Ok, its official...

[VetteVirgin]

There is not one single original part in my 61's driveline!
I had thought that perhaps the rear axel had a shot, but when I finally worked my way to that portion of the car this weekend I discovered a open 3.36 "BB" passenger car differential carrier that appears to be from '57 attached to a housing with both fill AND drain plugs plus a vent on the drivers side. I didn't look for numbers on top of the axel tube but wouldn't be surprised to find them there.
So now I have to decide what to do with what I believe is a pre-68 M21 and those 3.36 gears - I truly despise the amount of clutch slip required to get this thing moving from rest with that 7.39 initial ratio! Oh highway driving is lovely with 70 around 3k and 80 below 3.5k, but city driving is just one huge arguement for California stops!
My original thought was to replace the 3.36's with a set of Richmond 3.73's or a date correct 3.70 chunk but now I really don't want to waste money on this cobbled up rear end. I am real close to abandoning all hope of restoration in favor of resto-modding and installing a Meyer 4 link 9-inch set-up. I really didn't want to do anything that involved either cutting or welding the body or frame but at this point I think my best bang for the buck lies in mods or living with what I have. I can do a lot of mods for what a correct date coded entire driveline will cost and it would never be truly original anyway.
In the short term, I think I will solve my initial drive ratio blues by replacing the M21 with a wide ratio M20 which would give me a much more livable 8.6 initial ratio while maintaining the comfortable highway cruising. The net cost should be minimal once I sell the M21. Later I may go with a TKO or Richmond (love the 5 speed with O/D) but that decision can wait.
I do have a question for those that have installed rack and pinion either with a tube frame or the Meyer kit in a 61 or 62: How did you deal with the vin tag? Did you go to DMV before making the mod and get a vin sticker for the body? Or did you move the VIN plate or modify the original column to maintain the correct VIN location? I just imagine selling it out of state and seeing the buyer roll into inspection with the original steering column strapped to the passenger seat!
Sorry for the rant, but sometimes this Corvette archeology project gets a bit frustrating.

DT

 

[Mac]

You don't sound like you're ranting... just blowing off a little steam...

I expect the actual procedure for securing the VIN varies from state to state (check with your local DMV) but, regardless, keep good records of what you're modifying in case you're called upon to explain what happened...

-Mac

 

[maxphunn]

"I truly despise the amount of clutch slip required to get this thing moving from rest with that 7.39 initial ratio!"

Just curious, can you elaborate on the clutch slip thing?

 

[VetteVirgin]

Basically it feels like I'm starting in 2nd gear. Blip throttle to 2500 and S-L-O-W-L-Y ease clutch while applying more throttle (hence "slipping"). If I am not extremely careful with throttle and clutch it bogs. Off throttle in first it bucks like a bronco. I've read that some of you guys like the close ratio/3.36 combo, but its just not for me. Perhaps I'm just too used to my MGA with its granny 1st and 4.3 diff. Sadly, I chirp the tires in the little MG all the time in 1st and have NEVER had even a single squeek from the Vette (I have no desire to dump the clutch at 3000+ just for a little tire chirp).
Of course my crappy shift linkage contributes a lot to my hatred of this combo. It looks like they used a Hurst shifter and the original linkage from whatever they pulled the M21 out of. Reverse takes a hard slap from neutral to engage and first and second feel like they are binding half the time. I will be installing the BW/muncie shifter kit when I do the tranny swap.

 

[toms silver 60]

Try some shorter tires

The 2.20 and 3.35:1 ratio are a bad first gear combo. I can't imagine anyone being happy with it. You might try a shorter/fatter tire to bring the diameter from about 27 to 26 inches, ie 235-60-15. That should help it about 4%.

 

[VetteVirgin]

OK, I popped a few Midol and reevaluated with a better attitude. It's actually not as bad as I described above in my post inspection hissy-fit. I drove it to work today and can pull out without too much slippage with between 1 and 1.5k rpm, not the 2.5k my twisted memory spewed forth.
The real issue is the linkage and shifter since I have to make a concentated effort to put it in first and if I'm the least bit distracted I will find myself starting in 3rd.
I think I'll hold off on the the M20 swap temporarily - at least until after I have driven it with the proper BW shifter with muncie linkage.
Perhaps I also need to forget about wanting to at least maintain the "feel" of the orginal 283 driveline and trade my plans for an updated "270" engine (date coded 283 block, full roller cam and rockers, aluminum heads, Edelbrock dual quads) for the visceral pleasures of stroke and torque.
I saw this small block Dart 427 short block on ebay...
BTW does anyone know what would be the maximum size wheel and tire that will fit on the rear of a 61 with stock axel width and no trunk or fender surgery?

DT

 

[magicv8]

In the short term, I think I will solve my initial drive ratio blues by replacing the M21 with a wide ratio M20 which would give me a much more livable 8.6 initial ratio while maintaining the comfortable highway cruising.
DT

my 66 Sting Ray has a 3.08:1 diff and a 2.5:1 first gear muncie which should be the same final ratio as a 2.2:1 Muncie and a 3.36:1 diff. I have been happy with this combination for over 20 years, and I suspect that you would be too if your car had a little more torque in the lower rpm range. Changing to the 2.5:1 first gear gear set will help. Upgrading the engine to a higher horsepower level at higher rpm will diminish available low end torque.

With my setup behind a plain factory hydraulic lifter cammed 350, I can let the clutch out on a slight uphill grade at 700 rpm idle without touching the accelerator pedal. The first three gears have good torque for city driving and the final drive is the same as yours. I have 26.8inch tall tires, not low profile replacements.

 

[VetteVirgin]

You're still 5% lower than me in 1st. The idea of maintaining the original feel of a 61 is gradually fading away in favor of the driveability provided by massive quantities of low end torque.
I moved the vacuum adv from metered to full (against the explicit instructions that came with my Pertronix distributor) and the off-idle response seems to have improved. I still have no idea what is inside my mystery meat 350, but as long as it isnt puking its guts out it gives me time to amass the funds for the driveline upgrade. I'm beginning to feel like Wile E. Coyote - every time I look at my 58 MGA all I see is a new driveline!
I DO like the idea of "magic" numbers in terms of displacement and if I don't install a 283, a small block 427 WOULD be pretty cool. I'm thinking tripower (if it fits under the hood), super case M22W, Gear Vendors O/D and 9" rear in the 3.36 or 3.55 area. That would hit all my "nostalgia rod" buttons!

DT

 

[magicv8]

You're still 5% lower than me in 1st.
DT

If you change the Muncie to a 2.5:1 first gear, you're car will be 10% below mine. Easily done. I had my 2 spare Muncies rebuilt that way.

 

[Oz's 59]

Opposite problem in my "all orginal" '59 with 4:11... GREAT around town but really cranking at 70 mph (3700 rpms). Would love to change out my 4-speed for a 5-speed or perhaps even switch rearends but can't mess around with the car's value. Soooooo, C1 around town & very short trips (less than 1-hr) & C6 for unbelievable all around/anytime performance. Life is good !

 

[JohnZ]

The 3.36 with an M20 (2.54:1 1st gear) is an excellent all-around combination - that's what I have in my '67. There's a reason (which you noted) that the T-10's and Muncies with a 2.20:1 1st gear always had the 3.70 as the standard axle.

 

[maxphunn]

Can the ratio of 1st gear be checked by counting rotations of the crank balancer to rotations of the trans output shaft (with trans if first of course)?

 

[magicv8]

Can the ratio of 1st gear be checked by counting rotations of the crank balancer to rotations of the trans output shaft (with trans if first of course)?

check your speed at 1000 in 4th gear, then bring the car up to that mph in 1st gear. The tach shoud read about 2200rpm or 2500 rpm depending on the 1st gear ratio.

PS: the same applies to a trans out of the car - just twist the tailshaft 1 rev with the trans in 1st and the input shaft will give you the answer with 2.2 or 2.5 revs

 

[VetteVirgin]

I took a look on Craig's List for the heck of it and now I have a "0" ring early M20 with 2.56's sitting in the garage waiting to be installed this weekend. Zero mile rebuild never filled with oil that looks brand spanking new! If this tranny is as good as it looks, the wife will have to pry me out of the driver's seat after the swap!