Gearvendors Overdrive

[smilinsam]

Hi y'all! Is anyone familiar with the Gearvendors overdrive unit? I just bought a used unit that was installed on an F-350 Camper Special that was only used infrequently...the unit appears almost new. I am going to install it in my '72 F-250 that has a 428/C-6 drivetrain...the donor truck was a '67 350, long wheelbase, double wheel cab and chassis, with a 360/4 spd. manual, linked with a 2 piece driveshaft with a carrier bearing. Unlike the unit designed to couple directly to a C-6 with a one-piece driveshaft, this unit bolts in place of the carrier bearing, and takes a driveshaft input and output shaft. Now I called Gearvendors about an adapter that would bolt directly to my trans and the tech told me that converting this unit would be prohibitively expensive, since the front of the case is different and would have to be replaced in order to bolt to the adapter...but...no problem, he said my unit would work in the original location (stand alone) with mods to the driveshafts...I believe my wheelbase is just 6 inches shorter than the one-ton. The problem...(you knew this was coming!) is that the controls for an automatic are different than those for a standard...so, he said that'll be 380.00 bucks please! Now, I bought my unit for a good price, so I've got a lot of room between mine and a new unit, but it seems to me that the overdrive could be shifted with the manual switch...having it split-shift automatically gives you six speeds, and it's convenient, but my main concern is getting into OD when my FE is screaming at about 3500 rpms at 70 mph (and guzzling that premium fuel!) So, that's my question...is anyone familiar enough with this to offer some advice? I got the installation manual, schematic and parts diagram that is pretty thorough and self explanatory, but of course, it doesn't tell you what to do if you have a manual unit connected to an automatic...I will appreciate any input and I'll do some pics of the installation for others benefit in case they run into similar problems. I'll also share what it does for mileage if and when I get it all installed!.;...Thanks!

[72BahamaBlue]

I've had a couple old Volvos I converted the the Laycock OD, the GV units are the latest version.
The Volvos used a relay actuated by a switch on the steering column, switch looked like a turn signal lever but on the right side, and a light that illuminated when OD was engaged. I've thought adding a GV unit to my C6 as well, I even saved a switch from a Volvo for use on the truck. I'd like to have a manual operation as well. Some guys use a high beam switch on the floor to activate.
I'd be curious to see the GV instructions, do they include a schematic for manual operation? Perhaps similar to the Volvos, a relay, light, and reverse cutout would be needed, I recall using reverse with the OD engaged will destroy the OD.
I did save an enlarged copy of the 1972 Volvo 142E Overdrive wiring schematic I was going to use as reference for just this type of conversion, should be fairly easy to replicate on a truck.

[fmartin_gila1]

Way back when I was in the USMC in 1958, one of my fellow Marines had a 1956 Austin Healy Model 100-6 Sportscar. It had a 4 spd manual box and a Toggle Switch on the dash that operated a Laycock unit for OD. As I remember, he could toggle the switch in any gear. Don't have any thoughts as to how it was wired as it always worked for him and had no reason to look at it. This might give you another option to find info.

Fred

[gregamorton]

I have a automatic in my merc and I have my gear vendor on a switch. I have a new box for it to run on auto I just like the switch. I have one wire going to frame for ground and the other comes into cab to lighted flip switch which goes to 12 volt power. I hit the switch in 3rd gear when my diesel starts talking to me!!

[gregamorton]

Check this guy out on ebay. he builds some adapters and builds parts to make the earlier units work too. I bought all my stuff from him years ago. http://www.ebay.com/itm/gear-vendor-sum ... 43b9f3788a

[smilinsam]

Hey all!...thanks so much for the input...in reading the manual and looking at the schematic, I believe the OD unit can be operated manually and automatically with the switch I have, which is also typically used for operating a two speed differential. The toggle switch on the dash turns the unit off and on and it will shift automatically when you reach a certain speed, but you can leave that off and just shift manually with the Eaton switch. Seems like you could manually operate the auto trans and "split" shift the OD like a two speed rear-end. Anyway, I can't really see the need to split the gears unless you're towing a big load or running a lot of steep terrain. Like I said, my main concern is lowering rpm's at higher speeds. Meanwhile, this looks to be a fairly easy installation, and I'll try to do pics for everyone. I have to think that these units are available used,at a good price, if you look around.. but even if you have to save your nickles and buy a new unit, there's not a great deal of difference between buying a "built" AOD trans or a 5 or 6 speed manual and the Gear Vendors gives you much better ratio's...OR, you could buy a new truck...ugh...but who would want to do that!