to 1). It does not act like a true underdrive as it cannot give you a gear below 1st. I guess what they consider to be the underdrive is the gears possible between the regular gears. For instance, if you are going uphill or passing while on the highway, instead of having to downshift a full gear from say 4th to 3rd, you could put it into 3rd high (Gear-splitting) thus an underdrive 4th gear. It is really misleading. Its real feature is that it provides you with an additional overdrive gear that can greatly reduce your RPM for a given speed and being able to have the in-between gears. As for making the investment, look around and check ebay. All of the units are the same, the difference is in the coupling and adapter. If you can find one at a good price, you can order the adapter directly from gear vendors. They even can rebuild them for you if you get an older one. If you can deal with just having it on a switch, you can save even more because you wont need the rest of the equipment. It is a simple 12v connection that activates it. Mine cost me a total of $900 for a used unit and buying the coupler. Then you have to have your driveshaft shortened to accomodate the longer trans /overdrive length. If you plan on keeping your truck for a long time then I think its worthwhile.

 

OK, there are a few misconceptions that need to be cleared up about the GV unit.

First, it does not restrict you to 2WD only. The GV unit replaces the transmission output housing, feeding into the transfer case. It works in 2WD or 4WD.

As BLUELINERACING states, it is either an OD/Direct unit or a Direct/underdrive unit. The unit does allow you to split gears (your 4R100 becomes an 8 speed with a double overdrive). The web site is a bit vague, but I think it only allows you to split the gears when shifting manually.

The unit list for $3195. If it raises your fuel mileage 20% (at $4 a gallon) and you start with 15 MPG, you'd pay for the unit in about 72,500 miles.

 

I have the 3.55s and it sucks. What I'm saying is I have high gears already and it's terrible, and that's just on an F150 with the exact same engine as your SD and probably less drivetrain losses.

Now when I floor it, it screams. What it doesn't have is cruising power empty or towing. It's constantly downshifting. Honestly the power is embarrasing and it has recently been rebuilt.

Mike

 

your right on the money!! they CAN BE USED IN 4WD!!

the one that i saw a year or so ago, was bolted on a 4wd, cc, dually, they had 5.38 gears installed then the over drive unit. he used his truck for ranching purposes, so he wanted a LOW gear in the diffs (5.38's) for pulling equipment around the farm, and then the extra OD gears for over the road travel. this guy loved the heck out of the set up he had. he said going 70-80 wasn't an issue with the over drive unit, and it brought his rpm's back down to a "comfortable" cruzing speed on the highway. i did not ask him what specific rpm it cruzed at, but he didn't have larger than a 33" tire, so i can imagine what rpms would have been at 80mph with 5.38 gears.......

i looked into one, but when i went to the cost justification, it just wasn't there for me personally. but the people that have them and use them the on a daily basis tend to really like them!!