Overdrive, rear end questions - Pontiac GTO Forum
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post #1 of 11 (permalink) Old 03-17-2009, 12:49 AM Thread Starter
 
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Overdrive, rear end questions

Alright. So, I have a 455 in my goat that will pull up to 5000 rpms. It has 2.52gears in the rear end. Great for cruising, but the non-posi rear end is killing me for traction. I've also looked into overdrive units that can be bolted up to turbo 400's. Questions

What would be a good set of gears for the rear end? I'm definitely going with a posi. I want a rear end that will stand up pretty hard but still be pretty good on the street.

Also, does anyone have any experience or advice for the overdrive unit? They don't seem very cheap but I'd like a setup to where I'm not changing out rear ends for different applications (long highway trips, city driving, etc).

1969 GTO
Second Owner, 17 years old
Bored out 455, 7k3 heads, turbo 400 tranny with a shift kit.
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post #2 of 11 (permalink) Old 03-17-2009, 01:11 PM
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Check out Gearvenders. It's bolt-in, bulletproof, and you don't need to hack up your car. It bolts right to the back of your tranny. For an allaround gear with your 455, I recommend a 3.23---3.73 in conjunction with the overdrive. If I was running a 455 with NO overdrive, I personally would run a 3.08 rear with a posi. A 455 has enough torque that it doesn't need stiff gears.
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post #3 of 11 (permalink) Old 03-17-2009, 01:30 PM
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I'd be tempted to just use an Auburn posi carrier and keep the 2.52s.
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post #4 of 11 (permalink) Old 03-17-2009, 02:40 PM
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Originally Posted by geeteeohguy View Post
Check out Gearvenders. It's bolt-in, bulletproof, and you don't need to hack up your car. It bolts right to the back of your tranny. For an allaround gear with your 455, I recommend a 3.23---3.73 in conjunction with the overdrive. If I was running a 455 with NO overdrive, I personally would run a 3.08 rear with a posi. A 455 has enough torque that it doesn't need stiff gears.

I have a 455 with a 2.78. I plan on upgrading too. If you go with the overdrive I would put in gears in the 3.55/3.73 range. I'm probably going to go with a 3.55 to match up with my 4spd.
I'm surprised you're having traction problems with 2.52 gear. You must be running 14" wheels. I use 15" and have no traction problems. A buddy of mine went from 14" to 15" on his goat and noticed a huge difference. He said it was alot easier to break loose the 14". He has a posi 3.55 and a 400 HO.



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post #5 of 11 (permalink) Old 03-17-2009, 09:01 PM Thread Starter
 
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I was thinking about the 3.73's. I'm probably gonna end up going with that. With the 2.52 gears I have right now, it's only a 10 bolt rear end and non-posi. I'm pushing 450 ft. lbs of torque and it just ahnialates my right rear tire. If I just throw a posi onto that 10 bolt rear end, I'd destroy the rear end pretty quickly. I'm not sure how big the wheels are on it. I'll have to check on that. Thanks for the advice!

1969 GTO
Second Owner, 17 years old
Bored out 455, 7k3 heads, turbo 400 tranny with a shift kit.
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post #6 of 11 (permalink) Old 03-18-2009, 10:06 AM
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Ten bolt rear ends can stand a lot of abuse. You'd be surprised. If you're having traction probs. with the open 2.51--2.56 rear gear, installing an Auburn limited slip or comparable into your present carrier would be a good, cost effective solution. I think it would be something to consider....
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post #7 of 11 (permalink) Old 03-19-2009, 01:25 AM Thread Starter
 
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Originally Posted by geeteeohguy View Post
Ten bolt rear ends can stand a lot of abuse. You'd be surprised. If you're having traction probs. with the open 2.51--2.56 rear gear, installing an Auburn limited slip or comparable into your present carrier would be a good, cost effective solution. I think it would be something to consider....
Well, the car has 288k original miles. I don't know how well that 10 bolt will hold up if I put a posi on it. My dad's friend had a '70 gto back when he was a teenager and he had a 10 bolt posi in it. He said after a year of driving it with the posi, the rear end shattered. Should I even try a posi on the 10 bolt or should I just wait until I can afford a 12 bolt?

1969 GTO
Second Owner, 17 years old
Bored out 455, 7k3 heads, turbo 400 tranny with a shift kit.
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post #8 of 11 (permalink) Old 03-19-2009, 03:07 PM
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Set up correctly, with new bearings and all clearances set to spec, the 10-bolt should do just fine. Years ago, the guy that rebuilt mine was building 10 bolts that were being used in 800HP drag cars, and they were holding together. It's all in the quality of the parts, and the components. Of course, if you find a 12 bolt, you'll be ahead of the game. Your call!
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post #9 of 11 (permalink) Old 03-20-2009, 08:36 PM
 
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Have a 68 with 225/70/14 tires turns about 3100 at 70 ---with 3.55 posi --would maybe like to put in the gearvenders --figure that would drop the rpms to about 2400 at 70---any one know if the unit will fit in the tunnel with out whacking it up?
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post #10 of 11 (permalink) Old 03-20-2009, 08:45 PM
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The gearvendors unit is small, but can handle 1000 hp. It should fit easily in your tunnel without hacking. That's their claim to fame: no damage to vehicle. You will need to shorten your driveshaft. Call them and tell them what you have, and they'll be able to give you the measurements of the unit. I've experienced them, and ifI had $2400 burning a hole in my pocket or if I drove mine more, I would get one. I'm at about 2800 at 70mph with 3:36 gears in both my goats.
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