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usual 9 inch going into a nova questions

4K views 25 replies 8 participants last post by  big gear head  
#1 ·
i have a 75 nova and i am hopefuuly installing a 9 inch rearend out of a late 50's truck. it has disc brakes and 370 gears. i am going to install a mini spool also. the rearend has huge drums. i paid 175 for the rearend. well i am worried that with the install my stock driveshaft wont work due to size and getting a u joint to fit. also how hard of an install is that 9 inch going to give me?
 
#2 ·
If the width is right and the pinion offset is close then all you have to do is cut off the old brackets and weld on a set of Nova spring perches. The drive shaft might be too short, especially with the truck yoke. You might need to get a longer drive shaft. You know that the bolt pattern for the wheels is different.
 
#3 ·
Ok you say the rear end has disc brakes then you say it has huge drums, which is it?? No your stock drive shaft won't fit, you may have to have a complete custom built shaft made. If your stock one is long enough and is the proper diameter a good drive line shop may be able to fit and weld a 1310 or if need be a 1350 universal that will match up to the yoke on the 9" rear.

Your last question is totally up to your mechical knowledge and abilty.
 
#5 ·
Just wondering, is there something wrong with the 8.5 10 bolt that came in the car? What are you going to do with the 10 bolt?

You can get reproduction Nova spring perches from Moser Engineering, Tom's Differntials and several other places. They cost about $60 a set.
 
#6 ·
nothings wrong with the 10 bolt in it. i just dont think it will be strong enough for what i am trying to do. i have a 327 10.1 compression forged, cam is about 525 lift and 280 duration, the heads are cast but port and polished 1.94 valves bronze guides. i have a vic jr and a 750 dp holley. i have hedman big comp headers. 1.6 roller rockers. 7 qt moroso pan, mini torque gear reduction starter. msd hei dist 125 shot of nitrous. alummy rad 16 electric fans. a serpetine belt set up. it has a non posi 372 gear. i want a 411 gear wth a spool. will the ten bolt work and whats my guess hp and torque. cam is a solid flat tappet
 
#7 ·
The 8.5 10 bolt is a strong rear end when built right. I have built many of them with a new 30 spline Eaton Posi and 30 spline Moser c clip axles. This upgrade makes them comparable to the 12 bolt. If you were not so far away I would buy it from you.
 
#9 ·
Rickracer said:
There are a bunch of cars running 10s and high 9s on beefed up 8.5 rears, I don't think you're there yet, ;) :D
Last time I really looked there were guys in the mid 8's in the 1/4 on a beefed up 8.5" 10-bolt. Everything in them is close to the same size as a 12-bolt except the axleshafts, upgrade those, add a spool and the gears of your choice, a rear girdle cover, and weld the tubes to the center and you will be stronger than a junkyard typical 9-inch.

I've run a completely stone stock 8.5" with Richmond gears into the mid 11's, 1.6x 60' times for 15 years in a all-steel '72 Nova, lifting the front tires 6", 400+ 1/4 mile passes and have yet to break anything.

These are a lot tougher than people know or give credit for, it is the 8.2" 10-bolt that is a weak player.

Stay with what you have and beef that, don't waste your money doing the 9" Ford IMO.
 
#11 ·
well sounds good. i actually did not know that it was that strong. my only question is if i leave the 28 spline will they hold up good? i am just running short on the extra cash. if i mini spool do i have to do the clip eliminators if i dont will it hold up. with my set up what would make me the best 1/4 mile time 373 or 410 gears for that 10 bolt
 
#12 ·
I've run 28 spline for a long time in my Nova, but this is with a posi unit, spools are a lot harder on axles. I've got C-clip eliminators and would consider them manditory with a spool, just like the NHRA/IHRA track rules say - Any locked rear must have positive retention device on the axles.

Would need to know more about the torque converter and trans to pick a gear ratio, but if you are planning track time I am going to say you will be happier with the 4.10's. You can always try the 3.73's that are already in the rear with a spool or posi unit and see what they are like just to get an idea of which way you might want to go.

Your 327 will be happier with 4.56 gears if you don't have to hit the highway often, need to get it revv'ed up to get its power.

15 years ago I did a '76 nova for a girlfriend(her family was into racing too) with a 9-1 compression short rod 383, home ported 487x smogger heads, 2.02 valves, Crower 268/276° @ .050" .545"/.563" lift 108° seperation Solid cam installed 7 degrees advanced per Crowers instructions, Vic Jr and 750 Holley Vac Secondary, 1-5/8" headers, TH-350, 2800 stall, 4.11 gears. Went 12.50's with 12.10 potential, totally stock 28 spline 8.5" rear with factory Eaton posi from '75 Trans Am. Car was slow off the line(1.8xx 60" times) but had a good top end charge at 112 mph. 26" tall tire(McCreary/American Racer G-60/15 "dirt compound" IMCA tire makes a great DOT legal "cheater" tire). Car really needed 4.56 gears, or three more points compression LOL

There is a lot you can do to lighten the car in the bumper area - there are those heavy gas dampers that hold the bumper, and that heavy inner reinforcement beam inside the bumper shell on both ends of the car, almost 200 lbs in this excess stuff alone.
 
#14 ·
A mini spool does not require c clip eliminators. The c clip axles will work. A mini spool is designed for dirt track racing. If I was building this rear end for drag racing I would use a regular spool and a set of 30 spline axles with c clip eliminators. If you wanted to go even bigger I have a new set of 33 spline axles with c clip eliminators that a friend ordered and decided not to use. You can get a good deal on them, but you will need a 33 spline spool to go with them. I just wouldn't feel right about the stock 28 spline axles with a mini spool.
 
#15 ·
Agree with all of this ^^^, a mini spool is a poor choice on pavement(even though I have friends who have done it) and by design puts all of the power load on that skinny little cross pin in the case. IMO C-clip eliminators are mandatory with the mini spool even though you can install it without them, it is just safe insurance as you run a much greater risk of breaking a stock axle with the spool.
 
#16 ·
well i ahve the next two days off. so i can going to be getting alot done. i need to knwo how much you wanted for those axles big gear head? i am going tomm morning to hopefully find a posi in the u pull junkyard. hopefully i find something good. i was thinking of getting a 4.56 gear for the reason of it being a real redlight beast. but could i still drive like 70 and still punch it down the highway?dont need to go faster than 100
 
#17 ·
A 4.56 isn't going to be any fun on the highway. Your cruising speed is probably going to be around 45 MPH. I'll have to ask about the price onthe axles. They cost $495 new with the c clip eliminators. He will probably sell them for around $400. You will need a 33 spline spool to go with them.
 
#20 ·
well i actuall y havent installed yet but i know i have the room oin the face of the radiator. i am going to be looking into a posi over the spool. i only want to mess with the rearend once. can i do 65 with
410s?
 
#23 ·
If you are going to use a posi then you will have to use 30 spline axles instead of 33.

I have 4.11 gears in my car and I can run 80+ without a problem, but I have 32 inch tall tires. That makes a big difference. My 427 doesn't like to run below 2500 RPMs, so the 4.11 works well for me. A 26 or 27 inch tall tire is going to increase the RPMs a bunch with the 4.10 gears. If you can run a 28 inch tall tire then the 4.10 might be fine for you.
 
#24 ·
they make posi for 28 spilne dont they? they are all on ebay and what not. I wish they had a a 390 gear but all i have of a choice is 373 and 410, guess i will go with the 410 and just get bigger tires for my dialeys
 
#26 ·
Be carefull with those ebay differentials. There are a lot of people on there selling the Governor Lock as an Eaton Posi. The Gov Lock is made by Eaton, but it is not an Eaton Posi. If youa re looking for a stock 8.5 differential then you will be looking for a Traction Lock, which has the S spring in the center. Be sure that you get a 3 series and not a 2 series. The 3 series has the casting number 410408. Don't get the 410409.