View Poll Results: Which gear ratio for my 8"?
Voters: 6. You may not vote on this poll
3.55 or 3.80???
02-15-2009, 07:32 AM
#11
6th Gear Member
Join Date: Feb 2007
Location: state of confusion
Posts: 7,635
You MUST know what sort of transmission you will be running.
You MUST know the approximate size tire you will be running.
You must know the redline of the motor.
You MUST know the approximate size tire you will be running.
You must know the redline of the motor.
I'll also add that you need to decide just what you want to optimize your gear selection for. Maybe even as specifically as what speed you need to have available in which particular tranny gear.
I think that's what you're saying in your last three paragraphs (bottom quote here).
Take these givens and plug them into any one of the dozens of online gear ratio calculators. Then you will know for sure the exact gear you should look for.
When my motor was NA, I had the 3.89. I then changed the cam and increased the CR. This necessitated a new gear to keep the car at the correct RPM going through the traps. This is when I went to a 4.30. Then I installed a Paxton Supercharger and had to once again revisit the calculator to ensure I was installing the right gear for my combo. This is when I went to the 3.50. I have a Detroit Locker too. Extremely stout, but can get a little wiggly at times.
If this is a street car with less than 400hp stick with the LSD. If you plan on visiting the track with anything more than 400hp, you're better off with the locker due to it's durability. I had a LSD for the longest time, but it just could hold up any longer once I installed the Paxton.
If this is a street car with less than 400hp stick with the LSD. If you plan on visiting the track with anything more than 400hp, you're better off with the locker due to it's durability. I had a LSD for the longest time, but it just could hold up any longer once I installed the Paxton.
. Don't think I'd plan on running a Paxton with an 8" though (says the guy who gets away with running 3.73's in a 7.5"/7.625" axle with an 350-ish crank HP EFI 350 SBC for street and autocross).Norm
Last edited by Norm Peterson; 02-15-2009 at 07:38 AM.
02-15-2009, 09:19 AM
#12
Join Date: Apr 2005
Location: IL
Posts: 18
Hi Norm,
As long as you don't hook it, that rearend should be fine. It's when she hooks off the line that you SOON discover your weakest links. I discovered the hard way that I had to screw my tires to my wheels. I then discovered the hard way that my driveshaft wasn't stout enough. See below....
02-15-2009, 09:46 AM
#13
6th Gear Member
Join Date: Feb 2007
Location: state of confusion
Posts: 7,635
Yeah, street performance tires do make for a pretty good "fuse" as far as powertrain durability is concerned. The quality of starting line prep or even DR's or R-compound autocross tires by themselves would probably make for a different outcome (this may help the OP in his decision).
The 7.5", with its 26 spline axle shafts still seems kind of puny compared to the 8.8 that's in my S197 though . . . isn't 7.5/26 about what the 1960's Mustangs came with as sixxers?
Pardon the OT question, but what sort of engineering are you involved with?
Norm
The 7.5", with its 26 spline axle shafts still seems kind of puny compared to the 8.8 that's in my S197 though . . . isn't 7.5/26 about what the 1960's Mustangs came with as sixxers?
Pardon the OT question, but what sort of engineering are you involved with?
Norm
02-16-2009, 05:27 AM
#15
2nd Gear Member
Thread Starter
Join Date: Jul 2006
Location: Virginia
Posts: 206
Hi Norm,
As long as you don't hook it, that rearend should be fine. It's when she hooks off the line that you SOON discover your weakest links. I discovered the hard way that I had to screw my tires to my wheels. I then discovered the hard way that my driveshaft wasn't stout enough. See below....
As long as you don't hook it, that rearend should be fine. It's when she hooks off the line that you SOON discover your weakest links. I discovered the hard way that I had to screw my tires to my wheels. I then discovered the hard way that my driveshaft wasn't stout enough. See below....
03-05-2009, 07:26 PM
#17
Join Date: Feb 2009
Location: Mo
Posts: 9
03-06-2009, 06:56 AM
#18
2nd Gear Member
Thread Starter
Join Date: Jul 2006
Location: Virginia
Posts: 206
Well, had a last second change of heart....ordered the 4.11's with a Traction Lock unit. I got to thinking about, she won't be driven that frequently...only a fair weather ride...so I figured WTF let's build one that'll uproot the gates of hell! LOL!
03-08-2009, 10:33 PM
#19
Join Date: Apr 2005
Location: IL
Posts: 18
I made it out there 3 times last year and had problems each time. So last year was hor-E-bowl !! I still have to pull the tranny and find out what happened the last time I went. The clutch isn't working yet the pedal feels the same (same amount of pressure on it) ???
Oh well.......
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