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7 1/4 mods for corner carving?
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Author:  225dart [ Mon Mar 01, 2004 6:23 pm ]
Post subject:  7 1/4 mods for corner carving?
is there anything i can do to make a 7 1/4 rear stronger for corner carving/ spirited driving? for that matter what about an 8 1/4 also seeings howthey are built virtually the same. does anyone know if you can have 8 3/4 ends put on either housing and upgrade to bearings that will fit the stock 7 1/4 or 8 1/4 axles and those housing ends? my biggest fear is that a c-clip will break at an in opportune time will hanging it out in a corner.

--chad
Author:  kesteb [ Tue Mar 02, 2004 4:15 pm ]
Post subject: 
The 7.25" axles used in the A-bodies do not use C-clips. These axles are retained the same way as the 8.75". The 8.25" and 9.25" axles use C-clips.
Author:  Doc [ Tue Mar 02, 2004 6:52 pm ]
Post subject:  Re: 7 1/4 mods for corner carving?
Quote:
is there anything i can do to make a 7 1/4 rear stronger for corner carving/ spirited driving? for that matter what about an 8 1/4 also seeings howthey are built virtually the same. does anyone know if you can have 8 3/4 ends put on either housing and upgrade to bearings that will fit the stock 7 1/4 or 8 1/4 axles and those housing ends? my biggest fear is that a c-clip will break at an in opportune time will hanging it out in a corner.

--chad
Do yourself a big favor and swap-in an 8 3/4, you will be money ahead in the long run.
If you really are stuck with the "peanut" 7 1/4, there are some so called "Heavy Duty" parts and even a limited slip unit for them. (good luck finding that stuff)
Even with alot of work, the axle bearings, carrier caps, bolts and the spider gears are just too small to take any kind of serious performance work.
DD
Author:  225dart [ Wed Mar 03, 2004 5:22 am ]
Post subject: 
kesteb, hey thanks, i just assumed it was a c-cliped axle rear.

i know doc, i really should put one in but what im trying to avoid is costs. i sold all my 8 3/4 stuff when i put a dana 60 in my big block dart and then i picked this car up a year later. figures, huh? my worst fear was that of having an axle fly out around a hard corner but if they are not c-cliped then i wont worry about it. besideds, people parctically give 7 1/4 stuff away---except for suregrips :roll: . i think im going to stick with the 7 1/4 for now as i haven't broke anything yet but if i start on a breaking streak like i did with my big block car, i will certianally update.

thank you for your info and enlightening me gentleman

--chad
Author:  Doc [ Wed Mar 03, 2004 6:07 pm ]
Post subject: 
Spider gear failure is the biggest problem with the 7 1/4
One thing you can do to help reduce the failure rate is to shim the spider and side gears as tight as you can. I have gone as far as squeezing-in a motorcycle valve spring between the spider gears to add some pre-load. (the spring has the spider gear cross pin running thru the center)
This is a common "trick" which is sometimes called a "poor man's posi".

The other failure point are the carrier hold down caps. The only low cost thing to do there is to inspect them carefully and use good quality fasteners with large flat washers under the heads, to help spread-out the load.
DD
Author:  steponmebbbboom [ Thu Mar 04, 2004 8:14 pm ]
Post subject: 
That's an interesting suggestion. Are there any copper spherical washers behind the side gears that will wear out if this preload is put on them? Would I be safe doing this on a daily driver, or would you only recommend this for the strip? Precision Spring here has tons of spring overruns free for the taking. Any ideas what dimensions/spring pressures I should look for?

*rubs hands together*
Author:  Guest [ Mon Mar 15, 2004 4:48 pm ]
Post subject: 
don't sweat the 7 1/4..... my '64 valiant convertible has 63,000 HARD miles on the original 7 1/4 sure-grip & it still works fine.... truthfully the slant 6 does not produce enough power ( sans slicks ) to break the unit, pound the crap out of it & be glad you are driving a Mopar !
Author:  Doc [ Mon Mar 15, 2004 6:28 pm ]
Post subject: 
Quote:
don't sweat the 7 1/4..... my '64 valiant convertible has 63,000 HARD miles on the original 7 1/4 sure-grip & it still works fine.... truthfully the slant 6 does not produce enough power ( sans slicks ) to break the unit, pound the crap out of it & be glad you are driving a Mopar !
The key difference here is the addition of the sure-grip carrier.
With the sure-grip, the 7 1/4 is much stronger. These have a much stronger carrier and pre-loaded pinion gears / side gears that take the load much better.

With a tight 7 1/4 sure-grip I have successfilly broken axle shafts and even broke the yoke off a pinion. (failed right at the end of the nut thread before the pinion stem increased in size for the front bearing.)
DD
Author:  Charrlie_S [ Tue Mar 16, 2004 4:41 am ]
Post subject: 
I had been running 7 1/4 sure grip rear since 1974 untill last year. I thought I was pushing my luck running slicks on a 3200 car, doing 1.79 short times on nitrous. I did run the 7 1/4 on a turbo slant and for 2 years on nitrous. Did not break any, but did go for the 8 3/4.
Author:  sixinthehead [ Tue Mar 16, 2004 9:52 am ]
Post subject: 
FWIW, the LBP 7 1/4 axles used larger wheel bearings than the early axles and the axles were then tapered so the centers stayed the same. They should, therefore, be stronger at the wheel to handle higher cornering loads. I'm running a SG 3.55 7 1/4 behind a 318 auto in a 65 Val, and it's been great for over 100,000 mi! With KYB's and both bars, it corners like mad. The reduction in unsprung weight relative to the big axles helps it stick over bumps.
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