Hey guys and gals, I was hoping you could help me out. I’m looking at maybe getting a gear vendors overdrive unit for my 67 cougar with a c4 trans. I want to be able to get some kind of lol age out of the car and also not have a lot of fabrication to do, plus I hate the AOD(never herd a good thing said about the trans and the c4 is amazing)
My problem is this, I don’t know much about the GV unit and if it’s meant for a daily/spirited driver and also I’m having a hard time understand how they achieve overdrive without a lock up converter? I thought lock up converters were essential to making overdrive work? Am I wrong?
Installing a GV OD is a big deal and the units are big $$. They achieve OD by providing an over 1:1 ratio input to output. Lockup in a trans is just how they eliminate torque converter losses when at cruising speeds, it in and of itself has nothing to do with overdrive other than they both improve gas mileage.
Get an AOD would be my recommendation, most/many people do the swap and love them.
I have a hard time with doing the AOD because of how many bad things are said about it. Have the aftermarket rebuilds gotten better in the last ten years with them?
Lentech, probably makes the best Ford AOD & AODE/4R70W transmissions for retro applications.
you can contact Mark P he owns a trans shop and has done a few AOD conversions for Cougar owners.
https://classiccougarcommunity.com/forum/memberlist.php?mode=viewprofile&u=608
I have a gear vendors in my F 250 behind a C6, it had miles on it when I got it and I put about 100K on it towing a open trailer and a 24 foot enclosed trailer. Its kinda bullet proof. It was a bolt in we need to shorten the driveshaft and the wiring is very easy. Basacilly you remove the tail shaft from your tranny and use the tailshaft they supply. The GV is bolted on to the flange of the tailshaft which used the same mount that came with the truck. The unit has a switch manual or auto (keep mine in auto) and goes in to OD at about 40 MPH. You can engage or disengage it at speed with no problem. The good you kinda have a 6 speed it if you want to play with it, GV phone tech is very good and they can handle horsepower. I do not know the cost of a new unit and an exchange unit is 800.00.
The AOD has come a long way, they make cross members and I would think you would need to change the flywheel, starter and of course the converter.
You need to check out the costs and see which way you want to go either way the extra gear is nice, less RPM, less engine noise at speed and more MPG.
Good Luck
Here is a more direct way to talk to Mark: http://www.berkshiretransmissions.com/ I have never heard bad stories about AOD myself, most everyone loves them. In any case, Mark will be able to talk to both possibilities and is a very nice and knowledgeable guy.
All the top guys who race on Hot Rod Magazine’s “Drag Week” run the GV overdrives. So I’m pretty sure it can withstand any of the spirited driving that you can throw at it. 
Hers the thing: The GV also adds weight. It works well, but be prepared for some “engineering” to install it. It is VERY strong. Darg racers use it enough said. The AOD would be an easier install, but if you go that route, get one of the constant pressure valve bodies as part of what makes the AOD so failure prone is that the TV cable also regulates your pressure so if it somes out of adjustment, you are stranded from a nice little meltdown. And the tv cable doesn’t have to be that far out for it to happen. The constant pressure valve body will allow the TV cable to become a kickdown and nothing more. Of course I learned this too late.
So if you want bullet proof GV, if you want less expensive I would go with a NEW AOD and install the constant pressure valve bodies.
BTW, here’s a fun fact about GV OD’s. They use an OD unit that is found OEM on Volvo’s (and other cars I am sure), a unit made by Laycock, P-type to be exact. The magic (and why they are hard to come by without the OD) is the adapter part. GV keeps these mostly unavailable to keep people from making their own setup with an ebay drive and a adapter housing.
The AOD will drop right in without and modification to the tranny tunnel?
It seems like there is still a lot to do. New flex plate, started, xmember, linkages(which are fine) but getting a AOD built to withstand 300-400hp(probably closer to 300) and doing the conversion is still cheaper than just bolting on a GV?
I guess my biggest thing was hearing about how the AOD is just garbage compared to the c4 and just trying to understand how you can have OD without a lock up clutch. I thought they went hand in hand otherwise you’d burn up the torque converter.
FMX flexplate will work for AOD, not sure about C4. AOD will fit tunnel. Stock AOD should handle 300 HP no problem. Lockup and OD are two different things.
Put a pencil to it and you’ll see why GV overdrives are still around.
Both are good options. You just have to figure out what you want.
Yeah that’s what I’m trying to decide. I just rebuilt my c4. So on one hand It may be easier to just throw a GV unit and call it quits, no modifying and all just drop in and go. On the other hand if the AOD can be reliable and dropped in for the same money than I have less weight overall. I guess I’m looking for something that can be done easily and reliably so I can drive the vehicle atleast three times a week. I guess I have some comparing to do.
The AOD would be the cheaper alternative. But I WOULD install the constant pressure valve body just to add another measure of added assurance, and make the operation much simpler as far as tv cable. The other benefit is better shifts. For your power level which I thought I heard you say 300-400 hp, buy one of the TCI street fighter units and call it a day. Just be SURE to learn the TV cable line pressure adjustment procedure, or go with the aforementioned valve body. I would go TCI, and spend another $200 on the valve body and have fun driving it.
I appreciate all the advice guys. I’m thinking to go AOD now. Are there any build treads on here that people have done the swap already
Lots of good articles and threads on the swap. It’s mostly nuts and bolts.
You can buy all the parts for the AOD swap in a bundle:
http://www.cjponyparts.com/aod-conversion-kit-1967-1970/p/AODCK2/
Here’s the general info on the possible swaps, manual and auto.
http://www.mustangandfords.com/how-to/drivetrain/mump-0608-ford-transmission-swap/
If you want to get a used trans, you need to know what you’re buying. You’ll also need a local shop that can cut and balance the driveshaft.
Good to know about the swap bundles. Will pass this on to anyone who I find looking to do the swap.