73-87 Chevy _ GMC Trucks => 4 Wheel Drives => Topic started by: Doppleganger on February 26, 2019, 10:45:12 PM

Title: 3/4 vs 1 ton Axles
Post by: Doppleganger on February 26, 2019, 10:45:12 PM
I did a search but got alot of stuff that wasn't close, so I'll post this - if its redundant, please forward me to a previous version and delete.

Other than 1/4 ton, what is the actual difference between a 3/4 ton 4x4 and a 1 ton axles? Reason I ask.....I am dismantling my 85 K20 for a full on restoration. Is in great original shape but the PO's son messed and cobbled so much it needs gutted and a do over - plus add some comfy things like power windows, locks and a new AC setup. There is a fella locally that has been building high end race motors for 40 yrs. He can also rebuild dana axles in his sleep. He's pretty much retired now and I get the gist $$ is tight - I have been doing some side work for him and he acts uncomfortable as in he wants to pay something.....so I was thinking I could pick up some 1 ton axles and have him redo those for me ala barter. If there's no real difference - I could give him my 3/4's to go over as well.

Just wondering what it would take to make this truck into a converted 1 ton so to speak. There are 2 K30's in a yard about 45 min from me that would donate the axles and anything else suspension that is needed.

Title: Re: 3/4 vs 1 ton Axles
Post by: 75gmck25 on February 27, 2019, 07:33:00 AM
I can't verify the info on this page,  but it should be useful.  http://www.chuckschevytruckpages.com/73-87specs.html

It looks like you may find a D60 front axle in a K30, but the rear axle might be either a 14 bolt FF or 14 bolt SF, depending on the year.    However, you might also find that the K30 has 4.56 gears, while most K20's seem to use 4.10 gears.  Depending on the tire size, either one might work for you.

Title: Re: 3/4 vs 1 ton Axles
Post by: Irish_Alley on February 27, 2019, 03:23:40 PM
the main thing is the front axle, in a ½ & ¾ ton youll have the dana 44 or 10 bolt. and in the 1 ton youll have the dana 60 with bigger axles shafts. if you dont plan on abusing the truck the dana 44 and 10 bolt will hold up. in my mud truck ive turned 40" tires with the dana 44, but ive also broken a few axle shafts till i put a locker upfront.

so if you dont plan on mudding and not really maxing out your payload i wouldnt worry about an upgrade
Title: Re: 3/4 vs 1 ton Axles
Post by: Doppleganger on February 27, 2019, 04:15:57 PM
Thanks fellas - your infinite wisdom (as opposed to my infinite ignorance  ???  ) is much appreciated.

I do haul alot and intend to pull a car trailer (single - no 5th wheel). Wanted a K30 when this one came available. It arrived with frozen front brakes and I was out of town so I had a local shop I know do the front calipers and brake lines. Guy told me that the truck had the front setup from a HD 3/4 ton, but the rear was from a light duty 3/4. ?! It was all Greek to me - but he said he's seen this before and just figured GM used what they had in stock at the time. If I could make it a complete "HD 3/4 ton" - which the book shows has the same weight capacities as a 1 ton - that would be great too.

Is the suspension itself (other than axles) the same otherwise? It all needs redone - a place in Colorado had the suspension I wanted - just have to sell a kidney or something to get it. Dont really want a higher gear ratio - the 4.11 is bad enough. Got a 4L80e to try and help out there too.

Thanks again.
Title: Re: 3/4 vs 1 ton Axles
Post by: zieg85 on February 27, 2019, 04:33:18 PM
3/4 ton's in 1981 and newer had 14 bolt semi float rear axles and 14 bolt full float axles for the 8600 GVW.  In the different weight limits of the 3/4 ton I am not sure when the 14 bolt FF came into play, all that I know is my 8600 GVW 85C20 has one
Title: 3/4 vs 1 ton Axles
Post by: blazer74 on February 28, 2019, 02:29:00 AM
Your already 8 lug, so the best senerio  would be a 14 bolt FF out of a 3/4 ton 87 or older.
Direct bolt in spring spacing and generally cheaper. Maybe a conversion U joint
1 tons have a different spring spacing width .
88 and up have different spring spacing also as well as 6 lug and 8 lug versions of the 14sf which I wouldn’t bother with for your app.
Title: Re: 3/4 vs 1 ton Axles
Post by: 75gmck25 on February 28, 2019, 11:48:54 AM
The length of 3/4 ton springs is 52", but most 1 ton springs are 56" long.  Some guys have switched to 56" springs because they think they should flex a little better and improve the ride, but I don't really know.

If you buy an open differential 14 bolt FF you can very easily add in a locking differential.  Many 14 bolt FF axles also had the G80 gov-lok differential, but many Gov-Loks have been abused.  The lock engages using pawls that spin outward and lock as the axle speed goes up, and if you nail the throttle and it spins up too quickly you may break something as it locks in.

Title: Re: 3/4 vs 1 ton Axles
Post by: Doppleganger on March 01, 2019, 09:25:14 PM
Thanks for all the info fellas - will go to good use. There are 2 K30's in yards nearby - an 84 and an 85, so should have all I need. Will probably let the old guy go over them anyways. Needs new springs regardless - so if I swap in the FF rear axle, I would order the springs for a one ton truck, yes?

When the guy who did my brakes said the truck was half HD and half LD, he was probably referring to the rear axle as the LD part. This should work really well then.

Also - I found that the 4.10 rear axle is a "GT5" option, but there is also a GT4, that is 3.73 - on the one ton axles. Would that screw much up (with towing) to go 3.73? I've got a 99 Vortec 5.7 and 4L80e to go in this truck - so would have overdrive anyways.

As Colombo would say 'one more thing'......is it possible to convert a dual wheel setup to single? The yard has pics of the K30's and looks like they're both duallys.  Bummer.

Thanks again!  8)
Title: 3/4 vs 1 ton Axles
Post by: blazer74 on March 02, 2019, 12:05:48 AM
K30 & C30 and K20 & C20 rear  axles are the same internally assuming they are single wheel rears. We’re talking FF 10.5 ring gear. They are the same actual width WMS.

Dually rears are shorter axle width Housings period. Same 10.5 ring gear though.

30  1 ton frames are not the same width as a 20 3/4 ton frame so they are not direct bolt in meaning the spring perches on 30 axles to fit the 20 frame will have to be moved as well as the shock mounts. Also maintaining pinion/Driveshaft angles.

Your easiest route is a 20 series 14 FF single wheel axle with the correct ratio. Bolt right in.

Springs are chosen by the use of the truck.

A note on Dana 60 Fronts. They are pricey, even in need of rebuild.
That’s an upgrade of choice and direct bolt in.
Your Front should be a 10 bolt 8 lug and is fine for a driver.

This info is all applies to 73-87 squarebodies.
88 up is a different animal

If your original rear axle is a FF 10.5 your already there unless it’s completely trashed.
Title: Re: 3/4 vs 1 ton Axles
Post by: Doppleganger on March 02, 2019, 10:31:03 PM
Thanks for all the info Blazer....is very much appreciated.

Now if the weather would just break.....  8)
Title: Re: 3/4 vs 1 ton Axles
Post by: fitz on March 03, 2019, 09:22:01 AM
  As Blazer 74 pointed out, the spring perches are different from a 3/4 ton to a 1 ton 14 bolt.  If your going with the 1 ton a axle, make sure to get the front & rear frame brackets of the K30 parts truck.
  As for the Dana 60 front axle, make sure to grab the front sway bar from the k30 parts truck. The spring plates are different from the 3/4 ton sway bar.
  Unless your a hard core 4x4 guy, the step up to 1 ton axle in mostly done for bragging rights.
Title: Re: 3/4 vs 1 ton Axles
Post by: Doppleganger on March 09, 2019, 09:23:02 PM
Thanks very much for the info.  More I look at it and the fact that the 2  30's nearby are duallies, I'll probably just go with what Blazer suggested - 14 FF single wheel axle with the correct ratio. I know where there are a couple 20's and sounds like alot less hassle. Next time I'll find a K30 - no need to reinvent the wheel.

Thanks again fellas  8)