I have 4:10 in mine. Great for around town but way too low for hiway driving unless you don't mind the engine reving @ about 4200rpm @ 60 mph.

 

I have the same 4:10 in mine and you can forget the freeway with the M21 and a 4:10 or 3:73 for that matter. Even at over 4000 rpm driving our freeways here at 60 when everyone else is running 75+ you'll either get shot, run over/off or both. Best solution is to bite the bullet and get a TKO or T56; dollar for dollar one of the best changes you can make to these cars.

 

A M20 4-speed with a 2.54 first gear instead of the 2.20 that a M21 has would get you the same overall gearing in first gear without any increase in rpm at cruising speed.

 

This is what I suggest.

 

frankK, Does yours have the M21 ? If you made any change to yours what would you do ? Tranny or Gearing...

 

In mine I have the M33W gearset with 2.56 first gear with 3.73 rear gear. 2.56 x 3.73 = 9.55 is my first gear overall ratio.

Yours now is: 2.20 x 3.55 = 7.81 first gear drive. A bit low for starts.

You could be: 2.52 x 3.55 = 8.95. This is at the bottom range of recommended 9.00 to around 10.50.

The last option will allow you to keep the rear gearing and not negatively affect your highway driving.

 

I built a M23 for my Camaro and I used the 2.99 first gear set. This would give you plenty of tire smoking torque and you would still be able to drive it. Put the M21 away so that you can put it back someday if you want. The M22Z or M23Z will give you great gear ratios and you don't have to modify the floor, change the clutch or shifter to use them.

 

I has someone custom build a tranny in my 69z. Its 296 1st 220 2nd with 373 gears. That was almost 20 years ago. Today you can just get that gearing in heavy duty trannys. Works very well in the Z

 

I feel your pain. lol... My stock 69 Z has 3.73s & M-21, so its basically the gutless wonder. The 3.73s are to high too be quick off the line and too low for the highway, I tach 3800 rpm to 75.

 

I found out the hard way that the 2.52 m20 was 2 tenths quicker and 2 mph in my vette over the 2.20, same day 2 hours later.

Take trans out and have the cluster gear replaced, especially if yours is fresh or shot. If it is fresh, it will be cheaper, but if it needs a rebuild, change it out. I figure to change a gear,you are near $1,000 to take it somewhere?

Now if you do both, then you really have something

 

Tires are 15X7 bias 26" tall, I won't be taking it on long trips mostly weekend cruising/racing around town and maybe a few trips to the dragstrip now and then... I want to be able to smoke the tires and it won't with the current gearing. Thanks :smile2:[/QUOTE]
You are in that tough spot of trying to straddle 2uses and not getting either one right. Because of your stated use the 4.10's dont bother me. They'll cost you more in gas driving out for breakfast than the breakfast will. The M21 doesnt bother me either. Your back tires bother me. Your desires for the car's use die on that rubber in my mind. You are getting close to being able to launch the car but its gonna take a little more tire. You gotta decide if what you gain in the grin factor dept is worth it knowing you are eating the car up faster.
For me its no decision. When i got my 67 it had 4.10's in it. Except for a short experiment with 4.88's thats all its been. It will get new 4.10's soon but with a TKO which is a game changer. 50 years with 4.10 gears.

 

Take trans out and have the cluster gear replaced, especially if yours is fresh or shot.

If you're gonna change the cluster, you have to change the input gear at the same time. You can't change one without changing the other. The teeth won't mate up otherwise.

 

Agree with getting a 10:1 overall ratio.
And since the little 302 is spinning, why not?
It is made for this.
On the trans to speedo ratio, GM offered a reduction box on trans for 4.1X:1 and above, P/N 3892220, and figure the driving gear needed.
Remember, physics has not changed - one mile in one minute is 60 MPH.

 

Thanks for everyone's advise, it's nice to see I have so many options, UPDATE from my post yesterday... I assumed I had 3:55 gears because I researched the number on the axle tube and that's what it had originally, I pulled the cover and counted the teeth last night and in fact I already have 4:10 gears 41 ring 10 pinion, I was shocked with this discovery. I will check my rpm's at 60 this weekend, but am leaning toward replacing the M21 with either the M20, M22Z or M23Z or maybe the TKO. Knowing now that I already have the 4:10 gears which tranny do you think would give the best overall performance with these gears ? Just getting opinions before making a decision... Also, I was thinking the previous owner could have changed the internal gears in my M21 for it to act this way with 4:10 gears ?? Another question on the bias tires, do they grip more than a radial ? Could this be an issue with my current set-up not wanting to break the tires loose on take-off ?? Thanks everyone, this is an Awesome forum...:smile2:

 

IMO, T56 would be my choice as first four gears closely match a close ratio Muncie with a 0.50:1 overdrive.
302's were designed for horsepower, not torque. However, I have done some 4K RPM dumps ...

 

What all has to be changed if I go with the T56 ? Bell Housing ? Clutch, Shifting linkage ? Speedometer cable etc...

 

You can stick with the manual clutch set up and not go hydraulic, but you will need to get a different clutch disc and with an adapter plate you can run your stock bellhousing.

 

Yes, all mentioned

 

A thought that has been nagging at me as I've been following this thread is why can't you break the tires loose? Now that you have found out that you have 4.10 gears, I really question what is going on with your engine? A 4spd and 4.10 gears even with a mild powerplant seems like a tire smoking combination on street rubber unless the motor is very weak.

 

You might want to look into what floor modifications will be required if you use a TKO or T56. The Chevelles require a lot of modifications to the transmission tunnel to fit these transmissions, and I would assume that you don't want to cut up your floor. I don't know how much room the Camaros have for these transmissions. They will also require a different cross member and drive shaft.

 

When I got my car (1982) it had 4.56's in the back, but I got the original 3.73's with the purchase. I drove the car with the 4.56's for years, wasn't worried about interstate speeds then. One day I decided to move back to the 3.73's and put them in the car. The next day I changed back, the 3.73's were that bad with the 302. Now I run a TKO600 with 4.10's and a little taller tire. Its a way better situation all the way around.

Ray

 

thebat, I said the same thing to myself, it should be able to break the tires loose. The engine seems to be fresh and tight, no smoke, freshly rebuilt carb. tuned with distributor recurved, it has plenty of power after you get going a little bit runs like a scalded dog. The only thing I can figure is they could have changed the gears in the M21 or with the current tires and suspension it just grips too much for the low end torque of the 302. My wife's 68 Camaro has 17" wheels with radial tires that are 25" tall, I'm going to swap them with hers this weekend to see if that little bit helps. Using her wheels should change the output ratio to 4:26, taking (26"/25") X 4.10 = 4:26 I'll let you know Monday, I'm also going to check rpms at 60 with current set-up and check again with wheels swapped to see...

 

Polyglas tires gave gone into the 9's in th fast class, in pure stock low 11's.you need to learn how to leave soft without spinning, if they spin, they are hard to recover and go up in smoke. They do hook better than radial tires for sure.

I would put a wide ratio in it for sure if you have the 4.10, it will wake up the bottom end and still retain the same final ratio. The m21 was designed for the road racing car, as they are never in first gear.

 

Alvin I have the M20. If I made any changes to mine, I would try the 3:73's. You could smoke the tires easily and I think you could save the engine a lot on the hiway. I had 3:55's in my L78 Chevelle which was too high.

 

There is your transmission man. Jody can fix you up with just about anything you need, including M22Z, M23Z, McLeod clutches and one transmission that nobody mentioned yet, the LGT700. Give him a call.

 

You should be able to spin the tires with a 4 speed and 4.10's.

Do some research on here about swapping out the Muncie for a T56 or TKO.

From what I've read, the TKO is a cleaner swap with less chance of tunnel issues. I think you'd be fine with a TKO 500.

 

I've got a TKO600 in my 69. It's a big block car with about 450HP. I'm running a 9" rear with 3:89 gears. My tires are 255/60/15's which are about 27" tall.

Here's why I'm a big fan of a set up like this: around town I get all the fun factor of a big block with 3:89 gears. I get the grunt coming out of the hole, I get the quick wind up of gears and then if I decide to get out on the highway or hit a stretch of road where I can do more than 45-55mph, I shift up into 5th and I can cruise at say 2000-2300 RPM's comfortably.

You can swap out to a TKO600 without any tunnel mods but my understanding is that you WILL have to do some floor/tunnel mods to install a T56.

That leads to my next comment. Do you REALLY need a 6 speed? I've often wondered how much guys really use 6th gear. Especially for guys like us that use their car for mostly local seasonal cruising. I could understand if you lived in Southern California or Florida and drove your car year round, but here in the northeast where we have about 5 months to enjoy our cars and there's a local show or cruise night pretty much every weekend, I really have no use for that extra overdrive gear.

The cost difference in installing a 5 speed vs a 6 speed is significant and I'd do some serious consideration as to how your going to use the car before spending the extra cash for another overdrive gear.

 

Alvin,
For your overall consideration on what combo to go with, check out the link below to another thread discussing 5 or 6 speed conversions. I posted some thumbnails in my posting that show the rpm/mph relationships for a 4:10 and a 27" tire with different gears in the T56 (or similar gearing in a TKO). You could work up similar curves for your own situation. One thing to consider is that you'll be driving a no torque 302 so you may want the extra gear (5th) as Everett suggests. I use 5th quite a bit around town with my own no torque 302. The curves make it really easy to see what rpm your engine will be running for a given speed in a particular gear for the type of roads you typically travel. Just food for thought.

http://www.camaros.net/forums/27-transmission-driveline/362065-69-camaro-5-6-speed-conversion-2.html