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It's time to Order My Rear Diff, Front Disc Brake Kit, & Suspension Components.

3K views 57 replies 11 participants last post by  Baaad65 
#1 ·
I am hoping to spend some jack in the next month so that when spring/summer hits, I can get after re-doing the rolling chassis and need your help. It's a fair amount for me to wrap my head around and some decisions have to be made...the time has come.

I'm just going to throw out my thoughts and see what sticks...

1.) I need a front disc brake conversion kit and am leaning towards the smaller diameter booster for better clearance at the valve covers. I intend on using 15" steelies and am not concerned with originality. I just want better than stock drum braking that discs offer. Ames says you can get the 9" booster upon request. Here's what I'm looking at from Ames...

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Open for discussion...pros/cons with this kit?

2.) Next is the rear end and this one is making my head spin quite a bit. I currently have the stock 10 bolt with the 2.56 gears and want to go with something in the 3's. At first glance, the favorite ratios seem to be in the 3.23 to 3.36 range…BUT I am leaning heavily towards a Gear Vendors overdrive behind my 400TH. Now I’m thinking more like 3.55, but am open to advice. I will have maximized the space in the rear wheel wells for the widest treaded radial drags (without cutting the frame and tubbing). My motor build is not set in stone yet, but will land between 400 and 500 HP. I need to prepare for the higher end since “more power” is hard to resist. That leads me to want the 12 bolt or Ford 9”. One thing I could do is buy a Ford 9” without the gear set. This should allow me to rebuild the rolling chassis and make the gear ratio decision later, Right?

I want to buy a rear end that accommodates stock/aftermarket replacement suspension parts and bolts in without having to modify anything. I intend to upgrade to tubular suspension and add a rear sway bar that u-bolts to the axle, not the trailing arms (along with frame braces). I’ll take all recommendations for a company that offers this type of rear end service.

Another thing on my mind is ordering a custom width rear end to help guarantee that the widest wheel/tire combo can be installed. Do I need to buy my wheels and tires in order to figure that out?

I’ll think about drum or disc rear brakes later to keep my head form cracking open. I'm pretty sure I have the suspension parts figured out. Except what rear sway bar to get, but that depends on what rear end I go with, I suppose.
 
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#2 ·
I'll play: Have you thought of simply installing '68-'72 A body spindles and front brakes? Did a '65 GTO for a total of $90 years ago, which included all the parts. This was from a sa;avge yarde. Straight bolt on, no brackets to fail or come loose. Won't change front end geometry at all. Franks Pontiac Parts in CA may have the stuff.
If you are going to bother to upgrade the rear, a Ford 9" is head and shoulders superior to a 12 bolt. NO comparison. And MUCH easier to change gear ratios, since it's a 'drop out' unit. With a GV overdrive, I would run a 3.50 or even better, a 3.89 rear gear, knowing your plans. I would NOT bother with rear disc brakes. They usually have inferior parking/emergency brake capacity compared to the drums, and only do 25% of the stopping. I would only do rear disc brakes if I was going to track the car on a road race course in events that went many laps. Otherwise, total waste of money, and IMO, inferior to stock drum, which don't need failure-prone brackets and spacers and crap to work.
As for wheels and tires, that is the hardest part, and easy to mess up on. You will need to get your rear end installed and measured and go from there. If I were getting a custom 9" rear, I would likely get one that ran about 2 or 3 inches narrower than the stock 8.2 ten bolt that comes on these cars. I had a set of 11" slicks on my '65 years ago mounted on Chevy rally rims and they fit perfectly. Barely, but they cleared. No air shocks, etc.
 
#4 ·
I'll play: Have you thought of simply installing '68-'72 A body spindles and front brakes? Did a '65 GTO for a total of $90 years ago, which included all the parts. This was from a sa;avge yarde. Straight bolt on, no brackets to fail or come loose. Won't change front end geometry at all. Franks Pontiac Parts in CA may have the stuff.
If you are going to bother to upgrade the rear, a Ford 9" is head and shoulders superior to a 12 bolt. NO comparison. And MUCH easier to change gear ratios, since it's a 'drop out' unit. With a GV overdrive, I would run a 3.50 or even better, a 3.89 rear gear, knowing your plans. I would NOT bother with rear disc brakes. They usually have inferior parking/emergency brake capacity compared to the drums, and only do 25% of the stopping. I would only do rear disc brakes if I was going to track the car on a road race course in events that went many laps. Otherwise, total waste of money, and IMO, inferior to stock drum, which don't need failure-prone brackets and spacers and crap to work.
As for wheels and tires, that is the hardest part, and easy to mess up on. You will need to get your rear end installed and measured and go from there. If I were getting a custom 9" rear, I would likely get one that ran about 2 or 3 inches narrower than the stock 8.2 ten bolt that comes on these cars. I had a set of 11" slicks on my '65 years ago mounted on Chevy rally rims and they fit perfectly. Barely, but they cleared. No air shocks, etc.
I am hoping for a disc kit. Can the '68-'72 parts be found in a kit of new parts.

As far as the rear end and wheels and tires go...I'm thinking to stick with standard available back spacings and adjust the rear end width to them. I'm still noodling how to determine the rear width with my car off the frame and on a cart/dolly.

Thanks for "playing", the game's not over!
 
#3 ·
I did an 8" dual booster and can get the cover off easily and have real good brakes, almost 15 inches of vacuum with my cam and 1.6 rockers because of the 114 LSC and I have disc/drum, rear discs aren't necessary unless you want the cool Pro Tour look which if I had to do it over would have gone that way but it's more money. If you're thinking about it do it now because that's why I'm not changing to rear discs I would have to change the P valve, buy new E brake cables and spend a lot more money on the brakes....but you never know with me ;) I'll have a 12 bolt housing w/Strange axels and maybe brakes available in the narrower '65 width if interested but you might be to far away from Northern IL. You could look at the one I'm getting the Strange Dana S60, it has raised upper arm mounts to help eliminate wheel hop and multi position lower mounts...2600.00 at Summit plus tax and some add ones so about 3K delivered and bullet proof. And don't forget about the drive shaft with 1350's on both ends and the diff yoke.
 
#5 ·
I will have to do some reading on the Dana S60, your price point seems quite a bit lower than the first, and only, price check I've made on the Ford 9".

What do you mean about the yoke sizes (1350's). I realize that they may have to change styles from original, but I am curious to what you are referring to. At this point, I don't even know what was original to my car.

I'll be happy with drums in the back. My preference in wheels will not show the bling in the background. (y)
 
#7 ·
If you go with the Ford 9" rear end, don't forget to make sure your brakes fit with that rear end. Your GTO brakes won't work (or at least might require some different brackets). Ask me how I know.

I went with all UMI suspension parts, but I can't attest to how well they work just yet. The fit and finish was nice enough, though. A lot of people seem to like Global West too.

As for the axle-mounted sway bar, I've got my eye on either the Spohn or Umi, but that's later down the line for me.
 
#10 ·
I ordered out the rear 11" Ford drums for my Dana 60 in the GTO and they have been perfect. My son's '68 Firebird had the 9" diff and 11" drums and worked great. Then talked two of my friends into the 11" rear drums and they also really like the feel and stopping power. On the other hand, I've had friends in the GTO club that went with rear disc brakes and they have had trouble setting up the rear discs with enough stopping power and couldn't get them adjusted to have the rears do their share.

I've had quite a few vehicles with the single piston front discs and I really prefer the two piston or especially the four piston calipers. Just seems to have better feel and a more aggressive stopping ability. Now the single piston far outshines and out stops the drum brakes, but there is a noticeable improvement when more money is spent. I converted a '67 GTO to single piston setup off a '69 Grand Prix. Got the setup out of pick-a-part and by the time I rebuilt everything I wasn't any money ahead of just going with one of the full kits now available. My blue GTO was ordered with the 4-piston discs and they are massively better than the single piston units that were available in later years. Just a pain finding parts for the early calipers when it does come time to refresh things.

My latest endeavor is the '65 Catalina Safari wagon. That car was truly frightening when I first brought it home and every stop was a life threatening experience. Went with the 13" disc Master Power Brakes and 17" wheels and they really bring the big barge down without a problem. Overkill for a lighter GTO, but bigger proved better for the wagon.

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Friend and I made a dual order to save some shipping costs. Here is
the pair of Dana 60's with the 11" drums. We finally decided on the 3.73
ratio because of the 28" tall tires and the 5th gear ratio of the Tremec.

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#11 ·
That's the combo I'm dreaming about, how do you like it on the street? I was going to try and reuse my rear drums as they're only a few years old, Strange said I have to open up the hole on the backing plate for the bigger bolt in axle bearing. Maybe I should check into the cost of the bigger drum brakes.
 
#12 ·
The idea I was toying with was to pull my axles then suspended the backing plates without disconnecting the lines, make the holes bigger then pull the axles on the Dana and bolt my plates on. Idk if it's going to work and if the lines will work, my brakes are good and I was hoping to not have to bleed the brakes as I've finally got my master cover to stop leaking but if I have to I do.
 
#14 · (Edited)
As far as the price point mentioned above, the 12-bolt was the most expensive, then the 9", and the least expensive was the Dana 60 when we purchased ours. No idea why the 12-bolt was so expensive but it was another $600 over the others when ordered with all the upgrades.

Our original 9" drums are substandard by every measure and you just as well upgrade. The Ford big bearings are the only way to go with whatever rear you choose. I was thinking that the bolt pattern for the Ford backing plate was really different than the 10/12 bolt pattern but never physically checked. Hopefully the 9" drum will fit correctly in both the diameter of the center hole and the axle shaft is properly located to center the drums on the shoes. I was able to use both the emergency brake cables and brake lines with the new rear with the Ford brakes.

We were vacillating between the 3.54 and the 3.73 and I might have went with the 3.54 if I had a milder cam. Makes about a 5 MPH difference in optimum cruising speed with the 3.73's coming in about 78 MPH and 83 MPH for the 3.54's. The main problem is my fairly large cam wouldn't be happy when having to cruise at 65 with the higher ratio. There's always going to be a dead spot with a manual trans where 4th is spinning somewhat and 5th is somewhat low in the RPM range. With the 3.73's the indecision spot between 4th and 5th is between 55 to 60 while the 3.54's would have been 60-65, and there will be many times on the freeway I'd be stuck at or just below 65 in Saturday afternoon traffic. Not that big of deal either way with either gear, but I also prefer the slightly lower first gear final ratio for chugging along when traffic finally drops down to a crawl.

Ford 11" internals. You can see my not-so-pretty emergency brake cables attached.
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The extended mounts as mentioned above. This is the standard cover and
is still formidable. The available aluminum covers take things to the next level.
I did spring for the powder coating.
Bicycle part Personal protective equipment Handgun holster Machine Auto part



Besides the ring gear being larger in diameter, the tooth width is over a
half inch wider than the 12-bolt or Ford 9". Photo looses some perspective
of the size - that's 3" exhaust in the background.
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Last photo just to show we can practice re*neck techniques in SoCal.
The friend on truck is the one that ordered out the other Dana.
Wheel Land vehicle Tire Vehicle Automotive tire
 
#15 ·
As far as the price point mentioned above, the 12-bolt was the most expensive, then the 9", and the least expensive was the Dana 60 when we purchased ours. No idea why the 12-bolt was so expensive but it was another $600 over the others when ordered with all the upgrades.

Our original 9" drums are substandard by every measure and you just as well upgrade. The Ford big bearings are the only way to go with whatever rear you choose. I was thinking that the bolt pattern for the Ford backing plate was really different than the 10/12 bolt pattern but never physically checked. Hopefully the 9" drum will fit correctly in both the diameter of the center hole and the axle shaft is properly located to center the drums on the shoes. I was able to use both the emergency brake cables and brake lines with the new rear with the Ford brakes.

We were vacillating between the 3.54 and the 3.73 and I might have went with the 3.54 if I had a milder cam. Makes about a 5 MPH difference in optimum cruising speed with the 3.73's coming in about 78 MPH and 83 MPH for the 3.54's. The main problem is my fairly large cam wouldn't be happy when having to cruise at 65 with the higher ratio. There's always going to be a dead spot with a manual trans where 4th is spinning somewhat and 5th is somewhat low in the RPM range. With the 3.73's the indecision spot between 4th and 5th is between 55 to 60 while the 3.54's would have been 60-65, and there will be many times on the freeway I'd be stuck at or just below 65 in Saturday afternoon traffic. Not that big of deal either way with either gear, but I also prefer the slightly lower first gear final ratio for chugging along when traffic finally drops down to a crawl.

Ford 11" internals. You can see my not-so-pretty emergency brake cables attached.
View attachment 159699

The extended mounts as mentioned above. This is the standard cover and
is still formidable. The available aluminum covers take things to the next level.
I did spring for the powder coating.
View attachment 159700


Besides the ring gear being larger in diameter, the tooth width is over a
half inch wider than the 12-bolt or Ford 9". Photo looses some perspective
of the size - that's 3" exhaust in the background.
View attachment 159701


Last photo just to show we can practice *** techniques in SoCal.
The friend on truck is the one that ordered out the other Dana.
View attachment 159707
Wilwood has a great resource for the different bolt patterns here. It's what helped me figure out what I needed to order.
 
#17 ·
I ordered my Dana three years ago almost to the day. Looked up my invoice and it said "Late B.F. Drum Brake Kit". Also went with the Chromoly 1350 Yoke and the Dana Truetrac with the helical gears. Absolutely love the Truetrac - 100% traction to both wheels as soon as the gas is hit but operates like an open diff when driving normal.

The friend in my last photo has been bitten by the drag racing bug and is in pursuit of better strip times. A couple weeks ago we installed 4.10's in his Dana in place of the 3.73's. It was the first time I played with the threaded preloads and there was somewhat of a learning curve. Was used to the feel of loading shims for preload and was a little worrisome to just crank in preload without having a true reference point. Last time out he was dumping the clutch and bringing the front wheels off the ground about 4" and so far things are all holding up.
 
#20 ·
I've learned some things from this thread already and have "built" a 9" rear end off the Currie site and have some questions. Not that I am set on Currie...I just started there to get a feel for what's involved. Here's the fictitious build...

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Questions...ignore the ratio for the time being, but I suspect it will be between 3.25 and 3.89.

1.) Axle spline options are 31 & 35....what's a guy need to know to make the right choice? It makes over $700 difference in the final price plus the case option dollars that follow.

2.) If you choose 35 spline, you have to pick from an nodular iron "race" or aluminum "Pro" case. Picking the 31 spline, the options are the "sportsman" iron or light weight aluminum case. I'd bet this has to do with horsepower and/or weight loss, in general...where do I stand?

3.) What diff style to strongly consider? I here folks bragging about the Detroit and Eaton often enough...pros/cons? Why would anybody build a 9" with and open diff? Here is Currie's options...

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4.) The 1350 Yoke comes in Nodular Iron or Chromoly. How to make the $5 difference decision?

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5.) These are the drum brakes that come with the kit...looks like they are for the large bearing rear ends. The description is fairly nondescript, anything to question here?...

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6.) Wheel stud size options. I'd love to keep the OEM 7/16" size, but should I bump up to the 1/2"? Do the wheels that work on the 7/16" also work on the 1/2"? I guess that's my main concern.
 
#24 ·
I wouldn't stress to much about the diff. The great thing about the Ford 9" is you can always change your mind later! This is Currie's video that talks about the differences between their offerings. I went with the Currie TwinTrac for mine.

You can save a bunch if you get the housing and axle package, then buy the third member separately from them rather than a completely built rear end. Of course you'll have to put the axles/third member in yourself, source a brake kit, and paint it yourself. But it's about $1800 cheaper to do it that way.

1/2 studs should work with your wheels. They worked with my Rally II's off a Trans Am.
 
#22 ·
Lust makes an excellent point if you are running larger camshafts. You don't want your cruise RPM so low you will be 'off the cam' most of the time at cruise, which results in saggy performance and lugging. Have a friend who ran into just this problem and we ended up installing steeper rear gears. His was so bad he couldn't even use OD below 80-85 mph. New vehicles with VVT and all the electronics are happy going down the road at 1500-1800 rpm at 75 mph. A big cammed Pontiac, not so much. 2200-2600 rpm seems to be the sweet spot to be at the beginning of the powerband, get snappy performance at tip-in, and decent fuel economy.
 
#23 ·
Right now, I am being advised to not use anything more than a Ram Air IV cam, thereabouts, but the engine build is still a ways off. Not sure how that equates to decent OD conditions? I do know what you mean though...I had a peppy F@rd motor that lugged quite a bit in OD at 60 minus mph with an AOD transmission and 3.73 gears, but loved the T5 manual transmission. It was all in the control of when OD was used.

Side note: I did a quick 9" rear build on the Moser site and the price for a similar build was considerably lower. than the Currie build It is not comparing apples to apples since the options are not exactly the same, but relatively close. It's never easy. is it? I'll keep at unitl my money's gone!
 
#28 ·
...The great thing about the Ford 9" is you can always change your mind later!
I hear this all the time, but unless you are a race team and need several third members for different track conditions it doesn't make financial sense. The price of a set up third member is about two thirds the price of a complete axle assembly. Currie gets over $1,800 for their cast iron case third member fully set up. A Richmond ring and pinion gearset for the 9" is a little over $350. Most of us will still be changing out the ring and pinion on the 9" third member at the same cost as someone with a 12 bolt or Dana 60.
 
#29 ·
That's a good point. It's a lot spendier to pick up a fully set up third member. I like it for me because I'm not 100% confident setting the backlash of the ring and pinion just yet. I've never done it and it feels foreign to me. Reading the grease marks is like reading tea leaves in my mind. I'll never be confident I did it right. I like the peace of mind I get just bolting up a completed unit.

I'm sure someday I'll need to learn to do it. Every car I drive can't have a Ford 9" in it.
 
#37 ·
Cam is similar to the "Stump Puller" designed and sold by Dave Bisschop at SD Performance. We have six cars in our GTO club with that cam. It idles just a little better than the RAIV, much more power, and doesn't burn your eyes when you walk behind the car like the RAIV cam does. It's a good Choice.

I agree that either ratio will be fine. My suggestion is if you have 28" tall tires you go with the 3.73. The 3.55 ratio would work with stock tires around 26-1/2".
 
#38 ·
You can take this to the bank. What Jim said as well.
I like my Pontiacs to put out torque over HP, which means low rpm grunt and easy driving with less broken stuff.
I almost never drive my '65 GTO with its high-strung 11:1 389, rowdy Sig Erson cam, and steeper gears. If I changed the rear gearing I'd have to change the cam, etc. Maybe in my retirement I'll spring for aluminum heads so I can drive the darn thing in pump gas. Sigh....
 
#47 ·
here are a few pics of mine before I put it in. Can provide details late next week (full details from the build sheet if helpful) with measueres and stuff...I think.

There are some important particulars about axle tube ends, bearing style and flange type that will impact your brake selection. This is ESPECIALLY important if you are doing a 4 wheel disc conversion (I did Wilwood).
 

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#51 ·
I have used many a 9 inch in my Shelby or Ford arsenal. I don't think I would worry about 2+ horsepower when you have over 400+ ft. lbs. of torque. As for the noise.............that is one place you don't want to buy cheap gear sets. It is tempting as we all know. Cheap gear sets are noisy and I have experienced this. Slap in some good quality OEM gears from Ford, Ford Motorsport, or a reputable manufacturer of U.S.A. made gear sets and all smooths out!
 
#56 ·
Noise and efficiency - it's a basic design difference:
"The Ford 9-inch pinion is mounted lower in the carrier and has the greatest hypoid offset, which causes it to consume more power to drive it than the Dana 60 or GM 12-bolt."
Link to the article:
.

wait, I should add something funny/rude...
"remember to consider the hypoid offset when selecting NJ hookers or the TTOF gals at the all-you-can-eat-buffet...."
you're welcome. ;o)
 
#57 ·
Well,

My rear end search has taken a turn. I have found that the Ford 9" can be built to my needs from $3200.oo to over $5000 (that range is ready to go, including disc brakes, 35 spline axles, 1/4" tube walls, etc...good for 600+ HP...more than I need). The lower end is from state local "I build them in the shop out back" to the premium racing sites on the web delivered to my shop.

Here's my turn, a buddy has offered me a 12 bolt housing, flange to flange, that came from a late 60's Chevelle and was once in a late 60's GTO. It has the C-clip elimination mod and comes with the axles, rear aluminum cover, but no gears. The offer is free if it saves me money.

Now I have to research the 12 bolt and see if the savings is there to go to a rebuild scenario compared to all new.

Any advice on the 12 bolt direction would be great!

Do these photos show adjustable lower trailing arm brackets? The owner and his son are big into drag racing Pontiacs. I'm not sure what I am looking at here other than there are South Side Machine lower trailing arms on it that look pretty beefy...

Wood Gas Metal Machine Auto part


Wood Bumper Automotive tire Gas Automotive exterior


Here's a photo of the inside of the pumpkin in case someone sees something worth discussing. BYW, the diff cover has jack bolts built into it that firm up against the caps to help keep them tight (the caps with the yellow paint on them).

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I am open to the group's thoughts on this direction since I have been leaning towards a Ford 9", but now may have an edge to stay with the general. My HP ambitions are to be around 500 HP.
 
#58 ·
I'll guess you'll have to blast it then see if any cracks show up, what's the history was it raced? Also those don't look like my SSM brackets, now yes figure everything that has to go into it. Are you planning big sticky tires and racing it...remember I shattered a 12-bolt Yukon posi with 500hp just saying 😉
 
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