How strong is the 521 rearend?

[rebstew]

I'm tossing in a mild built small block. 300 to 350 HP. While this is not much it alot more than the 4 banger in my 70 521. So has anyone had issues with the rearend? How strong is it? If you look at the case it looks beefy but that may not be the case for the guts. I'd like to keep it because of the 430 gears but if I'm going to blow it apart I'd rather just switch it out now for something stronger. If it is strong enough does anyone make a spool or posi unit for it?

[ggzilla]

The H190 has a ring gear of 7.49 inches, and is good for ~285 lb/ft torque. So good for a smaller V8, up to 5 liters if not too powerful. For example the 1982-1984 Mustang 5-liters used a 7.5 differenial. But for 1985 it moved to the 8.8".

 

HP is not too relevant to this question. What size V8 you talking about? A chevy 283 at 350HP would probably be OK, but not a chevy 350 at 350HP.

[datzenmike]

It's as strong as all the 620 and most of the 720 trucks.

[rebstew]

The H190 has a ring gear of 7.49 inches, and is good for ~285 lb/ft torque. So good for a smaller V8, up to 5 liters if not too powerful. For example the 1982-1984 Mustang 5-liters used a 7.5 differenial. But for 1985 it moved to the 8.8".

 

HP is not too relevant to this question. What size V8 you talking about? A chevy 283 at 350HP would probably be OK, but not a chevy 350 at 350HP.

It will be a 355 Chevy with about 375 + pounds of torque maybe more.

Has anyone ever blew one of these stock rearends? I have ran a few V8 S10 that had some balls to them with the stock 7.5 rearend. I'm not saying they are strong but they will hold up to a mild built smal block.

 

 

So I guess the next question is?? Is there a rearend that is close to the same size that I could swap? Early 8" out of a Maverick or something? 8.8 out of a Ranger? welding on new perches is no biggie to me. What do you guys use for rearend upgrades?

[ggzilla]

375 lb/ft is a lot of torque. Not too many cars have this much. The last 350 Corvette had this much. The new 6.2 liter Corvette has 400 lb/ft.

 

Most guys with this much torque use the Ford 9". But a ford 8.8" can handle it, and it is a lot lighter than the 9" because it is a salisbury (integral) type without a removable center section.

 

520/521 rear axle is 53 inch wide drum-to-drum. 1990-1992 Ranger 8.8 is 57 inches. And has 5-lug axkes instead of the 6-lug of the 521.

 

If you need a narrower axle, take the Ranger axle, cut the drivers side of the housing and use two Ranger passenger side axle shafts and you are down to about 54" wide.

See http://www.jalopyjournal.com/forum/showthread.php?t=157008 Edited August 5, 2009 by ggzilla

[rebstew]

Man that is narrow. I don't want to get into cutting a rearend down if I can keep from it. If I do I will just send it off to Mosers to have it done. I just thought there may be something that is close to a bolt in.

Not to be a jerk but 350 horse 375 p/torque is mild for the crew I run with. Our road captain has a 69 Nova 454 that run high 10's in the 1/4. Another guy runs 10.40's in a 455 69 Buick and my 454 Chevy powered T/A should be deep in the 11's. All 3 cars are in street trim, other than slicks at the track and street legal:rolleyes: I took mine to the track two weekend ago but busted the radiator and didn't get to run the new engine. I guess for these little 4 bangers it is alot or torque but I'm going after something fast. What is the weak point in these stock rearends? Ring and pinion itself? axles? If it's a matter of case flex I could weld some gussets and bracing on the housing. Waist of time?

I'd really like to hear as much input as I can on this. I could deal with ringing out the rearend over a matter of time but if it's going to blow apart first time I nail it I want to swap it out. Lug pattern is not a concern. 6 or 5

[ggzilla]

The main limit is the physical size of the Ring & Pinion. Ask your big-block guys if any of them are running a 7.5" rear end, even with gussets or braces or whatever. Not a chance.

[motavated]

Here man. 327 power!!!! It will last a while.... Burn outs I think are out of the question.

 

http://forum.ratsun.net/showthread.php?t=11139

http://forum.ratsun.net/showthread.php?t=848

http://forum.ratsun.net/showthread.php?t=10263

[rebstew]

The main limit is the physical size of the Ring & Pinion. Ask your big-block guys if any of them are running a 7.5" rear end, even with gussets or braces or whatever. Not a chance.

LOL I'm running a 8.5 in my big block. same for the Nove and the Buick runs a 12 bolt. I'm not trying to stir up a fuss just getting some answers. lol

 

So the stock rearend is a junker for what I want. okay on to the drawing board.

[rebstew]

Here man. 327 power!!!! It will last a while.... Burn outs I think are out of the question.

 

http://forum.ratsun.net/showthread.php?t=11139

http://forum.ratsun.net/showthread.php?t=848

http://forum.ratsun.net/showthread.php?t=10263

 

Thanks for the links. I know now what the stock rearend will look like the first time into it.

[bonvo]

Not to be a jerk but 350 horse 375 p/torque is mild for the crew I run with.

 

i wouldnt say your being a jerk that is mild for a muscle car build but you got to remember this is a 60-70 japanies car forum most if us only dream about 350hp and 375 foot lbs out of out econoboxes :lol:

[nukeday]

I had a Ford 8" from a '77 Mustang II in a Luv V8. It was a very good fit, perhaps a couple of inches wider. Here's the codes:

 

WDW AA 6AB

2 79 8 53OD

 

I think V8's are more common in the Luv than any other import, might want to snoop around at http://www.luvtruck.com/

Edited August 6, 2009 by nukeday

[denveratsun]

I was just thinking Mustang II. :cool:

[b210in]

if you can score an 8 inch ford, use it. if i were you, i would hunt down a ford 8.8 from a v6 90's ranger ttruck. most of the four banger trucks had the 7.5, stay away from these. out of all the ford 8.8's the one that came in the ranger is narrowest at about 56 to 57 inches, with a 2 to 3 inch pinion offset from the factory. you can cheaply narrow this axle to 53 inches by only narrowing the left side (the side that has the longer distance from the wheel flange to the splines and re use another right side axle shaft), this will move the yoke closer to the center but still have a 9/16" pinion offsett, which is better than 2 to 3 inches from the factory. regarless of the whatever 8.8 you use, you still have the c clip issue. some tracks won't even let you race until you get c clip eliminators. this is a really common swap from guys that run v8 rx'7s.

Edited August 6, 2009 by b210in