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Discussion Starter · #1 ·
My 1963 Nova SS coupe still has its original rear end. I have researched all the words of wisdom stating the overall weakness and part replacement problems along with the 4 lug restriction of the original rear end. So I am stuck with the fact I will need to install a later 5 lug rear end. Also as I plan to install a high powered 327 and 4 speed some day I must consider the very special 4 speed I plan to install. I have a very rare what is called a BRUTE T10 all cast iron 4speed. It has a 342:1 first gear so I am looking for a rear end that can support a 2:29 or 2:56 gear set for good highway mileage. I want to use the transmission as a 3 speed with overdrive. I know that the original rear end can only go as low as 3:08. Is there any bolt in rear ends can I use, that will support these high gear sets? I would like to use a GM rear end if possable and only spend a reasonable amount.
 

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Absolutely nothing exists in your bolt-in stipulation, nothing.

The 8.5/8.6 10 bolt from and 2wd S-10 Extreme is the only thing strong enough and close enough to the right width....but it isn't just a bolt in. You'd have to move the spring perches on the housing.
It's also pretty rare, and commands top dollar on the used market.
Then you'd have to change the gearing, since notheing but 70's smoggers used that low rear gearing....The S-10 stuff will be 3.42 or 3.73.
And you'll actually have to find a good used set of those gears, because you can't buy thenm new anymore in those ultra low ratios.
Only other possibility is the 8.5" from mid 80's Olds 442/Hurst Olds or Buick Grand National/T-Type....it is right width but coil spring....you would have to cut all the suspension mounts and spring cups off, and weld leaf perches on.
It also commands top dollar on the used market because it is fairly rare, for transplant in to most of the other G-body cars that only got 7.5", like the Monte Carlo SS, Cutlass, Regal, Grand Prix
It also will only have 3.23/3.42/3.73 gears, nothing any lower so you'd have to swap those.

Everything else GM 8.5/8.6",... Camaro, Caprice, Truck is too wide or is the weak 7.5" 10-bolt (originally from Monza/Vega)that isn't worth using.

You don't want to hear it, but an 8.8" Ford swap would be the only low budget cost way, mostly due to tons of availability.

Another possibilty is narrowing a GM 8.5" that is too wide, from an 1970-81 Camaro, '71-76 Caprice/Impala, '73-77 Chevelle/Malibu/Monte Carlo that already has the low gear you want, and buying custom width axles for it from someplace like Strange Engineering, Mark Williams, Moser, Dutchman, Yukon.
The used market will probably also turn up a used 2 series factory 8.5" positraction differential, they pop up on Facebook, Ebay, etc.
2.56-Down fits 2 series carrier, 2.73-5.13 fits 3 series carrier.
 

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I don’t know that much about the Ford 8.8 axle gearratios but most of the ones people are looking for have 3.73:1 gears w/posi and disc brakes. I not sure if the 2.29-2.53 gears would even be available for it..

A Ford 9” is kind of a standard in the hotrod industry and people building cars to compete in land speed competitions don’t need differential launching gears like high 3.73 and up rather the lower ratios for top speed.

A GM 8.5 would be the next best option as there should be a bunch of them around with the door stopper gear sets you are looking for. They will all be too wide but that can be fixed..

We have a member here that has a differential shop in Northern California @JBimmolate. Maybe he can chime in with his thoughts.. Alternatively, you could contact him directly at the shop.
 

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Absolutely nothing exists in your bolt-in stipulation, nothing.

The 8.5/8.6 10 bolt from and 2wd S-10 Extreme is the only thing strong enough and close enough to the right width....but it isn't just a bolt in. You'd have to move the spring perches on the housing.
It's also pretty rare, and commands top dollar on the used market.
Then you'd have to change the gearing, since notheing but 70's smoggers used that low rear gearing....The S-10 stuff will be 3.42 or 3.73.
And you'll actually have to find a good used set of those gears, because you can't buy thenm new anymore in those ultra low ratios.
Only other possibility is the 8.5" from mid 80's Olds 442/Hurst Olds or Buick Grand National/T-Type....it is right width but coil spring....you would have to cut all the suspension mounts and spring cups off, and weld leaf perches on.
It also commands top dollar on the used market because it is fairly rare, for transplant in to most of the other G-body cars that only got 7.5", like the Monte Carlo SS, Cutlass, Regal, Grand Prix
It also will only have 3.23/3.42/3.73 gears, nothing any lower so you'd have to swap those.

Everything else GM 8.5/8.6",... Camaro, Caprice, Truck is too wide or is the weak 7.5" 10-bolt (originally from Monza/Vega)that isn't worth using.

You don't want to hear it, but an 8.8" Ford swap would be the only low budget cost way, mostly due to tons of availability.

Another possibilty is narrowing a GM 8.5" that is too wide, from an 1970-81 Camaro, '71-76 Caprice/Impala, '73-77 Chevelle/Malibu/Monte Carlo that already has the low gear you want, and buying custom width axles for it from someplace like Strange Engineering, Mark Williams, Moser, Dutchman, Yukon.
The used market will probably also turn up a used 2 series factory 8.5" positraction differential, they pop up on Facebook, Ebay, etc.
2.56-Down fits 2 series carrier, 2.73-5.13 fits 3 series carrier.
we take an 8.8 and cut it down with a mitler jig.
upgrade axles, center section, etc.
If you can weld this is a good option.
 

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Am I the only one that doesn't think a 3.42:1 first gear is all that low?
I didn't know your other gear ratio's but with a 3.42 first, 1:1 high and only a 26" tire this is what speed and rpm's look like. Left is 3.08 and right is 2.29 rear gear. It's even more absurd if you have a taller tire.
422300
 

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Am I the only one that doesn't think a 3.42:1 first gear is all that low?
I didn't know your other gear ratio's but with a 3.42 first, 1:1 high and only a 26" tire this is what speed and rpm's look like. Left is 3.08 and right is 2.29 rear gear. It's even more absurd if you have a taller tire.
I know that T5 1st gear ratios for a V8 F body are 2.95 and smaller engine applications have ratios ranging 3.35, 3.50, 3.76, 4.03 probably a couple more but the 3.42 1st isn’t that low by comparison. It’s just the application to a V8 by today’s standards is a little unusual..
 

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By no means am I an expert on this issue but if I remember correctly I swapped out a 10 bolt 1960's Camaro rear end in my 1963 Nova SS in high school and it fit without any changes. Am I wrong?
 

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Discussion Starter · #8 ·
Am I the only one that doesn't think a 3.42:1 first gear is all that low?
I didn't know your other gear ratio's but with a 3.42 first, 1:1 high and only a 26" tire this is what speed and rpm's look like. Left is 3.08 and right is 2.29 rear gear. It's even more absurd if you have a taller tire.
View attachment 422300
As I said I want to use the 4 speed as a 3+1 overdrive. Normal acceleration in the first three gears then use 4th as an overdrive. I want the car to appear to be period correct, yet drive better on the highway. With normal speed limits approching 75mph and most people driving 89-90. With a 3:08 gear your looking at 3500-4000 rpm at these speeds. Thats too high for me!
 

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I just went through this. My 10 bolt 8.2 was shot so I could either pile some money into it and still have a weak 8.2 or upgrade. There is no cheap upgrade as the diff is narrow and the perches re close to the backing plates. Perhaps you can find a used diff and have it cut down and buy new axles and hope the gears and bearings are ok and then there is the brakes to deal with. If you buy something new to bolt in it doesn't matter much if its a 9 inch, 12 bolt or Dana 60. The 9 inch could be cheaper by a few hundred (Currie) depending on where you go. The 12 bolt was the most expensive. I started with a narrowed Dana 60 with Ford big bearing ends for $450 (Cdn$) and it still cost $2500 all in and I did the assembly and used my existing brakes. You then have to fool around with brake lines, yokes, drive shaft lengths, etc. Sometimes I wonder if I could have lived with a rebuilt 8.2 :) It a lot of work and $$$.
 

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As I said I want to use the 4 speed as a 3+1 overdrive. Normal acceleration in the first three gears then use 4th as an overdrive. I want the car to appear to be period correct, yet drive better on the highway. With normal speed limits approching 75mph and most people driving 89-90. With a 3:08 gear your looking at 3500-4000 rpm at these speeds. Thats too high for me!
What size tire are you running?
 

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Here is the rough formula we use for rpm:
The 336 I think works with no converter slippage so this should work good for a 4speed car:


rpm = (mph x Rear End Ratio x 336) / Tire Diameter

2.56 rear gear x 336 x 70mph/26” tire:
2316rpm
 

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By no means am I an expert on this issue but if I remember correctly I swapped out a 10 bolt 1960's Camaro rear end in my 1963 Nova SS in high school and it fit without any changes. Am I wrong?
The '67-69 Camaro/68-74 Nova 10-bolts are 2"-2.5" wider than the '62-67 Rears
Spring perches are also 3/4" different ....you might have just flexed the springs enough to fit without realizing you did it, at just 3/8" per side.
Wheels would have gotten pushed out 1"+ each though.

NovaResource - Nova Rear Axle Codes
 

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I'm not 100% sure, but I don't think the 4 speed transmission will give you the "overdrive" you're looking for... you may have to go to a tremec type transmission to get overdrive..
 

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A 5 speed sounds like a better option to me and won't look any different when the car is on the ground.

By increasing the rear gear ratio you raise all of your gears not just 4th. I'm thinking if you have a high horsepower 327 that likes to rev (small displacement engine likely wants to run higher in the rpm to make hp) it isn't going to like running down real low in the rpms and 1st gear might suck.
 

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A friend of mine has a 37 Pontiac with a Gbody front frame clip with a 350/350 combo and I believe l it has the rear end from the donor Gbody as well. He’s had that car together for quite a few years and it’s been all over the place. San Diego, Ventura, Reno, and so on.. Back in 2012 we met up with him in Reno for the Hot August Nights for a couple of days and we road around with him in the 37. It’s not going to win many drag races but it is a very good highway cruiser. The engine and trans and rear end are nothing special but a lot of those Gbody 7.5” 10 bolt axles had gear ratios from 2.14, 2.29, 2.41, 2.56, 2.73, and 3.08. Having ridden in his car and knowing how civil the engine rpm’s are at highway speeds 75-85mph he must have a gear set in the 2’s. I thought maybe he had an overdrive trans but he has maintains that it’s just a 350..
0B8FEB76-C938-4519-996B-EECF14F4DFEB.png
 

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Seems a lot of guiys are missing the fact this guy has a vintage 4-speed that has a super low ratio gear set in it....call it super wide ratio if you like.
He isn't after an actual overdrive gear, he is looking to gear the rear axle so low that the shift into 1:1 4th in his super wide 4-speed gets him the cruise rpm just like as if it was an overdrive trans with a 3.42 or more rear gear.
Trans you have is called a Power Brute, gear ratios' are 1st -3.42, 2nd- 2.28, 3rd- 1.46, 4th- 1:1

if you ask me, the 327 isn't going to like the big rpm drops from each gear change, it doesn't make enough torque.
Your idea might be pretty good if you put a 383 in front of it instead.

Have you looked at this from the standpoint of starting line ratio(SLR)?
1st gear ratio x rear gear ratio = 10.00+ was the muscle car era standard, 12.00 dedicated drag use.
3.42 x 2.56 = 8.83
The 327 is not going to be real happy with that. Same SLR as a close ratio Muncie and 3.73 gears
I'd call 2.73's at 9.4 SLR barely acceptable. Just a little bit better than close ratio Muncie and 4.11's

Personally, with the 327 and that trans, I woulldn't go any lower on rear gear than 3.23 if you expect it to really move out, and just live with the couple hundred cruise rpm more than you goal..
 

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1969 Nova . . 2dr . . Chino Valley,Az USA
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I think I agree with ' Ericnova ' . . . . . You may be doing all "your around town , driving in 3rd gear .........
with u'r 327 . (because of the 'wide spread' gears' ) .
And , hi-way driving will / may still "lug-down" your motor also .

I went with the S-10 , T 5 o d trans , even with the 1st gear = @ 3.97 ; and 5th gear = 0.72 . (from my
stock P/G trans). But I'm still using my stock 8.2 rear = @ 3.08 gears .
Well , I really like it alot . . . . . . I 1st though the 1st gear #'s might be bad - - - like maybe more of a
"granny-gear 1st" . . . . . . but, they work good . I run around in town , through the front 4 gears , and going from Chino Valley to Prescott , (or any Highway trip) . . I do get too hit 5th gear .
(note : my engine is just - - - - - that beat-up ol' 250ci L-6 : but does go good) .

You should check out that NEW Trans by " Tremec " = the new TKX (5 speed , O.D. trans) .
Plus, I think u'r 327 might like that od ( 5th gear) much better .

TREMEC TCET18083 TKX Wide Ratio 5-Speed Chevy Manual Transmission{match_type}&msclkid=58ebd93871011db

just talking , here . . . . . . have fun .

later . . . jim
 
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