First Post - a lot of 4x4 and 3/4 ton questions

[Old_iron]

Hello everyone.
I have been looking for a while for a good project 3/4 ton 4x4 and finally closed the deal on one yesterday, a 1968 GMC. It was quite a drive to get it but I was able to get it for a good price. The body is a little rougher than I wanted but I'll get some good body work practice out of it!

I am not a stranger to restorations as I completely redid my 1971 Chevelle back in high school with my father, but I am new to 4x4 components so I'll probably have a lot of questions for you all in that area. This looks like a nice forum, I'm glad to be here.

-old_iron

[summitflier]

Good luck. I know what you mean about "the body being rougher than I wanted".
It is a lot of work, but many people have done it, and like us.. "are" doing it.

[Old_iron]

The goal for this truck is to mainly:
1. Plow snow in winter via detachable plow (like a Meyer)
2. Handle really well /stable in the snow and ice
3. Haul heavy loads of firewood and such out of the woods, and on 55mph roads
4. Utilize either a fixed or trailer-hitch-mount winch up front

Rarely:
4. Tow heavy trailered loads (maybe up to 12,000 lbs) short distances



What it currently has:
Mid-70s open Dana 60 rear, not sure of ratio yet
Not sure of the front
Mid-70s Np205 transfer case
Chevy 4 speed truck trans
305 v6
Non-power brakes
Non-power steering
Steel wheels (ignore the split wheels on the rear, have replacements for them).

I am going to swap in a moderate 350 with HEI.


My questions for all of you:
1. What rear ratio should I go with for the rear?
2. Does the front need to be the same ratio?
3. What type of rear should I run, open, posi track/limited, locker?
4. Are their differences between 1/2 ton and 3/4 ton power brake boosters/master and power steering units?
5. Will the stock 305 bellhousing , flywheel and clutch work with a 350?
6. I will probably want to lift it 2-3 inches. Is there front spring lift kits that are 3/4 ton specifically?
7. When lifting what parts have to be changed/replaced other than the springs?
8. Should I upgrade the suspension to 1 ton to handle having a plow in the front?
9. I have a set of steel Ford wheels (the front ones in my photo). The hub hole is larger than the hubs. With the loads I want to handle, is it important that I use Chevy wheels that have the same size hole as the hub to hold the load?
10. Is the stock granny-gear trans the best option?

Appreciate the advise, I am in over my head with some of this.

[Chknlyps2]

Originally Posted by Old_iron

The goal for this truck is to mainly:
1. Plow snow in winter via detachable plow (like a Meyer)
2. Handle really well /stable in the snow and ice
3. Haul heavy loads of firewood and such out of the woods, and on 55mph roads
4. Utilize either a fixed or trailer-hitch-mount winch up front

Rarely:
4. Tow heavy trailered loads (maybe up to 12,000 lbs) short distances



What it currently has:
Mid-70s open Dana 60 rear, not sure of ratio yet
Not sure of the front
Mid-70s Np205 transfer case
Chevy 4 speed truck trans
305 v6
Non-power brakes
Non-power steering
Steel wheels (ignore the split wheels on the rear, have replacements for them).

I am going to swap in a moderate 350 with HEI.


My questions for all of you:
1. What rear ratio should I go with for the rear? Depends on tire diameter and what engine rpm you want at highway speed
2. Does the front need to be the same ratio? Yes
3. What type of rear should I run, open, posi track/limited, locker? Let some guys who deal in your type of snow while plowing chime in.
4. Are their differences between 1/2 ton and 3/4 ton power brake boosters/master and power steering units?
5. Will the stock 305 bellhousing , flywheel and clutch work with a 350? I don't think a V6 bellhousing fits a small block but not 100% SBC are internally balanced so they take a non weighted flywheel.
6. I will probably want to lift it 2-3 inches. Is there front spring lift kits that are 3/4 ton specifically? The weight rating depends on number of leafs on each side and the lift depends on the arc they are bent to.
7. When lifting what parts have to be changed/replaced other than the springs? possibly brake lines and you could add lift blocks in the back if you are only going a couple inches.
8. Should I upgrade the suspension to 1 ton to handle having a plow in the front? You could get a spring pack with an extra leaf or 2, the guys that plow could better answer that.
9. I have a set of steel Ford wheels (the front ones in my photo). The hub hole is larger than the hubs. With the loads I want to handle, is it important that I use Chevy wheels that have the same size hole as the hub to hold the load? Chevy wheels are hub-centric, Ford is lug-centric. Both work.
10. Is the stock granny-gear trans the best option? It is a good option, it would cost a bunch to upgrade to an overdrive trans that is as strong as what you have. You may have an SM420 trans but I think SM465's came out in your year. An SM465 might be a little stronger than a 420 but still almost the same gear ratios, 4th gear is still 1:1 on both.

Appreciate the advise, I am in over my head with some of this.

My best answers above in red.

[Old_iron]

Thank you Chknlyps2 for all of your answers. Someone on here must know about snow plowing...

[Stocker]

Welcome to the board!

Can't help with snowplows but I'll try to add a bit to the above reply.

6. I will probably want to lift it 2-3 inches. Is there front spring lift kits that are 3/4 ton specifically?
Several years ago when I bought my front 2.5" Softrides, they only listed one for both 1/2T or 3/4T truck. I imagine some spring companies can custom build them for use with a plow.

7. When lifting what parts have to be changed/replaced other than the springs?
For a 2" or 2.5" lift, you need longer front shocks. Stock rear shocks will work just fine up front. Brake lines are long enough, nothing else needs changing.

[Old_iron]

Originally Posted by Stocker

For a 2" or 2.5" lift, you need longer front shocks. Stock rear shocks will work just fine up front.

So, put stock rear shocks up front, and keep stock rear shocks for the rear?

Originally Posted by 72 Copper C-10

Have you driven the truck? if so, whats it like to drive? I've only seen pictures of the 305 V6, I hope someday ill get to catch a glimpse of one, or maybe even drive one. They seem like really neat little engines! I have also heard they have a considerable amount of torque

It runs rough right now, needs the idle adjusted at the very least. With no power steering the closest thing I can compare it to is driving a very old tractor.

Originally Posted by El Dorado Jim

...you may want to upgrade to a dana 44 with disc brakes, from a 71-76 K20, and you will need to use a master cylinder/brackets and booster with braces,from a 71-72 K20 or C20..

I do want power brakes.
a. What are the benefits of having discs up front instead of drums?
b. Are there different booster/master cylinder units - one that I specifically will want/need compared to others? I want robust and dependable braking.

Originally Posted by El Dorado Jim

..you have a sm465 trans if it is mated to a 205 tcase, that is the best you can get , I have a couple of those combo's in my trucks, (bulletproof)how to tell if you have a sm465 for sure is if you put it in reverse you have to push shift lever away from you and down, sm420 pull it towards you and down,

Rear is all the way to the right, and down. Sounds like sm465?

Originally Posted by El Dorado Jim

...4:10 gear ratios for these trucks that haul heavy loads and tow heavy trailers is about the best

Do I have to pull off the inspection covers to find the ratios of both axles? Do I take the numbers on the ring gear and plug them in somewhere to find the ratio?

Originally Posted by wbc409

For use in snow, never use a posi or locker in the front. It will cause the front end to wander, like stepping on the gas in a front wheel drive car.

Thank you, I heard that I should keep it open.

Originally Posted by wbc409

Especially your lock out hubs.

It's missing one of the front hubs to I was going to get some used Warns. Are there ones that are stronger than others?

Originally Posted by wbc409

A posi or locker would work well in the rear.

With driving on ice wouldn't a locker possibly break traction when it locks and make turns more difficult? Again, I don't have a clue, I'm trying to sort through things I've read other people post and try to find the relevent info for my situation.

Originally Posted by old Chevy guy

If you swap the v6 for a 350 you may not have to beef the front springs. That 6 weighs a few hundred pounds more than the 350. The bell will need to be changed for sure. Does that 6 run now? I had one in a 62 4 x4 and it pushed snow like it was its job. It's heavy right on top of the front axle which is always good and it has a ton of low end torque. That thing will push a house over. It's not speedy but all the ones I had (which numberd 3) were always turn key runners. If it runs good and drives try it out before you just change it. You can always put in a 350 after if you decide it's not the deal.

Thanks, that is good advise. Yes, it runs and drives. The main reason I plan on the 350 is the wide availability of parts/upgrades and because I am more familiar with it.

[Old_iron]

Are their differences between 1/2 ton and 3/4 ton power brake boosters/master and power steering units?

Do they differ between 1967-1972 and 1973+? Can I bolt on 1973+ braking system and power steering system?

With the loads I want to haul, is it important that I use Chevy wheels that have the same size hole as the hub to support the load instead of the studs?

Originally Posted by Alex V.

If you're keeping stock diameter tires 4.10 sounds like the ratio you want, and yes, both axles need to be the same ratio for extended use. If you're increasing tire diameter to 35", 4.56's might be better, 33's may be a draw. Torque peak on your monster V6 is at just 1,600 RPM, FWIW. (Most truck-spec small blocks of the era peak from 2,000-2,800.)

I'm probably going to end up with 31.6" tires (not sure what the stock diameters were). What ratio would work best in my application? 4.10, 3.54?


I may able to buy pair of 4x4 3/4 ton axles (D44front D60rear) in 4.10 with Posi from a 1973+ Chevy. Are there any downsides to swapping these in?

Any additional parts needed for this?

Are those axles wider / make the wheels stick out further?

[Stocker]

Originally Posted by Old_iron

With the loads I want to haul, is it important that I use Chevy wheels that have the same size hole as the hub to support the load instead of the studs?

No. You'll likely get differing opinions, and while hub support isn't a bad thing, studs will support more than the truck can carry. I don't recall when the stud size changed from 1/2" to 9/16" but I would stick with the larger ones, which is what my '72 K20 has. I have hauled many cords of green hardwood with no issues, and once weighed a load of topsoil on certified scales at 6,000 pounds. Drove kinda weird and I don't recommend it but nothing broke. Aftermarket wheels with no hub support.

[Old_iron]

Originally Posted by Stocker

No. You'll likely get differing opinions, and while hub support isn't a bad thing, studs will support more than the truck can carry. I don't recall when the stud size changed from 1/2" to 9/16" but I would stick with the larger ones, which is what my '72 K20 has. I have hauled many cords of green hardwood with no issues, and once weighed a load of topsoil on certified scales at 6,000 pounds. Drove kinda weird and I don't recommend it but nothing broke. Aftermarket wheels with no hub support.

Thanks Mike, good to know. Do you have any tips about my other questions?

[72 Copper C-10]

Have you driven the truck? if so, whats it like to drive? I've only seen pictures of the 305 V6, I hope someday ill get to catch a glimpse of one, or maybe even drive one. They seem like really neat little engines! I have also heard they have a considerable amount of torque

[El Dorado Jim]

Hi, welcome to the forum! another K20!!!! yay! I can answer some of your questions.If you want to raise your truck a couple inches and not change shocks, use an add-a-leaf kit,comes with a couple new leaves you add in the front and one thicker one for the rear, this will add some more strength to your existing springs and some lift, for less than $200.00, I have these in several K20's you may need to get longer Ubolts, but not always.I know guys that have snow plows on dana 44 front ends with no trouble, you may want to upgrade to a dana 44 with disc brakes, from a 71-76 K20, and you will need to use a master cylinder/brackets and booster with braces,from a 71-72 K20 or C20....you have a sm465 trans if it is mated to a 205 tcase, that is the best you can get , I have a couple of those combo's in my trucks, (bulletproof)how to tell if you have a sm465 for sure is if you put it in reverse you have to push shift lever away from you and down, sm420 pull it towards you and down,not sure about your v6 bellhousing? only know small and bigblock chevy v8's...4:10 gear ratios for these trucks that haul heavy loads and tow heavy trailers is about the best ...that is what I have in all my trucks, hope this helps you, please ask all the questions you want, we love to help...love to see these old trucks get back to health!

[wbc409]

For use in snow, never use a posi or locker in the front. It will cause the front end to wander, like stepping on the gas in a front wheel drive car. For plowing snow I would go with the add a leafs. Plows add a lot of weight to the front. Make sure you go through the front end on the truck, plowing snow will find the week parts. Especially your lock out hubs. A posi or locker would work well in the rear. I helped my cousin plow snow for several years, he had many customers. He had to put all new u joints in the truck every year. It was a 1 ton ford.

[old Chevy guy]

If you swap the v6 for a 350 you may not have to beef the front springs. That 6 weighs a few hundred pounds more than the 350. The bell will need to be changed for sure. Does that 6 run now? I had one in a 62 4 x4 and it pushed snow like it was its job. It's heavy right on top of the front axle which is always good and it has a ton of low end torque. That thing will push a house over. It's not speedy but all the ones I had (which numberd 3) were always turn key runners. If it runs good and drives try it out before you just change it. You can always put in a 350 after if you decide it's not the deal.

[Dieselwrencher]

Welcome to the forum and that looks like a pretty nice truck to start out with! You've gotten a lot of good info so far. I'll reply to the locker on ice. Most lockers ratchet or unlock during a turn not under heavy acceleration. They are great IMO. The disc brake front end will be easier to get parts for over the years too.

[Old_iron]

Originally Posted by Dieselwrencher

...to the locker on ice. Most lockers ratchet or unlock during a turn not under heavy acceleration. They are great IMO.

When turning on ice, wouldn't that be a problem? Trying to figure this all out. The goal is to have it be as stable as possible in ice and snow, whether driving unloaded, plowing, or loaded.

Originally Posted by haysonj

You might look at the front axle to see if the tag is still on it. The tag will tell you the gear ratio and most likely the rear would be the same. It would be on one of the cover bolts.

Thanks, I'll do that first.

[Dieselwrencher]

Originally Posted by Old_iron

When turning on ice, wouldn't that be a problem? Trying to figure this all out. The goal is to have it be as stable as possible in ice and snow, whether driving unloaded, plowing, or loaded.




Thanks, I'll do that first.

It depends on the scenario really. If the front end loses traction the rear will push the front of the truck straight or what ever direction the tires are turned. If the rear loses traction, then you'll slide/swing which ever direction the inertia base is greater. I'd still rather have a posi/locker for pushing snow than not have one. Without one then you really only have 1 tire in the front applying power and one in the rear. It doesn't work well in deep snow and I'm betting you'll see your fair share.

[wbc409]

For plowing snow you are going to to have a couple hundred pounds extra in the box anyway to help traction. I would start at about 500 extra and see how it handles. You may need more.

[Alex V.]

If you're keeping stock diameter tires 4.10 sounds like the ratio you want, and yes, both axles need to be the same ratio for extended use. If you're increasing tire diameter to 35", 4.56's might be better, 33's may be a draw. Torque peak on your monster V6 is at just 1,600 RPM, FWIW. (Most truck-spec small blocks of the era peak from 2,000-2,800.)

The NP205 is about as tough as you can get. I had one in a '74 K10 (behind a TH350 - ha ha ha) and upon researching its merits and what lube it needed, the consensus was use whatever lube the transmission ahead needs (80w90 or ATF) and that it would hold over 800 lb.-ft of torque. :shock:

[Stocker]

Not really, at least no good honest reliable information!

Your SPID (glove box door sticker -- if it's still there) will show the original tire size, and I think also the gear ratio. If the tires were 7.50-16s, then yes, 31.6" would be about the right diameter.

[Alex V.]

That tire diameter sounds right - I can't imagine it was any taller than 32" from the factory. Then if you plan on keeping your SM465, my opinion is 4.10's are the way to go. 4.56's will give even more grunt, but will limit your speed more than 4.10's. Regardless of where the power peaks are at on your V-6, I'm not sure what's considered safe sustained RPM for them and that may play into how limited you'd be if you were to go with 4.56's.

I can't answer any of your other axle questions - I'm not versed in what years interchange best. I have the hydraulic assist "hydro-boost" brakes on my '85 1-ton and they work well - all other factors aside I think about the toughest setup you could get on a budget would be the brakes (including hydro-boost) and axles from an 80's K30 or heavy K20, but the equipment your truck already has under it already certainly isn't too weak for the task.

[Old_iron]

Thanks Alex and Mike.

[Chknlyps2]

With a 31.5" tall tire and the 1 to 1 4th gear ratio that your SM465 has, at 55 mph your rpm with different gear ratios will be as follows.

3.73 = 2188 rpm

4.10 = 2405 rpm

4.56 = 2675 rpm

I also think 4.10's would be your best bet.

[Old_iron]

Originally Posted by Chknlyps2

With a 31.5" tall tire and the 1 to 1 4th gear ratio that your SM465 has, at 55 mph your rpm with different gear ratios will be as follows.

3.73 = 2188 rpm

4.10 = 2405 rpm

4.56 = 2675 rpm

I also think 4.10's would be your best bet.

Thank you, thats great information to have. The rpm for 4.10s seems a little high to me but I guess that is the trade off for more power transfer at slower speeds? 3.73s would probably limit my low end power?

Dale, thanks for the welcome!

[Old_iron]

Along with my question above, are open knuckle D44s in the front weaker than my closed knuckle 44 will be for how I'm going to be using it?