Sure grip 7 1/4 strenght?

[Charrlie_S]

In short, yall play around with your little 7.25s. I'll be wavin at you when I drive by in something with an 8.750, or 8.25.

I'm not backin off my opinion. Yall do what you want, but the FACT is that stock slant six cars BROKE 7.25 rear ends. They are weak, sure grip or not and I don't give a rat's *** who tells you some who shot john about how long they ran one behind ten thousand horse power for 150 years, the FACT is if you run a 7.25 behind pretty much anything with any semblance of power, you may end up walking. "I" am not going to ever stand up and tell somebody on here or anywhere else how "good" a 7.25 is or that they should run one. Because they SUCK.

Some may say something REALLY stupid like "the rear tires break loose so the rear end will hold up". Lemmie clue you in on something. Ever heard of spider gears? Got any idea how fast they turn? The answer is REAL FAST. And here's a little physics lesson for you. The smaller the diameter of a gear, the faster it's spinnin. Get me? Here's some more physics for you. Even if it's a sure grip, the axles CAN spin independently of each other. Got any idea how fast ONE SIDE axle and spider gears turn? That's right, follow along with me. There are two axles so that means if only one is spinning, it's spinning TWICE as fast as both together. Yeah. It's COOKIN. And on that TINY LITTLE cross shaft that the spider gears ride on building up all that heat.

The 7.25 is the smallest most fragile rear end from Mopar. They will tear up if you sneeze on them good. Just because some few got lucky doesn't mean it will always happen. But believe what you want and good luck with that. lol

I'll put it like this. If ALL I had was a 7.25 under my car, I would wait until I swapped it out before I drove the thing. Simply because I don't like walkin.

I'm not saying to put a 7 1/4 in any car. I am saying they are not as weak as some say. I ran mine because the NHRA rules said I had to. Then when the rules changed to allow a better rear, I just stayed with the 7 1/4. When I found an "afforable" 8 3/4, I swapped to that. Then I built a "low buck" car, which didn't allow spending more then $500 just for a rear, so the well used 7 1/4 went in. When the sure grip clutches started slipping, rather then put new clutches in the 7 1/4 I built a 8 3/4 and installed it, as security, since I no longer had to meet my budget restraints.

In my opinion, it is a matter of money, whether to keep the 7 1/4 or up grade to something better. I personally can't see spending the kind of money for a stock "A" body 8 3/4 that most people want to charge. Plus parts (axles, brake drums, etc) are getting hard to find.

I like a "dropout" center, because I drag race, but I would probably use a 8 3/4 from a bigger vehicle (cheaper) and have it cut down to fit an "A" body, or maybe a 8 inch Ford (almost a bolt in). In a street car, or even a drag car, where gears are not going to be changed, consider a 8 1/4.

PS: My 7 1/4 always had slicks at the track. Granted mine is a slant six, but made over 350 ftlbs of torque, 8 inch converter, and would 60 foot in the 1.8 to 1.90 range. Since I put the 8 3/4 in I am now about 400 ftlbs of torque, and 60 foot in the 1.72-1.79 range at over 3200 lbs.

 

[Charrlie_S]

Charrlie, We did the gear swap in a "67" 904 case and yes you have to change the front pump/input from a 68 up. Can't say about a 66 case for sure.

I think the 66 and 67 should be the same.

CharrlieS yer rite on the no-go gear swap, the splines on the output shaft are diffrent 'bummer'

That's what I found, when I tried to do the swap on my 65 trans, and you can't swap to the later output shaft, due to the rear pump, cable park assy, and flanged output. It might be able to be done with some machining, but I don't think it is worth it.

 

[1970Duster]

Simple go buy an 8.25 rear out of an A Body (they're pretty cheap). Then go hit the junkyard for a 96 or older Jeep Grand Cherokee. Once the jeep is found pop the rear disc brake setup off and set that aside for you to buy. Pop the axles out and throw them in the Jeep. Pull the gears out of the jeeps rearend (most have 3.55 or better) and take that sure grip unit as well. Now take your new acquired gears, suregrip Unit, and rear disc brake setup and go up front pay the people and go home. Install all that stuff you just bought and install them into your A Body 8.25 rear. It's a simple bolt on/in process. You now have a much stronger rear (than the 7.25 piece of crap) with 3.55 or better gear with suregrip and rear disc brakes ready to bolt in and go! Enjoy.

 

[Hipo65]

1970Duster i like yer idea,qustion those jeep axles are not sbp are they? if so thats exctly what ill do. I currently have an abody 8 1/4 drum to drum. Belave me i know theyll take a serious beating!

 

[1970Duster]

1970Duster i like yer idea,qustion those jeep axles are not sbp are they? if so thats exctly what ill do. I currently have an abody 8 1/4 drum to drum. Belave me i know theyll take a serious beating!

You can not use the jeep axle in an A body rear (the jeep axles are too long). In the way I was talking you use the A body axle out of the A body 8.25 rear.
Unless you re-drill the axle to sbp it will be BBP. 14" BBP rallyes are not hard to find/come by.

 

[Hipo65]

Gotcha,thought that was to easy. Thanks.

 

[one mile]

I had the same delima as you Hipo65 while I am still building my Daughters '65 Barracuda. I decided to leave the Sure Grip 7.25 for now in the car (money tight right now) BUT I am gathering parts for a 8.75 and will buy strange Axles the right size and bolt pattern because I have a set of wheels I also want to keep. Drop out gears and strength are the biggest plus for the 8.75 (stating the obvious). Alot of good knowledge here on this Forum and alot of it is First hand, some not. GOOD LUCK no matter what you decide. Keep Us Posted ! Tim (Dad)
:thumblef:

 

[Hebrews10:26]

Hello Hipo65!

From my understanding its the 7 1/4's axles that are weakest of all the internal parts of this particular rear differential. Most 'none sure grip style' 7 1/4 rear ends fail due to the axle splines stripping away. The idea is that distributing the torque between both axles will prolong the life span of the axles and give the 7 1/4 more ability to handle increased loads/torque output.

 

[1970Duster]

Unless the axle shafts are junk there is no reason what so ever to change the axle shaft if you can keeping the 4" (why people want to keep that is WAY beyond me, when 4.5" pattern has WAY more wheel options).

 

[sazzlefrats]

Got a friend with a 375hp 318, his 67 cuda tore up the first 7 1/4. I think he said he launched gears through the case. His 2nd 7 1/4 he shredded the gears inside which was good so he just had to replace the gears. He is working on his next set of gears right now, I can't hear the howl, but he says its starting already.

If you aren't shocking the rear end you'll be find, but if you do what my friend's been doing... yeah short life.

 

[my66fish]

Hipo 65, I have a 7 1/4 SG with 3.23 gears in my 66 fish and I have a worked 273 pushing 325 hp, with a 904 and a 2500 stall custom made converter, and I have no issues with it to date. I also didn't want to loose the SBP because I have a beautiful set of Cal Shelby slots on my baby.