'70 gto 12 bolt

cadiwumpas

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  FWIW Tolerances stack and each is probably a little different on spacing from the inner wheelhouse to
the tire sidewall. My 86 Grand National was a little over 1/4" different side to side. Not a big deal until you
start pushing the limits on availible space.
 

Chris S

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Ted, its a good thing nobody took you up on your bet.....

Its home and its a 12-bolt, 3.07 posi in pretty good shape.

Here's some pictures....

Dv8
 

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dave brode

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DV8,

Measure flange to flange where the back plates bolt on. I have a bare '68-'70 chevelle housing here. We can tell if it's 65-67 or 68 up.

Look at axles where the wheel bearing ride. They often wear. Look in at edges of posi clutch plates. Some years used slotted discs, and often break between inner id and inside of slot. You can see the edges of the slots if they are as such. Hold one axle and see how much torque is required to cause other axle to "break-away". Not hard to tighten the unit up with some #3 shims.

Dave


link=topic=1068.msg11118#msg11118 date=1112478051]
Ted, its a good thing nobody took you up on your bet.....

Its home and its a 12-bolt, 3.07 posi in pretty good shape.

Here's some pictures....

Dv8
 

dave brode

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DV8,
Probably too deep for you, but I have a set of never run, thick [for 3 series carrier] Richmond 4.10 gears that I'll take $115 shipped for. They were setup and then removed [with no run time] with pinion depth tool, and have shim on them, so they *should* go into another housing with same shim. 
Dave
 

Chris S

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Dave, from backing plate flange to flange is approx 54 3/4" , axle face to axle face is approx 61 1/2".

Discs look kinda "ridged" on the edges to me, this the same as slotted.  I assume the other style is smooth?  None seem broken.

How exactly would I measure the torque?  We bolted 2' bars to the wheel studs and couldn't get it to break loose...

I won't get a chance to check out the axles for a couple days.

You can just see the discs on the left side in this picture - see the ridges?

DV8
 

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dave brode

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DV8,
My '68-'70 housing is bare, so I can't give a outside axle measurement.

From the surface where back plates bolt on, it's 55 & 3/8". From inside to inside of those flanges, it's 54 & 3/4". Axles for it measure 29 & 15/16" from drum surface to end.

Can't see your clutches in the pic. One axle has to break free to go 'round a turn. If there's nothing wrong with yours, it must be darned tight.
Dave
 

Chris S

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It's in really nice shape inside - must have been a low mile donor car.  We have those around here occasionally, it's the only good benefit of the salt & crap they spread on the roads in the winter....

Been doing some more research and have come up with a couple of options.

1)  Sell the 12 bolt on Evil-bay and use the extra $ to get an 8.5 with factory retainer plates and 3.42's or 3.73's, and put the balance towards better rocker arm setup.

2)  Just use the 12 bolt and keep my eyes open for 3.42 or 3.73 gear set. 

On option 2, I am getting the feeling that if I convert to rear disc brakes I wouldn't really need to worry about the c-clips?  Makes sense 'cause the axles can't walk out if the caliper is holding it back......might be a little cheaper than putting new ends/axles on it and still having drums....

That way I wouldn't have to buy better axles right away either.  I figure I will get aftermarket axles soon enough, but am more concerned about loosing a wheel at this point.  (3 wheel car hard to steer!)

DV8
 

dave brode

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DV8,

< Been doing some more research and have come up with a couple of options.

1)  Sell the 12 bolt on Evil-bay and use the extra $ to get an 8.5 with factory retainer plates and 3.42's or 3.73's, and put the balance towards better rocker arm setup.

Cleaned and painted, it's probably bring $600-$750 at a big swap meet near here [Carlisle, PA]. More if it had 3.55s or 3.73s. The pre '73 8.5" isn't that easy to find, but you might end up with money in pocket. The 8.5s would be 28 spline. Not sure if that's a big issue to you.

< 2)  Just use the 12 bolt and keep my eyes open for 3.42 or 3.73 gear set. 

Fyi - there is no 3.42 GM gearset for 12 bolt car. I hate aftermarket gears, fwiw. The 3.42-1s are really common for the 8.5s.

< On option 2, I am getting the feeling that if I convert to rear disc brakes I wouldn't really need to worry about the c-clips?  Makes sense 'cause the axles can't walk out if the caliper is holding it back......might be a little cheaper than putting new ends/axles on it and still having drums....

It would keep the wheel in, but it'd still not be legal for NHRA.

< That way I wouldn't have to buy better axles right away either.  I figure I will get aftermarket axles soon enough, but am more concerned about loosing a wheel at this point.  (3 wheel car hard to steer!)

Fwiw, the axles are fairly tough, although you *could* break one.

DV8

 

dave brode

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DV8,

How much wider is the '68-'70 12 bolt compaired to a '78-'87 rear? Watch how easy it is for me to spend your money [LOL].

Another option;

Buy my new Superior gear/Tom's Differentials 33 splined axles for $150 [$400 new, afaik]. They are apx 2" shorter than your '68-'70 axles. Total width would be apx 4" less than the current 12 bolt rear. Buy the $65 weld on ends and $X Ford bearings to allow them to fit.

Either [1] buy a 33 splined spool or posi unit. Not certain that there are 3 series posi units sold for 3 series gears with 33 spline. If not, a 4 series would work, with "thin" 3.73-1s. Sell the 3 series posi on e-bay [should bring $200+]. Sell stock axles. They fit 68-'70 chevelle, and also Camaro/Nova 12 bolts, but I'm not sure which year they went to that length.&nbsp;

Or, [2] buy 33 spline side gears for your posi. Afaik, drilling the center hole where the axles fit is only mod needed.

You would have a kick ass 33 spline rear, with no c-clips. Would also work to build a kick ass 8.5".
Dave



< Been doing some more research and have come up with a couple of options.

1)  Sell the 12 bolt on Evil-bay and use the extra $ to get an 8.5 with factory retainer plates and 3.42's or 3.73's, and put the balance towards better rocker arm setup.

Cleaned and painted, it's probably bring $600-$750 at a big swap meet near here [Carlisle, PA]. More if it had 3.55s or 3.73s. The pre '73 8.5" isn't that easy to find, but you might end up with money in pocket. The 8.5s would be 28 spline. Not sure if that's a big issue to you.

< 2)  Just use the 12 bolt and keep my eyes open for 3.42 or 3.73 gear set. 

Fyi - there is no 3.42 GM gearset for 12 bolt car. I hate aftermarket gears, fwiw. The 3.42-1s are really common for the 8.5s.

< On option 2, I am getting the feeling that if I convert to rear disc brakes I wouldn't really need to worry about the c-clips?  Makes sense 'cause the axles can't walk out if the caliper is holding it back......might be a little cheaper than putting new ends/axles on it and still having drums....

It would keep the wheel in, but it'd still not be legal for NHRA.

< That way I wouldn't have to buy better axles right away either.  I figure I will get aftermarket axles soon enough, but am more concerned about loosing a wheel at this point.  (3 wheel car hard to steer!)

Fwiw, the axles are fairly tough, although you *could* break one.

DV8

 

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< On option 2, I am getting the feeling that if I convert to rear disc brakes I wouldn't really need to worry about the c-clips?&nbsp; Makes sense 'cause the axles can't walk out if the caliper is holding it back......might be a little cheaper than putting new ends/axles on it and still having drums....

It would keep the wheel in, but it'd still not be legal for NHRA.>


As long as the wheel stays in - - how many others are running their cars and don't have anything in this area?&nbsp; Does Norwalk ever actually check for c-clips?&nbsp; Seems to me they would only if there was a mishap - and I shouldn't have a mishap it there was a caliper?

Sorry about the 3.42 gearset - I assume sometimes and you know what that gets you!&nbsp; What I was figuring on was something in the 3.42 range if I ran 28" slicks and 3.73 for 29".


It's about 2ish inches wider per side? ( I measured it exactly but it's written on cardboard in the garage at home.....)&nbsp; The 7.5 is 58.25" total drum face to drum face.

You know, I was thinking it could be narrowed at the same time as installing different ends.&nbsp; Hmmmmm......

Ford bearings fit your axles?&nbsp; Where exactly are these $65 weld on ends - I've been finding $80 ones that have about 3 different bearing sizes listed.

And 33 spline side gears... Hmmmm...


DV8
 

dave brode

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DV8,

< As long as the wheel stays in - - how many others are running their cars and don't have anything in this area?  Does Norwalk ever actually check for c-clips?  Seems to me they would only if there was a mishap - and I shouldn't have a mishap it there was a caliper?

Good point.

< Sorry about the 3.42 gearset - I assume sometimes and you know what that gets you!  What I was figuring on was something in the 3.42 range if I ran 28" slicks and 3.73 for 29".

Afaik, there are aftermarket 3.42s for 12 bolt car, if 3.55s are too deep.


< It's about 2ish inches wider per side? ( I measured it exactly but it's written on cardboard in the garage at home.....)  The 7.5 is 58.25" total drum face to drum face.

Hmm. Removing 2" per side would put you close to that.

< You know, I was thinking it could be narrowed at the same time as installing different ends.  Hmmmmm.....
Yep.

< Ford bearings fit your axles?  Where exactly are these $65 weld on ends - I've been finding $80 ones that have about 3 different bearing sizes listed.

The axles were built for the special ends, which allow a Ford bearing [no pricey and leak prone c-clip eliminators needed], and they accept the GM backing plate, so stock GM brakes can be used. Mark Williams and Moser have the ends.

< And 33 spline side gears... Hmmmm...

99.9% sure you can buy them to retro-fit to the stock posi unit. Probably pricey though. Tom's differentials has them.
Dave

 

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Looks like Toms has 2 options on the 33 spline side gears&nbsp;

1) set of 4&nbsp; for stock posi $180.00

2) set of 4 FORMED 10-17 $85.00

What gives?&nbsp; I figure the $100 dif is in strength but what makes them different?

Axle ends are $115 pr no bearings.&nbsp; Good deal - now here's a question.&nbsp; Do the Ford bearings fit stock axles?&nbsp; And aftermarket axles?&nbsp; Or is there a conversion bearing in there somewhere?

I'm just having a hard time believing that Ford bearings will fit both stock & aftermarket gm axles....

Chris
 

dave brode

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DV8,

link=topic=1068.msg11404#msg11404 date=1112892727]
Looks like Toms has 2 options on the 33 spline side gears 

1) set of 4  for stock posi $180.00

2) set of 4 FORMED 10-17 $85.00

<What gives?  I figure the $100 dif is in strength but what makes them different?

No idea, but I'd call Moser and ask about 33 spline side gears. Please let me know what you learn.

<Axle ends are $115 pr no bearings. Good deal

$65 or $70 from Moser and MWilliams, afaik


< now here's a question.  Do the Ford bearings fit stock axles? And aftermarket axles?  Or is there a conversion bearing in there somewhere?

For bearings will not work with stock axles, or stock ends. The deal with the weld on ends, and Ford
bearings requires that the axles be made for that deal.


<I'm just having a hard time believing that Ford bearings will fit both stock & aftermarket gm axles....

They don't, and akaik, there is no bearing that'll press onto the stock axle and work with the stock axle tube ends. Prior to the special ends being made, the options were: 1 - c-clip eliminators, or 2 - weld on ford or mopar ends, and use the backing plates for the ends used. The "special" ends, and axles made to work with them allow the ford press on bearings [no c-clip eliminators],&nbsp; but they accept chevy back plates/breaks.
Dave



Chris
 
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