Rear Diff

[Racing6]

What is the most common width for a FED?

[jspell]

Depends on main hoop dimension, mine is a 21" with a 32.375" housing.

[fuel749]

Depends on the width of your shoulder hoop and what you have for wheel back space. Don't forget tire bulge. Be careful of the dimensions you get, some might give you bare housing width while others might give you axle to axle width. Pretty easy to figure out what you need if you own the wheels, tires and chassis.

[dreracecar]

21" OD shoulder hoop
Tire bulge to wheel flange surface  5 1/8"
Olds bearing ends
27" bearing flange to bearing flange
works out to 3/4-7/8 tire side to body if using drum brakes or early airheart style (hat behind axle flange)
If useing over flange brake hats (example- Wilwood) you can either have more clearence or reduce the overall flange to flange by 1/2"

[wideopen231]

mines 33" bearing to bearing 39 flange to flange. Should have been 40 but I forgot to allow for spread at rear of chassis.

[Racing6]

Thank You All for the information

[dreracecar]

WO231

With all your posts about droping weight, By narrowing up the rear end you eliminate pounds of steel both static and rotational and the wheel weight does not change because all one does is move the offset

[rooman]

WO231

With all your posts about droping weight, By narrowing up the rear end you eliminate pounds of steel both static and rotational and the wheel weight does not change because all one does is move the offset

Bruce, is amazes me that more people do not figure this out. We did it on a pro stocker that we ran in the late 70's in Australia. Those were also the days of the heavy shank style wheel nuts and we replaced them with hard anodized top hat section sleeve/spacers and used regular hex nuts--saved quite a bit in rotational inertia.

Roo

[dreracecar]

Roo,
With some people, going on a diet means eating a double cheeseburger with a diet Coke

[wideopen231]

I more than understand narrowing the rearend mean less weight.Understand rotating mass lot more important . Thats why I paid extra for drilled  with extra lightend flange axles.I also understand the tire has to clear frame.Running 4" bs now. Not much less I can go. Need 3"bs . New housing is 31" and flange to flange is still 39". Can not get any less. Cage 25 os tire bs counting bulge 5.75(x2) 1"(x2) clearance 38.5 total.Actually axles where ordered for 37" and had to pull them out 1" each leaving 1.25" spline engagement which is .25 more than strange says is the minimum and I am not happy about that. But it is what it is.

Just spent two days and cpl hundred bucks  fabricating moly rearend housing to replace mild steel piece.Cheated and took page out of Parks book.  15 lbs lighter than old one I had in it. Only thing I should have done different was install some sealed blank offs as fillers in bottom on each side to reduce capacity. Figure 4.5 wide pieces of 20 guage cant't weigh near as much as fluid.Trying to find out level fluid has to be at for proper lubrication. I figure with sealed bearings it can be lower since axles do not need any. If you look at the design you will see the bottom has slow tapper from center to ends.If level it at normal level  it will take 8 or 10 quarts. with blank offs I figure I can save half or more of that and thats 6 to 8 pounds.

NOW IF LEVEL  can be lot lower then Im good.

[dreracecar]

2 1/2 to 3/4 qts is all I put in my housing and its been in there since '95

[masracingtd1167]

Chris my housing is a fabricated one also . To fill mine to the sight plug in the chuck is about 5 quarts of oil . I have been told that I just need enough in the bottom of the housing for the ring gear to pick up . I just never felt comfortable doing this so I just keep the 5 quarts in it . Last year a friend of mine had a pinion bearing go bad and it locked up for a second at 190 mph . It unlocked and he was able to stop the car thank God !   

[masracingtd1167]

Roo,
With some people, going on a diet means eating a double cheeseburger with a diet Coke

    That's like the fat lady in Dunkin Donuts who orders 3 jelly donuts and a coffee with sweet and low !

[wideopen231]

Just proves that stupid is running ramped over the country. Still not as bad as those I see sucking oxygen because of lung problem while puffing a cancer stick.

I've seen 300 lbs guys getting into racecar that has ton of weight saving items on it. Jenny Craig lot cheaper than titainium. Bypass the fast food and candy bars save that money to buy new parts to go faster and live longer.

 Down 45 lbs (.045 in 1/4)since start of building car. Can't afford junk food. Work late and not snack in front of boob tube.  Win Win Win deal. Loos weight,healthier and go faster.

[masracingtd1167]

Wow 45lbs is a lot Congrat's!