C2 engine/transmission/rear axle combo

[Mark H.]

From what I have read in the archives, it looks like my '64 has a less than optimal (awful?) engine/transmission/rear axle combination - it's an L75 with a '68 M-21 transmission and 3.08 gears in the rear. Starting from a dead stop is a bear to say the least. To make this car drivable (around town, some highway crusing), would changing to an M-20 (or at least swapping out first gear in what I have) and a 3.36 rear axle be the way to go?

Thanks.

[Mike M.]

Re: C2 engine/transmission/rear axle combo

If it were never to run interstates, i'd go with a 3.7 or 4.11 to 1 ring and pinion. hell, go for the 456's. Seriously, 3.7 : 1 is ideal for quick acceleration and interstate RPM's that won't kill the SB. At 70 mph and with 3.70: 1 , you'll be running about 3000 RPM. easy way to remember, 370 , three K @ 70. mike

[Duke W.]

Re: C2 engine/transmission/rear axle combo

I recommend swapping the CR for a WR that was used with the L-75. A WR will shorten the first three gears about 16 percent. Of couse, you'll have a much bigger gap between third and fourth, but the 3.08 is a great freeway cruise gear, 3100 at 80.

You don't know what doggy around town means until you combine a SHP engine with a CR and 3.08. That's what I have in my SWC, but I love it. Way back when I never lost a street race if I had enough road in front of me. The 3-4 shift at 6500 is 127 MPH.

Duke

[Wayne K.]

And I'll bet the front end really drops ......

between that 3-4 shift at 127 mph.

[Mark H.]

Re: C2 engine/transmission/rear axle combo

How many RPM do you have to turn to prevent stalling when you start from a full stop? I have yet to master a truely graceful start from a standing stop - I need more RPM and clutch slip than it seems to me should be necessary to get going. Reverse works fine, though.

[Joe L.]

Re: C2 engine/transmission/rear axle combo

Mark------

A wide ratio transmission is the best for street operation, hands down. You can't just "swap out first gear in what you have" to convert your close ratio to a wide ratio. You need to change the input shaft/gear AND the cluster gear. You don't need to change the first gear, at all.

Your best bet for a rear end ratio for OVERALL driveability is going to be a 3.36:1. A 3.08 will work ok, though, for your engine with a wide ratio four speed.

[Duke W.]

Re: C2 engine/transmission/rear axle combo

The 300 HP engine should be easier to launch than a SHP, and FI might be the toughest depending on how it's tuned.

I usually ease out the clutch at idle (900) with no throttle until the engine just stumbles to just get the car moving, then give the throttle a little blip and quickly release the clutch. This doesn't make for real smooth starts (I just tell people it's a "race car".), but miminizes clutch wear. My worst nighmare is having to stop on an upslope.

It might help to have the idle mixture set a bit rich. When you let out the clutch and revs drop, manifold vacuum drops too and there isn't enough to draw fuel through the idle circuit. That's why it stumbles.

If you block the heat riser it is even worse, but wiring the valve open is okay.

Duke

[Jim T.]

Re: C2 engine/transmission/rear axle combo

I sure agree with Joe that the wide ratio would be fine in your 64 with the 3:08. That is what I had in my 64 L75 and I really liked it. Its been a long time, but it could really wind the gears. Taking off in 1st was not a problem even after installing a Crower mild hydraulic cam and lifers.