What's new
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.

Which axles fit under a blazer without serious modification

N

nsxxtreme

1/2 ton status
Joined
May 9, 2008
Posts
1,049
Reaction score
0
Location
Oregon
I have an 87 Blazer its got a rebuilt 350 in it. I have 35" tires and a 10 bolt rear end with 4.56 gears and a 700r4 transmission. It has no where near enough power to tow my boat which is approx 4000lbs. I have to keep it in 2nd to mantain 55mph up a hill.

I think I chiped the current ring and pinion it makes a ticking noise while driving forward it goes away if I throw it in nuetral. I have yet to find the time to pull the cover off the axle and look. Its not a U-joint already broke those and replaced them. :)

I am kind of tired of spending money on the motor and think I would be better off with lower gears. I'm thinking 4.88 or 5.12 gears this truck is rarely used so I am not concerned with gas mileage. What are the chances of a good quality ring and pinion in a 4.88 or 5.12 lasting in a 10 bolt? I have read a few guys around hear running them and have had them last.

If I go to a 12 bolt axle in the rear will it bolt right up or will it need additional modification? Will my current wheels still bolt up? I'm not an American Truck guy so any additional details is appreciated.
 
with a 12bolt, you'd just be polishing a turd..... do you wheel it at all??? if so you need to go 3/4 ton atleast....a 14bolt rear end out of a 3/4 ton truck will bolt into yours(1 ton needs spring pads/shock mounts moved) then convert the front to 8 lug, regear to 5.13's and buy new rims, and call it a day....
 
Thanks for the information. Although everytime I buy a part for my truck I feel like I'm polishing a turd :D

I don't do a LOT of wheeling but I do do some. Most of the time I just tow my boat and tow my dirt bikes. I wasn't wanting to buy new wheels. It is an option just wasn't wanting to do it.

So can I keep my 10 bolt front axle and just buy a 8 lug wheel conversion?

would a 12 bolt get me by or am I looking about the same amount in costs and might as well get a 14 bolt?

My other option is to rebuild my 10 bolt. I know most people say a 4.56 is the lowest set of gears you should put in a 10 bolt but have others had any success with lower gears and a quality ring and pinion?
 
14bolt axles are a bit of an odd situation..... its an extraordinarily desireable part... thats dirt cheap. Especially in your case, you dont sound like you need a full floater 14 bolt axle, so a 3/4 ton semi-float will get you by, and you can probably find a complete axle for 100-200 bucks. ready to just bolt in. The added perk, you can find a newer one, with disk brakes and Drum in hat parking brakes already installed. major upgrade over drums. :bow:

for the cost, and benifit, the 14bolt axle is a no brainer. sell the 12 bolt to someone building a hot rod.

EDIT - also, the 3/4 ton 14 bolt was available as a six lug, so you wouldnt have to drop coin on the 8 lug front conversion and new rims. i dunno if the six lug axle had disks though :dunno:
 
You can find a 3/4ton suburban rear that's a 14bFF available and drops in. If you're gonna spend the money why not do it once and save yourself hassle? At least go 14b semi float. 12bolt is turd if you're upgrading. Well unless you get one free.
 
Mountain_man said:
You can find a 3/4ton suburban rear that's a 14bFF available and drops in. If you're gonna spend the money why not do it once and save yourself hassle? At least go 14b semi float. 12bolt is turd if you're upgrading. Well unless you get one free.
Click to expand...

There really isn't much of a difference between a 12 bolt and a 14 bolt semi floater.

Martin
 
82355 said:
There really isn't much of a difference between a 12 bolt and a 14 bolt semi floater.

Martin
Click to expand...

yes there is

12 bolt : 8.5" ring gear diameter
14 bolt semi-float : 9.5" ring gear diameter

12 bolt : 28-spline axleshafts
14 bolt semi-float : 33-spline axleshafts

larger u-joint used at the pinion

a 10/12-bolt can handle up to 35's under mild use. A 14BSF can handle up to a 38" tires under moderate use.
 
Its sounds like you want to keep unnecessary complications down, so I suggest that you find a 6-lug 14-bolt semi-float rear end. They were used in '88-98 Light Duty 3/4 ton and heavy duty 1/2 ton GM trucks.

They have everything in common with the 8-lug 14Bolt semi-float ,except the 6-lug studs. The 10-bolt that you have or a 12-bolt are barely adequate for what you're doing with it. The 14bolt semi-float is more than adequate.

2 things. The leaf spring pads on top of the axle are spaced so that it will not bolt directly in to a K5. Buy a new set of spring pads and have them welded on at your K5's spring-width. You will need a conversion u-joint at the axle end of the driveshaft. All bigger auto part stores carry them. AFter that just bolt up the brake lines, bleed the brakes and re-use your wheels and tires. Simple
 
82355 said:
How so?

Martin
Click to expand...

Disk brakes offer vastly improved stopping power. so much so in fact that many install an adjustable proportioning valve to setup the brakes so the rears dont lockup all the time. Added benifit, the drums will pack full of mud if you offroad in wet or muddy areas, basically lubricating the rear brakes, disks are self cleaning. For trucks (opposite with cars) drum brakes weigh more than disks, ive heard of guys cutting as much as 70lbs from the rear axle by doing a disk swap. And last but not least, the factory Drum in hat parking brake lets you still have an ebrake to get through inspection, which you wont get by doing the typical disk brake conversion that uses front disks and calipers from a 3/4 ton application.
 
G-Force8 said:
Its sounds like you want to keep unnecessary complications down, so I suggest that you find a 6-lug 14-bolt semi-float rear end. They were used in '88-98 Light Duty 3/4 ton and heavy duty 1/2 ton GM trucks.

They have everything in common with the 8-lug 14Bolt semi-float ,except the 6-lug studs. The 10-bolt that you have or a 12-bolt are barely adequate for what you're doing with it. The 14bolt semi-float is more than adequate.

2 things. The leaf spring pads on top of the axle are spaced so that it will not bolt directly in to a K5. Buy a new set of spring pads and have them welded on at your K5's spring-width. You will need a conversion u-joint at the axle end of the driveshaft. All bigger auto part stores carry them. AFter that just bolt up the brake lines, bleed the brakes and re-use your wheels and tires. Simple
Click to expand...

Exactly the info I was looking for. I'll head to a wrecking yard and see what I can find. I dont real care if I get disc vs drum brakes. I just want to keep the complications down. Main duty for this truck is towing my boat. Any 4 wheeling I do would be considered very mild from most of the users on this forums point of view. One thing I'm not sure on do I need a new axle or just a new u joint for my existing axle? How hard is it to find a 6 lug version of this axle?

I'm thinking if I get a 14 bolt I would put 5.12 gears in it. Maybe then I can make it up the hill faster then 55mph in second.

What's in my truck now is a 10 bolt not a 12 bolt. Just wanted to clear that up.

Thanks to everyone that contributed it was really helpful! I'll let you all know what I find.
 
K5dreamer said:
Disk brakes offer vastly improved stopping power. so much so in fact that many install an adjustable proportioning valve to setup the brakes so the rears dont lockup all the time. Added benifit, the drums will pack full of mud if you offroad in wet or muddy areas, basically lubricating the rear brakes, disks are self cleaning. For trucks (opposite with cars) drum brakes weigh more than disks, ive heard of guys cutting as much as 70lbs from the rear axle by doing a disk swap. And last but not least, the factory Drum in hat parking brake lets you still have an ebrake to get through inspection, which you wont get by doing the typical disk brake conversion that uses front disks and calipers from a 3/4 ton application.
Click to expand...

Actually drum brakes are better than disc, they just heat soak easier.

Martin
 
Just wanting to let ya know with 5.12 gears on 35 inch tires your going to be turning 4406rpm pulling a hill in second at 55mph. Have you considered that it might be a power issue rather than gearing? Horsepower is always an equation of torque by rpm = the amount of work done. Changing gear ratios will allow you to add more load but require a slower speed for all things to be equal. 1lbs at 10,000 rpm vs 10,000 lbsft torque at 1 rpm.

By all means replace the weak junk with something that will stand up to the power you need to pull. the 1/2 ton stuff is hardly adequate with a sizable tire. add extra load and your just waiting for the thing to blow.
 
nsxxtreme said:
Exactly the info I was looking for. I'll head to a wrecking yard and see what I can find. I dont real care if I get disc vs drum brakes. I just want to keep the complications down. Main duty for this truck is towing my boat. Any 4 wheeling I do would be considered very mild from most of the users on this forums point of view. One thing I'm not sure on do I need a new axle or just a new u joint for my existing axle? How hard is it to find a 6 lug version of this axle?

I'm thinking if I get a 14 bolt I would put 5.12 gears in it. Maybe then I can make it up the hill faster then 55mph in second.

What's in my truck now is a 10 bolt not a 12 bolt. Just wanted to clear that up.

Thanks to everyone that contributed it was really helpful! I'll let you all know what I find.
Click to expand...

The 6-lug version isn't as easy to find as the 8-lug 14-bolt semi float or the 14bolt Full Floater,but not that hard. Their production was limited compared to the other axles GM offered in the trucks. Just browse craigslist in cities in your area under vehicle parts and plug in "14 bolt axle" or "chevy truck parts".....something like that, and you'll come across trucks that are being parted out. I just found an '89 Chevy truck being parted out about 45 mintues south of me with the 6-lug 14BSF axle under it for $200.

A new u-joint for your current 10-bolt axle will not work. The 14 bolt uses a bigger u-joint, therefore, the conversion u-joints have one side that will bolt up to your stock driveshaft and one side that will bolt up to the 14-bolt.

4.88:1 gears should be fine. If your truck is really sluggish with 35's and 4.56 gears then either your engine is very weak or there may not actually be 4.56:1 gears in the axle. Did you have the gears installed or were you just told it had 4.56:1 gears?
 
14bsf re-geared.. switch to 8 lug and get some tires with a decent load rating and 16"+ wheels, or at the very, very least make sure the rubber you got will hold up the weight and when you get 8 lug 15's make sure they have a good weight capacity.

Then make sure your engine is up to snuff.

82355 said:
There really isn't much of a difference between a 12 bolt and a 14 bolt semi floater.

Martin
Click to expand...


Only about an inch of ring gear, much bigger bearings, bigger axle shafts, etc... :rolleyes:

Now the 10b and truck 12b.. they are equals. Anyone that thinks the truck 12b is realistically any stronger than a 10b really needs a reality check.
 
G-Force8 said:
A new u-joint for your current 10-bolt axle will not work. The 14 bolt uses a bigger u-joint, therefore, the conversion u-joints have one side that will bolt up to your stock driveshaft and one side that will bolt up to the 14-bolt.
Click to expand...
Good to know.

G-Force8 said:
4.88:1 gears should be fine. If your truck is really sluggish with 35's and 4.56 gears then either your engine is very weak or there may not actually be 4.56:1 gears in the axle. Did you have the gears installed or were you just told it had 4.56:1 gears?
Click to expand...
All these engines are weak 220hp. The motor itself has less then 2000 miles on it. I want to be able to do 55mph in 3rd gear not second. I'm currently stuck in second because the truck slows down if I shift to 3rd while going uphill. I have a 700r4 transmission. So I am thinking I can tow in 3rd and when not towing the boat use overdrive.
 
82355 said:
They self actuate, look it up.

Martin
Click to expand...

um... yes, that is how drum brakes work. but still, comparing drums to disks, disk brakes have shorter stopping distances. its kinda why most production vehicles these days are 4 wheel disk brakes........ why do you think disk brake conversions are so common among hot rodders and four wheelers??? its not just cuz they look pretty. disk brakes are superior technology in just about every regard.

self actuation is just a big word for saying the shoe wedges against the drum. big words dont mean better operation. but then again, you also think a 12 bolt rear end is no different than a 14 bolt rear..... just sayin. :rolleyes:
 
You must log in or register to reply here.

Latest Posts

Top Bottom