[nev68]

Now some of you may think this is a dumb question but anyway....
How do I figure out what is the best rear end ratio for my 68?
What factors do I need to consider to selct the right gearing?

Here's some more information that may help.

@ 6,000 rpm = 434hp (probably won't rev it much higher maybe to 6,500) I know this isn't much power, but it's enough for me right now.
@ 4,500 = 443lb-ft
Stall converter = 3,000
Trans is T350 (1st = 2.52, 2nd = 1.52 and 3rd = 1.00)
Rear tyre diam = 26.1" (at the moment)

[big gear head]

What do you want to do with the car? What type of driving will you be doing, city or highway? Will it be raced, and what type of racing?

[HwyStarJoe]

Originally Posted by nev68

@ 6,000 rpm = 434hp (probably won't rev it much higher maybe to 6,500) I know this isn't much power, but it's enough for me right now.
@ 4,500 = 443lb-ft

Not much?! I'd take that much power any day!

[98blackburb]

Play with this maybe....hope it helps if at all..................
http://www.golenengineservice.com/html/calculators.html

[nev68]

Originally Posted by big gear head

What do you want to do with the car? What type of driving will you be doing, city or highway? Will it be raced, and what type of racing?

I suppose I am looking for street / performance compromise
I may take it out of the city 50 to 100 miles occasionally but most of the driving will be in the city, but I still want to do a bit of 1/4 mile drag racing.

[big gear head]

I didn't see any information on the rear end that you have. Is it the 8.2 10 bolt? If it is then you might want to think about upgrading it to an 8.5 or 12 bolt with the power that you are making. If you stay with the 8.2 10 bolt then it needs some upgrades to make it strong enough to live with your engine. I recommend an Eaton Posi, 3.55 gears and a set of after market axles. A good installation kit wiht Timken bearings and proper gear set up are important. This rear end needs to be built as well as possible to live with a lot of power.

[nev68]

Originally Posted by big gear head

I didn't see any information on the rear end that you have. Is it the 8.2 10 bolt? If it is then you might want to think about upgrading it to an 8.5 or 12 bolt with the power that you are making. If you stay with the 8.2 10 bolt then it needs some upgrades to make it strong enough to live with your engine. I recommend an Eaton Posi, 3.55 gears and a set of after market axles. A good installation kit wiht Timken bearings and proper gear set up are important. This rear end needs to be built as well as possible to live with a lot of power.

Currently I have a 10 Bolt with 2.56 gears
I want to change the rear end to a 12 bolt for a few reasons.
1. I believe the 12 bolt is stronger than the 10 bolt
2. Existing rear end is a Single wheeler
3. 2.56 gears will be far from optimum

I am thinking of a Moser "crate" rear end with either 3.55 or 3.73 gears with a Eaton True Trac.

What do you think?

[USA69Z]

i think that sounds sweet Nev

3.7 all the way

Gav

[big gear head]

Nev, send me an email at biggearhead@bellsouth.net and I'll give you some information on Moser.

[nev68]

Originally Posted by USA69Z

i think that sounds sweet Nev

3.7 all the way

Gav

You'd know Gav, I haven't heard much about yours after the install.
How's it going?

[nev68]

Originally Posted by big gear head

Nev, send me an email at biggearhead@bellsouth.net and I'll give you some information on Moser.

Thanks.
email is on the way

[USA69Z]

Originally Posted by nev68

You'd know Gav, I haven't heard much about yours after the install.
How's it going?

Hey Nev , ive only driven around the block a bit and didnt give it a squirt yet .Now ive sold the wheels , so I cant drive it. I guess i just really researched all the cars on all of these sites and there engine /trans /diff combo's and noticed it seemed to be the main choice of most rear ends to suit my need. I had the same ratio /rear end you have now ... it should liven the car up a lot. Im not into going super fast , i like aceleration more .. its a comprimise id say..

Gav

[nev68]

Originally Posted by USA69Z

Hey Nev , ive only driven around the block a bit and didnt give it a squirt yet .Now ive sold the wheels , so I cant drive it. I guess i just really researched all the cars on all of these sites and there engine /trans /diff combo's and noticed it seemed to be the main choice of most rear ends to suit my need. I had the same ratio /rear end you have now ... it should liven the car up a lot. Im not into going super fast , i like aceleration more .. its a comprimise id say..

Gav

I'll look forward to hearing how she goes once the new wheels arrive.
Phil is helping me with a 3.73 Moser, so we'll see how it all goes.
I am a bit the same with the speed.
I just want the old girl to hold her own against the rice burners.
Hopefully that won't be too much of a problem, I think I got the horsepower just gotta get right rear end.

Also thinking about a gear vendors overdrive a bit later, that way I might be able to do a few long runs in the country.

[RichSchmidt]

You need at least 3.55's with 26 inch tall tires and a 3000 stall convertor since anything less will overheat the convertor at cruise speeds.With taller tires you will need even more gear.The only exception would be if you had a lockup convertor.

I just put together a 3400# 79 Camaro with a 408 that makes about 420 hp at 5600 rpm.I put it in with a 3200 stall convertor,th 350 and 3.90 gears and 26 inch tall tires.I attempeted to drive it to work once and got towed home.The engine was screaming like the rods were going to come out of it and it was running 4000 rpm at 75 mph and little old ladies with their Camarys were honking for me to get out of their way{normal speed on my commute is about 85 to 90 mph].I have a 500 over stock convertor laying around and I just took delivery of a set of 2.73 gears that I won on an Ebay auction.I will also be upgrading to 28 inch tall tires soon.I figured the car would have run low 12's the way it sat if I had slicks on it,and if I change everything it should run high 12's,but I already own a 9 second street race car so I dont need another beast to drive.With this car I want to be able to cruise at 80 mph at about 2000 rpm.

So my advice here is that you shouldnt underestimate how fast you will really be driving this car on the highway and base your gear selection on RPM at 60 MPH charts,and dont underestimate just how annoying engine speed is,since anything over about 2500 rpm for long trips takes the fun out of it for most people.I grew up in a town where you were lucky if you could hit 25 mph with all the stop lights and traffic,but as soon as you hit the highway,you had to blast to 80 mph or you would get rear ended by tractor trailers going 80mph in the SLOW lane.I live in a suburban area now,and everywhere I go is at least 60 mph.Just keep that in mind.

[nev68]

Originally Posted by RichSchmidt

You need at least 3.55's with 26 inch tall tires and a 3000 stall convertor since anything less will overheat the convertor at cruise speeds.With taller tires you will need even more gear.The only exception would be if you had a lockup convertor.

I just put together a 3400# 79 Camaro with a 408 that makes about 420 hp at 5600 rpm.I put it in with a 3200 stall convertor,th 350 and 3.90 gears and 26 inch tall tires.I attempeted to drive it to work once and got towed home.The engine was screaming like the rods were going to come out of it and it was running 4000 rpm at 75 mph and little old ladies with their Camarys were honking for me to get out of their way{normal speed on my commute is about 85 to 90 mph].I have a 500 over stock convertor laying around and I just took delivery of a set of 2.73 gears that I won on an Ebay auction.I will also be upgrading to 28 inch tall tires soon.I figured the car would have run low 12's the way it sat if I had slicks on it,and if I change everything it should run high 12's,but I already own a 9 second street race car so I dont need another beast to drive.With this car I want to be able to cruise at 80 mph at about 2000 rpm.

So my advice here is that you shouldnt underestimate how fast you will really be driving this car on the highway and base your gear selection on RPM at 60 MPH charts,and dont underestimate just how annoying engine speed is,since anything over about 2500 rpm for long trips takes the fun out of it for most people.I grew up in a town where you were lucky if you could hit 25 mph with all the stop lights and traffic,but as soon as you hit the highway,you had to blast to 80 mph or you would get rear ended by tractor trailers going 80mph in the SLOW lane.I live in a suburban area now,and everywhere I go is at least 60 mph.Just keep that in mind.

I hear what you are saying.
I am just trying to optimise the engine / trans set up I have by putting in a set of rear gears that will be complimentary.
I figure that with a 3.73 the motor should be revving at approx 3,360 @ 70 mph (our highway limit is 110 kilometres /hour which is just under 70 mph) which may be annoying for longer trips but I think most of my driving will be in suburbia so at 40mph we should see 1,920 rpm with the 3.73 gears.
If I find I want to do more highway /country driving I will probably look at a T700 trans or a Gearvendors O/drive uint.