12 Bolt rearend

[eddie1]

I have a 63 Chevy with a 12 bolt rear end. All the gear vendors list 12 bolt 64 & up. Is my the 12 bolt in my 63 different. Can I use the gears listed for 64 & up or do I need to find a new rear axle?

[pheengurs]

I've read in a few places where they say the 12 bolt rear didn't come out until 64 and only produced until 72...

my 64 stepside 4x4 has a 12 bolt rear. the stamp on the frame says the frame is a 63, but I've read that is normal. my particular truck had alot of modifications done to it -- it's got a 63 grill, but the front end is an aftermarket fiberglass unit... and it's got all the earmarks of a 64 such as the power brakes, and 3 lever deluxe heater assy in dash... and I've got conflicting vins between the cab and engine bay... though I don't personally care bout that, cept when it came time to insure it...

if your truck has gone through as many hands as mine, I'd suspect maybe yer stock axle was a weaker dana 44, and was swapped with the stronger 12 bolt... you might have to do some cleaning and start noting the vin stamps and casting stamps to confirm / deny it...

or maybe late year 63's got the 12 bolt as an option?

perhaps there's an expert around who can clear it up...

offhand tho, I'd say if you've got 12 bolts on the diff cover, and the diff cover is shaped sorta like a D, facing the right way, not up or down, then it's a corp 12 bolt, and you should be buying parts for it, instead of the other stock axle options like the 10 bolt Dana 44's & 60's...

[Captainfab]

The truck 12 bolt was used from 1963 thru 1982. Not all parts listings are accurate as far as what years a unit was produced. The way to ID a '63 12 bolt is by the pressed on brake backing plates. There will be no flange where the backing plate bolts on. The one other difference with the early 12 bolts is that the '63 & '64 12 bolts used 17 spline axles and corresponding spider gears. '65 and up used 30 spline axles. Other than that all the internal parts in a truck 12 bolt will interchange except for the 2 different lengths of axles.

[Heater63]

Originally Posted by eddie1

I have a 63 Chevy with a 12 bolt rear end. All the gear vendors list 12 bolt 64 & up. Is my the 12 bolt in my 63 different. Can I use the gears listed for 64 & up or do I need to find a new rear axle?

What exactly are the components you are asking about? The ring and pinion set?
When you say axle, you have 2 axles; are you talking about the housing?
Yes, there were 12 bolt Chevy TRUCK rear ends in '63. I have one. It may have pressed on brake backing plates, mine does. Those are not easily converted to rear discs without fabbing on a caliper mount. Its not a simple bolt on and off conversion like later housings.

First, Identify which rear diff/housing you have by looking at the diff cover plate. There are several internet sites that will help you with that.

Second, determine the rear ratio you have. There is a cutoff between the 3 and 4 series carrier, and you can't make a drastitic gear change, such as go from 4:11 to 3:08 without changing the diff unit.
Third, determine if it is a posi unit or not. If you want posi, you can get the traditional limited slip disc posi unit or a helical gear posi. For street where both tires are always on the ground I like the helical gear.

If you do have a '63 Chevy 12 bolt, there are vendors like Early Classic with 5 and 6 lug axles, you can get posi units and gear sets from Summit or Jegs, the bearings and seals are standard pieces.

[eddie1]

Originally Posted by Heater63

What exactly are the components you are asking about? The ring and pinion set?
When you say axle, you have 2 axles; are you talking about the housing?
Yes, there were 12 bolt Chevy TRUCK rear ends in '63. I have one. It may have pressed on brake backing plates, mine does. Those are not easily converted to rear discs without fabbing on a caliper mount. Its not a simple bolt on and off conversion like later housings.

First, Identify which rear diff/housing you have by looking at the diff cover plate. There are several internet sites that will help you with that.

Second, determine the rear ratio you have. There is a cutoff between the 3 and 4 series carrier, and you can't make a drastitic gear change, such as go from 4:11 to 3:08 without changing the diff unit.
Third, determine if it is a posi unit or not. If you want posi, you can get the traditional limited slip disc posi unit or a helical gear posi. For street where both tires are always on the ground I like the helical gear.

If you do have a '63 Chevy 12 bolt, there are vendors like Early Classic with 5 and 6 lug axles, you can get posi units and gear sets from Summit or Jegs, the bearings and seals are standard pieces.

I have a 12 bolt Chevy truck rear end that is the factory installed rear end on my 63. I want to change to the 5 lug rear axles, change the gear ratio, add a posi rear end, & possibly rear disc brakes. Early classics list the axles for 63-69 but every gear set or posi unit I see lists ring & pinion sets & posi units as 63-82. What I am getting at is, will these parts listed 63-82 work in my rear end or do I need to find a later rear end.
I am not 100% sure what gear ratio I have now but my 6 cylinder truck sound like the motor is going to come apart at anything over 60mph. I am just about finished swapping in a 454 & I want a more highway friendly cruiser.

[Heater63]

Eddie,
Your rear end is going to be no problem, but I recommend you stop and plan your final drive ratio, since you are worried about highway rpms. You are swapping a BBC, but what transmission are you using? A lot of us are going to overdrive units, either modern automatics, manual 5-6 speeds, or even adding an overdrive unit. You need to know your rear tire size and top gear transmission ratio (1:1 or overdrive), THEN you can calculate what rear end gear set you need.
Use an online calculator like: www.wallaceracing.com

I am using Early Classics 5-lug axles, they are great, but have a higher spine count, but you want to change to posi anyway so no problem.
Again, if you have pressed on backing plates you will have to remove them and fab and axle flange to mount rear discs. I chose just to stay with drums on the rear. CaptainFab might be able to help you with this

A posi unit to accept 31 spline axles, new ring and pinion for your chosen ratio, seals and bearings, can be picked up anywhere, Jegs, Rock, Summit.
I will pm you the actual part numbers i used when I get home later.
And talk this over with whomever is doing your diff assembly!

[eddie1]

Originally Posted by Heater63

Eddie,
Your rear end is going to be no problem, but I recommend you stop and plan your final drive ratio, since you are worried about highway rpms. You are swapping a BBC, but what transmission are you using? A lot of us are going to overdrive units, either modern automatics, manual 5-6 speeds, or even adding an overdrive unit. You need to know your rear tire size and top gear transmission ratio (1:1 or overdrive), THEN you can calculate what rear end gear set you need.

I am using a 700r4, I know the rear tire size & the gear ratios of the transmission & what rear end ratio I want. The question is can I use the ring & pinions & the posi units that are listed for 64-82 12 bolt rear ends in my 63 12 rear end or do I need a new rearend?

[jimmydean]

Since you are changing everything over, I would say yes, you can use your housing with new gears/axles/posi since they should all be the correct spline count. Just make sure the length is correct and know that you have pressed on backing plates and will need to address that if you want discs.

[padresag]

rear axle identity you can find in the inc link. you will see letters stamped in the passenger side axle housing and they will be letters such as HF or HA or JQ which is for a 4:11 postitract rear axle

http://cid-9169aad55cfc6d79.skydrive...0&sa=797795060
ron

[Heater63]

My 63 truck housing has NO stamping on the tube. My 68 Camaro did.
Even if it is stamped, that doesn't mean it still has the original diff/ratio it was built with. Its been 48 years! A PO might have changed diff or gear set.
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[padresag]

Originally Posted by Heater63

My 63 truck housing has NO stamping on the tube. My 68 Camaro did.
Even if it is stamped, that doesn't mean it still has the original diff/ratio it was built with. Its been 48 years! A PO might have changed diff or gear set.
Posted via Mobile Device

that is quite possible that it could be changed, but then again it may not be. it is a starting place
your 63 more than likely has the stamp, you just haven' found it yet
the stamp is not always in the same place around the tube
ron

[Heater63]

Originally Posted by padresag

that is quite possible that it could be changed, but then again it may not be. it is a starting place
your 63 more than likely has the stamp, you just haven' found it yet
the stamp is not always in the same place around the tube
ron

I blasted the tubes to bare metal and repainted. There is no stamping on mine.


Eddie,
You need to talk to the guy that is going to rebuild your rear end to get the assurances you are looking for. But, the '63 is not different from 64, 65, etc, except for spine count that has been mentioned in this thread already. To use the 5 Lug axles from ECC you will need to change spider gears or install a new diff unit that accepts the 30 spline axles.

I can't tell you what you have, but I have a '63 that was a 3:73 peg leg, and it was rebuilt with:

ECC 5 lug 30 spline axles, bearings, seal kit for 63-69 902-6569AXLK

Detroit TruTrac helical gear posi- Jegs 913A315 3:73 and up; all yrs up to 1982

3:73 Ring and Pinion - Summit racing MGR-GM12-373

[Captainfab]

The ring and pinion gears and posi/lockers for any truck 12 bolt will fit any truck 12 bolt housing made from 1963 thru 1982. Just because someone lists their parts for only fitting certain years, doesn't necessarily mean that they only fit those years. Not everyone writing those listings knows what they're talking about.

Originally Posted by eddie1

I am using a 700r4, I know the rear tire size & the gear ratios of the transmission & what rear end ratio I want. The question is can I use the ring & pinions & the posi units that are listed for 64-82 12 bolt rear ends in my 63 12 rear end or do I need a new rearend?

Since you do have a '63 12 bolt with the pressed on backing plates, converting to disc brakes will require welding on a set of caliper brackets. If you were to find a '64 and newer housing, you could bolt on a set of rear disc brake brackets.

[1963c-10]

I have a 17 spline Eaton posi for my 12 bolt. It will be going in my 63 which has the factory rear diff. Its been professionally rebuilt and has the new carrier bearings installed. Besides fluid, pan gasket, what else should I be looking at for a conversion from a one legger?

[CRoss]

So am I correct in saying that if I keep drum brakes on the ‘63 rear ended I will not have any cutting or fab work by going with aftermarket (cpp) 5 lug 30 spline axles? From the above post it seems like the cutting and fab for brake backing plate is only to go with rear disc???.. My goal is to swap to 5 lug axles, posi trak with gearing for overdrive transmission all while using the original ‘63 housing with drum brakes.
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[Captainfab]

That is correct. If you stay with drum brakes on your '63 truck 12 bolt, there is no cutting or welding involved. The '63 truck 12 bolt has the backing plates pressed onto the axle tubes. Just install the parts in the center section and slide the axles in.

[CRoss]

Thank you for the help
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[hopalong]

Originally Posted by Captainfab

That is correct. If you stay with drum brakes on your '63 truck 12 bolt, there is no cutting or welding involved. The '63 truck 12 bolt has the backing plates pressed onto the axle tubes. Just install the parts in the center section and slide the axles in.

Hi, I read the entire old post and have one question based on the quote above. If you used the 5 lug axle with the oem pressed on backing plate did you drill out the 6 lug brake drum to 5 lug pattern or did you find a later model 5 lug brake drum that fit upto and over the pressed on backing plate. Thanks in advance

[The Rocknrod]

Originally Posted by hopalong

Hi, I read the entire old post and have one question based on the quote above. If you used the 5 lug axle with the oem pressed on backing plate did you drill out the 6 lug brake drum to 5 lug pattern or did you find a later model 5 lug brake drum that fit upto and over the pressed on backing plate. Thanks in advance

Check out what CPP says about brake drums on theyre 5 lug axle conversion - https://www.classicperform.com/Store.../6369RAC-5.htm

[hopalong]

thanks much I'll check it out

[hopalong]

think I can use a 1971 drum which has the same 11" x 2 " dimensions of the 6 lug drum but just 1/4" deeper at the mounting hub and is the same 5- 4.75 bolt pattern as the Moser axle and would fit over the axle hub mounting center of 2.75 i.d.

?

[Heater63]

Originally Posted by hopalong

think I can use a 1971 drum which has the same 11" x 2 " dimensions of the 6 lug drum but just 1/4" deeper at the mounting hub and is the same 5- 4.75 bolt pattern as the Moser axle and would fit over the axle hub mounting center of 2.75 i.d.

?

Whoa there. You said 5 x 4.75. Thats GM car size, is that what you meant? or is that a typo? 5 x 5 is the later year truck size and what i am running. The CPP link above is 5 x 5.
yes, the later year GM 71-72 5 x 5 drums work on the 63 backing plate, and they are a little bit larger, and finned, so you end up with a "heavier duty" drum brake.
Do I need to look up what part numbers I used for you??

[hopalong]

Thanks so much for replying that I can use the 71 brake drum that I have which is 5 on 4 3/4 car type drum (guessing same drum in car and truck with just different bolt pattern). Yes I understand the CPP kt has the 5 - 5x5 but I'm doing the 5- 4 3/4 car thing for I have wheels for that and running that pattern on two of my chevy cars. I have an 8.5 rear available but the width is 60" and the truck 12 bolt is exactly centered in the fender at 63.5" which I don't need to tub it. My wheels have the correct back spacing to fit up like the 12 bolt is now. I'm using a posi w/ 30 spline.
Moser has an axle set w 30 spline for this truck using 5- 4 3/4 with the center of the hub at 2 3/4". Hub on the existing 17 spline axle is 3 1/2" and the 71 drum center opening is only 2 3/4 and would not fit over the 5x5 axle if it was 3 1/2" hub.

[cwcarpenter98]

Hopalong,

Is the drum you want to use a factory, truck drum that has been re-drilled for the 5x4.75 pattern, or is the drum you want to use a car drum that you are trying to make work with a truck axle?

[hopalong]

The drum I have is a factory 71 chevelle drum w 5 on 4 3/4 that is exactly the same id and width as the existing 51 truck drum with exception of the distance from the drum axle mounting surface to the outer perimeter edge is 1/4" longer. The 71 drum is hd and finned. Going to use a Moser 30 spline axle 5 on 5 on 4 3/4 same length as the 6 lug 17 spline axle

Thanks