Rear End - Is it Strong Enough?

[76Vett]

I have a 76 L-82, rebuilding engine and putting in a 700R4 trans. Car will be a driver but will see occasion 1/4 mile at the local drag strip. I'm building the car to run mid to low 12's. Presently have stock rar with 3:08 gears and will put in 3:55's when I get them. Is the stock rear, half shafts, etc, strong enough or should I plan on an upgrade there also.

 

[Hib Halverson]

To run mid to low-12s will require rear axle mods such as different axle ratio, premium diff case, HD clutches, upgraded fasteners and professional assembly. You'll need those, 3.55s. You'll also need 3" halfshafts the 2.5-in drive shaft.

The 700R4 will need to also be modified to improve its reliability/durability with the 450-500 hp you'll need to get into the low 12s. You might need a high-stall torque converter as well.

Needless to say, the L82 is going to need a lot of changes to make that kind of power.

 

[GTR1999]

I've built plenty of these to handle up to 1000hp, but none are in the stock configuration. You will find guys telling you the stock diff's will hold up or a stock rebuild is all you need, I wouldn't make that statement. HP, traction, and driving style will play a huge part in how long the diff last.

A 76 diff is ok, has some good points and some weak areas. The posi cases are rough and will crack under loading like hammering the gears. The clutches used are what I call snowflakes and will break under load as well. The ring gear bolts should be the hardened shoulder type with lock washers but GM starting switching over to the flange head bolts around then and many of those backed out. The stock 76 side yokes are soft and usually have well over 050" endplay in them. I replace all those parts with much stonger parts but I never use Fiber coated clutches.

If you're under 450hp and blueprinted diff may be all you need, again depending on traction and use. Over 450hp to maybe 550 I build what I coined as the Super 10's which have a lot more features to them then any stock unit. Once you get over 550hp I never use a 10bolt, I fit the 12 bolts and use Tom's gears for the setup.

You can find all the pictures on the build on DC or just PM me for the link. If you have questions just let me know. 373 may be better suited for your application as well.

Good luck