Need rear end gear ratio advice - Ford Mustang Forum
 
LinkBack Thread Tools
post #1 of 9 (permalink) Old 04-14-2009 Thread Starter
Rookie
Classic Member
 
ottawa1967's Avatar
 
Joined: Apr 2009
Location: Kanata
Posts: 2
 
Need rear end gear ratio advice

Hey Guys, I thought this question should be in the classic talk and not the classic tech section because the answer is pretty subjective. But thats what I want to hear.
I have a 67 fastback with the stock 8" rear end-it's coming out.
I recently installed a 347 stroker that I guestimate at 400hp/425 lbs of torque at 6000rpm. The transmission is a 5 speed TKO 600.
Here is my question. Whats a good street gear? I plan on running a 18" 285/35 tire with a trac loc posi. I want it to hook up in first gear at around 2000/2500 rpm or so with a soft/medium compund at 75 degrees of pavement temp.
I am wondering if a 4.11 is too radical. Any input would be greatly appreciated.
ottawa1967 is offline  
Sponsored Links
Advertisement
 
post #2 of 9 (permalink) Old 04-14-2009
Top Dog
V6 Member
 
05horse's Avatar
 
Joined: Nov 2008
Location: Centerville
Posts: 9,413
 
Send a message via AIM to 05horse Send a message via MSN to 05horse Send a message via Yahoo to 05horse
welcome to the forum i think 4.11 would be great, would sure gt u off the line in a hurry, that or 3.90
05horse is offline  
post #3 of 9 (permalink) Old 04-14-2009
GT Member
Classic Member
S197 Member
 
Jonk67's Avatar
 
Joined: Dec 2007
Location: Smyrna
Posts: 1,997
 
'Whats a good street gear?' What do you consider street gear? 0-30mph, 30-60, 70+ hwy? Be sure to be honest with yourself as to what 90% of your driving will be. That said, here's a neat calculator where you can add all your variables - tire size, rear gear, RPM, MPH and see what each gear size will do. I put them all into a spreadsheet so I could look across the columns and picked the gear that met 90% of my driving time.
Randy's Ring & Pinion. RPM Calculator.
Jon

'67 Coupe 289 stroked to 333, AOD, 9" w/3.50:1, PDB, Candyapple red w/red deluxe int., PS, ext. decor group, light group, foxbody seats.
'09 Black Warriors In Pink with glass roof - the wifes Mustang.
"If it ain't broke, I haven't fixed it yet" -Jon
Jonk67 is offline  
post #4 of 9 (permalink) Old 04-14-2009
Made Member
 
gtjoe's Avatar
 
Joined: Oct 2006
Location: San Antonio
Posts: 386
 
I assume you are putting a 9" in. I also assume you are seeking advice based on personal experience. A third assumption necessary is the operating range of your 347, 2000-6000 rpm; probably peaking power around 5800 with a sweet spot from 3500 on up.

That being assumed, with the 5 speed, you need at least 3.50 gears. Personally, I think 4.11 is the maximum for any regular street use, even with the 5 speed. Personall, I have a 306 with an E cam and am running a 5 speed with 3.50 gears and it is just fine. Sure, 4.11's would get me down the quarter quicker but I don't go to the track often.
gtjoe is offline  
post #5 of 9 (permalink) Old 04-14-2009
Made Member
Classic Member
 
65BlueHorse's Avatar
 
Joined: Feb 2009
Location: Bedford
Posts: 386
 
I think 4.11 would be a little low for street driving but with a 5 speed you can easily use 3.50 or maybe the 3.90. Try the calculator that Jonk67 posted and put in different gears.
65BlueHorse is offline  
post #6 of 9 (permalink) Old 04-15-2009 Thread Starter
Rookie
Classic Member
 
ottawa1967's Avatar
 
Joined: Apr 2009
Location: Kanata
Posts: 2
 
Hi guys, great forum and thanks for the reponse to my question.
I'm looking for a good one two pull up to around 50-60mph.
I just want it to hook up fairly good. Not going to do any 1/4 mile stuff on a regular basis. I took a look at the calculator and when I punch in the numbers for my second gear ratio and a 25.8" tall tire I get 5760 RPM at 60mph (right in the sweet spot)
I think I have my answer. And yes, it is a 9" that's going in.
Thanks for the calculator.
ottawa1967 is offline  
post #7 of 9 (permalink) Old 04-15-2009
Apprentice
Classic Member
 
RemRem123's Avatar
 
Joined: Mar 2008
Location: Charlotte
Posts: 208
 
i'm running 3.73's on mine and it seems to come off the line quick and highway rpms were good (with a 302)

1968 Mustang Coupe with 331 stroker, Explorer 8.8" rear-3.73 Posi, '88 T-5,hydraulic clutch, dual Flowmaster exhaust, 4-wheel discs!
RemRem123 is offline  
post #8 of 9 (permalink) Old 04-15-2009
GT Member
Classic Member
S197 Member
 
Jonk67's Avatar
 
Joined: Dec 2007
Location: Smyrna
Posts: 1,997
 
Measure your actual tire height also, I found the tire ht. calc. to be off from my actual tire height.
Jon

'67 Coupe 289 stroked to 333, AOD, 9" w/3.50:1, PDB, Candyapple red w/red deluxe int., PS, ext. decor group, light group, foxbody seats.
'09 Black Warriors In Pink with glass roof - the wifes Mustang.
"If it ain't broke, I haven't fixed it yet" -Jon
Jonk67 is offline  
post #9 of 9 (permalink) Old 04-19-2009
PONY Member
Classic Member
 
Little Mule's Avatar
 
Joined: Jun 2008
Location: Williamsburg
Posts: 395
 
Send a message via Yahoo to Little Mule
Hey RemRem, when you say highway rpms were good - at what speeds and where abouts where your rpms sitting? Mine is mainly for driving around town but I want to be able to take random road trips down the highway if I want. Thanks.

Kris
Little Mule is offline  
Sponsored Links
Advertisement
 
Closed Thread

Quick Reply
Message:
Options

Register Now



In order to be able to post messages on the Ford Mustang Forum forums, you must first register.
Please enter your desired user name, your email address and other required details in the form below.

User Name:
Password
Please enter a password for your user account. Note that passwords are case-sensitive.

Password:


Confirm Password:
Email Address
Please enter a VALID email address for yourself, otherwise you will not receive the necessary confirmation email needed to confirm, validate and activate your new AFM member account.

Failure to provide a VALID email address, will result in the cancellation of your new AFM member account registration.

Email Address:
OR

Log-in









Human Verification

In order to verify that you are a human and not a spam bot, please enter the answer into the following box below based on the instructions contained in the graphic.



Thread Tools
Show Printable Version Show Printable Version
Email this Page Email this Page



Posting Rules  
You may post new threads
You may post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is Off
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are On

 
For the best viewing experience please update your browser to Google Chrome


1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182