3.50??? or another???
Thread Starter
4th Gear Member
Joined: Sep 2007
Posts: 1,458
From: Colorado
RE: 3.50??? or another???
It seems to me, there should be an "all around" gear ratio to use. One that is good for city and highway use. Now the strip is a totally different situation. I am thinking the 3.75 is that "all around" choice, with a 5 speed overdrive tranny of course.
3rd Gear Member
Joined: Mar 2006
Posts: 971
From: Apison, TN
RE: 3.50??? or another???
ORIGINAL: Aussie66Fastback
you might wanna consider some decisions on the 5 speed before the rear end. sorry if you're already a step ahead of this
2 things
1) you want the box that can handleyour [unspecified] torque (which may or may not be a standard T5)
2) you want to know the ratios, particularly for 1st and 5th.
examples
too lowratio 1st with a 4.11 means early change (eg '84 SVO T5, engineat 5000rpm = 21mph).
too highratio 5th with 4.11 means still revving fairly high at highway speeds (4.11 with 0.87 5th = 3.57 final drive).
too low in 5th with 3.75 meansless pull in 5th (3.75 with 0.69 5th = 2.58 final drive)
you might wanna consider some decisions on the 5 speed before the rear end. sorry if you're already a step ahead of this
2 things
1) you want the box that can handleyour [unspecified] torque (which may or may not be a standard T5)
2) you want to know the ratios, particularly for 1st and 5th.
examples
too lowratio 1st with a 4.11 means early change (eg '84 SVO T5, engineat 5000rpm = 21mph).
too highratio 5th with 4.11 means still revving fairly high at highway speeds (4.11 with 0.87 5th = 3.57 final drive).
too low in 5th with 3.75 meansless pull in 5th (3.75 with 0.69 5th = 2.58 final drive)
5th Gear Member
Joined: Sep 2006
Posts: 2,266
From: Australia
RE: 3.50??? or another???
different 5th gear - 0.69 in this example, 0.87 5th in the other one
3.75 x 0.69 = 2.58 on my calc
but thats the point...unless you know which gearbox (and therefore what the overdrive 5th ratio is) you may end up in a part of the rev range you dont wanna be.
3.75 x 0.69 = 2.58 on my calc
but thats the point...unless you know which gearbox (and therefore what the overdrive 5th ratio is) you may end up in a part of the rev range you dont wanna be.
5th Gear Member
Joined: Nov 2006
Posts: 2,106
From:
RE: 3.50??? or another???
If I might add, their is not a lot of difference between the .82 5th and the 1.0 4th gear. Also, if its a low hp and low torque engine, then the .82 may be better. My 428CJ runs about 3000 rpm at 60 mph. A .67 final would be very nice in this situation. Use the calculator and factor the tire size before you spend money.
2nd Gear Member
Joined: Nov 2006
Posts: 359
From:
RE: 3.50??? or another???
Just in case you or anyone else is interested. I have a 9" third member ready to drop in sitting in my garage. It has 4.11 gears with either a locker or spool, not sure. All you will need is your pinion and a gasket and your ready to bolt up. Email me if interested.
6th Gear Member
Joined: Aug 2007
Posts: 5,896
From: Elk Grove, CA
RE: 3.50??? or another???
You can't mismatch pinions and ring gears. They both have to be machined together, and you have to set the pinion depth properly, which is hardly what i'd call 'bolt on.'
2nd Gear Member
Joined: Nov 2006
Posts: 359
From:
RE: 3.50??? or another???
Opps, did not mean pinion, meant the pinion yoke. I just had to swap my original out with the one that came on the diff that I ordered. yes this is true bolt on and go. Pinion depth is already set. Oh, it is 28 spline. Forgot to add that in.