Rear Differential Questions?

Addicted_2_II · Dec 7, 2005

Ok let me just start out by saying that I know very very little about Rear Differentials!

What I do know:
* I currently have 8.0" 3.00 Gears (Non-Lock) in my car (Stock)
* I have 8.0" 3.80 Rear Differential (Non-Lock) (Spare I picked up cheap)
* My current Differential works fine no issues
* I will soon be going with taller tires on the rear (26" Probably)

What I want:
* Both tires to spin or grab really!
* More low-end as I really never need to go over 110
* To try to keep the $$$ Down but I do have some money to spend
* Run down the track a couple of times but will mostly be on the street

So now what do I do? Can I use the 3.80's? Are they going to be steep enough with the 26" Tires? How do I get/make a locking rear-end? Is this something I should have a shop do since I have never worked in this area before? Maybe I should just buy an entire Locking Differential with the gears if it will be a lot of hassle?

Also maybe somone knows of a good website where I could educate myself? I have looked but I am unable to find any that really help!

I hope someone can help,
Chad

Blue Thunder · Dec 7, 2005

You need some special tools, such as a magnetic dial indicator to set up the gears in the chunk, and you should have installation experience before you attempt it, too, or have someone who's good at it to show you how it's done. If you have someone else do the job, they'll probably charge about $150 labor. Get a trac-loc carrier, and use the 3.80 gears, since you already have them. Going from 3.00 to 3.80 is a very noticeable leap in torque to the rear wheels. With a manual trans, the tires will probably just go up in smoke with anything steeper than the 3.80s anyway. If the 3.80 set is old, have the installer check them for wear and/or damage before using them.

If you can find an 8" locker chunk in good shape really cheap, I would go that route, but you still need to have it checked out to make sure the bearings, spiders, ring and pinion and clutches are all good. It seems most used locker chunks have 3.50 to 4.10 gearing in them.

Addicted_2_II · Dec 8, 2005

Blue Thunder, sent you a PM

Blue Thunder, I sent you a Private message... Did you get a chance to take a look at it?

- Chad

1badII · Dec 8, 2005

Blue Thunder said:
You need some special tools, such as a magnetic dial indicator to set up the gears in the chunk, and you should have installation experience before you attempt it, too, or have someone who's good at it to show you how it's done. If you have someone else do the job, they'll probably charge about $150 labor. Get a trac-loc carrier, and use the 3.80 gears, since you already have them. Going from 3.00 to 3.80 is a very noticeable leap in torque to the rear wheels. With a manual trans, the tires will probably just go up in smoke with anything steeper than the 3.80s anyway. If the 3.80 set is old, have the installer check them for wear and/or damage before using them.

If you can find an 8" locker chunk in good shape really cheap, I would go that route, but you still need to have it checked out to make sure the bearings, spiders, ring and pinion and clutches are all good. It seems most used locker chunks have 3.50 to 4.10 gearing in them.

I think she meant that she already has an assembled 3rd member. I have 3.80's in mine, and I think it's the perfect ratio for my car. Nice and low how I like it, and if I get on the highway, my .59 overdrive brings it down to about 2500 rpm at 65 mph. When I put a 9" under my car, I will be going with 3.90's.

Blue Thunder · Dec 8, 2005

Addicted_2_II said:
Blue Thunder, I sent you a Private message... Did you get a chance to take a look at it?

- Chad

yep, responded.

78CobraII · Dec 9, 2005

Are you planning on improving your traction any (stiffer springs, traction bars, wider tires)? If not, I wouldn't go as deep as 3.80 rear gears.

Given your lack of an overdrive and the percentage of time that you plan to drive on the street vs. track, you will be revving that 302 quite a bit just in everyday driving.

I checked out your website...the restoration looks great. I'd like to see some interior pics and read more about your restoration work.

Addicted_2_II · Dec 9, 2005

78CobraII said:
Are you planning on improving your traction any (stiffer springs, traction bars, wider tires)? If not, I wouldn't go as deep as 3.80 rear gears.

Given your lack of an overdrive and the percentage of time that you plan to drive on the street vs. track, you will be revving that 302 quite a bit just in everyday driving.

I checked out your website...the restoration looks great. I'd like to see some interior pics and read more about your restoration work.

78CobraII,
I have a few weeks off toward the end of the year and have planned many website improvements!!!

I just purchased:
* 2 New "Mickey Thompson Indy Profile S/S Tires G60-14" for $143 (25" Tall)
* 2 New Leif Springs 2" oversized

Still looking for:
* Front Springs
* Shocks
* Rear Sway Bar
* Traction Bars
* Motor Mounts
* Power Steering Pump Pulley

If anyone has suggestions on the items above, I would love to hear them! I have no idea how heavy of springs I will need + I am not sure if I am going with aluminum heads yet?

Thanks so much for your feedback on my restoration project. I have put a lot of hours into it but it still needs many more!

So if I get the items above, do you think the 3.80's will be ok?

FYI, I just bought a new oil pan from http://performance.drivewire.com for $43... I had them Double/Triple check it was the right one. We will see!

Chad

Blue Thunder · Dec 9, 2005

I'm using a standard 302 passenger car front sump oil pan on my II, because the factory II pan wouldnt fit over the steel mainstud girdle. I needed to buy a high torque mini-starter, otherwise the factory starter would hit the pan, and I have a Manual steering rack on my car, so I'm not sure if a factory power rack would cause interference with the standard pan or not. It's pretty close. Going this route allows for a much broader(almost unlimited) availability of front sump oil pan designs, including some of those deep sump race versions for greater oil capacity and baffling.

Addicted_2_II · Dec 20, 2005

An update on the oil pan I ordered!

Addicted_2_II said:
FYI, I just bought a new oil pan from http://performance.drivewire.com for $43... I had them Double/Triple check it was the right one. We will see!

Chad

An update on the oil pan! It did not fit

The back part of the pan was about 1 1/2 inches too low and would never clear the power steering rack! I thought about doing a bit of work on the new pan to make it fit but my old pan sat on the steering rack so I would have to hammer it in 1 1/2 inches... I am afraid I would just destroy it!

Chad

welder4956 · Dec 21, 2005

Addicted_2_II said:
An update on the oil pan! It did not fit

The back part of the pan was about 1 1/2 inches too low and would never clear the power steering rack! I thought about doing a bit of work on the new pan to make it fit but my old pan sat on the steering rack so I would have to hammer it in 1 1/2 inches... I am afraid I would just destroy it!

Chad

I could probably take out 1-1/2 inches in the back and tig weld it for you. I have a new tig welder that works great on sheet metal. If you don't find one that fits, and you want to modify it let me know.

Addicted_2_II · Dec 21, 2005

welder4956 said:
I could probably take out 1-1/2 inches in the back and tig weld it for you. I have a new tig welder that works great on sheet metal. If you don't find one that fits, and you want to modify it let me know.

Thanks Welder4956... My current oil pan works but some jackass stripped out the oil plug threads and it is pretty dented up. I will just look for a NOS or one that is in good condition. I am not very happy with this company and kind of just want to send this thing back and be done with them!

Thanks so much for your offer though! Welding is one thing I want to learn with the years I have left! There are many things I need to weld right now, but just no time to take them in

Chad

78CobraII · Dec 21, 2005

Chad,

If you don't take Welder up on his offer, you could look for a race shop that does fabrication. Carry them your factory 302 pan and your new one and get it modified.

You had asked for suggestions on sources for a few other items...

Sway bars: either junkyard or Addco (http://www.addco.net/)

If you get junkyard rear swaybars, make sure to get all of the mounting hardware. That includes the leaf spring axle plate and the bar-end attaching plates. There are both 3/4" and 5/8" rear sway bars, but you'll have to look a little harder to find the 3/4" ones. You could always call one of the MII used parts suppliers. Addco will supply their own mounting hardware which will likely be different from the factory arrangement.

Springs:
Eaton Springs (http://www.eatonsprings.com/) or ESPO (http://www.espo.com/)

On the front springs you can just specify whether you have a V8 with all the accessories, or a V8 with no accessories. That should get you a pretty accurate spring rating.

Traction Bars:
Calvert Racing (http://www.calvertracing.com/) or Stumpy's Fab Works (used to have a store on eBay, anyone know how he can be contacted?).

Stumpy sells(?) a copy of the old Southside Machine LiftBars that seem to work very well with the MII. The Calver Racing CalTrac looks like a great idea, but its pretty pricey. They have a listing for a late Pinto that would probably work with the MII, but I'd get some measurements before ordering.

Addicted_2_II · Dec 21, 2005

Great info 78CobraII, thanks for taking the time to gather it all up for me! I might just take my current oilpan and see if I can get it rethreaded. I am currently using one of those self-tapping (Slightly Larger) drain plugs but it leaks If I can't get that to work, I may have to take Welder4956 up on his offer or just get one fabricated!

I asked my local sport performance shop about my front springs (Owner has a MII), he said that as long as I keep the iron heads, the front springs should be good for now. He had a few other suggestions but they were out of my $$$$ Range

I have been watching Stumpy's eBay auctions for the traction bars... No luck yet! This is pretty much a bolt-on so I am in no great hurry to get them.

Thanks again 78CobraII,
Chad

Blue Thunder · Dec 30, 2005

They make drain plug bung repair kits for oil pans. I think Summit had them.

joeythesaint · Dec 30, 2005

Hey, Chad, here's an idea. This was handed to me by one of my father-in-law's hot rod buddies, and it's how (he says) they used to do it when they were young and broke.

Keep your open rear end. Mount an adjustable air shock on your right rear tire. Load it with enough pressure to keep that tire down. You get the smoothness of an open rear end but no one-wheel spin when you burn 'em. You'd have to play with the pressure in the air shock, of course; and traction bars will help, too. But with the adjustable shock and a set of slapper bars, you should get a pretty good launch and at least avoid the "one-tire fire."

I'm going to try this as soon as the weather stops sucking. I'll keep everyone posted.

Addicted_2_II · Dec 31, 2005

Joe,
Hey thats a great idea... I think I have hit my limit on how much I am going to spend on parts this year (2006) I have nearly $1,200 in parts laying in my garage ready to put on as time allows! I think that part of my traction issues will have to wait until next year! Or maybe I will get a good bonus this year

Here are my new tires/wheels for when I go to the strip!

Mickey Thompson Indy Profile S/S Tires G60-14 (25" Tall) on 9" Alum Wheels

I may have to work on the rear suspension when I drag but for now I am taking the cheap whay out!

My new leafs and shackles should set the car up a bit more in the back. Plus these springs have one extra leaf to make them stiffer!

You can see how tired the old ones where:

I just cross my fingers and hope that everything goes together well!

Chad

Wart · Dec 31, 2005

joeythesaint said:
Hey, Chad, here's an idea. This was handed to me by one of my father-in-law's hot rod buddies, and it's how (he says) they used to do it when they were young and broke.

Keep your open rear end. Mount an adjustable air shock on your right rear tire. Load it with enough pressure to keep that tire down. You get the smoothness of an open rear end but no one-wheel spin when you burn 'em. You'd have to play with the pressure in the air shock, of course; .

power

SERGE and his buddy are going to have harsh words for you ....

cyberbudda · Dec 31, 2005

hello,
ok for mor info on II's goto mustangii.org and mustangii'.net
and for parts you will find a supplier called Mustang II speciallty shop run by a guy named Phill schmit. a good guy and he has any part you need. one more source for info is the http://carbdford.com/

as for your rear end..........you are on the right track and since you have the complete rear 3.80 diff i would just put it in and see how it works out. you may get lucky and it will work fine. if not then it only takes about 30 minutes to pull it back out. the biggest problems with used diff's is they are noisy and have a littl whine to them.
Second problem you might run into is your tire size and the spacing of your new rims....have you checked the tire and rims for clearence under your fenders?? the 25" tires will fit but only with the correct backspacing(how far in or out the tires sit under the fenders) of the rims.the max tire with that will fit correctly in back is 225 and a tight 235
the best way to fix this is to get rims that fit correctly cuz tubbing or cutting the fenders is cheap and easy but kinda destroys the look of the car.
need any more help or parts ask....
buddha
http://members.tripod.com/cyberbudda/mycobra.htm

cyberbudda · Dec 31, 2005

Oil pan:
the oil pan,bellhousing and exhaust manifolds are unique to the mustang II. the one you bought you should probablly send back cuz i am sure the money could be used elsewhere. stick with the stock oil pan. just use a helicoil to fix the threads or drill and tap it larger.

Blue Thunder · Jan 3, 2006

cyberbudda said:
just use a helicoil to fix the threads or drill and tap it larger.

The threaded hole is merely stamped sheet metal, if you drill it out, it will eliminate the stamped section that supports the threads, which means, all you'll have left is a sheet metal hole. You'd need to either weld a nut on the inside of the pan that matches the threads of the plug, or buy a kit with an internally-threaded hollow through-bolt, gaskets and nut, that when installed, creates a properly threaded drain bung. Just like those transmission pan drain plug kits.

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