I'm re-building a 67 Camaro Coupe with a Muncie 4 spd, ZZ4 Crate engine and a 12 bolt rear end. The rear currently has an open 3:31 in it but I want to put in a posi unit and wonder what the best gear ration for it would be, given I don't want it to be a dog on the street, but will be using it 4-5 times a year for 2-5 hour highway trips. Your help is appreciated. By the way, the Muncie has a 2:56 first gear and I plan on running 28" tall tires. Thanks.

[This message has been edited by 67killerb (edited 08-07-2000).]

373's are hard to live with on the street, cruising 65 mph at around 3K can get old in a hurry.......You'd probably be better off with something in between what you've got and the 373's, I think that would be 356's?????

Well it has been my experience that 3.23 posi with 4 spd is just about perfect. Get solid acceleration and good rpms for crusing on highways. You would probably be around 2300-2500 at 65mph maybe a tad more depending on tires sizes. Good luck.

In your case, my vote is 3.55's. W/your M-20 low 2.56 1st gear it will be equivalent to a 4.13 gear w/an M-21 or M-22 at least off the line.

if it weren't for the long hiway drive i'd go for the 3.73's,but as it is stick with your 3.31's and get a locker( goes in place of your spider gears ,easy at home job )But if you switch to a 700R4 get 3.73 - 4.11's.
but thats what i would do if it were mine.




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My68Camaro (http://hometown.aol.com/Dougs68Camaro/index.html)
Doug G.
68 Camaro
406 ci.

Hey, Thanks for your suggestions.

why dont you keep the gears you got with the 28" tall tires for hiway use.... get an extra set of rims and get something like 235x60 15 which are 26.1 " tall that will give you the low end for around town

Hey 67killerb,you ever hit Georgie Porgies on highway 100?

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67 RS RAGTOP # matching
4X4 Chevy truck
4X4 Suburban

67killerb,

I have 3.73's and when I had a turbo 400 that was too much gear for highway use BUT since I have changed to a R700, It is perfect.

The difference between your 3.31's and a 3.55 ratio are not significant enought to justify buying the new gear set IMO. SO I would keep the 3.31's for now.

But I do think that the 3.55's would be slightly better in your case and if you didn't mind spending the extra money, I would do it.

How's that for mixed signals????

67Drake, You bet. And every Wednesday I head over to Solid Gold McDonalds on 76th. It seems Georgie Porgies has better overall quality rides, whereas the Solid Gold cars are at times either very nice inside and out, or they look fairly nice from 20 ft, but up close and under the hood or inside the interior, not so hot at all. I didn't make it tonight, had a birthday party for my 74 yr old mom. Going to show at Iola tommorow am.

I did'nt go today either,worked till 8pm.If you go next week keep your eye out for a stock looking black 67'RS ragtop,thats me.I work 2nd shift,so I've never been to the McD's.

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67 RS RAGTOP # matching
4X4 Chevy truck
4X4 Suburban

Go with 3.73's. I'm running a ZZ4 with a 4 speed and 3.73's. The engine is turning 3100 rpm at 65 mph, and is happy to do it all day! I did alot of research on this motor when I installed it last winter and everyone that has one said they love to spin the R's. I started out with 3.42's and swapped to the 3.73's this spring and they're perfect. Go for it!

the 3.42 is too close to 3.31 to warrant a change.

With 355's and 28" tires I spin about 3100 at 65-70.

355 or 373 are ideal gears.

For street use, I run 25.5" high BFG Drag radials in the 275/50/15 size. Highway, your 28" are fine, I have some 31" 285/70/15 BFG radials I'm planning on using for long cruises. ( 300+ miles).

55's are mint. 73's might be a bit high for highway. 31's are a little sluggish on accel, but nice on cruise. But again, tire diameter changes can give you these ranges.

if you opt to keep the 331, try a set of 225/50 BFG Drags. That'll give you a 3.70 equivalent gear for ripping. They will, however, look a bit small as they only stand 23.5" high.

If you don;t mind the small tire look and having to change tires once in a while, short slicks and your 331 will be fine for harassing mustangs.

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Gene C.
67 Chevelle SS 427/L88 (http://www.chevelles.com/showroom/chaas00.jpg)

427TRI made a VERY GOOD POINT about using tire diameters to get the effective gear ratio you need for a particular application. Tall tires for the highway, shorter tires for the street.

It may be slightly more expensive to buy an additional set of rear wheels and tires, but I think that is the better overall solution.

If you keep one set of tires and play with the rear gear ratio, you will either not like driving on the highway due to excessive RPM (and engine noise) or you will not like around town acceleration.

I completely disagree that 3.73s are the "perfect" gears. Maybe from a performance standpoint, but that's not the only issue to consider (at least not for me):

1. Have you ever ridden in a car equipped with 3.73s and a Flowmaster exhaust on the highway for 8 hours? It's not pretty - you are virtually deaf by the end of the day.

2. Forget installing a quality sound system - you won't be able to hear the quality over the engine noise.

3. Crappy gas mileage. Not high on the list, but nice to have. My car gets around 13MPG on the highway.

4. Finally, how many of you have been cruising down the highway at 75MPH with your 3.73s (at almost 4,000 RPMs) and had a Mustang whiz by you? It really sucks because with a 6,000 RPM redline, top speed is only 120MPH. You get left in the dust even though you clearly have the better car.

If you have the $$$, go with a low gear like 3.73s and install an overdrive tranny. That was my solution.

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Hugger Orange & white 69 Camaro with supercharged 350, Tremec TKO, and 3.73 12-bolt

See my website updated 8/13/00 at:

www.geocities.com/gheatly (http://www.geocities.com/gheatly)

Hey man, have you ever heard of gear vendors.There system is really cool because you have 2 of each gear and a .78 overdrive.So if you even went with 4.10 rear gears you would still have a high gear ratio of 3.20.Thats tire smokin,accelerating gears with your long trips in mind.Think about it.

The Gear Vendors setup sounds interesting but I always lost interest when I heard the price...big bucks.
For that kind of cash I'd go for the really heavy duty o/d trans...forgot the actual model but its the one that is basically a TURBO 400 with od.

Extra tires/wheels are nice if you can afford them. I have an M-20 with 4:10's. It's busy on the street but my driving is point and shoot for 1-2 hours so it works. The 355 doesn't seem to mind revs, either. However, if I was going to change, I'd put in 3:73's. In my case, 55 mph is 3 grand but then again I inherited 225/60-14's.

the 3.31's with say 24" tires that are as wide as you can get will drag fine. And 27/28" tires kinda thin and narrow will do very well on the highway.

Try mph = rpm x tire Dia./rear gears x 336 to play with gears and top end speeds.

I ran a pair of 29.5" dia. mud and snows on my car using the stock 14 x 6 steel rims and at 5500rpm with my 3.31's it would go right at 145mph. I had ta raise my body until my rear bumper was up about 8" over stock ta keep them from rubbing. It looks funny,but beats h-ll outa changing gears!!! pdq67

Hey pdq67,
Were the mud and snow tires rated for 145 mph? Ha, ha, ha, ha, ha, ha.

http://www.camaros.net/forum/smile.gif

I have a 3:73 rear end and 265/70/16 BFG's and at 65-68 mph there is no noise like some have said. I also have the turbo 400 "I think" I dont know the rmp's but cant be high, cause I dont hear anything, now at 80mph yeah, but below nothing.

Ron

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'89 Suburban/454tbi/2500/3:73;G80 rear/3 speed/1qt oil per 800 miles
'95 Nissan xe-v6/extra cab/automatic