Pontiac GTO Forum banner

1 - 11 of 11 Posts

·
Registered
Joined
·
19 Posts
Discussion Starter #1
As I am doing my frame off restoration of my 66 GTO Clone I have been doing alot of research as to where I am going to end up with the drive train. Right now I am leaning towards a 455 with either 87 or 96cc big valve heads, an m20 muncie for the wide ratio, and 3.73 gears. Probably a 750 Holley and a decently big cam. I want it to be decently fast but still streetable on 93 octane. I am curious peoples opinion on this setup, and also what rear I should put in it. 10 or 12 bolt posi, or go with a 9inch set up.
 

·
Registered
Joined
·
714 Posts
If you're set on 3.73's and you plan on doing any freeway driving, I'd recommend an overdrive.
 

·
64-67 Expert
Joined
·
8,569 Posts
3.73 is too much gear for a 455. They don't like to run down the road at 3500 rpm due to their design. And they make so much torque, they have no need for a deep gear like a small block chevy requires. I like your idea, with aluminum 87cc or iron 96cc heads, but with a 3.08 or 3.23 rear gear. Stick with the stock 12 bolt that came on '70 455 GTO's for ease of installation. With a 3.08, you'll still get rip-your-head-off performance, but good highway manners and economy as well, without the expense of an overdrive.
 

·
Registered
Joined
·
256 Posts
I have a 455 with 96 heads and a 10 bolt 3.55 rear end. It is my daily driver and I'm will be switching to 3.23 or 3.08 to keep the rpms down.

Sent from my DROIDX using AutoGuide.Com Free App
 

·
Former Moderator
Joined
·
2,895 Posts
I'd say overdrive and 4:11's if you can swing it and if not then my second choice would be the 9 inch Ford for easy gear interchangability. 3:08's for the hiway and 5:13's for wheelies lol.

Seriously, you need to access what your goals are and be realistic.

If you plan on a weekend toy with some track time the gears will have to be optimized for your planned MPH and ET (ie what RPM are you planning on going through the traps at).

If it's a cruiser/bruiser I'd think something in the 3:23 to 3:55 area would be ideal.

If you plan on "Power Touring" I'd go with 2:56 to 3:08.

With the 9" it would be simply a matter of swapping center sections (used to do it on Friday evenings and got it down to 30 minutes in my younger days).

With the overdrive trans, all this is mute. I run 4:11's, it has nearly identical ratios in 1st thru 4th as the wide ratio Munce and on the hiway 5th gear at 2300 RPM is 70 mph+. :cool:

I run a 12 bolt Chevy currently and in retrospect I would have gone with a 9" or my first choice would be a Dana 60. The Dana rear makes all others look like toys. The 9" offers the most gear ratio's and parts availabilty and brake options. The Dana offers ULTIMATE strength period. I literally replaced every component in my 12 bolt but the housing, axles, diff, gears and brakes. The only thing it offered to me was more strength than the original 10 bolt and it would bolt into the car.

OP, I'd recommend looking at Strange Co. they offer pretty much every option for rear axles and they have top quality components and great customer service. PM me if you want to buy my 12 bolt and as soon as I recieve the funds I'll be buying an S60 from them! :cheers
 

·
Registered
Joined
·
19 Posts
Discussion Starter #7
I'd say overdrive and 4:11's if you can swing it and if not then my second choice would be the 9 inch Ford for easy gear interchangability. 3:08's for the hiway and 5:13's for wheelies lol.

Seriously, you need to access what your goals are and be realistic.

If you plan on a weekend toy with some track time the gears will have to be optimized for your planned MPH and ET (ie what RPM are you planning on going through the traps at).

If it's a cruiser/bruiser I'd think something in the 3:23 to 3:55 area would be ideal.

If you plan on "Power Touring" I'd go with 2:56 to 3:08.

With the 9" it would be simply a matter of swapping center sections (used to do it on Friday evenings and got it down to 30 minutes in my younger days).

With the overdrive trans, all this is mute. I run 4:11's, it has nearly identical ratios in 1st thru 4th as the wide ratio Munce and on the hiway 5th gear at 2300 RPM is 70 mph+. :cool:

I run a 12 bolt Chevy currently and in retrospect I would have gone with a 9" or my first choice would be a Dana 60. The Dana rear makes all others look like toys. The 9" offers the most gear ratio's and parts availabilty and brake options. The Dana offers ULTIMATE strength period. I literally replaced every component in my 12 bolt but the housing, axles, diff, gears and brakes. The only thing it offered to me was more strength than the original 10 bolt and it would bolt into the car.

OP, I'd recommend looking at Strange Co. they offer pretty much every option for rear axles and they have top quality components and great customer service. PM me if you want to buy my 12 bolt and as soon as I recieve the funds I'll be buying an S60 from them! :cheers
What transmission are you running?
 

·
Former Moderator
Joined
·
2,895 Posts
Tremec TKO 600+. The + is cryogenicly treated gears and synchros. I don't "abuse" it per se but my car puts out over 750 at the tire and the trans has'nt even wimpered yet but it also never dead hooks, even with 12.5 x 29.5 MT ET Streets. Mcloed 12" clutch also. Shifts just like the stock Muncie did and I love it. Second best mod I made to my car lol. Guess the first :D. Even if and when I put the Pontiac motor back in I'll just leave the Tremec and the deep gears.

Originally I really want'ed a Jeffco trans but could'nt swing the $4500 for the three speed and did'nt want to hack my car up that much. I had to "slightly" alter the trans tunnel for the larger TKO but it's unnoticeable really. Well worth it IMO.
 

·
Registered
Joined
·
19 Posts
Discussion Starter #9 (Edited)
Are you running the .82 or .64 5th gear? Hyd or mech clutch? After reading alot of info online I am really thinking I want to go with the tremec 600 and stick with the lower gears. The trans sounds great. In addition to buying the trans, what extras did you have to get to make it work?
 

·
Former Moderator
Joined
·
2,895 Posts
.82 overdrive which is plenty because I run a fairly tall rear tire and my engine does'nt like lopeing along on the highway at 1500 rpm. I would work out your combination before ordering so you get the highway RPM you want. A lot of people talk up the 6 speed but I just don't see the point, plus they wiegh 100 pounds more.

I got my TKO from Keisler and the clutch and flywheel from Mcloed. Trans came with the shifter, I just used my stock stick (had to slightly modify it to bolt up) Keislers kit came with a nice billet shifter that is smooth as yogurt. Kit also came with speedo cable and sheet metal to mod the trans tunnel.

I made my own tubular crossmember that actually bolts to the frame rather than the stock type that sits in the rubber "mittens" or whatever. I also use mechanical linkage and TOB.

Kiesler offers a lot of options too. They have a new Tremec trans with a narrower profile that supposedly goes in with no floorpan mods but I have'nt really heard much on those.
 

·
Former Moderator
Joined
·
2,895 Posts
First clutch I tried was the Centerforce. It lasted about 300 miles. Nuff said.

The Mcloed is a little stiffer but has yet to slip. Eventually I'll probably go with their Dual disc.
 
1 - 11 of 11 Posts
Top