[Goatracer1]

I installed a Currie 31 spline unit 20 years ago in my GTO when it had a 421 and ran 12 seconds flat. Eventually the car ran high 10's. I have never had to do anything to that unit. Couldn't recommend them more highly. Just unbolted old rear, rolled it out, rolled in new one and bolted it up. Same driveshaft. Minor bending of brake lines and adjustment of parking brake cables. If you buy complete unit you dont have to chase for parts. Just plug and play.

[avman]

Thanks. Currie was my first choice, but I'm going with Quick Performance. Checked off some nice options and still 25% ($1,000) cheaper than the other 3 companies I called including Currie.
Should bolt right in.
Thanks for the reply.

[Jack P.]

Can I add a question to this? I believe the 9" has a pinion angle different then a 10 bolt or 12 bolt. About 1.5" lower? The OP's car looks like a sits a little high in the back now, or even if it is stock height will he need to lower the back of his transmission a bit to get a better pinion angle?

[avman]

Thanks Jack. I didn't think about that. I will ask Quick Performance about that. I haven't followed up with them for details regarding replacing the current shock+spring+airbag suspension components on the broken stock rear axle with adjustable struts.
Thanks again for the "heads up".
I will follow up here with additional information. It may be a month or two before I can place my order.

[pokey1]

Recently purchased a 9" for my 67 GTO from quick performance. Asked Mike from quick performance about pinion placement and here is his answer:


"When we build a rear end like the 9" you received for your 1964-1967 GM A
body car, we duplicate the stock suspension mounting locations as well as
pinion location."

Only reason I need to change driveshaft is I am also going from a Muncie to a T56 Magnum.

[avman]

Thanks Pokey1.
One less (additional) question I have to ask them!
I'm really looking forward to taking a few 1320 trips after the new rear end is broken in. I anticipate the "posi" vs open rear axle will make a big improvement in time, and the 3.3 to appx 3.8 ring and pinion gears will help too. Our goal is mid 12s, 12.8 or quicker.

[pokey1]

I would think going to the posi should make a good difference. Track I tried last summer is at 4200 ft elevation and was running 13.0 and 13.1 with crappy 60 ft times and bad launches. Hoping the trans and rearend change will get me significantly better times. After that I can turn on the 150 shot and try it.. Have not tried that at all yet.

[avman]

Well Crusin' the Coast is 8 weeks away and it's going to be close on getting the rear end ordered and installed. Appx 3 weeks from order placement to my door. I spoke w/Max at Quick Performance and that's definitely who I'm going with! Also going with the same configuration as stock regarding suspension setup-thanks for the advice and info!
I'll probably start a new thread after the rear axle is installed and broken in. Gotta report our next track day results!

[avman]

Update on the Quick Performance rear axle assembly. The 65 GTO has power drum brakes all around. I have been wanting to upgrade the front brakes to discs, and a "2 chamber" or "modern" master cylinder that has redundancy vs the factory master cylinder. Since I have gotten the go ahead from the finance director (wife) to order the rear axle assembly for her car, I would like to get discs on the rear axle with parking brake option, and Wilwood front discs (big ones since it has 17" wheels) and a Wilwood power master cylinder. Quick Performance said they can sell me the whole brake system with the rear axle assembly, and then I will have a line lock installed too (3 pedal car). So it looks like the 421GOAT is going to get a nice upgrade. I just hope I can get everything done by the 29th of September!

[64speed]

Originally Posted by avman

Update on the Quick Performance rear axle assembly. The 65 GTO has power drum brakes all around. I have been wanting to upgrade the front brakes to discs, and a "2 chamber" or "modern" master cylinder that has redundancy vs the factory master cylinder. Since I have gotten the go ahead from the finance director (wife) to order the rear axle assembly for her car, I would like to get discs on the rear axle with parking brake option, and Wilwood front discs (big ones since it has 17" wheels) and a Wilwood power master cylinder. Quick Performance said they can sell me the whole brake system with the rear axle assembly, and then I will have a line lock installed too (3 pedal car). So it looks like the 421GOAT is going to get a nice upgrade. I just hope I can get everything done by the 29th of September!

I didn’t put a “true” wilwood kit on the front of mine but I did put the D52 caliper replacements with the explorer disc in the back. If you are ordering all at once tell them you want the spaced rings attached to the axles for the explorer discs other wise you have to mess with these little half moon spacers that suck to try to install. If you tell them ahead of time they can drop a full ring around the axle before pressing on the axle bearing

[avman]

Great advice and not a minute too soon. I am calling them within the hour.

[avman]

So I ordered the rear axle assembly today. New upgraded nodular iron center, 3.80 ring and pinion gears, explorer 11" rear disc w/drum parking brake, fill and drain plugs, jack pad, rings on the ends as suggested, 31 spline QP axles (same alloy as Moser) Wilwood 12.19" upgraded front discs, Eaton TrueTrack posi, black powder coat.
When I get my spec list I'll post it up.
I believe the 3.80 (vs the 3.3 stock Pontiac) R&P gears are really going to wake up the built 421, and with the 25" tires on it now, 3,500 RPMs are manageable at 70 mph.
I also looked at the space available between the 275/40/17" Toyo Proxes TQ drag radials that are on it now, and I have no space to the outer rear quarters, but 2" to the inside, so I have the rear axle assembly specd for 2" narrower than stock that will give me 1" inside and maybe a little room for wider tires.
On the same 9"x17" rim I have 315/35/17s on my 70 Roadrunner, and they fit great.

[avman]

Here is the list of options and stuff that I wound up getting. Steep total price, but that includes 4 wheel discs, 12.19 Wilwood front and 11" rears all drilled and slotted.

[Sirrotica]

Too late now to make any difference, Speedway motors has 9 inch packages too.

[avman]

I was 3 pages deep and a number of months into this thread. I appreciate all of the posts. I went with what I think will work best for me all around.
Once everything is installed and I have some time with it I will post a new thread with a link to it in this thread.
Thanks !

[avman]

These lower lift bars replace the lower control arms and reduce wheel hop and use the torque of the axle housing to press down on the tires. The uppers allow for adjusting the pinion angle.

[avman]

If you look at the list of options and upgrades I uploaded, you'll see that this rear axle assembly has significant additions to the basic setup, including $1,000 in disc brakes front and rear. ANY of the other vendors would have cost $800 to $1,000 more. Just look at the list. There is $2,265 in add ons and upgrades!
I appreciate all of the suggestions and advice. The best recommendation was to check out Quick Performance!

[avman]

I'm adding these 2 products to the upper and lower control arms replacement items shown above.
Might as well do it now....
Rear shock tower brace.
http://umiperformance.com/catalog/in...roducts_id=930
Bracket that ties the upper and lower control arms together.
http://www.umiperformance.com/catalo...roducts_id=285

[avman]

Here is the breakdown of the Quick Performance rear axle assembly, upgrades, and brake system I got.

[avman]

The factory 9" power brake booster has about 1/8th inch clearance between it and the aftermarket valve cover. Also with the 4 wheel drums the brake pedal was like a light switch, not much pedal motion between off and locking up the brakes.
The Wilwood front 12.19" discs and rear 11" disc brakes will be actuated by a 1" diameter Wilwood master cylinder, for more pedal travel.
I bought this brake booster to replace the stock one and I have been told it will work fine.
Opinion or experience is welcome!