7.25" rear end question

[Bruceynz]

Hi Everyone,

I am new to the forum, been around mopars for a while even though I live in New Zealand, USA cars here have quite a following here although they are not technically allowed on the road here because they are left hand drive the government makes allowances for private imports to be used here, there are some catches to it, like age of car and how long you have to keep it for, but all good we are allowed them.


I imported for myself a 1983 Cordoba, I found the build sheet and it has the 7.25" rear end, have heard they are not to strong but hey this car has done 73,000 miles and the rear end is quiet! How strong are they, will it handle an RV grind cam and a 4bbl carb and intake?

I have sitting in my parts bin, Holley 1850s, Edelbrock Performer intake, new distributor and module, cam shaft, lifters, springs, doubler roller timing chain, harden push rods etc. I don't have to run the cats here so they will come out and a nice flowing exhaust will go on, the factory one is so restrictive. Cam specs below.

Camshaft Kit Part Number	Application	Power Range	Idle Quality/special requirements	Valve Lift Int/Exh	Duration Adv. Int/Exh in degrees	Duration @.050 Int/Exh in degrees	Lobe Centerline
CK3004-1	SB Chrysler 273 318 340 360 with hydraulic flat tappets	idle-4400 rpm	Good torque, good pulling, offroad and highway mileage. Smooth idle	420/443	278/278	204/214	112

I know my cam is not a HP cam, but its not HP that breaks things, I don't do burn outs or loose traction, all driving will be on the road, am I likely to kill my 7.25" with my proposed setup?

Many Thanks in advance for all your help and advice.
Bruce

 

[Blackbirdsrt78]

Not likely going to kill it as long as it is in good condition to start with. I know of folks that kept 7.25 rears with a 440 its not recommended but people do it. As long as you dont have a lead foot should be fine. no donuts, no burn outs, no hard acceleration, just normal driving.

 

[Bruceynz]

I do like the odd good take off but not wheel spinning

 

[slant6billy]

I've snapped 2 7 1/4s doing smokey burnouts, so they are made with some limitations. 7 1/4 should say they are not meant for foolishness. But I am a special kind of idiot. You might want to see if a ford 8.8 out of an explorer would transplant under it. I think there is a thread to do so

 

[Jack Meoff]

For years I've been hearing about how weak these 7 1/4" rears are....but all three of my cars have one. Granted, I have a stock 318 in one and Super Sixes in the others....but I don't exactly baby them and they've held up beautifully in all of my cars...

 

[slant6billy]

I don't trust myself. The 7 1/4 could be considered solid or even bullet proof, just not "Billy Proofed"

 

[Jack Meoff]

I don't trust myself. The 7 1/4 could be considered solid or even bullet proof, just not "Billy Proofed"

Lol!
Not sure a whole lot of cars would be Billy proof....

 

[Blackbirdsrt78]

its not the burn out that breaks em its the hook up. if you know what I mean. I would run the 7.25 untill I pieced together a stronger diff.

 

[MiradaMegacab]

The spider gears split in half .

 

[Blackbirdsrt78]

The spider gears split in half .

for sure

 

[Slodoba]

Your best bet is to find an 8&1/4 shipped from a diplomat police car. An even stronger option is an 8&3/4 from a 66-70 B body car. It can be adapted very easily. I blew out 3 7&1/4s with my sock 318 before I put in an 8&1/4 then when I built a bigger motor I then installed an 8&3/4

 

[alf44]

there is NO good reason to swap a ford 8.8 or 9 inch in to your mopar .your combo wouldnt need the money spent trying to fit that ford into a mopar. to me that doesnt make any sence as mopar rears are better suited to your mopar. a 8 1/4 or dana 60 rear will work better that any ford rear with your combo. there are people using ford 9 inch rears but they run more power that you do. i have read that for a given combo. a ford 9 inch requires more power to turn than a mopar 8 3/4 or dana 60 so you would lose power running that ford rear.

 

[80mirada]

A Dana would be over kill, an 8 1/4 would be your best bet

 

[9secRR]

8-1/4'' diff will be all you need. I ran a 520 hp 410'' stroker for 3 years with a 8-1/4''. they are stronger then most people think.

dana 60 is way overkill. not needed. 8-3/4'' if you plan on making more power in the future. cheaper to do it once.

 

[greymouser7]

if you get a sure grip for your 7 1/4 it would be enough, but there are plenty of rear ends from the 265ci hemi 6/318ci V8 etc. cars from australia or new zealand that would be your cheapest bet.

 

[Slodoba]

I woundnt say plenty. I've been to Australia recently and Mopars are scarcer then hens teeth. I believe the Australian charger was based off the valiant A body platform so the track is narrower. His best bet it to get an 8& 1/4 shipped from the states. fords unfortunately are very popular and plentiful down under. The cheapest alternative is to swap a rear end from a ford.

 

[Bruceynz]

Investigated the Australia options and the problem is the width, I am trying to get one from the USA. I have a friend in SC who can help ship to me. So trying to find one in SC area if we can.

 

[greymouser7]

I woundnt say plenty. I've been to Australia recently and Mopars are scarcer then hens teeth. I believe the Australian charger was based off the valiant A body platform so the track is narrower. His best bet it to get an 8& 1/4 shipped from the states. fords unfortunately are very popular and plentiful down under. The cheapest alternative is to swap a rear end from a ford.

do they have ford 8.8 or 9 inches available? I know so little about ford's - people say the ford 8.8 from the explorer already has the disc brakes on it-there is arguement over strength- but should be stronger than a 7 1/4

i think shipping would be too expensive

 

[Bruceynz]

Whats the width like on a ford explorer, yes we have them here but not many, freight for a rear end will cost me about $700NZD which allows 1 cubic meter and up to 1 ton, I have bought some other bits already, XXX714 heads, fender extensions, sway bars etc to make up a pallet to bring over, just need a diff if I can.

 

[Bruceynz]

if you get a sure grip for your 7 1/4 it would be enough, but there are plenty of rear ends from the 265ci hemi 6/318ci V8 etc. cars from australia or new zealand that would be your cheapest bet.

As far as I know the diffs in Aussie cars were Borg Borner and I could be wrong here but 7.25" sure grips are as rare as rocking horse poo. In Aussie the gov said that the cars had to have so much aussie made content in them, the 265 hemis also had borg borner auto transmissions some of the early valiant had 904s but the later ones as far as I know didn't, on that note I am not in Aussie nor would I call myself an expert on Aussie mopars. I know the 67/68/69 Valiants in Aussie were right hand drive dodge darts! They could of even been sold in South Africa not sure. The 318s had the 904 and the 360 probably had the 727, the Aussie made a valiant Limo had a 360 in it.