8 inch Rearend

cjperry81 · Feb 11, 2010

Where is a good place to hunt down an 8 inch or 8.8 inch rearend to upgrade my 66?

2+2GT · Feb 11, 2010

The 8" was stock in the 64-66 Mustang, so a complete bolt-in assembly should be no problem. The 8.8 is a modern piece, so a whole lot of adapting is required. What rear do you have now?

tx65coupe · Feb 11, 2010

Are you doing an I6 to V8 conversion? If your car is a V8 car, it should already have an 8 inch rear.

cjperry81 · Feb 11, 2010

I was always want to do an I6 to V8 conversion but as of recently Ive decided that a hopped up I6 is the best and most affordable route for me. Besides it will be fun to roast some V8's with an I6. SO the answer is not i will not be converting it. I have no idea what rear is in it now. Its bone stock and never been changed. When talking about engine mods on here someone suggested that I bump up to an 8 inch. So i figured Id ask about it.

shoguun · Feb 12, 2010

your kinda in a limbo situation. You want power but you want to keep the 6 and you have a bone stock weak 4 lug rearend. 8 inches are plenty strong enough to hold up to any v6. The only problem is they are 5 lug and you need new rims and convert the front to 5 lug setup 2. Your best off going to the 8 or 9 inch.

2+2GT · Feb 12, 2010

cjperry81 said:
I was always want to do an I6 to V8 conversion but as of recently Ive decided that a hopped up I6 is the best and most affordable route for me. Besides it will be fun to roast some V8's with an I6. SO the answer is not i will not be converting it. I have no idea what rear is in it now. Its bone stock and never been changed. When talking about engine mods on here someone suggested that I bump up to an 8 inch. So i figured Id ask about it.

The stock I6 rear was the 7" integral carrier design. Unless you are going all-out in upgrading your I6, the 7" should hold up. The two most common ratios on 7" rears was 2.80 and 3.25. Naturally, the 3.25 is better for your purposes. The best was the 3.50, but it is extremely rare. I have seen one. It was also an Equalock, and it sold for some serious money.

A few years ago one of teh six-cylinder performance outfits was working on getting the 3.50 gears made, but I never heard any more about it.

cjperry81 · Feb 12, 2010

I was actually kind of figuring that I would switch over to a 5 lug set up any ways.

tx65coupe · Feb 12, 2010

If you switch over to 5 lug then I would upgrade to front disc brakes and 5 lug in the front as well. I think I would go with an 8 inch rear for what you are wanting to do. That way if you ever want to convert to V8 later you have alot of the work already done. Take a look at Clifford Performance for I6 hot rod parts.

D.Hearne · Feb 13, 2010

Sixes can and do develop a lot of torque, if you're going to upgrade, you may as well go to an 8.8 or 9 inch rear. The easiest to find in a junkyard is the Explorer 8.8. It will take some changes to fit, but they're advantage is they're all 31 spline axles and many have traction-loc units. You can shorten the long side, then relocate the spring pads to fit a Stang.

D.Hearne · Feb 13, 2010

2+2GT said:
The stock I6 rear was the 7" integral carrier design. Unless you are going all-out in upgrading your I6, the 7" should hold up. The two most common ratios on 7" rears was 2.80 and 3.25. Naturally, the 3.25 is better for your purposes. The best was the 3.50, but it is extremely rare. I have seen one. It was also an Equalock, and it sold for some serious money.

A few years ago one of teh six-cylinder performance outfits was working on getting the 3.50 gears made, but I never heard any more about it.

I wonder if that 3.50 geared unit was a 5 lug rear ? If it was I know where one's at. Got pics of it too in my photobucket page.

2+2GT · Feb 13, 2010

D.Hearne said:
I wonder if that 3.50 geared unit was a 5 lug rear ? If it was I know where one's at. Got pics of it too in my photobucket page.

No, strictly 4-bolt, it was a sad case. 1965 CV, silver/bright red, 200, 4-speed, 3.50:1 Equalock rear. Owner started stripping the paint, then died. Family left it sitting in the rain for years, top down.

D.Hearne · Feb 13, 2010

The one I have pics of is under a 65-66 Stang sitting behind a freind's house. It looks to be the original rear by all indications. The front wheels are 5 lug too. But it's definately a 6 banger car.

zookeeper · Mar 3, 2010

Just a little FYI, but I have a set of 3.40's in the 8" in my car and I beleive they may have come from a Pinto/Bobcat. Lots of those (particularly wagons) had 8" rears and although limited slips are rare, the 3.40's are not. Before I spent too many sleepless nights worrying about it, there's a guy on ebay that used to sell brand-new 8" limited slip rears units with any ratio you want for under $400. Who knows, he may still be selling them. Much easier and cheaper in the long run than scouring the countryside hoping for an ulra-rare part of questionable condition.

phutch11 · Mar 4, 2010

Those rebuilt eBay limited slips are crap, don't buy one. They are originally open differentials that were converted to be limited slip.

Do some google searching on the topic and you'll see.

Save a few more pennies and get a Tru Track.

zookeeper · Mar 4, 2010

Could you be more specific? Where did yours break at? You did buy one, right? I mean I hate it when people simply repeat what they read on the internet as fact. But if you do have some experience with one, either good or bad, please report all the necessary problems you had, I for one would be interested in what exactly you broke.

danny clemens · Mar 4, 2010

If you did go with a bigger rear than an 8" the 57, 58 and 59 Ford rear would be the easiest swap.

zookeeper · Mar 4, 2010

Very true, but when I swapped in a '57 9" from a wagon into my '65 fastback, I had to have a new driveshaft made since the 9" uses larger U-joints.

tx65coupe · Mar 5, 2010

I have an Ebay 9 inch third member with 3.50 traction lock. I got it from RMustang I think was the seller. I know that there is also a seller that has what he calls torque lock or something like that. Those are different. I'm not sure I would buy one of those.

D.Hearne · Mar 5, 2010

zookeeper said:
Very true, but when I swapped in a '57 9" from a wagon into my '65 fastback, I had to have a new driveshaft made since the 9" uses larger U-joints.

You never heard of combination joints ?

57fairlane · Mar 5, 2010

D.Hearne said:
Sixes can and do develop a lot of torque, if you're going to upgrade, you may as well go to an 8.8 or 9 inch rear.

I would say that depends on if you are going with a stick, or keeping an automatic AND if you plan on going to the track at all.

Stick + 8" + slicks will break stock parts in a hurry.

The auto doesn't "hit" the rear end as hard and can live a lot longer.

I made 265rwhp/270rwtq with a c4, and ran a lot 7.80s-7.90s in the 1/8. Switched to a t5 made 300rwhp/310rwtq (same motor, just differences in losses) and broke the drivers side axle on the 2nd pass.

You can buy mosers but from what I can tell, 300hp/300tq is kind of the limit of being able to keep the 8" alive for a long time. Drive it around on the street fine but don't expect 1.70 60fts from it.

8 inch Rearend

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