chpseat987

I have a 72 Nova I just baught on this site and the guy said the rear end is a Chevy 10 bolt 4:56 built. Thats all I have, I have not opened it up yet but my Chevy truck 1989 has a 10 bolt under it and looking at the 2, the one under my car the pumpkin is twice as big as the one under my truck. Is there different 10 bolts how do I find info on the one I have I am scared my new 550 to 600 Hp 427 is going to rip it out from under the car. Are there casting numbers? or any way I can dertermin just what i have

TopspeedLowet

If you are not embellishing on your power #s you should remove the tinker toy piece for something more substantial for the long term. 10 bolt means almost nothing but how many bolts hold the ring gear on the carrier. It could be a GM 8.5" gear set like the grand national and older pickups used to use or it could be a trans plant and has a 7.5/8" ring and pinion. the low power chevelles used a variation of this set up 8.2" as well. you will need to remove the cover which by bolt pattern alone will tell you most of what you need to know. your parts store usually has a picture of the gasket surface for each which is an easy way to tell if it is 8.5 of 7.625 job. the 8.5 I have used with some luck with 500 HP on it but requires frequent checking to be sure you don't destroy it. Your axles will be toy 28 spline if you have 7.625 car. some Tahoes used 30 spline but both are stock wimpy pieces so spooling should not be concidered ever. I hope this helps you get started.

chpseat987

Wow ok so ill remove the cover and see if there are 10 bolts holding the ring gear on the carrier would i be able to measure the ring gear as well to determin what it is?

TopspeedLowet

The size is part of the gear set # often clearly stating. If you have an aftermarket gear set it will be noted on the ring gear. If the cover is smooth it is likely a 7.625 if it has a bump out for the ring gear like a 12 bolt it is likely a 8.5. When you see the carrier bearing caps, you will be on board with what I mentioned about TOY piece.

us7race

You can sometimes get lucky and it may still have the stock pinion nut which would be 1 1/4 if it is a 8.5
But if it is a 1 1/16 it is an 8.20

chpseat987

After a couple friends looked at the rear end it does have scars on the ring gear but they are richmand after market gears so the rear enf has been upgraded, even though it still is a 10 bolt, I dont have alot of money to fix or upgrade because of what the engine is costing me, So I am going to run it until it goes, but I noticed that there is a re-in forced cover for sale with bolts that touch the main caps with only about 10 pounds of tourque on them for 150 bucks, If I was to get one of these covers would it help or would I be wasting my money, hopefully the rear end will make it this season and next winter I can save some money and I want to back Half the car with ford 9 and make a big tire car. :?

TopspeedLowet

You are going the right direction. I ran that with billet caps with studs and that is about all you can do to strenghten a GM piece. you will be ok without the billet caps. That is just all one can do to prevent the carier from being ejected out the rear.

us7race

With my 8.5 10-bolt (stock caps and cover) I have only broken 1 set of gears and that was right at the end of this past season.
My 60' are 1.32-1.36 at 2865lbs. I wouldn't be worried at this time. JMO.

TopspeedLowet

Nice looking shot! You should advertise for GM powertrain / proving grounds. ('')

JEFF69Z28

CALL MOSER YOU CAN GET A SPOOL 33 SPLINE AXLES AND C-CLIP ELIMINATORS FOR ABOUT 650.00.33 SPLINE AXLES ARE GOOD UP TO 1100 HP THATS WHAT MOSER TOLD ME AND THATS WHAT I GOT FOR MY 8.5 10 BOLT OUT OF A BUICK GN.