Am I just lucky with my 7.25?

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jrc4y4

jrc4y4

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Hi all, I see a lot of nay sayers on the 7.25. I have a non sure grip 7.25 on my 72 Scamp with 2.76 gears. It's got a 318 bored .030, .454 lift cam, and 4 barrel intake and carb. Trans is a 904 with 2800 or so stall and shift kit. I have raced it at the track and ran mid to low 15's, done I don't know how many burnouts, launched hard with no tire spin, etc. and the back end is still holding up.

With that being said, I want to get some 3.55s in the back. It's 60 foot time is 2.3X and has no tire spin at all if I heat up the tires. Am I just lucky it hasn't blown? Or is just because it's not delivering all the power at the launch because the stall (no tire spin but it doesn't start going hard till car is moving about 25 mph)? I brought it to the track plenty before I put the stall in as well.

Has anyone on here actually installed gears on their 7.25 and made it work (don't shoot me!)? If I swap an axle, I'm doing shocks, springs, etc, whereas if I just do the gear, I'm doing that and a rebuild kit. Open to ideas but I am on a budget currently. Thanks!
 

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If you ever hook really good you may feel the pain. I know you don't want the hassle and expense of the upgrades associated with the large bolt pattern rear but it can be done on the cheap usually. Just spend a little time spotting up different junk yards for a B body 8.75 or A body 8.25 and lots of cars can donate front disc spindle setups. I've seen a few posts on 7.25 rebuilds but not sure what ratios are out there.
 
The SG unit is like 2X as strong as the one legger, I blew a one legger behind a 340 but it took a neutral drop going backwards down a driveway. Not your typical sutuation. In a light car, they may survive.
 
Not much strain on the 2.76's but id say its time for at least a 8.25 but hey you never know till you try it
 
Also depends on tire size. Spinnin aint winnin and grippin is rippin, when you hook thats when things break
 
My 2.76 open 7.25 came apart behind my stock 318... but it may have been one too many burnouts, which are really hard on it... ;)
 
That is a REALLY nice lookin car.
 
For the money and difficulty in locating parts it might be easier to just upgrade to an 8 ¾ rear. The like the 7 1/4 sure grip but it is not easy to find anymore.
 
Consider yourself lucky and change the rear to at least a 8 1/4. Why put money into a tiny 7 1/4?
 
pishta said:
The SG unit is like 2X as strong as the one legger, I blew a one legger behind a 340 but it took a neutral drop going backwards down a driveway. Not your typical sutuation. In a light car, they may survive.
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Yeah, I've never neutral dropped it. I have shifted from 1st to 2nd during a burnout contest but only did that once. If I'm on water, it spins both tires every time, if dry, one tire. So it does fine at the strip for what little I go.
 
71DodgeDemon340 said:
Also depends on tire size. Spinnin aint winnin and grippin is rippin, when you hook thats when things break
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It's tires are about 27 inches tall and pretty narrow (225/70R14). I have no traction issue off the line at this point if I heat up my tires for a couple seconds. It doesn't get raced regularly but I do launch it on the street a fair amount.
 
SGBARRACUDA said:
Consider yourself lucky and change the rear to at least a 8 1/4. Why put money into a tiny 7 1/4?
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I can get a gear for the 7.25 for $200-250 and an install kit for about $100. I didn't plan on putting in a sure grip until I HAVE to change the rear end.
 
I was able to find a sure-grip for a 7.25 years ago and had it rebuilt with 3.23 gears. At the time I had a warmed over 318 with a 2500 stall convertor. It surprisingly lasted about 4 years after much abuse; it eventually went bang when one of the pins holding the diff together came loose and had a nasty meeting with the ring and pinion. Long story short, upgrade to at minimum an 8.25. And that is a good looking scamp!
 
jrc4y4 said:
The 904 has been gone through: clutches, bands, shift kit, stall, etc.
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Doesn't really matter much (well, it kinda does actually) what has been done to the trans, if the rear end fails with a good driveline shock, the 'sprag' in the transmission can/might/will fail too.
But the problem is, you won't notice that right away. You WILL notice it the next time when the car is ran through the gears and the transmission will literally explode into pieces.

Nice car though.
Get yourself an 8-1/4" axle.
 
jrc4y4 said:
With that being said, I want to get some 3.55s in the back. It's 60 foot time is 2.3X and has no tire spin at all if I heat up the tires. Am I just lucky it hasn't blown? Or is just because it's not delivering all the power at the launch because the stall (no tire spin but it doesn't start going hard till car is moving about 25 mph)? I brought it to the track plenty before I put the stall in as well.
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That's because of the gear, putting 3.55's in it will put a smile on your face. I did the same thing when I got my car, I changed the stick and a few other mods and it was still a dog from a start.

I bought a B body rear, completely rebuilt it, installing a suregrip and 3.55's. Wow, what a difference it makes.

With that said, I would seriously look into swapping the entire rear out to at least an 8 1/4. Save your pennies and form a plan, and do it all at once. You won't be disappointed.
 
Good news! My buddy's neighbor says he's got an 8.25 that came out of a 73 Dart. Not sure if small bolt pattern or big bolt pattern. Either way I can get 15s on the back if BBP.

I will keep you guys posted. Thanks for all the input, I appreciate it.
 
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