7.25 gear upgrade or 8.75

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mikeyb0013

mikeyb0013

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I just had my 318 redone and now I'm considering what to do with the rear end. I was considering changing the gears in the stock to 3.55's or find an 8.75. Any suggestions on pro's and con's?

Thanks

Mike
 
If you can find a sure grip unit for the 7 1/4 it may live a while. But by the time you buy a good one and the gears and bearings and do the install your going to be well on your way to the cost of the 8 3/4.
 
How hopped up is your 318? A 7.25 with a sure-grip is a surprisingly stout piece as I ran one at the strip for over a year on slicks. The s-g units are not easy to get though.

I will warn you quickly about 8.75 rears though as it is to easy to tie up $1200-$1500 in one without trying. It's not a bad idea to use one if you
plan on adding more power down the road. The s-g units new are anywhere from $600-$800.

For a 318 car like you have, I'd look for an 8.25 and find a sure-grip; The rears are not that expensive and the s-g units are not terribly overpriced either. New sure-grip units for these are in the $300 range. I've seen them as cheap as $50 in used condition though.

Hope this helps
-M
 
I'm pretty sure you'd be kicking yourself if you put any money or effort into the 7-1/4. They are truly weak. You might consider an 8-1/4 though......
 
Definitely get the 8 3/4. You will not be disappointed. I think the 7 1/4 axle was just a cheap weak axle to get a mopar car off the assembly line...
 
Yes deffinately get a 8 3/4..you can blow up a 7 1/4 with a slant six...
 
Thanks guys. I'm pushing 330 HP with the 318. I think the eventual goal is to swap it again for a 360. I'm hearing that the 7.25 can work but an upgrade of some sort is probably the way to go. Thanks again for the input it's nice to have a knowledeable sounding board to bounce this stuff off of.

Mike
 
grimreaper said:
I'm pretty sure you'd be kicking yourself if you put any money or effort into the 7-1/4. They are truly weak.
Click to expand...

I agree my 4 cylinder toyota is a 7.5 inch rear and, youve got 4 more cylinders AND triple the hp. just go with something better. if you invest money into the 7 1/4 and you blow it up youve wasted your money. not to mention youll be concerned about blowing it up. if you get a good rear end you wont have to worry about it. ive got a grand into my 8 3/4 with a suregrip unit and moser axles. you might be able to go cheaper if you get a ford rear end or something but that might take some fabrication. but think about it after finding a suregrip getting gears then if you have someone install it id imagine thats at least 500 bucks rite? i wouldent want to throw 500 bucks away if it breaks. but its your call.
 
stroked 340 said:
Yes deffinately get a 8 3/4..you can blow up a 7 1/4 with a slant six...
Click to expand...

My modified/6 could not blow the 7.25 Sure-grip I had. An open 7.25 rear is a bomb waiting to go off and I agree at his hp/tq level he is best to go with an 8.75.

An 8.25 would be ok for now, but if you go with a 360 later on; an 8.75 now is something that can stay with the car as it gets more powerful.

You'll need a different driveshaft and different shock plates to begin your upgrade. Good luck
 
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