With the torque your producing with that 402 a 3:42 gear should be plenty. No need to go the 3:73 in my opinion. A bit more elaboration here..i hit the button before i was done. I think the 3:42 with you setup will give you the perfect combo of wheel spinning/rear end sliding and a relatively decent cruising gear.

 

Hey BBG , I cant recommend a gear but I can tell you from experience that you don't want to be stuck with a really low gear. I'm running a 4:11 myself and it ain't no fun cruising at 60 or 65. But she will get sideways off the line and its lots of fun from 0 to 60. Thats all I got.

 

3.42 or even 3.23 would be fine behind a 402. You've got plenty of torque.

 

My 71 formula with a 455 and 3.42 would destroy the 265-15 tires with posi. I think it's a perfect gear, and then the addition of overdrive, sweet mileage.
Dale

 

Michelle -

Which rear do you have? The reason I ask is not all ratios are available for all rear diffs. I will try to go back through some of your other posts and see what engine specs you have, convertor stall speed, and what diameter rear tires you're running. All of that comes into play to some degree.

I have a 402 with a very mild cam (a Crane Resto grind that is the 396/360HP equivalent) and a TKO600 (2.87 1st), and an 8.5-inch 10-bolt with 3.42. When I fired it up last week, anything over half throttle in 1st or 2nd just blows the rear tires off. Some of that is the small tires I have on now, but if I can't hook it up on a "normal" size tire like a 255 60 15, I will actually be changing to a "higher" numerically lower set of gears.

Your TH400 has a 2.48 1st gear, so a 3.42 or even 3.31 or 3.23 would be fine. If you want to really be able to cruise and plan to do the 700R4 down the road, even a 3.08 or therebouts is good (700R4 has a 3.06 1st gear).

Now if you're running a tall, wide rear tire, you may want the 3.42 or so to get things moving.

 

I would go for the 3.42's... then down the road a GV overdrive or 2004r

 

I think I'd go with the 3.42 with either transmission. The 3.42 will be better on the highway with the TH400 and will work better with the 700R4's low 3.06 first gear.

 

Ok...sorry for not giving more info...I have the following:

402 BBC .30 over wtih mild cam (.280/.520)...etc...
TH400
TCI Stall Saturday Night Special (i think up to 2000 stall...)
2:72 10 bolt
Rear tires = 245/60/15 (26.57")

I think you should be able to see what the car looks like on my picture attached to my profile.

Since I posted last night, I also ran my specs through an RPM calculator and found that the RPM at 65 MPH is only 270 RPM lower than the 3:73. So, now I guess either one would need a 700R to cruise at 65. Doest that sound right?

BTW, Here is the site I used: http://www.differentials.com/calc.html

Thanks for all you input!!!
-Michelle

 

Ok...sorry for not giving more info...I have the following:

You're excused.

I think you should be able to see what the car looks like on my picture attached to my profile.

Very nice ride.....nice rock on the finger also!

Since I posted last night, I also ran my specs through an RPM calculator and found that the RPM at 65 MPH is only 270 RPM lower than the 3:73. So, now I guess either one would need a 700R to cruise at 65. Doest that sound right?

Strange, I thought of the same thoughts this AM, but was called to a meeting before posting.

Thanks for all you input!!!
-Michelle

You're welcome. My thoughts are these, you only want to do this gear change once, because of cost and time. If you are planning on swapping to an OD trans later, I'd go with a 3.73 because of the final engine rpm. With OD and a 3.73 ratio, this will put the engine into a more efficient rpm by placing the engine into the main fuel circuit and get it out of the off idle circuit. I'm sure I'll get comments on this.

If not anything else, it will be better music to your ears with the windows rolled down. Besides, it sounds better when you tell others you have a 3.73 than it does when you say 3.42. Try it in front of the mirror, you'll see what I mean.

But then, I'm not a professional advisor either.

 

That is a very nice Camaro. Where were the girls like you when I was looking for a wife? 2 big block Camaros in the garage would have been awsome!

 

Thanks! What gear and transmission did you say you are running?

 

Nice car. And you like hunting & fishing too !!

I would stay with 3.42 gears for street use. You should be able to get sideways with your 402. I run a fairly mild 427 with 3.31 gears and M20 and would not want lower gears for highway use.

Good luck.

 

Yeah, I am a big red neck...but it is a lot more fun that sitting around painting my nails! O, wait..i don't hav eany nails...

 

Unless you built the car to go on a lot of long highway trips, I'd go with the 3.73 gears. It'll be more fun around town from stoplight to stoplight.

 

I like this calculator because it lets you see different RPM values for different gear sets at the same time. It is a little hard to look at though.

http://www.angelfire.com/fl/procrastination/rear.html

If you have the original 8.2-inch 10-bolt, I am fairly certain 3.42 is not an option for you. It's 3.08, 3.36, 3.55, or 3.73 in off the shelf R&P for the 8.2.

And, as you can see by the varying opinions, there are a bunch of things to think about, and it is all about making it all work together. You really have to sit down and run through the calcs for each ratio in each trans gear, and compare that to what makes your engine happy.

 

If you have the original 8.2-inch 10-bolt, I am fairly certain 3.42 is not an option for you. It's 3.08, 3.36, 3.55, or 3.73 in off the shelf R&P for the 8.2.

QUOTE]

The local driveline shop told my brother that i coudl go to a 3:42 and use the existing carrier or spool or whatever it is. I will double check to make sure.

 

I run a 3:55 and that is also a very nice option. Its all opinion but 3:73 would suck for anything over 55-60mph...again my opinion. Unless you put in an overdrive.

 

Just wanted to let you know that so far, your info should help me build a case to convince my husband to let me buy a 700R.

Has anyone bought the TCI Streetfighter or are you guys just rebuilding used ones?

 

your last post bigblockgirl. the guy told you you can use original carrier. well in your original post you where tired of spinning 1 wheel. you need a new carrier with posi. there different carriers. unless he intends to weld the spiders together. than turning corners no good you will be tearing axles out. ill would put in 3.73 cause it is only a quarter turn more on driveshaft speed. would only raise rpms about 2-3 hundred than a 3.43 but if you decide on a 700r4 than 3.43 a little low as when it goes into 4th gear and lockup your engine will bogg around 40-50 miles an hour.like putting a stick shift into 4th gear around 20 mph and go lol. later model camaros with 700-r4 run 3.73 or 4.11 from factory.sorry to put twist on things lol. wish you wait till summer to make a decision on it moving to tenn in july- august and got 10 bolt with 343 gears can put it in your car and see how it goes lol

 

your last post bigblockgirl. the guy told you you can use original carrier. well in your original post you where tired of spinning 1 wheel. you need a new carrier with posi. there different carriers. unless he intends to weld the spiders together.

I couldn't remember what he said..that is why I put same 'spool, carrier or whatever it is'... Spool sounds more familiar. Maybe that's it. Either way, there was something that I wouldn't have to replace. But..no issue..because I will replace whatever I need according to my decision.

 

Contact a member here by the name of "big gear head" aka Freddie, for a good deal. Seems he gives sound advice and a good product as mentioned by other members.

If you do have a 2.73 carrier, you will need to change it to a limited-slip carrier to fit a 3.XX gear ratio. And change bearings along with C-clip eliminators for the axles. Plus labor for set-up and changeout in car if you elect professionals to do it.

 

Now I need some more information. I was assuming that you had the 12 bolt rear end, but now I'm not sure. If you have a 12 bolt then your options are 3.42, 3.55 and 3.73. If you have the 8.2 10 bolt then your options are 3.55 and 3.73. If you have a Nova 8.5 then your options are 3.42 and 3.73. Your car should have been equiped with the 8.2 10 bolt originally if it had the 327 and an automatic transmission.

You will want to think about the 3.06 first gear in the 700R4 before going with the 3.73 gears. Your TH400 will have a first gear of 2.48 I think. Multiply this by 3.73 and you get a final drive ratio of 9.25 in first gear. Multiply the 3.06 first gear by 3.73 and you get a final drive ratio of 11.41. That is the same as the TH400 with a 4.56 rear end gear. You don't need a low gear with the 700R4 to have fun because of the very low first gear. That is why I recommend the 3.42, or 3.55, depending on which rear end you have. This will give you a lower RPM on the highway while you still have the TH400, and will still be lots of fun with the 700R4.

 

Now I need some more information. I was assuming that you had the 12 bolt rear end, but now I'm not sure. If you have a 12 bolt then your options are 3.42, 3.55 and 3.73. If you have the 8.2 10 bolt then your options are 3.55 and 3.73. If you have a Nova 8.5 then your options are 3.42 and 3.73. Your car should have been equiped with the 8.2 10 bolt originally if it had the 327 and an automatic transmission.

Ok...so I guess I have an 8.2 on the car now. (I also have the original 327 decorating my garage.) My brother has an 8.5 from his 70 Nova that he said I could have if I wanted it.

I believe I am going for the 3:73 and just save up for the 700R.

Thanks everyone for all your advice!
-Michelle

 

I've got a 3:42 behind my BB in my nova with an M20 and its still at 3200 at 70MPH so I ordered a TKO600 with overdrive!

 

If the '70 Nova has the original rear end then it will also be an 8.2. The 8.5 wasn't used in the Nova until '72.

 

I am not sure if it is original but he does have an 8.5 housing.

 

Big Block Girl,

I had a 1969 Camaro w/ a 396. It had a THM400 and a 12 bolt w/ 3:73's. Like you, I got sick of the one wheel peels with the previous rear end I had back there.... That car originally was a 327 2bbl, Powerglide and 10 bolt with an open 3:08. When the camshaft went flat in my 1984 Z28 (I hate 305 engines!!) I had to drive that car from Chicago's South Side to the Northwest Suburbs for work. This was 6 days a week 30 miles one way and 30 miles back. Many times in traffic. Other times not. The car was fine on the highway with the BBC, THM400 & 3:73's If you want to save money and feel it twist go w/ the 3:73's. It's a great gear!!

I mean no disrespect when I say this but many of the old 50 something geezers (ha ha ha) who own these cars forget what it was like to drive cars without overdrive tranny's. Including non-Camaro's. I had a 1977 Pontiac Ventura w/ a 231 oddfire V6, a 1979 Caprice Calssic with a 350, 4 Camaro's (yea I know the two third gen's I owned had overdirves aka the 700R4 and boy were they fun even with 3:73's back there on the highway. And I'm not even 40 yet!!

Anyway with a Big Block and a Turbo 400, the 3:73 will be fine. You will like it. And Everett is right on the money. Ok the 50 somethings can send me their hate mail. Just kidding you know I love all you guys and not in THAT way.


SSG&H

 

What funny about the 3.73's with a close ratio 4 speed, is that you start out in 1st and think "this isn't so bad" until you go another city block and you're in 4th spinning at 3,000 rpm's. Both my rides are 3.70ish (one's a 9" and one's a 12 bolt) and I wish I was more in the 3.50's. The BBC's have so much torque that they don't need the ratios those guys running the mouse motors do!!!!! LOL

 

I had the 700r installed in my 69 with 350 Qjet camaro, right before snow fell. Its been sitting waiting to go stretch her legs and that might happen this weekend finally as the snow is meltling quickly.
I have the 12 bolt with 3.08 posi I got from Big Gear Head. My goal is the best highway mileage I can get cruising with lowest RPMs. My goal is 26mpg on the highway trips. Im also counting on the low 1st gear of the 700r to surprise a few folks on occasion as well. I found a local 70 year old retired tranny guy to build up a mid 1980's 700r for me. You folks know enuf car guys around there to find a good tranny guy, get some quotes, it might not be as bad as you think. Good luck, thats an awesome looking ride :thumbsup: