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The 14 Bolt Bible
By BillaVista
I Intend to use this article to gather all the info and pics I can find on the venerable GM "corporate" 14 Bolt (14b) full-floating rear axle, also referred to as the 10.5" (after the size of the ring gear in inches.) There are "other" 14b axles out there - a 9.5" ring gear semi-float for one, and even a 11.5" ring gear full-float version. This article is NOT about them.
It is almost certainly destined to be a perpetual "work in progress" as I gather more and more info.
US Military CUCV manual 14 bolt excerpts
I compiled them all into a single 14 bolt manual in pdf format.
Identification, data, and specs
The 14bolt is found in a huge number of GM 4x4 pickup trucks and vans, 3/4 and 1 ton, from the 70s right through until at least 2000. You can find it in:
As well as a whole lot more cab and chasis trucks, delivery vans, etc.
This is what it looks like in my rock buggy.
It is most easily distinguished by its huge, uniquely shaped diff cover that is, of course, held on with 14 bolts.
It is also fairly easily distinguished from other 1 ton full-float rear axles by the removable pinion support, that can be clearly seen just behind the pinion yoke in the above picture.
Being a full float (FF) axle, it of course has full floating wheel hubs and axle shafts. I simply love full-float axles, and would never go back to running anything but a FF axle, for some very good reasons:
Before we delve deeper into the 14bolt, let's just talk about why this is such an awesome axle. It has a number of distinct features / advantages:
Of course, there are drawbacks too:
Overall, I think they are a superb choice for a heavy duty off-road machine. I'll let H8Monday, from the PBB, sum it up, as he does so well. H8 is a rock crawling competitor, devout throttle crazy maniac, who runs a 14b behind a very healthy 5.0. He says:
Closer look at the hub (brake disc or drum removed, looking at it from the back [inside]) and wheel bearing / spindle hardware.Note that the spindle threads are the same as for Dana 60 front and rear axles and Dana 70 rear axles. This means all the different styles of spindle nuts (4 slot, 6 slot, hex, rounded hex) and lock washers can all be interchanged. Part numbers for the spindle hardware, courtesy of KWTMECH, from left to right are:
Spindle flat washer: Dorman 618-048,
Spindle nut: Dorman 615-130,
Spindle lock washer: Dorman 618-049,
Spindle nut: Dorman 615-130
Watch out for this when you go to remove the wheel hub outer bearing and race. The bearing does not simply fall out of the end of the hub on most FF axles - its OD keeps it captive. Instead, a snap ring in the hub, accessible from the back of the hub (yellow arrows) needs to be removed so the wheel bearing can come out the back.
Blue arrows show corrosion, indicating requirement for replacement bearings and races.
The snap ring
Spindle OD is approximately 1.985"
Spindle ID is approximately 1.540"
Take the cover off, and you discover the massive 2 piece carrier and 10.5" ring gear.
The bearing caps have small integrated locking devices that serve to lock the carrier preload adjusters into place
Bearing caps and adjuster locking bolts removed
These pics are of the carrier removed. Mine is fully welded up making it a huge spool. I have read about some folks just welding the spider / side gears by filing in the valley's between the teeth and then reinstalling them. I personally have never understood this. It's not as if you need to save the carrier, since they are cheap and extremely plentiful. Also, I would think that in this manner, those welds would see quite a bit of shock loading. It's also a real bugger to reassemble the carrier and gears after you have just welded up the teeth and are trying to save the carrier.
With the carrier removed, here's a look inside the diff:
Close up of pinion support bearing
Threaded carrier preload adjuster and 1/2" thick axle tube
Housing.
The shafts are different length L and R. The Left is the short side at 31-5/8". The Right is the long side at 37-5/8"
They are a large 30 spline axle. However, the pressure angle on the splines is not the same as other manufacturers (Dana, for example)
Dimensions on the shafts are:
Spline Diameter (yellow arrow) 1.59"
"Neckdown" (green arrow) 1.367"
Operating diameter (purple arrow) 1.351"
Spline length (blue arrow) 2.165"
Spline engagement (red arrow) short side 1.418"
Spline engagement (red arrow) long side 1.569"
Axle diameter by the flange - 1.458"
The following pics, courtesy of Benny Langford (Bigger Valves) and Clay Moulton (yotacowboy) illustrate an alternate method of retaining the wheel bearings in the 14 bolt. For the record, the truck is an '87 1 ton Chevy V30 (crewcab 4x4 350 tbi).
It's very simple setup that consists of one hub nut, one key, and one clip ring. The nut accepts the regular 6 prong 14 bolt socket and has 6 square grooves around its inner diameter. These grooves are what you line up with the spindle groove to make the key way.
I just tighten down to the correct preload and then tighten until the next groove in the nut lines up with the spindle groove.
Then you simply slide the key in the key way and put on the clip ring. The clip ring has a curved end that fits in the spindle groove to securely block the key from backing out. The clip is very thin and flimsy which makes it easy to remove with just a screwdriver and allows it to fit snugly around the spindle in the threads. Part numbers for this style spindle hardware, courtesy of KWTMECH, are:
Hub nut: Dorman 615-132,
Key: Dorman 615-140,
Clip Ring: Dorman 615-141.
Dana catalogue page on GM 14 bolt (10.5")
West Coast Differentials Catalogue page on the GM 14bolt (10.5")
GM 14 Bolt Specs
(all data for SRW truck 14 Bolt axle - others may vary - see table on "different 14 bolts" below)
By BillaVista
I Intend to use this article to gather all the info and pics I can find on the venerable GM "corporate" 14 Bolt (14b) full-floating rear axle, also referred to as the 10.5" (after the size of the ring gear in inches.) There are "other" 14b axles out there - a 9.5" ring gear semi-float for one, and even a 11.5" ring gear full-float version. This article is NOT about them.
It is almost certainly destined to be a perpetual "work in progress" as I gather more and more info.
US Military CUCV manual 14 bolt excerpts
I compiled them all into a single 14 bolt manual in pdf format.
Identification, data, and specs
The 14bolt is found in a huge number of GM 4x4 pickup trucks and vans, 3/4 and 1 ton, from the 70s right through until at least 2000. You can find it in:
- 73-96 C20, C2573-00 C30, C3573-00 G30, G3573-00 K20, K2573-00 K30, K3584-88 CUCV
- 88-91.5 V30
As well as a whole lot more cab and chasis trucks, delivery vans, etc.
This is what it looks like in my rock buggy.
It is most easily distinguished by its huge, uniquely shaped diff cover that is, of course, held on with 14 bolts.
It is also fairly easily distinguished from other 1 ton full-float rear axles by the removable pinion support, that can be clearly seen just behind the pinion yoke in the above picture.
Being a full float (FF) axle, it of course has full floating wheel hubs and axle shafts. I simply love full-float axles, and would never go back to running anything but a FF axle, for some very good reasons:
- The axle shaft does not support the weight of the vehicle, but merely transmits torqueBecause of the above - FF axle shafts are not subject to bending loads like semi float (SF) axles are and can therefore be made of harder materials making them capable of carrying greater torque loadsIf you should ever break a rear FF axle shaft, you will not loose the wheel too.If you need to change a FF rear axle, it is extremely easy and simple to do.The hubs run big, strong, common, reasonably cheap wheel bearings, races, and seals (14b Dana 60 and 70 bearings, front and rear, are all the same)
- The wheel bearings are not pressed onto anything, if need be they can be removed and replaced with nothing more than a screwdriver and big hammer.
Before we delve deeper into the 14bolt, let's just talk about why this is such an awesome axle. It has a number of distinct features / advantages:
- Gear strength - 10.5" ring gear, 1.750" 30 spline pinion, huge 2 piece carrier made of 8620
- Heat treated alloy steel, extra pinion bearing support
- Shaft strength - 1.5' 30 spline full floating shafts
- Housing strength - massive cast iron center section, 3.25: x 0.5" tubes
- Comes in two widths - 63" and 67" wms-wms, easily converted from one to the other (shafts are common)
- Removable pinion support, unbolts from the rest of housing, makes for easier gear setup
- Diff housing has built-in threaded carrier pre-load adjusters, makes for easier gear setup
- Because the carrier is so large and strong, a "full" detroit locker fits in the stock housing, and is therefore easy to install without gear setup changes, and is much cheaper than other 1 ton FF lockers
- Pinion yokes commonly available for 1350 series u-jointsFairly commonly came stock with 4.10 and 4.56 gears and Detroit Lockers
- Cheap and easy to find, buy, and build
- Easy to convert to disc brakes
- Easy to "shave" for 2" inch gain in clearance
- Pinion length shorter than other 1 ton ff rear axles (D60, D70), for improved driveshaft length and angles
- Large ID spindles
- Common spindle nut threads with Dana60 front axle, meaning only one style of spindle nut and socket need be used / carried
Of course, there are drawbacks too:
- Lack of traction aiding differentials - especially spoolsLack of available gearing - only down to 5.13
- Lack of aftermarket alloy axle shafts
- Carrier break. Most 1 ton ff also have a carrier break though, so it's relative
- Uses a crush sleeve to set pinion preload heavyLow clearance in stock form
- Heavy in stock trim
Overall, I think they are a superb choice for a heavy duty off-road machine. I'll let H8Monday, from the PBB, sum it up, as he does so well. H8 is a rock crawling competitor, devout throttle crazy maniac, who runs a 14b behind a very healthy 5.0. He says:
Let's have a closer look at the beast."One of the best things about the 14 bolt, other than they are dirt cheap and nearly indestructible, is the cost of building them. It is very common to find them with 4.56 gears, and often axle shops and junk yards will have used factory sets. They are very easy to set up, because they have an adjustable backlash. Spare axle shafts are nearly free, and the shafts are the same for the C&C or standard version. Not that spares are usually necessary with a 1.69" axle shaft diameter, (splines are 30). But, the best thing is, because the stock carrier is a monstrous hunk of an assembly, you do not change the carrier with a Detroit,(its basically a massive lunch box locker). So detroit only cost about $325(and that's if you don't shop around). My disk brake conversion didn't cost over $150 ($40 each for rotors, $40 for loaded calipers, plus about $20 for brake lines. I had about $1000 into my entire 14 build up, including cost of the axle, gears, locker, disc brakes, and new lug nuts. Not bad for a full floater, rear axle with discs, 4.56 gears and a detroit."
Closer look at the hub (brake disc or drum removed, looking at it from the back [inside]) and wheel bearing / spindle hardware.Note that the spindle threads are the same as for Dana 60 front and rear axles and Dana 70 rear axles. This means all the different styles of spindle nuts (4 slot, 6 slot, hex, rounded hex) and lock washers can all be interchanged. Part numbers for the spindle hardware, courtesy of KWTMECH, from left to right are:
Spindle flat washer: Dorman 618-048,
Spindle nut: Dorman 615-130,
Spindle lock washer: Dorman 618-049,
Spindle nut: Dorman 615-130
Watch out for this when you go to remove the wheel hub outer bearing and race. The bearing does not simply fall out of the end of the hub on most FF axles - its OD keeps it captive. Instead, a snap ring in the hub, accessible from the back of the hub (yellow arrows) needs to be removed so the wheel bearing can come out the back.
Blue arrows show corrosion, indicating requirement for replacement bearings and races.
The snap ring
Spindle OD is approximately 1.985"
Spindle ID is approximately 1.540"
Take the cover off, and you discover the massive 2 piece carrier and 10.5" ring gear.
The bearing caps have small integrated locking devices that serve to lock the carrier preload adjusters into place
Bearing caps and adjuster locking bolts removed
These pics are of the carrier removed. Mine is fully welded up making it a huge spool. I have read about some folks just welding the spider / side gears by filing in the valley's between the teeth and then reinstalling them. I personally have never understood this. It's not as if you need to save the carrier, since they are cheap and extremely plentiful. Also, I would think that in this manner, those welds would see quite a bit of shock loading. It's also a real bugger to reassemble the carrier and gears after you have just welded up the teeth and are trying to save the carrier.
With the carrier removed, here's a look inside the diff:
- Threaded carrier preload adjusters
- 3/8-NC16 diff cover bolt hole (14 in total)
- Extra (third) pinion support bearing
- Magnet for attracting and holding metal particles / debris in the gear oil
- Are where my 14b has been ground down for clearance
- 3.25" x 1/2" thick axle tubes
Close up of pinion support bearing
Threaded carrier preload adjuster and 1/2" thick axle tube
Housing.
The shafts are different length L and R. The Left is the short side at 31-5/8". The Right is the long side at 37-5/8"
They are a large 30 spline axle. However, the pressure angle on the splines is not the same as other manufacturers (Dana, for example)
Dimensions on the shafts are:
Spline Diameter (yellow arrow) 1.59"
"Neckdown" (green arrow) 1.367"
Operating diameter (purple arrow) 1.351"
Spline length (blue arrow) 2.165"
Spline engagement (red arrow) short side 1.418"
Spline engagement (red arrow) long side 1.569"
Axle diameter by the flange - 1.458"
The following pics, courtesy of Benny Langford (Bigger Valves) and Clay Moulton (yotacowboy) illustrate an alternate method of retaining the wheel bearings in the 14 bolt. For the record, the truck is an '87 1 ton Chevy V30 (crewcab 4x4 350 tbi).
It's very simple setup that consists of one hub nut, one key, and one clip ring. The nut accepts the regular 6 prong 14 bolt socket and has 6 square grooves around its inner diameter. These grooves are what you line up with the spindle groove to make the key way.
I just tighten down to the correct preload and then tighten until the next groove in the nut lines up with the spindle groove.
Then you simply slide the key in the key way and put on the clip ring. The clip ring has a curved end that fits in the spindle groove to securely block the key from backing out. The clip is very thin and flimsy which makes it easy to remove with just a screwdriver and allows it to fit snugly around the spindle in the threads. Part numbers for this style spindle hardware, courtesy of KWTMECH, are:
Hub nut: Dorman 615-132,
Key: Dorman 615-140,
Clip Ring: Dorman 615-141.
Dana catalogue page on GM 14 bolt (10.5")
West Coast Differentials Catalogue page on the GM 14bolt (10.5")
GM 14 Bolt Specs
(all data for SRW truck 14 Bolt axle - others may vary - see table on "different 14 bolts" below)
Pinion Bearing Preload(Inch lbs) | 25 - 35 (new bearings) 5-15 (reused bearings) |
Preferred Backlash(.001 inch) | 5 - 8 |
Ring Gear Bolt Torque (Foot lbs) | 120 |
Bearing Cap Torque (Foot lbs) | 135 |
Pinion Nut Torque | Tighten as necessary to obtain correct preload |
Pinion Bearing Retainer Torque (Foot lbs) | :65 |
Diff Cover Bolt Torque (Foot lbs) | 35 |
Axle shaft flange Bolt Torque (Foot lbs) | 115 |
Spindle Nut Torque (Foot lbs) | 50 |
Carrier Adjuster Ring Lock Bolt Torque (Foot lbs) | 20 |
Pinion Assembly Bolt Torque (Foot lbs) | 65 |
Axle Shaft Spline Length (inches) | 2.165" total |
Axle Shaft Engaged Spline Length (inches) | short side 1.418" |
Axle Shaft Engaged Spline Length (inches) | long side 1.569" |
Axle Tube Dimensions (inches) | 3-3/8" x 0.5" thick |
Spring Perch Span and Width (inches) | (1980 1 Ton 4x4, SRW, non Cab and Chasis) 42.5" x 2.5" |
Axle Shaft Length (inches) | Right 37-5/8" | Left 31-5/8" |
Axle Shaft Diameter (inches) | @ splines 1.54", @ neckdown 1.367", operating diameter 1.351" @ flange 1.458" 30 splines |
Axle Flange Bolt Pattern | 8 on 3.523", 1/2" holes, bolts are 1/2-NC13x1.5" |
Pinion Yoke U-joint Strap Bolts | 7/16 " head, 1.296" x 5/16-NF24 |
Diff Cover Bolts | Fourteen (14) 3/8-NC16 x 3/4" |
Ring Gear Bolts | Twelve (12) 9/16-NF18 |
Pinion Nut Size | 1.5" |
Axle shaft to Hub bolts | 3/4" head, 1/2-NC13, approx. 1.5" long |