OVERDRIVE

[TAKEA]

I just convinced my wife that we should buy a Corvair convertible (she fondly recalls the one I owned when we were married in 1973). In order to drive it long distances on California highways, I'd like to have overdrive. Is there a manual or automatic tranny with overdrive available as an aftermarket item?

[bbodie52]

Welcome to the Corvair Forum! Congratulations on your 40th anniversary year. My wife and I were married in April 1972, and we have also been driving Corvairs since we started dating and still drive a Corvair! We have driven Corvairs all over the USA and in Europe while I was in the Air Force, and I've never felt that an overdrive transmission was needed. However...

There is a five speed transmission conversion available for the Late Model (1965-1969) Corvair, but it is not cheap...

Q: Where do I get one, and how much are they?
A: Clark's Corvair Parts made a special arrangement to sell ten units, on a first come, first served basis, for an incredible introductory price of $2295.00, including free shipping. Clark's has sold all ten of those units. Linn Richardson is working on another run of ten units, to be priced at around $3,000.00, depending on kit options. Contact Linn at (425) 485-9807 to check on the availability.

http://aboxer.tripod.com/

Shift Your Corvair Into Overdrive

With The World's Only 5 speed!

The new AMERICAN BOXER R&D, LLC 5-speed, based on the venerable Borg Warner T-5, is a giant leap forward in getting the most out of your Corvair. From mileage to performance you haven't experienced anything quite like the feeling of shifting your Corvair into overdrive.

You will marvel as you purr along in 5th gear at 60 miles per hour, turning barely 2200 RPM (depending on configuration) compared to 3000 RPM with your current transmission. See the chart for available ratios and how they compare to your stock set up.

The transmission is available as a complete unit and is sold with the custom mounting bracket, shift linkage, and all necessary installation hardware included. You can contact us directly by calling Linn Richardson at (425) 485-9807. Or send inquiries by e-mail to: aboxer@juno.com.

Improve Your Fuel Economy*
Add Enjoyment to Your Driving
Greatly Enhance Your Performance

Created by
AMERICAN BOXER R&D, LLC
Corvair Performance Parts Engineering
*A T-5 equipped Corvair averaged a winning 29.75 MPG in the 1999 Spokane, WA Economy Run.

[TAKEA]

Thanks for the info, Brad. After I buy a car, I'll drive a while and then decide whether to contact Linn. As you say, it's pricey.

I will definitely buy a 65-69. I previously had 2 '65 converts (a Monza and a Corsa) and 1 '66 (Monza), all with 4-speed, plus a '64 Greenbrier with automatic. The converts handled beautifully; in those days there was nothing like them. Interestingly, I could corner the Greenbrier hard and not tuck the axle under; I presume that's because it had a higher roll center than the 60-64 cars. I'm 77 now and drive much more conservatively.

I enjoy a stick, but my wife would prefer an automatic. I wonder if changing the final ratio on an automatic to lower the RPMs would overload it and burn the fluid. Chances are no one has done that to find out.

-- Bob

[bbodie52]

The two-speed Powerglide transmission has a solid reputation. I have read that some even prefer them in some forms of racing (such as autocross). Considering that high performance and hard work environment involved without failure in competition, and that Corvair automatic transmissions do well without the need for an external transmission fluid cooler, I would not think that a different differential ratio gear set to keep the engine speed down on the highway would be any problem at all for the Powerglide. If the clutches and bands are already in good condition and not slipping due to incorrect fluid levels or pump problems, once the planetary gear set has fully engaged it would not start slipping or have a difficult time "locking in" simply because of a higher final drive ratio.

Evidence of internal automatic transmission slippage is discolored transmission fluid with a burned odor. If the fluid level is maintained at a correct level and is clean, the Powerglide transmission is usually reliable — especially for continuous high speed highway cruising for long distances. Pulling a heavy load – such as with a fully-loaded Corvair or when towing a trailer – makes an automatic transmission work harder, as does driving on hilly or mountainous terrain. Automatic transmissions are also slightly less-efficient than manual transmissions, since a little torque converter (fluid coupling) and internal pumps do absorb a little horsepower when compared with a clutch and manual transmission.

With regard to the desire for increased fuel efficiency and lower highway engine speeds, here are some considerations other than a five-speed overdrive transmission or a differential final drive ratio change...

Late model 1965-1969 Corvairs have a lot of room in the rear wheel wells, and unlike the EM Corvairs the speedometer is driven by the left-front tire instead of a cable from the transaxle. So it is possible to fit some oversized rear tires with a larger outside diameter to obtain a slightly-higher final drive ratio and a slightly slower engine RPM at highway speeds without changing the differential gears or installing an overdrive transmission. A computer-controlled Electronic Fuel Injection (EFI) and a distributorless ignition system can also be fitted to a Corvair engine, and the modern computer-controlled fuel and ignition systems do a better job of regulating fuel usage, providing somewhat greater fuel efficiency and perhaps enhancing operation using less-expensive Regular gasoline instead of Premium with 110 hp and 140 hp engines in LM Corvairs — if you want to consider that option (approximately $1500). High ambient temperatures, hilly terrain, or a heavily-loaded Corvair might limit your ability to run on Regular, low-octane fuel, however.

Here is of useful link that describes Corvair tire and wheel options if you want to move away from the original 13" wheel size (which also gives you many more tire options as you switch to 14", 15", 16" or greater-diameter wheels). A larger-diameter wheel coupled with a modern low-profile tire can result in an overall tire diameter on the front that is very close to the original 13"Corvair tire diameter (which maintains speedometer accuracy). As previously mentioned, rear tires with a larger outside diameter can be fitted on the rear, to provide you with slower engine speeds. The drawback with two different tire sizes on your Corvair is that you cannot rotate the tires to improve tire wear patterns and enhance tire life. Modern all-weather radial tires do offer better handling, braking, and tire wear performance than older designs. Tire options in 13" sizes are increasingly limited in that obsolete size, too. I made the switch to 14' or larger-diameter tires in 1970 and would never consider going back to 13" sizes (unless I was concerned about some form of Corvair show competition where having an all original Corvair would be a concern).

Sizing Corvair Wheels and Tires
http://autoxer.skiblack.com/tires.html

Hete is a link to some further Corvair Center comments regarding the use of a different final drive ratio in your differential...

http://corvaircenter.com/phorum/read.ph ... 088,475199

Here is a link that describes an Electronic Fuel Injection conversion kit for the Corvair that makes use of many standard GM components.

Corvair TBI Fuel Injection

http://corvair-efi.com/



The above engine is in a modified LM Corvair sedan that was part of the Corvair of the Month competition in October 2013. The owner/builder is Jon Crisman (vairynuts) of Cedar Falls, IA. If you were interested in the EFI conversion, you might consider sending him a Private Message (PM). He might provide you with some user feedback regarding this installation on his Corvair.

viewtopic.php?f=15&t=6438&p=44110&hilit ... efi#p44110