7.25 Rear Durability

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MOPARJ

MOPARJ

What can I upgrade now?
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HELLO. MY 73 DUSTER IS EQUIPPED WITH A 318 WITH 80,000 MILES, A COMP 260 CAM,COMP LIFTERS, DOUBLE ROLLER TIMING CHAIN, EDELBROCK PERFORMER INTAKE, EDELBROCK 600 CARB, AND MAGNAFLOW 2.5" DUAL EXHAUST. THE CAR HAS A/C. THE 904 WAS REBUILT WITH A MILD TRANSGO SHIFT KIT. I ESTIMATE MAYBE 240 HORSE AT THE CRANK FROM THIS CRUISER. THERE ARE NEW U JOINTS AS WELL.THE REAR IS THE SMALL 7.25 REAR WITH 2.76 GEARS. I EVENTUALLY WANT TO SWAP IN A 8.75, BUT TIME AND MONEY PROHIBIT THIS FOR THE NEXT YEAR OR SO AT LEAST, SO I HAVE TO LIVE WITH THIS REAR FOR NOW. IT DOES NOT MAKE NOISES AT ALL. THE FLUID IS CHANGED AT REGULAR INTERVALS AND AT LAST CHECK, EVERYTHING LOOKED GOOD. I ROLL ON BF 235/70/R15 REAR TIRES. THE CAR IS DRIVEN TWICE A WEEK(ABOUT 100 MILES TOTAL). IT IS SOLELY A CRUISER, BUT IT WILL STILL RUN A 15.5 E.T. WITH THOSE GEARS, WHICH IS DECENT AND GOOD ENOUGH FOR ME(MY 69 FORMULA S CUDA IS FOR MY ALL OUT SPEED FIX). ANYWAYS, WITH JUST THE CRUISING AND SOME HARD ACCELERATION JAUNTS ONCE IN A WHILE, WILL THIS 7.25 HOLD UP FOR A WHILE? I REALLY NEED IT TO. ANY ADVICE ON AFTERMARKET PARTS TO ENHANCE IT? LIKE I SAID, NO PROBLEMS WITH IT SO FAR, EVEN WITH ABOUT 320 FT/LBS OF TORQUE AT THE CRANK AND A HARDER THAN STOCK SHIFTING TRANS. THANKS FOR ANY USEFUL INPUT. MOPARS AND A-BODIES FOREVER!!! :salute:
 
If your real nice to it, it'll be there for a while.
I reallly really really would look into a 8-1/4 swap. You'll need to shorten the driveshaft about 2 inchs though. Totally worth it. ($50 done local)
This pictured suregrip equipped 8-1/4 was picked up for $200 and promtly upgraded to 11 inch drums. Given a scrape down and new black paint for good looks, new oil and additive, I read the ring gear to have 3.21's.
Sometihng like this would be head and shoulders above a preped/rebuilt 7-1/4.
Total additional cost was simply brake shoes and hardware since I had the drums from another donor car and stainless brake line for like $40 -$50 bucks.

3.21's were stock and not to hard to find. This would suite your build well.

(P.S. Caps are yelling.)

100_0826.JPG
 
dont put any sort of sticky or big tire on there. i think it will be ok for a bit. I ran a 7 1/4 in a 360 dart with little cheap tires, headers, performer intake and holley car. lasted many burnouts (would spin both for a few feet lol), some reverse burnouts and ebrake checks. it held up and got tore up, oh and fishtailing lol
 
If you use it "just for cruising" and "occaisional hard acceleration" the 7 1/4 will probably last quite a while. Burnouts, neutral drops, max-effort hole shots, or anything which involves slicks will wear it out real quick. Thats the bad news. The good news is junkyards are full of these rears, so if (when) you break it just go get a few spares for cheap.

As rumblefish indicated, an 8 1/4 would be something to keep your eyes open for. An 8 3/4 is probably overkill for a street driven 318, especially if dollars are an issue.

Bottom line, a 7 1/4 will hold up under normal "use" but will tolerate very little normal "abuse".
 
never heard those 2 words together... ( 7 1/4 and durability )

i have a 8.25 like mentioned above, w/ 3.2x's... i keave a 4 grand on slicks and its hel up for 2 years like that...
 
i agree with everyone, that 7 1/4 may not live for a long time if you punish it but a 8 1/4" rear will take alot more abuse than most thinks! my 8 1/4" rear has lasted a few years behind a strong 318 and the last 3summers behind a pretty evil 340 that easily smokes the tires from a 20mph roll, when the transmision kicks down into low gear ;) dont know about racing on a prepped track but for the street its ok
 
I had the 7 1/4 rear in my car when I first got it. Changed (not because it broke) to an 8 1/4, changed that (not cause it broke---Mopar Performance told me on the phone one time that they(8 1/4) will take 400 horse easy all day long) to the 8 3/4 I have now.

Lee
 
Well all said has its truth to back it, but on the other hand. I completely thrashed the orig. 7 1/4 in my valiant for about 3 years solid, that was durring the kick A$$ years of H.S. going to the strip every friday, leaving my parking spot sideways almost every time I went some where, and of course racing friends from light to light. I never did break it. That was with my 360/904 combo with 3 23s. I unfortunately had to swap to another 7.25 for some 276s so I could make a very long trip that never happened. I cant afford to get much now but I wish I had the other gears back anyhow! lol good times on behalf of the abused 7 1/4!!!! Ahhh heck itll be fine!!!!! besides you'll have a cool story to tell if ya' break it!
 
My 73 came with a 318/904/7 1/4, the second I installed a 4bbl and exhaust that little rear met it's maker. I didn't even get on it all I did was pull out of the carwash and into traffic and then KACHUNK. Swapped in a 8 1/4 out of a 74 dart in a u pull it yard for 50 bucks and never had any problems.
 
Getting ready to change out the 7.25 in my son's 68 Dart and replace it with a 8.75 unit. Need to backing plates for the 8.75...will the 7.25 backing plates work or where can I get a set??? Its the small bolt pattern on the axles..

Thanks
Rick and Rickey Jr.
 
My brother had a 66 cuda 273 4 speed car, 7-1/4 rear with 3.23's. First time clutch was dropped at 3000 the pinion shaft broke. But driven easily, it will last a long time.
 
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