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Gear Vendors Under/Overdrive

Catalog Item # 20070d
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The finest quality Auxiliary Transmissions offer the ultimate in horsepower and performance.
Most auxiliary transmissions are just dual ranges — low gear for towing and high gear for running empty. Gear Vendors Under/Overdrive is built for gear-splitting (giving you a progression of gears with half the drop in rpm) so you maintain power with close ratio performance. Gear Vendors is the only auxiliary transmission that permits shifting under any throttle condition. After it’s installed, your vehicle will have twice as many underdrive ratios plus 3rd-direct and an overdrive gear (3rd-over) for towing. Provides increased engine performance of more than 40 hp and 60 lb. ft. of torque without modification to the engine. The overdrive will pay for itself in fuel mileage alone. In addition, your engine slows down 22%, so the same rpms that currently take you 500 miles will take you 640 miles. Mfr. 2 year warranty for noncommercial use. USA. Special Order.

Technical Specs

Tech Specs

Weight: 57 lbs.

Manufacturer: Gear Vendors Inc

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Gear Vendors Under/Overdrive: Customer Reviews

Camper's Choice Rating

(5 Based on 10 Reviews)

Reviewed by 10 customers


one excellent product

171 out of 303 people found this review helpful.
January 17, 2006
This unit is well built, does exactly what it says,and adds that extra gear just wear you need it. I will always have one on any tow vehicle I own in the forseable future
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Great engine saver

214 out of 370 people found this review helpful.
March 12, 2006
I bought this unit July of '05. The La Mirada, CA store handled the transaction for me. I had it installed on my '03 Superduty with a V10. It was so nice to be able to pull Mill Creek Grade at 40 mph without my engine pushing 4,500 rpms. In one short runI had to run it in first gear for about a half of a mile. Now I do it in "2nd under". I am using 3.73's axles in my 4X4 but I think it would be better with 4.30's. But I can wait until I see what she does cross country. Getting the hang of shifting is a little tricky, but it's a really well made unit. I recommend it for the V10 motorhomes.
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Gear Vendors

204 out of 388 people found this review helpful.
May 29, 2006
This is worth the money in every way - even if it doesn't pay for itself in fuel savings (which it might at today's prices) - The biggest improvement is finding the power spot when climbing a hill. The Gear Vendors Under/Overdrive adds ratio possibilities that weren't there before and wouldn't be there in any Ford or GM transmission. Reduced RPM's equals more interior quiet. It Turned My 1989 31 foot Travel Master into a new RV. Thanks GV and Thank You Camping World for installing it.
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Gear vendors over-under drive. Wonderfull!!!!

267 out of 723 people found this review helpful.
September 20, 2006
I have one of these in my 1984 Ford F250 4X4. I have 5:16 limited slip gears. The engine is a 6.0 ldiesel with an add on turbo. I average 12 MPG pulling my 1985 Prowler 5th wheel. Even better without! Well worth the cost. I am outpulling other fords and chevy's and dodges (Even the NEWER models) on most hills. Arizona is mostly 75mph, on the freeways, and I can cruise all day at that speed and get that mileage. Just returned from a cross-country trip, and with the price of diesel now-a -days, I was sure gald I had this installed. My over-drive unit is over 12 years old and still going strong.!!!
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New life in an old rig

0 out of 0 people found this review helpful.
March 09, 2010
I installed this unit in a 1986 Pace Arrow that I had been driving for 10 years in 2006 and set out from NH to WA and CA. The first thing I noticed was dramatic noise and RPM difference at highway speeds. I then noticed an increase in mileage of almost 2 mpg. This unit is billed as under/overdrive, but in reality it is a direct drive/overdrive. When the unit is not engaged the ratio is 1:1, when engaged it is something like .78:1. My old motorhome has a 3 speed automatic and this gives me 6 gears:1, 1.5 ,2, 2.5, 3, 3.5. Second gear overdrive is excellent on hills, even the Rockies. It seems to be a tough unit and I never regretted installing it.
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Gear Vendors

312 out of 496 people found this review helpful.
October 04, 2006
After an exhaustive review of all the products to improve the performance of our tow vehicle, the Gear Vendors product was selected. Our tow vehicle is a Ford F-250 6.0L diesel with a five speed auromatic transmission. It pulls a Glendale Titanium 5Th. wheeI. It has adaquate power with torque and no more power was needed. A bigger gear selection was needed and this is where Gear Vendors product fit the bill. This is an engineered product with an excellent track record. Dependable to boot. Our Gear Vendors was bought at the new Myers Camping World in Syracuse, New York. I give this store a rating of Five Stars, with total customer satisfaction, follow up, service and personal service, bar non. This is a great addition to the Camping World family of stores. I would recommend this facility to all campers for products. By the way, the product works as advertized, and I am very happy with the performance. The unit has reduced RPM's and improved our fuel mileage. It is awsome.
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Works well. Very challenging to install

35 out of 55 people found this review helpful.
June 03, 2008
I bought the unit through Camping World back in March 2008 after having several discussions with Gear Vendors about my particular application. After being assured their kit was indeed designed for my truck I decided to purchase the unit. As things turned out many of the parts were wrong (or missing) and had to be supplied/replaced by Gear Vendors. On one occasion I went to their web-site to view the picture of the kit I was supposed to have and had to tell the Gear Vendors associate what I needed based on that picture and what I encountered while attempting installation. The kit was missing a 1 thick spacer, had the wrong coupler, and the wrong speedo unit (which I discussed with the Gear Vendors salesman before I made the order). To top it off the replacement coupler wasn't right either as the outside diameter didn't fit the mating bearing and had to be centerless ground. Because I own a machine shop and have a lot of business contacts, I was able to fix the second coupler without waiting for Gear Vendors to send me a replacement, which always took at least a week, and they didn't bother to send the larger shims required for the different coupler, so I had to solve the problem myself. I made my own. I finally completed the project last week and the unit functions well and I will be testing it more in the next couple of weeks when I tow my 31 foot 5th wheel. I understand that my 1978 Ford isn't something Gear Vendors sells units for very often but at the same time if they are going to sell it they should do their homework and be sure what they sell actually fits the application as they claim. And replacement parts shouldn't take a week to receive either. Requests to send the correct parts faster than UPS ground were ignored. I don't know what a person would do if they didn't have access to a machine shop if they ran into the same situation I did. I will say all reviews I read prior to purchase were good. I hope mine was just an isolated case.
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The Big Test

7 out of 15 people found this review helpful.
June 26, 2008
After towing my fifth wheel for the first time I found the unit to function as promised. Shifting was smooth after getting the hang of it. As far as benefit, I find the unit is really good when used as an overdrive when not towing. When I used it in a lower gear (in overdrive mode) when towing for hill climbing I found the benefit less than expected when climbing a steep grade but for lesser hills the Gear Vendors unit worked very well. Because of the installation issues I listed in my previous review and the benefit I received after using the unit, if I had to decide again whether to invest in this unit I can honestly say that I don't know. Did it help? Yes, it did. Is it worth the major investment in time and money? I'm not sure, but I think I would say yes.
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Excellent Product A Must Have

0 out of 0 people found this review helpful.
September 02, 2011
I had a 454 automatic Chevrolet Dully Crew Cab which I used to pull a 20,000# fully loaded farm trailer. I thought the 454 engine would be enough, however on hills it bogged down and used extra fuel. I personally installed a Gear Vendors O/U drive and the hills were no longer a problem. I did not have to down shift from High Gear anymore all I did was flip a switch and the Gear Vendors slipped my vehicle into under drive which is ½ down, not a full gear down when you need just a little more pull, slip the GV O/U down and you have a gear and ½, instead of dropping two full gears. It does all this within a blink of an eye and unlike other overdrives there is no grinding of gears, as it is an automatic. As an Overdrive it gives the vehicle better mpg when shifted into high!
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great unit

0 out of 0 people found this review helpful.
October 14, 2014
I had my gear vender installed in 2000 in my 1991 ford f-350 and have placed almost 100,000 miles on the unit, it has saved me a lot of fuel.
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