Transmission swap

[Steve D.]

I have a '63 that I would like to drive daily on a 20 mile (one way) commute mostly on the freeway. Is there a workable transmission swap for a later transmission (5 or 6 speed) with higher gears or overdrive ? Does the drive shaft have to be modified or replaced ?

[Ed Jennings]

Re: Transmission swap

Might be a whole lot simpler and cheaper to swap differential gears. If you currently have a 3.70 or 4.11, going to a 3.08 or 3.36 would make a big difference.

[Steve D.]

Re: Transmission swap

Ed

I think the current rear end is a 3.36. I 'm trying to verify that. Although I haven't measured the tires and checked the speedometer gear to see if everything matches up yet, I have observed that at 65 to 70 mph the tac reads in the 3000 range. I was trying to get the cruising RPM down towards 2000.

Steve

[Ed Jennings]

Re: Transmission swap

That sounds more like 3.70 numbers. A 3.08 will get you down closer to where you want to be.

[Ed Jennings]

ps

I had a 71 with LS5 and a 3.08. Seems like it ran about 2250 or so at 65-70. Been a long time ago, maybe some one with a tall geared car can give you some current numbers.

[Duke W.]

Re: ps

Multiply the tire revs/mile times the axle ratio to determine the revs at 60 MPH. The OEM 6.70-15s are 760 revs per mile; 225/70R-15 are the same; 215/70s are 775 and 205/75s are in this ballpark.

3.70 x 760 = 2812

3.05 x 760 = 2341

Revs can be determined at any other speed by linear proportioning, or just make an x-y plot using the origin and the revs at 60 to draw a straight line.

A Richmond 5 or 6-speed can be installed, but it's expensive and not easy.

My recommendation is to get a beater to drive to work and save the '63 for weekend fun. I don't think it makes much sense to use a collectable car for everyday yeoman tasks.

Duke

[Walt McGaw]

Duke beat me to it.

I was getting the info Duke was posting and recalculating my rpm's at 60. I have a 3.08:1 ratio in my 72 with an automatic. At 60 mph on the highway, the engine is turning right between 2300 and 2400 rpm. It calculates out to 2346, but the tach isn't that detailed. At 80 mph, the engine is turning just over 3100 rpm.

Walt

[Walt McGaw]

Tire size i s 225/70R15 (762 revs) *NM*

[Joe L.]

Re: Transmission swap

Steve----

I agree with Duke; this probably isn't the kind of car that you'd really want to use for commuting. However, if that's what you want to do, I'd recommend a change to higher (lower numerically) rear gears, too. Go to 3.08 or, even, 2.73 which were once available from GM for the 63-79 style Corvette differential assembly. However, if you currently have a close ratio 4 speed, I'd recommend changing that to a wide ratio. This will be a direct, bolt-in swap and will give you much better first gear performance with the higher rear gears.

A 5 speed Richmond is a fairly straight-forward swap, although some modifications will need to be made to the driveshaft and other components. A 6 speed, either Richmond, Borg-Warner T-56, or ZF, is a MAJOR effort. I DO NOT RECOMMEND a swap to either a 5 or 6 speed, though. The car will lose MUCH value and you will NEVER gain enough in terms of gas mileage or reduced cruising noise to justify the expense of such a swap.

[Eric H.]

Re: Transmission swap

Steve -

I have been driving my 65 small block to work about 2 to 3 days a week (when weather's clear), about 50 miles round trip. I have 3.36 rear gears. Does 70 (verified by GPS) at about 2800 to 2900 RPM. Frankly, I enjoy the humm.

Ric

[Steve D.]

Re: Transmission swap

Thanks everyone.

[David D.]

Re: Transmission swap

Daniel, Another alternative is the GM Tremec 5 speed. Check it out on Fortes website, www.fortesparts.com. I am always glad to hear of people who want to actually DRIVE their cars. Dave

[Duke W.]

Re: Transmission swap

You didn't mention what engine you have Steve, but my SWC has the SHP engine with a CR trans and a 3.08 axle. This makes it a great freeway cruiser with enough top speed to almost lift the front end off the ground, but with a 75 MPH first gear, it's not very enjoyable in traffic - like a five speed with no first gear.

Also, I expect that terrible seat and some marathon drives as a young man are the primary cause of my middle age back problems. I love the car, but would rather be keel-hauled than have to do stop and go commuting in it, today.

Duke

[Dennis F. King]

Re: Transmission swap

Steve
Contact Dennis Rosenthal in Newnan GA. AllMusclecars.com He may be about to do a swap on a '67 BB. He might share the experience. Dennis