Need help
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Pro
Joined: Jan 2008
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From: WEST MILFORD NEW JERSEY
Need help
My 66 Big block has an FB rear (IE) 4:11 and I have a M21 trans my problem is I am not sure what the performance is going to be like, gas RPM's overall performance. I am looking for recommendations on gear ratio"s I will probably be using the car for street driving as well as highway use. The drivetrain is all stock tires are the correct size. Any help would be appreciated .Thanks ,Wes
Thread Starter
Pro
Joined: Jan 2008
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From: WEST MILFORD NEW JERSEY
Race Director
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From: Close to DC
C2 of the Year Finalist - Modified 2020
Conv or coupe, side exhaust or under body? With 4:11 gears I do not know exactly what RPM you will be at doing 60mph, but I'll bet it will be about 3000-3100rpm. Great low end power. That will create quite a roar especially if you have side exhaust. Gas mileage might be 10-12mpg. I agree with goastrider20, good cruising gear would be 3:36 or 3:55. 
Dennis
Dennis
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From: Washington Michigan
Team Owner
Joined: Aug 2008
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From: Rochester NY
St. Jude Donor '09 thru '26
As others have said, 4:11's are low end gears - you'll come off a stop like you were launched from a cannon (if it gets traction) but your top end will be lower. My '67 had 3:36's and I remember many times racing some lesser-powered car with stiff gears. They might stay right with me for a while, but they would be well into 3rd gear when I was into 2nd. About the time they were done, mine was starting to wake up and would leave them behind.
It's been many years, but I seem to recall my car with 3:36's didn't get too much above 10 mpg when I was behaving myself. So 4:11's would be turning a higher RPM at the same cruising speed and would probably get worse mileage.
Hope that helps.
It's been many years, but I seem to recall my car with 3:36's didn't get too much above 10 mpg when I was behaving myself. So 4:11's would be turning a higher RPM at the same cruising speed and would probably get worse mileage.
Hope that helps.
Le Mans Master
Joined: Aug 2005
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From: Temple Terrace Florida
Tremec
If you want the best of both worlds, put in a Tremec 5 speed. I have 4:10s in my 66 small block. Nothing like getting on the highway and shifting into 5th gear and watching my RPMs drop down to 2300. You can always keep the Muncie transmission, shifter and drive shaft for the next owner. A .62 overdrive with 4:11s will give you an effective rear ratio of about 2:55. Jerry
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Race Director
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From: Central Arkansas
I agree that 3.70 is an excellent rear gear selection for all around use. As far as the 4.11 gears are concerned, I'm assuming this is a 425 HP car - response in all gears can be brutal. I was cruising along in mine at about 45 mph in 4th one day and had some sort of foot spasm which jammed the accelerator down and the hard acceleration jump and sidepipe roar startled the heck out of me. Took a neighbor for a ride years ago and had casually accelerated in first and part way through second, and just as he probably thought I was about to casually shift into third, I floored it - scared the crap out of him - he let out a yell and his arms flew up towards the dash trying to grab ahold of something. Great fun.
Racer
Joined: Feb 2011
Posts: 299
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From: Troy New York
for what it's worth...
I have a modified 327 in my '59 with 4:11 rear end with the stock 4 speed...great for taking off the line but not so good at higher speed.... double my tach equals my speed...that is, at 3500 I do 70 mph....it takes me 4000 rpm to do 80 on the interstate...needless to say, I avoid interstate driving unless I want to stay in the right lane.... thinking about going to 3:55 when I have the $$$
I have a modified 327 in my '59 with 4:11 rear end with the stock 4 speed...great for taking off the line but not so good at higher speed.... double my tach equals my speed...that is, at 3500 I do 70 mph....it takes me 4000 rpm to do 80 on the interstate...needless to say, I avoid interstate driving unless I want to stay in the right lane.... thinking about going to 3:55 when I have the $$$
Race Director
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From: Inverness FL
St. Jude Donor '07
when selecting RER's it's also necessary to consider cubic inches & torque curves. a 427 is going to have more available low end torque than a 283... then you have to consider torques curves... a 327 300hp is going to have more available low end torque than say, as 327 365... therefore, a 327 300 can utilize a 3.55 (or even a 3.36) much easier than a 327 365. and with a 283 things get even worse.... 
Bill
Bill
Racer
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From: Troy New York