3.07 gears

[X33RS]

How many 69 Z's have you guys run across with 3.07 gears?   

[KurtS]

1, out of more than a 1000.

[X33RS]

Wow, I figured scarce but not like that.  I believe I happen to have one Kurt.  Actually glad you responded.   Now that I'm finally digging into this car after 30 years of sitting, I was thinking of getting in touch with you with the info on this car with some pics, to both help with your records and with any luck turn up some history.
   I'm going to say with 99% certainty that this rearend has never been out of the car, has correct casting and is dated prior to the Dec 68 build date of the car.   It's basically a no option Z with the exception of deluxe houndstooth and the RS package, doesn't even have power steering.   All these years I assumed it would have had the standard 3.73's as well.  I find it very odd someone would have paid extra for 3.07's??  Then didn't spring $42 for positraction?  Guess it's safe to say someone didn't want a stoplight stormer and preferred a highway cruiser.
   Anyway, as far fetched as it may sound, if you or someone you know may ever pass through Arizona I'd be more than willing to show the car if someone is interested in verifying what I'm seeing.  I plan to pull the cover and change the gear oil, at which point I'll check the stampings on the gears, but I have no reason to believe it isn't what the BL code is telling me.

[69Z28-RS]

With 3.07 gears, I'd bet that car has gone thru a LOT of clutches....  slipping the clutch in attempt to get it moving from a stop with those gears....  (I can't imagine!)...

[BULLITT65]

Wow, I have driven a Z with a 3:50 rear, and I thought that was a dog out of the hole.....

[X33RS]

Actually I've had 2 other cars with 3.08 gears and 4 speeds, and as long as you run a M-20 in it with about a 26-27" tire on it, it's really not that bad.  I drove those cars everywhere.   One of them I had a smog 307 sbc, stock heads and compression untouched, 218 @ .050 cam, performer intake and 600 dp and it went 14.56 and mph in the mid 90's.  It was actually a ball to drive.

That gear with a 2.20 Muncie however I agree would be pretty tough on a clutch.  I wouldn't even enjoy driving it around town to be honest.

[X33RS]

Wow, I have driven a Z with a 3:50 rear, and I thought that was a dog out of the hole.....

With a 2.20 Muncie, yes.  If you run a 2.52 Muncie in front of those gears, it's actually better with more gear multiplication than the 2.20 and 3.73 setup you see most of the time in these cars.
You would have to run 4.10's behind a 2.20 Muncie to equal and only slightly improve gear multiplication over a 2.52/3.55 setup.

[BULLITT65]

Well both my current 3.73 car, and that 3.50 car had M-21 transmissions (2.20 1st gear), and seemed like you had to rev that 3.50 car so much more to get it going, and then had to have the thing humming farther up the rpm scale to have the power band kick in.  On the other hand I have driven my friends 4.10 car with the M-21 and I could hardly tell the difference with his and my 3.73 car. I could only tell once I got on the freeway that it was turning more Rpms at 65 mph.
I am not disagreeing with your math, just my interpretation behind the wheel
Just my 2 cents..

[69Z28-RS]

Actually I've had 2 other cars with 3.08 gears and 4 speeds, and as long as you run a M-20 in it with about a 26-27" tire on it, it's really not that bad.  I drove those cars everywhere.   One of them I had a smog 307 sbc, stock heads and compression untouched, 218 @ .050 cam, performer intake and 600 dp and it went 14.56 and mph in the mid 90's.  It was actually a ball to drive.

That gear with a 2.20 Muncie however I agree would be pretty tough on a clutch.  I wouldn't even enjoy driving it around town to be honest.

You are correct that the WR transmission is very helpful (even with the std 3.73 gear), but your mathematics are a little 'off'...   

 2.52*3.07= 7.73, whereas  2.20*3.73 = 8.206.    8.206/7.73 =1.062 .. Thus the CR 2.20 trans with 3.73 has more than 6% better 'low speed' gearing than the WR 2.52 with 3.07...

A stock Z28 302 ci engine has such little low rpm torque, than higher rpms are required to start even with WR and 3.73 (that is what I have in mine). 

Most of the CR trans sold were for 4.11 or higher numbered rears (for racing).

Gary

[X33RS]

Actually I've had 2 other cars with 3.08 gears and 4 speeds, and as long as you run a M-20 in it with about a 26-27" tire on it, it's really not that bad.  I drove those cars everywhere.   One of them I had a smog 307 sbc, stock heads and compression untouched, 218 @ .050 cam, performer intake and 600 dp and it went 14.56 and mph in the mid 90's.  It was actually a ball to drive.

That gear with a 2.20 Muncie however I agree would be pretty tough on a clutch.  I wouldn't even enjoy driving it around town to be honest.

You are correct that the WR transmission is very helpful (even with the std 3.73 gear), but your mathematics are a little 'off'...   

 2.52*3.07= 7.73, whereas  2.20*3.73 = 8.206.    8.206/7.73 =1.062 .. Thus the CR 2.20 trans with 3.73 has more than 6% better 'low speed' gearing than the WR 2.52 with 3.07...

A stock Z28 302 ci engine has such little low rpm torque, than higher rpms are required to start even with WR and 3.73 (that is what I have in mine). 

Most of the CR trans sold were for 4.11 or higher numbered rears (for racing).

Gary

I was referring to Austins 3.50 gear example when I made that comparison.  He runs a 2.20 in front of it.  With a wide box in front of that, it would actually be better than a close box and 3.73's.
  I never had a single issue with a weak 307, a wide box, and 3.08's around town.  Tune was important, a fair amount of initial timing lead with limited advance and vacuum advance hooked to manifold vacuum makes all the difference, especially with a large overlap cam.

[X33RS]

Well both my current 3.73 car, and that 3.50 car had M-21 transmissions (2.20 1st gear), and seemed like you had to rev that 3.50 car so much more to get it going, and then had to have the thing humming farther up the rpm scale to have the power band kick in.  On the other hand I have driven my friends 4.10 car with the M-21 and I could hardly tell the difference with his and my 3.73 car. I could only tell once I got on the freeway that it was turning more Rpms at 65 mph.
I am not disagreeing with your math, just my interpretation behind the wheel
Just my 2 cents..

I think my comments are being misconstrued.  Maybe I didn't come across very well.   I was trying to explain that if you put a wide box in front of that 3.50 geared car, the 1st 3 gears give you better gear multiplication than your other example with a 2.20 box and 3.73's.   I wasn't referring to my 3.07's.

2.20 x 3.73 = 8.20..........2.52 x 3.50 = 8.82
1.64 x 3.73 = 6.11..........1.88 x 3.50 = 6.58
1.28 x 3.73 = 4.77..........1.46 x 3.50 = 5.11

My 3.07's with a wide box really isn't too much different than your 3.50 gears and a 2.20 if you want to compare....Actually you could say the 2.52/3.07 setup is slightly better however not enough to tell
2.52 x 3.07 = 7.73.....2.20 x 3.50 = 7.70
1.88 x 3.07 = 5.77.....1.64 x 3.50 = 5.74
1.46 x 3.07 = 4.48.....1.28 x 3.50 = 4.48

On a side note, better gear multiplication in the first 3 gears of a wide box is why a lot of the PS guys that prefer a stick will choose an M-20 box over the close ratio, even the large rpm drop on the 3-4 is of little consequence with momentum on your side and the cars tend to run a little quicker this way.

[69Z28-RS]

I did mis-understand your point, as I took it as 3.07's in a Z28 as being 'non roadworthy'...  I wouldn't want any gears less than a 3.55 (even with a WR trans)..

PS:  The 'weak 307 engine  you referenced, with it's longer stroke,  has more starting line torque off idle than the 302...

[X33RS]

No biggy, we'll see.  I've been down this road before and find it acceptable.  Being that this is going to be a daily for my wife in a way I'm actually kind of glad, less wear and tear on this brandy new DZ motor.   Right off the bat I was going to drop in a TKO600 because I didn't want her buzzing this thing at 75 mph with 3.73's (the gear I assumed it would have).   This gear will make the trips to Phoenix less stressful.  Now I can wait and see if she still prefers the 5 speed or not.

[bcmiller]

   I'm going to say with 99% certainty that this rearend has never been out of the car, has correct casting and is dated prior to the Dec 68 build date of the car.   It's basically a no option Z with the exception of deluxe houndstooth and the RS package, doesn't even have power steering.   

Anyway, as far fetched as it may sound, if you or someone you know may ever pass through Arizona I'd be more than willing to show the car if someone is interested in verifying what I'm seeing. 

I get down to Phoenix every few years or so.  I have a friend that lives south of Sierra Vista that I go visit. Might try to contact you before the next time I go there.  What color is the exterior of this car?

[X33RS]

Thanks Miller,
  Originally frost green, someone put a quick thin coat of primer over the outside, some of the original black stripes show through in spots, however door and trunk jambs still have original paint.  Has white deluxe houndstooth.   Someone added spoilers and cowl hood way back when, probably when they threw a quick coat of primer on the whole thing just to make it all one color again, but I believe the car to be a flat hood and no spoiler car.  Been sitting like this for 30 years, before that not much history and car hasn't moved.   Trim tag reads X33, interior is 729, paint 59,  and is a 12D build. 
I'm still up in the air on the rearend because I don't know what the date spread would be on the axle housing during that time period at Norwood.  The rear predates the data plate on the car but I'll have to get back under it and do some cleaning to get a good read on all of it.  it's caked with 46 years of grime.  Planned to move this thing over to the lift soon, clean, power wash, start on the brakes etc...I should be able to read the casting numbers better that way.  From what I can see so far it's the early casting housing and I can make out the model year of 8 (1968), I need to clean more to see the month clearly.  I can also make out C....BL   so it's stamped with the C spaced away from the BL for some reason.
  Anyway, you are more than welcome Miller, just give me a shout on here before hand, I'll give you contact info and set something up.  I'll be at BJ this year as well.