Thread: Rear end width questions -

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Howdy and welcome to me -

Being new to this forum, I am trying to find the answers to my few questions.

First - I have a 1934 Ford with stock frame.

1 - I need a 58 inch hub to hub Ford 8.8 inch rear end - Posi trac - about 3:50 range
gears.

2 - What Ford would have that measurement width with posi - trac for my project?

3 - What is the difference between the Ford "tru loc" and the GM "Posi-trac".

4 - Since I want BOTH tires to connect at the same time power is added, which type
of Ford locking rear end should I look for? They have several - Air lock, Tru lock
limited slip, etc.

Appreciate any and all honest help.

31 Ford 31 Ford
Rear End Widths
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Representative for comparison purposes only
Ford
Outside
Width Year Model
56.50 1969-1977 Maverick 8"
57.00 1974-1978 Mustang II 8"
57.25 1957-1959 Ford, Ranchero, Station Wagon
57.25 1965-1966 Mustang
58.00 1966-1977 Bronco
58.00 1964-1965 Falcon
58.00 1977-1981 Granada/Versailles
58.50 1977-1981 Versailles
59.25 1967-1970 Mustang, Fairlane, Comet, Cougar
60.00 1967 Cougar
60.00 1958-1960 Edsel
61.00 1964-1971 Ford Full Size
61.00 1949-1951 Mercury
61.25 1957-1972 Ford F-100 Pickup
61.25 1960-1964 Ford Full Size
61.25 1971-1973 Mustang
61.25 1967-1973 Torino, Ranchero, Fairlane
63.00 1970-1979 Ranchero & Torino
63.00 1972-1979 Ford Full Size & Intermediate
63.50 1967 Fairlane (Coil Springs)
65.25 1973-1986 Ford F-150 Pickup
65.25 1978-1986 Bronco
65.25 1973-1986 Ford Van 3/4 Ton
68.00 1972 Ford Van 3/4 Ton
69.25 1977-1986 Ford E-150 Van


Chevy
Outside
Width Year Model
54.25 1983-2004 Chevy S10 2WD, GMC S15 2WD
57.75 1962-1964 Chevy II/Nova
57.75 1965-1967 Chevy II/Nova
58.00 1978-1988 Chevy Malibu, Monte Carlo
59.50 1968-1982 Corvette
60.00 1955-1964 Chevy Car
60.00 1967-1969 Camaro
60.25 1968-1979 Chevy II/Nova
60.50 1984-1995 Corvette
60.50 1964-1967 Chevelle
62.00 1955-1959 Chevy Pickup
62.50 1968-1972 Chevelle
62.50 1970-1981 Camaro/Firebird

Mopar
Outside
Width Year Model
55.60 1960-1976 7 1/4 A-body
55.60 1973-1976 8 1/4 A-body
55.60 1966-1972 8 3/4 A-body
55.60 All 8 3/4 A-body
56.00 1932-1934 All Mopars
57.40 1963-1972 7 1/4 A-body
58.54 All 8 1/4 F-body
58.54 All 8 1/4 M-body
58.54 All 8 1/4 J-body
59.00 1935-1936 All Mopars
59.14 1966-1970 9 3/4 B-body
59.20 1962-1970 8 3/4 B-body
60.00 1937-1948 All Mopars
60.70 All 8 3/4 E-body
60.70 All 9 3/4 E-body
62.00 All 8 1/4 B-body
62.00 1971-1974 8 3/4 B-body
62.00 All 9 1/4 B-body
63.40 All 8 1/4 C-body
63.40 1971-1974 8 3/4 B-body S.W.
63.40 All 9 1/4 C-body
GM & Mopar Body Style Codes

Last Update: 04/21/09

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G. McDowell
carnut@carnut.com
est. 1996

JW, welcome to the forum. On your questions:

1 & 2. 79-93 Mustangs use a 57 inch wide rear axle. 94-98 Mustangs use a 58.5 inch wide rear axle. I don't know of anything OEM (in recent years) that's exactly 58", and those older units are getting harder & harder to find after the rust bucket tax program cleared out a lot of good old stuff.
3 & 4. From what I've seen on the Mustang posts, Ford had Equa-lock and Traction-lok but I haven't ever seen a tru loc mentioned. I believe that all of the OEM traction assist axles, unless you get into true lockers in their 4x4 applications, are a clutch pack carrier we all knew as "posi traction" back in the day. What I used is a Detroit Eaton Trutrac Performance Products | Detroit Truetrac Differentials which is a spiral gear unit that is all but bullet proof in normal operation, locks solid under power, but allows slip side to side for good manners on the street, and no additives required. A really sweet unit.
Hope that helps. (Looks like prpmmp had a more comprehensive list, and was quicker!!)

Rear End Widths There are a few 58" widths here ...And welcome to CHR

Here are some Ford Ranger/Explorer options in the 58.5-59.5 range....The Ford Explorer 8.8-Inch Rear Axles

Thank you guys for the great answers. I guess to meet my required fit, I will have to get a rear custom cut to fit for a whole lot more money. I guess that is part of the car game.

Originally Posted by JW Hansen

Thank you guys for the great answers. I guess to meet my required fit, I will have to get a rear custom cut to fit for a whole lot more money. I guess that is part of the car game.

If you're going that way check out John's Industries. Ring and Pinion Gears He'll supply you with a housing & axles, or complete. My roller came with his 9" smooth back housing and axles, then I went with a pumpkin from Just Rear End's Ford 8 and 9 Inch Posi's, Housings, Axles which is a father/son shop in Reno - great guys to deal with, and they know their stuff!

Just what is dialing you into exactly 58.0 inches???? Tire and wheel backspacing???? If its wheel back spacing, maybe a different rim width/backspacing could solve your puzzle????????Whats the bolt pattern? Lots of Mustang rears are 4 bolt axle flange
And why just a ford 8.8???/ The Granada/Versile rears were 9 inchers with disc brakes at 58 inches

What suspension method are you using???Leaf springs??Triangulated 4 bar???all these items can direct the choice to sometimes a better beginning--------

"Jerry" - Running Posies paralell leafs. Where would I find a Granada or Versille now days? Prefer 5 bolt pattern. Going to have
Wheel Smith or Wheel Vintique make the wheels with proper setback once I get the rear. Yes, to clear rear fenders and body.
Thank you.
_______
"Roger" - Reno is quite a hike from me here in AZ. Shipping is also steep. If I could find someone local that is going to Reno maybe
I could sell them on the idea of tossing a rear in the back seat on the way home. (IF their "boss" wouldn't mind - HA)
Thank you.

JW

Your in Arizona????Check your salvage yards---

I have a complete one, but being from midwest its rusty and would need sandblasting---complete with the discs and brakes including parking brakes---they are set up for leaf spring brackets but off top of my head don't recall the spring spacing---I'll measure next time at the storage place

Originally Posted by JW Hansen

"Roger" - Reno is quite a hike from me here in AZ. Shipping is also steep. If I could find someone local that is going to Reno maybe
I could sell them on the idea of tossing a rear in the back seat on the way home. (IF their "boss" wouldn't mind - HA)
Thank you.

Just as a point of reference, the pumpkin I bought, new 4.11 gears, yoke, and D/E TrueTrac was $1072.50 plus $60.50 shipping to my door, $1133.00 via UPS 10/2009. All new parts, set up and ready to go. I don't have a breakout on the John's Industries price for the rear housing - it was in the roller price.

If you can find the rear you want that's a little off from 58" your wheel guy can adjust the back spacing a little on each side to make it work just fine. It'd be a whole lot cheaper if you can find a salvage unit, but there's some comfort in new stuff if it's in the budget.

Just a little tidbit of info for the rest of you galoots....
The Romans determined that the track (axle width from the center of one wheel to the center of the other wheel on the same axle) for the azz end of two horses pulling a chariot worked out best at 4 ft., 8 1/2 inches (56 inches).
Builders of continental railroads in this country in the 19th century decided that 56 inches would be a good width between the tracks.
Henry Ford decided that if it was good enough for Roman chariots and the railroads, it was good enough for his straight axle cars, so Henry's cars were built with a 56 inch track.

Using a yellow tire crayon, make a mark at the center of the tire. Now go to the other side and make a mark in the center of the other tire on the same axle. The measurement between the marks is the TRACK. You don't need to do any disassembly to find the track of your candidate differential in this manner.

Knowing this makes it easy to scrounge through boneyards and find the exact width rear for your Henry, or any other car/truck, once you know the original track.

I would of thought a 58" wide axle with 8 x 15's too wide for the 34, usually on fendered cars we use a 55" or 56"

.

My 65 Ranchero had a 58 but it was not a posi. My 67 mustang was over 59 and it was not posi either.
I think the only one with a 58 with posi was the early Bronco, if you want a ford rear end.
You may also get lucky by checking the early AMC Jeep or truck styles for posi units.
But really those could have about anything in them from Ford, GM and Dodge