I have a 1960 4x4 with a newly rebuilt 300 six that I want to use as a daily driver. I will be putting a C6 tranny behind it. I am looking into having the tranny customed 3 speed with overdrive or even a 4 speed with overdrive if possible. I will be driving an hour twice a day at 70 to 80 mph to and from work and need help figuring out the gearing for the front and rear on my 4x4. Yes I do realize that I will not be driving at anywhere near those speeds in 4 wheel drive! Besides the engine and tranny the rest of the drive train is original. I would like to upgrade the pumpkins and install lockers both front and rear to do some off roading(maybe one of the new Yukon grizzlys). If possible an electric locker for the front and/or rear so I can selectively choose between the amount of wheels locked at a time but not sure how that would work out. Any help of suggestion of where I could go to get some direction would be great. Thanks.

 

In my opinion if you are gonna install a 300 six with a fresh rebuild and a c6 money must not be a concern. I didnt even know a c6 would bolt to a 300 six let alone turning a c6 into a 4 speed auto? If your throwing that kins of money at it with gears and a front and rear electric lockers why not just replace the front and rear axles with something newer and stronger and save the originals for someone that could use them. If you are gonna be 4 wheeling to the point you need lockers it wont be long and you will be replacing the front axle anyway. After it breaks that is. Then it will be worth about 6 cents a pound. Just my thoughts.

 

As far as I know, the C6 is a 3 speed, and I do not know if you can get another gearset in the case. You could always go the AOD if you wanted an overdrive fourth gear. Be careful of total transmission length, because of frame flex and movement of engine/transmission and transfer case you will want a prop shaft from the transmission to transfer case that is at least about 10"to 12" long with the setup on a 60.

For comfortable daily driving at your speeds you will want your final drive ratio to be around 2.75 to 3.25 to 1 (if you will be using an overdrive gear, multiply your axle ratios by the overdrive ratio to get final drive ratio). Also pay attention to the front axle angles - the stock front drive axle has pretty agerssive kingpin and caster angles that are not too friendly at high speeds. You cannot change the kingpin angle except if you change the axle, but you can use taper shims (caster shims) to change the caster angle.

But for off roading, particularly where you will need lockers front and rear, you will want your axles to be somewhere between 3.89 and 4.56 to 1 unless you will be in 4L most of the time. A compromise might be axle ratios in the mid to high 3's - you give up some on cruising and also give up some off road capabilities, but have a happy middle

 

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A brake upgrade is probably needed also if you plan on 70-80 mph speeds. The stock drum brakes suck at high speeds or for panic braking. they fade pretty fast.
Personally, I would look at swapping both axles for something more modern.....

 

Great advice 3414! Thank you for the help. The off roading won't be anything drastic mostly just travel on snow covered roads to get to some hunting spots.

On the suggestion from tinman for new ugraded replacements. Any suggestions that I could use for both the front and rear that would fit? Maybe I could grab a set at a salvage yard for a reasonalbe price that I could bolt on with modifing? I assume I would also then have to change the transfer case, is that correct.

 

No need to change the transfer case if you change the axles.

And from personal experience, a locker in the front on snow covered roads can surprise you. Powering into a curve you just might keep going straight. When you lift off the accelerator (or shift to 2 wd) you will start to turn.

 

Has anybody ever tried installing a 9 inch axle in the front? I think for what I need the 9 inch will plenty strong enough and I have a friend that will give me one. I have also been looking at a Gear Vendors overdrive system to help with highway travel. Any opions on these?

 

You have a friend that will GIVE you a FRONT 9". Uhm get it, get it, get it!

 

NO a rear 9" that I would do a pinion change on with a kit from Curry.

 

You know a "pinion kit" won't make it a steer axle?

 

yes, Curry will sell the entire conversion kit/parts necessary. Converting it will not be an issue. I was questioning if anyone has ever done it and how they thought it worked out.

 

I have never seen a kit to convert a 9 inch rear to a steer axle, but one may exist. Given enough time and money it could be done, would involve cutting, machining, welding, sourcing steer knuckles, custom axle shafts and so on. Unless you are building a one of a kind show truck on an unlimited budget, I would stay with a Dana steer axle.

The Gear Vendors overdrive was more popular years ago. Unless you can get a used one at a very good price, I would not bother with it, as they are pricey. By the way, what kind of budget do you have for this project?

 

Ok, If I stay with the Dana (which is ok by me) how should I upgrade it to accomodate the daily driving that I want to do. Brakes are a no-brainer, would new gearing then be necessary? I guess I would have to upgrade the king pins/knickles from what I have been reading. I have a good budget but not unlimited. I have read a couple post discussing swapping out the existing axle with a dana from a 70's F150 because it has the upgrades already in place. Would that be a better option for me? I am good with engine rebuilds, changed out a lot of motors & trannys, replaced bearings, and I'm pretty handy over all but haven't really had much expierance with 4x4 axle/gearing so I take any advice I get very seriously.