What can the 7.25 handle?

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Zorro38

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So this might be a bit of a weird question for you die hard Mopar guys but I have a 74 Valiant that I removed the 225 from and now have an OM617 Mercedes turbo diesel in it. My question is: will the rear end handle the motor? I am still working on a drive shaft so I haven't driven it yet but was looking for opinions. The 225 supposedly put out 105hp@3600 and 180ft-lbs@1600 whereas the diesel makes 125hp@4350 and 185ft-lbs@2400 in stock form. Will the 7.25 hold up or should I go for an 8.8 swap since I have a yard full of explorers and rangers?
 
With an auto trans it should hold up pretty well.
 
do not rely on the 7 1/4. they were marginall ok with highway gears install and a slant. that is it. A better option would be the 8.8 or actually an 8 inch ford out of a 60's mustang. perfect width on the 8 inch rear if you can find one. the 60's mopar B body could work also but is slightly wider.
 
Thanks for the input, I'm not trying to make a speed demon so I do want to keep the highway gears for use with the diesel so it looks like I might go with the 8.8. I was just trying to avoid unnecessary work if the 7.25 would have handled it.
 
I realize I am pushing my luck, but I have been driving a 350hp 5.9 Magnum with a 5 speed OD in front of an original all stock 7.25 for months and have even done block long burnouts with it.
Yea, they are not made to stand up to that, but they are not quite the total sissy everyone who isn't spending the money says they are either.
They came out behind 318's for frickin decades, and are still out there running and driving every day 40 years later.
Being behind a 125hp diesel with an auto would be a breeze for it if it's ok and not already going out.

That said, if you can put a better stronger rear in it why not do it?
 
If had several aspens, variants etc. Seems the 7.25 rear is tough enough to handle about half the power of the stock six banger. Spin a tire on ice a lol bit, hit a spot of dry pavement and watch the parts fly out!!!! Jus my opinion but I've never had one last VERY long
 
My 318 Barracuda came stock with a 7 1/4. It has over 100k hard miles without issue. Lots of 1 leg burnouts. Engine was slightly modified with headers and 4 barrel. Stock the 318 was rated at 230 hp and I don't remember the torque. I would keep your 7 1/4.
 
do a 7.25" experiment, run it and get back to us! it all depends on rear tire size and how the nut behind the wheel drives
 
TrailBeast said:
I realize I am pushing my luck, but I have been driving a 350hp 5.9 Magnum with a 5 speed OD in front of an original all stock 7.25 for months and have even done block long burnouts with it.
Yea, they are not made to stand up to that, but they are not quite the total sissy everyone who isn't spending the money says they are either.
They came out behind 318's for frickin decades, and are still out there running and driving every day 40 years later.
Being behind a 125hp diesel with an auto would be a breeze for it if it's ok and not already going out.

That said, if you can put a better stronger rear in it why not do it?
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i just blew mine with the same set up.. took a lot of abuse then just blew out of no where with normal driving.. 8.8 is almost done:)
 
I have had a few last for a decent amount of time but discovered that the 7-1/4 cannot stand to have one wheel spin and then get sudden traction. The pinions and cross shaft rip right out of the case. I live in an area that gets ice and snow throughout the winter and have a pile of seven destroyed 7-1/4 rear axles and the most power applied to any of those came from a 273 two barrel. Even when I tried to be careful on ice with a slant six the 7-1/4 would sooner or later fail the pinions. If you have a stronger rear axle available I would recommend a change.
 
My 71 Challenger 318 2bbl had a 7.25. Unless it had been put in afterwards, I can't be sure but I very much doubt it as this car was bought as an unmodded family car. Chrysler wouldn't have used this diff in a heavy car with a 318 unless they were reasonably confident it would handle the load. Think about this, a Challenger with its rated 5 people and their luggage (not much in the trunk, but let's say it is full), that's a fair load for a diff with a 318. The fact that all these people have given them abuse and many of them still handle it means they are stronger than most people might think just going by the numbers. They were only meant for normal use, not being abused. Having said all that however, a look inside mine showed that a small chunk of crown wheel was in the bottom. About half oz of metal. But it didn't affect operation.
 
Zorro38 said:
The 225 supposedly put out 105hp@3600 and 180ft-lbs@1600 whereas the diesel makes 125hp@4350 and 185ft-lbs@2400 in stock form. Will the 7.25 hold up or should I go for an 8.8 swap since I have a yard full of explorers and rangers?
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Those HP/Torque numbers aren't that much off. If this isn't a racing application, which it sounds like it isn't, I would give it a try. Worst thing that happens is that it breaks and you have to move on to the swap anyway. For normal driving, I suspect it will be just fine.

I have owned many 7 1/4 rear equipped cars and only managed to break one in the past. And all of those cars had a lot of mileage on them.
 
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