I'm new to Mopars (quite a bit of experience with Fords and my turbo T-bird) so I'm not quite up to speed on the various Mopar rears and their strengths.

How strong are the 7.25s, and what can be done (cheaply) to improve on them? Lockers? Gear sets? Thanks. This is for a 75 Dart w/ 225 automatic (904) that I will be turbo'ing w/ MegaSquirt. I'm shooting for 350-400RWHP. I'm not going to be doing any transbrake launches on slicks or anything, just normal street driving with decent street tires (and beating on Chevys/Fords).

In addition, is there a different (stronger) rear that I can find cheaply at the local j/y, and will swap in without major modification? The 8 3/4 looks interesting (I *love* the Ford 8.8 ).

Thanks guys!

The best way to improve the 7 1/4 is to replace it with an 8 1/4 or 8 3/4. Both the 8 1/4 and the 8 3/4 came in A bodies. The 8 3/4 only came with the pre-73 small lug pattern, which is 5 on 4". This is a pain in the ass to get decent wheels for. Aftermarket axles with the more common 5 on 4.5" pattern are available from the aftermarket. The 8 1/4 came with the bigger pattern. I'm not sure if ALL of them did-I suspect so, as the 8 1/4 replaced the 8 3/4 as the heavy duty A body rearend in '73. This was also the year that all A bodies started getting the big bolt pattern. Now, for strength: The 8 1/4 is probably strong enough for what you want to do, especially without slicks and hard nitrous/transbrake hits. I have one in a heavy-ass '86 ramcharger with a 400 and a helluva hard hitting shift kit. No problems so far. As you probably know, turbos are particularly easy on drivetrain components for any given power level, which would be added insurance for the rearend. An 8 3/4 would be basically failsafe behind the motor your describe.

When looking for either of those rearends, don't limit yourself to 340 cars, or even v8 cars. Slant six cars came with both of those rearends for no apparent reason. Case in point: The slant six powered '74 duster I bought to eventually turbo myself has an 8 1/4 in it. It had no towing packages or anything like that-it just came with the rearend. By the same token, plenty of 318 cars came with a 7 1/4. Go figure.

I like the 8.8 too, though I've never owned one. Plenty of people I know have, and they'll take considerable punishment. As I'm sure you know, the axles will generally fail before the centersection, and aftermarket axles are cheap for those. They're pretty cheap for an A body 8 3/4 too, come to think of it. If you wanna know how strong a stock 8 3/4 is, I have another firsthand example: I used to have another '74 duster with a 440 stuck in it. The car had an 8 3/4 out of some other line of car, probably a B body. I eventually ran a 10.98 with a 1.54 short time in that car. The car weighed about 3100 lbs without me in it. I was leaving on 200 hp of nitrous, right off idle. On a good pass, it would leave with the front end high enough in the air that I couldn't see the track in front of me. (the slow ET for that kind of launch was due to a screwed-up motor combo that involved stock cast pistons and a low lift solid cam to clear the pistons. Yes, stock cast big block chrysler pistons will take that much nitrous and more) When I retired that car, I pulled the rearend out of it. The internals were STONE STOCK. The ring gear has a date stamped in it. It's sometime in 1969. The suregrip unit appears to be the stock factory unit from 1969. It was starting to fail there at the end, which makes sense. The damage to the unit: Two SLIGHTLY chipped ring gear teeth. The kind of chips so small that the gears don't make any noise. Nothing ever went wrong with the rearend, except for the failing suregrip unit. I sold it to another guy who wants to build up an A body. So, if a stock 8 3/4 will take that abuse, a turbo'd slant six shouldn't break one.

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Everyone driving slower than me is a moron. Everyone driving faster than me is an idiot. With all these morons and idiots on the road, I can't get anywhere!

Lots of good info! How heavy are the 8.25 and 8.75 rear ends? Have you heard of anyone swapping the new bolt pattern flange onto 8.75 axles? Thanks again!

If you want big bolt pattern on an 8.75" you can buy $200/pair new axles from moser.

Yeah, those are the axles I was talking about, I just couldn't remember who made them. I didn't know they were quite THAT cheap though. As for weight, I don't know exactly, I'd say the 8 1/4 is somewhat lighter than the 8 3/4, but not tremendously so. 50 lbs would probably be a good guess.

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Everyone driving slower than me is a moron. Everyone driving faster than me is an idiot. With all these morons and idiots on the road, I can't get anywhere!

How strong are the 7.25s? All I know is I will be replacing my "40 years of use one" with a 70 Duster 7.25 I am freshing up. BTW until a couple years ago cover had never been off and seals/bearings had never been done. Worn pinion gear is the culprit after 40 years of service..strong enough for me....Dave

It's not that they're strong, it's that they're durable. That may sound like the same thing, but my definition of durable is that they'll survive normal or light use for a long time. If you think a 7 1/4 is strong, put a well built smallblock, particularly a 360, in front of one. Then you'll get to see how strong an 8 1/4 or 8 3/4 is.

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Everyone driving slower than me is a moron. Everyone driving faster than me is an idiot. With all these morons and idiots on the road, I can't get anywhere!

Don't mean to harp, but for a daily driver that will never see 4000rpm or track use its doing what it was designed to do. If running a stout v8, of course a upgrade is necessary and with companies such as Reider Racing providing performance parts for the 7.25 someone other then me believes in them. I get tired of the "one is better the then other" debate. Everything is relative. How's that going to effect others new to slants with a limited budget and limited knowledge when they are bombarded with "first thing to replace is that 7.25" even if they have no intentions of any immediate modifications and have never done such mechanical work. I call this type of negative advice "the v8 mentailty" and is the reason I drive a slant. Sure, I'd take a 8 3/4 if it fell on my doorstep ready to install, but the cost involved to modify my Dart could be better spent....Dave

Absolutely true. That's why they're durable.

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Everyone driving slower than me is a moron. Everyone driving faster than me is an idiot. With all these morons and idiots on the road, I can't get anywhere!

I understand where you're coming from. This guy I knew at tech school had a bone stock, immaculate 95 Mustang GT. It was an automatic and he was planning to swap to manual. Rather than just go to the boneyard and grabbing a T5 tranny and all the swap parts for $200, he was looking at spending $$$ thousands to buy a brand new tranny, brand new parts, have someone swap it in, etc. He didn't want a regular T5 either, he wanted a T56, because the "T5 isn't strong enough" and he was worried about it breaking. I was incredulous. I reminded him that he had a BONE STOCK car and a regular old, plain jane junkyard T5 will last a lifetime with the way he drives and the power his car is putting out. But he heard stories about someone breaking a T5 while powershifting a 400+HP motor and was paranoid.

However, getting back on topic, I started this thread because I am actually planning a high-horse slant buildup (in the neighborhood of 300-400HP), and I need a rear end that's not going to shatter like glass when I put power to it.

The Ford 7.5" rear is a good, durable rear end as well, but even a mild turbo 4-banger can and will break one of those things pretty easily. So, I don't think the 7.25" is a good choice for my setup.

Didn't mean to be such a a*%. Believe me When I build up a six the first thing to go will be the 7.25. I'm approaching it from the standpoint of several post i've read where the slants are stock and will not be modified in the foreseeable future and the persons are on the learning curve with limited budgets. As has happened to all of us, we all started with baby steps until we were afflicted by the slant mistique and now we can't get enough wrenching and modifying . It will also happen to the newcomers. Allow them to make a informed decision and support each other otherwise we would all be driving Cheebies or something worse!....Dave

A 7 1/4 is fine for a stocker and a budget but once the power goes-up, the 7 1/4 will die.
truth is that with some special parts and careful building you can get a 7 1/4 to last.... a while.
Your time and money is better spent on a stronger unit, I go with the 8 3/4 just to get the drop-out center section, it is overkill from a strenght standpoint.

Yeah, the whole reason I advised the original poster to pitch the 7 1/4 is that he's planning a good bit of hp. I'm not against the 7 1/4 in stock or near-stock slant six applications-I have 2 of them now myself. The original poster also asked about upgrading the 7 1/4. I don't think too many people would seriously advise someone to upgrade a 7 1/4 when much stronger stock rearends are available.

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Everyone driving slower than me is a moron. Everyone driving faster than me is an idiot. With all these morons and idiots on the road, I can't get anywhere!

How heavy is your FOOT?

I've blown up several 7 1/4s behind a stock 2 bbl 318. They were cheap and swapped back in easily, so I kept running used 7 1/4s after I blew up the original one, two years after I got the car. I found an A body 8 1/4, finally, and have only had a couple minor problems with it over the past 6 years. I got it from a Slant 6 '75 Valiant with 3.21:1s to replace the 2.76:1's that were in my 7 1/4s.

That 8 1/4 is getting swapped into my Dart Wagon 225 car when I get done building a large pattern 8 3/4 for my 318 Duster. Hopefully I get this done before I blow up the 8 1/4, too.

If you stay out of the throttle, it doesn't matter TOO much. If you can't stay out of the throttle, you'll break everything, even bulletproof Mopar stuff.

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"When applied at precisely the right time, Ignorance is a powerful tool, usually even surpassing knowledge" E.J. "Michigan Madman" Potter.