79 GMC C30 to K30 conversion questions on front axle
 

Hey guys,
I've been converting my 79 GMC C3500 to a K3500 for the past almost 3 years. It's a cab and chassis model and has a dump bed. Started out as just an engine swap because the one that was in it threw a rod one day. Then my buddy gave me a parts truck (1980 Chevy K20). I used a bunch of things off of it and then decided to put all the 4WD stuff on my truck.
It's been a fun and frustrating project so far. I've basically now done a restoration of the whole truck. It's my very first one ever so it's not perfect like most of the ones I see on here. I do have a question regarding the front and rear axle ratios though...
The C30 has 4.10 gearing in the 14 bolt dually rear end which I want to keep because it's better for it remaining a dump truck. The rear axle of the K20 had 3.73 gearing...so I can only assume the front axle has the same 3.73 gearing. I would also assume that it would not work with the 4.10 gearing I am leaving in the rear end. Do I switch the ring and pinion gears out or is it easier and less hassle to change out the entire axle? I'm not too concerned with it all just yet because I can always pull the drive shaft off and not use the 4WD. Just want to be prepared for what I need to do when I do make things jive up.
What are all you guys' suggestions??
Thanks in advance!

Re: 79 GMC C30 to K30 conversion questions on front axle
 

Find a Dana 60 front axle with 4:10s. for a dual wheel. Probable the simplest way

Re: 79 GMC C30 to K30 conversion questions on front axle
 

Does it have to be from a dually or can it be from a K20? I was just assuming that if it has the right gearing it would work. Thanks!

Re: 79 GMC C30 to K30 conversion questions on front axle
 

If you want an "true" 1 ton then needs to be a 60. You can pick up dually axles cheaper than a single axle. But still can use the 44, just won't be a dually inless you can get the dually adapters off a newer chevy, they bolt on. But definitely need to have the gears match.

Re: 79 GMC C30 to K30 conversion questions on front axle
 

The rear axle is a dually right now. 14 bolt rear end full floating axle with 4.10 gears. The front axle was from a donor truck and has 3.73 gears. I need to get a front axle to match the 4.10 gears in the rear

Re: 79 GMC C30 to K30 conversion questions on front axle
 

Do you still have the 14b with the 3.73s? Swap that in. The SRW and DRW are the same axle, just the backing plates out are different. The housing and shafts are the same.

Re: 79 GMC C30 to K30 conversion questions on front axle
 

not the way you worded it b454rat . . . yes same axle BUT the flange for the backing plate to bolt to that is welded on the axle is located further in and would need to be moved .

also the srw to drw hubs are different .

and the leaf spring pad location as shock mounts are different .

if both are 14ff then just swap the gears and pinion support all as one and reset backlash and check pinion depth and be done .

if you were closer i have a ready to go dana 60 drw 4.10 front .

Re: 79 GMC C30 to K30 conversion questions on front axle
 

I thought about that but I'd like to keep the 4.10 rear setup as it is now because I do plan to use it as a dump truck still. That gear ratio is better for hauling loads. I also put helper springs on it for increased payload so I'll need the gearing that way.

Re: 79 GMC C30 to K30 conversion questions on front axle
 

Sue me lol. Been a long time since really messed with this stuff!! 4.10s gear for the front would be easy to get, and not crazy expensive....

Re: 79 GMC C30 to K30 conversion questions on front axle
 

Yeah. I talked to a friend of mine and he actually said rebuilding one is more involved than just replacing the whole axle. I figured I could fine one with 4.10 gearing somewhat easily and cheap. Anybody know of one? I'll have one with 3.73 gearing for sale once I get the 4.10 one installed.

Re: 79 GMC C30 to K30 conversion questions on front axle
 

I know you dont want change rear axle, but for reference, the rear axle could be different widths depending if it's a dually truck or a cab&chassis truck
Also the k20 front axle, be it a dana44 or Corp 10bolt, is nowhere near what a dana60 is..
...you might look around for a 4.10 front, but I wouldnt waste much time ...I'd change the gears in what you have...its not that hard...
Or get a d60 with 4.10s..which is what I'd do considering the heavy load that could possibly be put on it being it's a dump truck..

Re: 79 GMC C30 to K30 conversion questions on front axle
 

I assume the d60 is a front axle? I'll have to look into that.

Re: 79 GMC C30 to K30 conversion questions on front axle
 

Yep..dana60 front axle

Re: 79 GMC C30 to K30 conversion questions on front axle
 

Thank you! I'll definitely start looking when I'm ready. I still have a rear drive shaft to get made and a few other odds and ends. Then I have to redo the dump bed as well since it has a lot of metal that's rotted out.

Re: 79 GMC C30 to K30 conversion questions on front axle
 

All the differences between a 3/4 and 1 ton are annoying to try and swap over.

The 1 ton dually rear probably has the 3.5" rear drum brakes and not the 2.5" which your going to want for sure with a dump truck. The shocks are different as well between a 3/4 and a a 1 ton.

In the front you will want a dana 60 for the front axle for the bigger front calipers or you will be downgrading to 3/4 ton front brakes (dana60 vs dana44/10bolt calipers use different size threads for brake lines on the calipers).

I looked but didnt see anyone putting dana 60 calipers on a dana 44 or 10 bolt, usually the other way around for fitting smaller wheels.

Re: 79 GMC C30 to K30 conversion questions on front axle
 

I'm keeping the original dually rear end that's on the truck. I recently got new drums and shoes and have cleaned it all up very nice. I'm just needing the 4.10 geared front axle so I can make sure it has the same gears as the stock dually rear end (4.10's as well).
Are there certain years of the Dana 60 I should be looking at to put on my truck? It's a 1979...
Also, if the brakes are bigger, will I need to be getting different calipers for it? Mine are new now and I'm hoping they'll still work if I get a Dana 60 with 4.10 gearing.

Re: 79 GMC C30 to K30 conversion questions on front axle
 

Gm 60s went from 76 I think to 91. From 88 to 91 there only gonna be cab n chassis and crew cab. But anymore finding one any year is getting harder, and people think they are made of friggin' gold.

Re: 79 GMC C30 to K30 conversion questions on front axle
 

I'm not sure if the c30 and k30 front calipers are the same. I ended up with a 10 bolt.

Re: 79 GMC C30 to K30 conversion questions on front axle
 

Nothing is the same on 2wd vs 4wd front, other than 8 lug....

Re: 79 GMC C30 to K30 conversion questions on front axle
 

c30 to k30 same caliper and pads .

just watch out if american or metric thread bolt for the caliper to brake hose .

77-91 for dana 60 front under 1ton trucks . lucky for you drw tends to be cheeper than the srw as everyone wants srw .

also like i said before i have a 4.10 60 front :rolleyes:

Re: 79 GMC C30 to K30 conversion questions on front axle
 

Thanks a ton! The front axle I have under it now came with all the brakes and everything. Just needs 4.10 gears. So the Dana 60 with 4.10's you have...is it for sale?

Re: 79 GMC C30 to K30 conversion questions on front axle
 

Is the C&C axle a 10.5” or Dana? (Can you pull the pinion from the front with the removal of 5 bolts? Or do you have to pull the chunk?

Re: 79 GMC C30 to K30 conversion questions on front axle
 

CnC axle will be a 14ff. Dana 70 was the full width dually axle.

Re: 79 GMC C30 to K30 conversion questions on front axle
 

Yes if it is still original, but just trying to clarify. He could just swap chunks and use the front axle he has for now, if the k20 has a 10.5 rear. It SHOULD being an 80 model, but it could have been changed also thru the years.

Re: 79 GMC C30 to K30 conversion questions on front axle
 

Yes, the parts truck I have is a 1980 K20. It does have the 10.5" ring gear...it's the same size as the dually rear end that I'm keeping on the truck I'm redoing.

I'm not concerned with the rear at all. It's all good to go. I just need to find a front Dana 60 axle with 4.10 gearing so that it matches the 4.10 gearing I have in the stock dually rear end.

The front axle that I currently have under the truck is the one from the 1980 K20 parts truck. I took the leaf springs, brakes and all with it when I put it on the C30. It is a 10 bolt and it should have 3.73 gearing since the rear axle of the truck it came from has 3.73 gearing.