Hey guys,
I just bought a 79 Bronco with a 390m, c6, and np205. No lift, all original.
I'm putting a built 460 (500hp) into the bronco and want to twin stick the np205. I'd like to keep the c-6, but I want an overdrive to get me to where I'm going.
I've read quite a bit of chat about putting an E4OD and scrapping the c-6. I have had both transmissions in different vehicles and have been more pleased with the reliability and cost effectiveness of the c-6. Plus, I heard you have to modify the trucks floor pan to make the E4OD fit in the 79 bronco.
Here's my question, has anyone ever put a GV overdrive in between the c-6 and twin stick np205 so that you can run overdrive in front wheel drive? I went to the GV website and have a call into them as well for more answers, but would like your input.
Do I rebuild and reuse my 4x4 c-6 or can I use my 2wd c-6 that is already built and couple the GV OD to the c-6 and NP205. I assume that the OD will change the crossmember location, drive shaft lengths, pinion angles and so on. How hard is what I'm trying to do?
Thanks

 

The E4OD idea should be scrapped right now. It's fully electronic and requires all sorts of input from the on-board computer that also drives the engine. There isn't one in your 79. The add-on OD setup would be the option to pursue unless you want a fully automatic overdrive. I don't recall if the AOD was ever available behind the 460 (I doubt it) but the AOD used a TV (throttle valve) cable instead of electronics or vacuum for shift modulation. This would make the swap interesting but not impossible. But again, I don't honestly recall whether the AOD will even bolt to a big block.

 

78 and 79 Broncos only came with either a 351m or 400 that's it.

Besides if you put a better ignition system than the factory one with the stock engine you will get great gas mileage and performance, go better plugs better cap and rotor better wires and better coil(I used a TFI one out of a 1990 f150) plugs gaped at .60.
Advance the timing with new style 3 keyed timing gears and chain.

Install headers and full duel exhaust, install new cam and intake and bigger 650 cfm carb.

You really don't need a 460 when there is so much you can do for cheaper and better and easier.

If you install the 460 say goodbye to fuel economy.

You said you are going to twin stick it my guess is for more traction so why not look at putting in airlock diffs front and back or piggy back another 205 onto the one you have to make a Bronco that will climb a wall.

What you are talking about doing seems like an awful lot of money time and brain power for not a lot of return.

Rick.

 

oops, I meant 351m. Thanks.
Thank you for the responses.
Back ground: I already have the 460 in an 85 f350 crew cab long bed 2wd that i no longer use for my business. It's already paid for and proven. A real camaro killer. That's not the point I'm getting at. The power is there, but I don't want a short wheel base vehicle that is "jumpy". I'd loose the rear end in the heavy rains we get in houston if it was rear wheel drive because I personally have a heavy foot and I hear the brakes suck on 79's. This is the first 4x4 that I have ever owned and have never had to deal with a transfer case and front driveshaft.
If I twin stick it, it's for traction on the road by using front wheel drive only. I seriously doubt that I will ever travel on anything but loose gravel or sand and I know I will never rock crawl. Just not my can of worms if you know what I mean. My wife and I love to camp in the woods and I want a truck that will get us there in style and not get stuck on a 4x4 trail on our way to the site.
Not that money is not important, but I really don't have a budget limit in mind to get exactly what I want. I got the shell, now i want the capability of a good 4x4.
I read that the AOD was a weak design to start with and would be too expensive to make handle the hp I'm running. I believe bellhousing adaptors are available for a 460, but the literature all leads toward a more stout platform such as the C-6, E4OD, or 4L80E, the last of which I'm sure won't fit. Plus the last two need stand alone contollers to even work. I already have the two c-6's and have been very happy with their performance. I will bullet proof the c-6 4x4 like the 2WD c-6 if that is the way to go.
Does the GV overdrive simply replace the c-6 tailhousing and maintain the factory length or does it move everything else further back? Gear Vendors website only prices out an overdrive that couples with the back of the transfer case for overdrive in RWD only and electronically deletes 4WD. I have an E-mail into them about their "racing version" that is overdriven 4WD. I just didn't know if anyone had tried what I'm trying.
Sorry for the long post. Any advice is always appreciated.

 

Change the gear ratios in the front and rear differentials and stay with your twin stick and the air lockers.

Use manual locking hubs and forget the GV overdrive I believe you can get the same thing or close to the benefits with the gear ratio change.

That would take the jumpiness out of it give you better fuel mileage and quieter ride on the hwy.

I have a 1979 Bronco with a 351m and did the ignition part of this upgrade my performance and fuel economy increased dramatically, the only weak point is the truck came with a 203 fulltime transfer case, that will be corrected this summer I will be installing a 205 and manually locking hubs.

The ignition system I installed is an MSD "StreetFire" cheap and cheerful and it let me change from the .42 to.45 stock gap to .60.


I believe if you sell the 460 to a speed nut the profits from it will pay for all or most of the upgrades I have suggested.

My next move will be making a half cap or cab for my 79 Bronco.


Rick.

 

For the cost of a GV unit, you could buy alot of gas. For the cost of a GV unit, you could almost have a 460 prepped AOD. Don't get me wrong, OD would be great, but about the only way I see it as a cost effective fix is to go with a ZF5speed manual. Good luck.

 

The brakes on a '79 don't necessarily suck, they do tend to get hot. You are stopping a fair amount of weight and if you drive in a hilly area you are on them alot. I used to drive mine in the mtns in Colorado and never had them fail. Had to replace the pads on an annual basis. You might want to look into a vented rotor. I don't know about ceramic as I've been told their not worth the additional cost.

 

https://www.ford-trucks.com/article/...d_Broncos.html F350 brakes for 78/79 broncos.

 

I'm not opposed to a manual, but I'd have to add the third peddle and I already have the c-6. Plus, my wife wouldn't be able to drive it (that might not be so bad).
It seems that the GV OD is not a popular product in this circle! Is it the cost or the performance? I'll do some more research into the AOD. I read that they had oiling problems at the rear of the tranny that caused excessive heat. I'm waiting to hear back from GV and if I don't like what they say then I'll consider getting rid of my two C-6's and going another route. I have never owned or driven an AOD. None of this is happening tomorrow so the decision has not been made.
I still don't know if the length changes with a c-6 and GV overdrive, with an AOD, or an E4OD. Do I have to reposition my crossmember? Change my driveshafts? How long is too long for the front driveshaft? How short is too short for the rear with no lift? Pinion angles with a stock driveshaft?
Thanks as always.

 

I read that article on upgrading the brakes and that is exactly what I plan on doing as soon as I get the vehicle.

 

That is EXACTLY why my signature lists the F-150 and the Bronco specs with that little (at the moment) after them. Also the ONE of the reasons the Sky Redline has a manual.

 

GV contacted me back and said that the overdrive model that goes inbetween the c-6 and the np205 moves the T-case back by 14 inches and might not work in the bronco with the short wheel base. Luckily for me there is no lift, so the angles might still work. I wonder if there are cable driven twin shifters for the T-case since that would put my shifters in my consol!
It's starting to sound too complicated. Maybe an overdrive tranny is the better way to go instead of an auxillary transmission.

 

FWIW, a Windsor will drop right in, and then you can use an AOD. I put a 300 I6 in mine, but still used a C6, and original np203 for cost savings. When I decide to redo the body, I'll put the AOD and np208 in then.

 

Lots of great ideas. I need to get my hands on the truck (waiting for transport from Oregon) and I'll see what I have to work with.
Thanks for all your advice!

 

Your 2 wd C6 would have to be torn down to change the tail shaft etc to hook up to the stock 205 transfer. I thought my C6 in my Bronco was getting bad and I had a good 2 wd C6, but decide not to use it because it would be as much work as overhauling the 4x4 C6. Fortunately, the 4x4 C6 healed itself with adjusting the front band and adding some Lucas. I've been rock crawling with it for a year since then.