If I am looking for 3/4 running gear are there particular years/vehicles I'd should be specifically looking for? Should I only be looking for 3/4-ton donor vehicles from the same general years (73-91) or are other years acceptable? Is there anything I should be sure to avoid? Thanks!
CK5
Register an account today to become a member! Once signed in, you'll be able to participate on this site by adding your own topics and posts, as well as connect with other members.
3/4-ton running gear for 76 K5 Blazer
- Thread starter JohnNoble
- Start date
Any year k20 should be a bolt in affair. If you can weld you could also do a 1 ton 14ff or aam 10.5 out of a newer truck. Both of those will require moving spring perches and shock mounts.
You will need a conversion u joint for the rear end swap
You will need a conversion u joint for the rear end swap
I suggest looking for a 3/4 ton that has a full float 14 bolt and not a semi float 14 bolt. The semi float will bolt in but the full float is stronger.
not the best comparison pic but it will work Your looking for the flanged axle shaft with the bolts
not the best comparison pic but it will work Your looking for the flanged axle shaft with the bolts
correct
These pics may help clarify things a hair more as they are of each type of K20 rear axle.
The 9.5” semi-floater ( most commonly found in 1982 ~ 87 squares ) has only lug studs where as the 10.5” full-floater ( most common on 73~81 C/K 20’s and on all C/K/V/R 30 single rear wheel squares through 1991 - also still used to this day on GMT400 on up trucks ) has wheel studs AND axle flange to hub bolts in the center of the lug studs.
Here are pics of both plus what each diff cover looks like to help identify each axle.
The full-floater is first.
Both are good axles but the full-floater design is far superior so while your at it get the best available.
HTH’s
The 9.5” semi-floater ( most commonly found in 1982 ~ 87 squares ) has only lug studs where as the 10.5” full-floater ( most common on 73~81 C/K 20’s and on all C/K/V/R 30 single rear wheel squares through 1991 - also still used to this day on GMT400 on up trucks ) has wheel studs AND axle flange to hub bolts in the center of the lug studs.
Here are pics of both plus what each diff cover looks like to help identify each axle.
The full-floater is first.
Both are good axles but the full-floater design is far superior so while your at it get the best available.
HTH’s
There is nothing wrong with a 9.5" semi-float 14 bolt for street and mild tail use. It is a major upgrade over the original 1/2 ton rear axle. It also offers better ground clearance for of road use that the 10.5" full-float 14 bolt. I always recommend the 9.5" with for up to 35" tires and the 10.5" if you run larger than 35" tires. The K20 versions have smaller brake drums than K30 versions. You do not want the cab/chassis version 10.5" 14FF.
Any K20 rear axle is a bolt in with only a conversion ujoint and new wheels. Any K30 rear axle requires moving spring perch and shock mounts.
On the K20 front axle, there are two versions of the Dana 44 from 1973-80 and two versions of the 10 bolt from 1977-91. You do not want the 1970-72 Dana 44 front axle. Any of the squarebody apps will bolt in with no changes other than wheels.
1973-76 Dana 44 is small bearing/spindle with the large, external lock out and passenger side flat top knuckle. They used to be the good option for adding crossover steering, but you can buy aftermarket knuckles these days already tapped.
1977-80 D44 went to the large bearing/spindle. The pass side flat top went away and they changed to the same internal lockout as the 1/2 ton.
1977-88 10-bolt front, same bearings and spindles as the 77-80 D44 but 10 bolt center section. 28 spline axle shafts at the carrier.
1989-91 10-bolt, changed to 30 spline axle shafts at the carrier.
Any K20 rear axle is a bolt in with only a conversion ujoint and new wheels. Any K30 rear axle requires moving spring perch and shock mounts.
On the K20 front axle, there are two versions of the Dana 44 from 1973-80 and two versions of the 10 bolt from 1977-91. You do not want the 1970-72 Dana 44 front axle. Any of the squarebody apps will bolt in with no changes other than wheels.
1973-76 Dana 44 is small bearing/spindle with the large, external lock out and passenger side flat top knuckle. They used to be the good option for adding crossover steering, but you can buy aftermarket knuckles these days already tapped.
1977-80 D44 went to the large bearing/spindle. The pass side flat top went away and they changed to the same internal lockout as the 1/2 ton.
1977-88 10-bolt front, same bearings and spindles as the 77-80 D44 but 10 bolt center section. 28 spline axle shafts at the carrier.
1989-91 10-bolt, changed to 30 spline axle shafts at the carrier.
@kennyw , thanks for all the details! I am going to look at a couple of sets of 3/4-ton axles in the next few weeks - waiting on funds - and really don't know exactly what I'm looking for or, more importantly, any red flags to look out for. I know I want to run 37" or larger tires so I'm set on a full-float 14-bolt. Will I be able to recognize a 70-72 Dana 44? Is there a preference, in strength, between the 73-76 and the 77-80 Dana 44? I really appreciate all the feedback.
One other question: pricing. I am in Montana so maybe have less options nearby but the 3/4-ton sets I'm looking at are priced at $850. The same place has 1-ton sets, with Dana 60 front, for $2000. Does this seem reasonable? Thanks
I want to say no only because i remember the old days lol
those are pretty standard prices for where I am from for a match set. im sure you can find them cheaper if you keep searching but if they are currently available then its also a convenience.
Some areas of the country 2k for chevy d60 alone is cheap. I would have to spend at least that here in AZ.
If they are a matched set and not full of water I'd buy the d60 set.
If it came out of a cucv might be 4.56 ring and pinion even better fir 37s.
Be sure the d60 is for leaf springs passenger side drop
Tape measure is your friend measure yours measure thiers
If they are a matched set and not full of water I'd buy the d60 set.
If it came out of a cucv might be 4.56 ring and pinion even better fir 37s.
Be sure the d60 is for leaf springs passenger side drop
Tape measure is your friend measure yours measure thiers
@Wes Harden , you recommend spending the extra $$ to get a Dana 60 for the front but I notice in your signature block that you list a Dana 44. My gut feeling is that I should get the Dana 44 and spend the +$1000 on cross-over steering/springs/engine rebuild/etc. instead. Curious about your recommendation; assuming you're making that recommendation because that's what you'd do if you were doing it all over again. Will the Dana 44 be suspect with 37" tires? Will the springs/suspension/steering I put on the front also work with a Dana 60 if I decide to go that way in the future or will everything have to be replaced?
Thanks!
Thanks!
you will probably get all sorts of opinions on your axle questions. I personally wouldn't be scared of a Dana 44 front and even a 14 Bolt Semi Float with 37s. it all depends a lot on your driving style. if you come to an obstacle and get mad that you can't crawl it and hammer down you will break stuff. if you take your time and pick a good line and work it and drive it you will be fine. there is one guy on here I know of that runs D44/14SF with a doubler on 37s and used to wheel it. lots of reduction in gearing. I am not saying you need a doubler just illustrating that the axles will hold up to the reduction.
let's say you run 37s and find some axles with 4.10 gearing. that would put you at around 2600 RPM doing 70 assuming since your Blazer is a 76 it has a T350/NP203 combo.
I say build it simple at first and see what you like. if you find you are breaking front axle shafts you can always upgrade them. RCV (
https://www.rcvperformance.com/ultimate-dana-44-cv-axle-set-for-gm-k10-k20-71-81.html) are guaranteed up to 40" tall tires.
since you already have the 44 front with 4.11 you can just change from the knuckles out for 8 lug. you could find an 8 lug front axle; either a 44 or 10 bolt and swap them parts over. if you find a 44 you can pull the axle shafts to have spares when you do go to Moab. finding a rear then would be a whole lot easier to find a 14 bolt in 4.10 gearing. you will lose some clearance with the FF vs the SF but if you find a rear in good shape go for it. either one from a 3/4 ton 4x4 or 4x2 would work without having to move spring perches.
get it going again and no reason you couldn't take it to Moab just like it sits
One thing i dont think i have seen you say is what are your plans for the blazer? are you going to be rock crawling it? mud bogs? town driving? or mountain roads?
Yes I am also running 33 inch tires. Your stated preference is 37 big difference, much more leverage and weight.
As I said $2k + for d60 anywhere within 500-1000 miles 1 way for just the d60.
I do have a 14bff 4.88s neither axle is a replacement both are factory in my truck only the r&p and front carrier are updated.
If I were buying new axles and a d60 with a 14bff were near me fir 2k they'd be in my garage. Even if I had to buy a new rig to use them.
As I said $2k + for d60 anywhere within 500-1000 miles 1 way for just the d60.
I do have a 14bff 4.88s neither axle is a replacement both are factory in my truck only the r&p and front carrier are updated.
If I were buying new axles and a d60 with a 14bff were near me fir 2k they'd be in my garage. Even if I had to buy a new rig to use them.
Last edited:
my first truck i got a 44/14ff combo and did the 36" tsl swampers and used it as daily driver / mud fun / trail fun / recovery fun .
6 months i was on my 2nd blown 44 front and i said nope not doing a 3rd . scored a 60 front with 4.10 to match .
that 60 front is now under truck #4 of its life and only thing i have done is pinion seal / rebuild wheel bearings via clean and repack .
do what you want but if you wish to do it 1 time and done go 60 front and enjoy it .
and 2 of them truck and 1 is current push a 9ft fisher snow plow .......
6 months i was on my 2nd blown 44 front and i said nope not doing a 3rd . scored a 60 front with 4.10 to match .
that 60 front is now under truck #4 of its life and only thing i have done is pinion seal / rebuild wheel bearings via clean and repack .
do what you want but if you wish to do it 1 time and done go 60 front and enjoy it .
and 2 of them truck and 1 is current push a 9ft fisher snow plow .......
@tarussell @kennyw there is also the unicorn van 14b, for same width as front. Ive never seen one in flesh - dont recall, do they have the right spring pad and shock mounts like k20 (i believe so) and bolt right in or are they k30 mounting?
