Hello all,

Found out about something new today. I have been making plans to change the tranny and rear end on my 73. (See: road race set up) I spoke with one of my local suppliers today and he has come across a gear set up that goes into a m20/m21 4 speed manual transmission. After some discussion with him as to how this works, it appears that the 1:1 ends up in 3rd and 4th ends up being approximately 1:1.2+ ratio. Or in other words a 20% plus overdrive. This means I can keep the 3.73 rear end, wide ratio trans and have a final drive appearing to be 3.13 if my math is correct.

Has anyone heard of this before?

I will keep you posted as to what I find out about this.

Alex

I haven't heard of a setup like that before, but I'd be interested in learning more about it. I've given some thought to switching to a 5 or 6 speed tranny to save a little while cross country cruising. But didn't like the aspect of losing some "originality" of the car. If the price is reasonable this setup sounds like it would be a good alternative.

Thanks!

If what you are saying is you replace third with fourth and put the new gear in as fourth, sounds like you would lose a lot of RPMs going from 2nd to 3rd. ??? I think I would leave 1st, 2nd and 3rd alone and just change fourth to the new ratio of 1:1.2

changing just 4th gear sounds like a better idea you would lose too much rpm between gear changes otherwise.

Well...
After some additional research, it appears that I was on a wild goose chase. Although there are some prototypes of the 4spd O.D. there are none that are holding up to use and abuse. These are not ready for sale for at least 6 months, if ever.

Well the quest continues for a good setup of rear ratio and tranny. I am thinking maybe a richmond 6 speed but the $2500 is a little steep.

Any other suggestions?

Alex

how about a 6 speed in a C3......http://www.corvetteforum.com/techtips/viewsubtopic.php?SubTopicID=203&TopicID=3

Alex,
I think you will have to have a really DRAMATIC increase in gas mileage to justify over $2000.00 to get overdrive. I know we have machinists out here on the forum so maybe you should direct the question to them.....can any of them make a gear for a 4 speed to give a more economical 4th gear for a price that is reasonable enough that you do not have to live in the car to get a good cost to return on your investment?
I guess actually it would be cheaper to make a form and pour the steel into it ??

looking at it another way you might be able to find a 4 speed with shorter 1-2-3 gears easier. Then install a taller rear gear giving you the same final rate in 1-2-3 and a taller final gear in 4th. Better mileage/same acceleration/much cheaper/easy installation.

I am now considering a Paul Newman conversion in my C3. Basically a transplant of C4 drivetrain and suspension into the '73. I have seen these in straight axle cars and they are tremendous. They also come with a tremendous price tag. One that is local is reported to have cost $100k. I am not interested in such an extreme, but what the heck, I am allowed to dream, huh?

Alex

I was reading a car magazine within the past two weeks and read an article on rebuilding M22 transmissions. It lists four different gear sets, the fourth of which is a fourth gear overdrive. The case is a "super case" designed to withsatand more punishment than the standard case and the cost of the case was listed as $300.00 ( if memory serves ). There were no prices for the gear sets. If you are still interested, I will go back through the magazines and try to find the article again and post where I found it.