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FC Axle ratios (?)
Posted by: Paulsgt ()
Date: July 31, 2022 07:52PM

I'm reading the Corvanatics web site information about the available axle ratios for 1961 FCs with Powerglide. Looks like you could get 3.27 or 3.89 is that right?
How does one drive with a 3.27 and PG? Looks like mine is 3.27/PG. I have built a 95hp engine on an FC block so it will have a bit more power but should I consider going with 3.55 or 3.89?

Please discuss. I'll be going through the diff this week.

Thanks very much!

Enjoy the Corvair!

Paul Sergeant
CORSA Central Division Director / CORSA Treasurer
Lee's Summit, MO
CORSA since 1975
Member – HACOA, Corvair Minnesota, CORSA, Little Indians, POCI


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Re: FC Axle ratios (?)
Posted by: SteveInMarietta ()
Date: July 31, 2022 08:38PM

Paul,
The 3.27 option was only available briefly in 1961, probably because it wouldn't be great for a lot of in-town driving. Maybe others with first-hand experience can be more specific.
Steve

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Re: FC Axle ratios (?)
Date: July 31, 2022 09:20PM

Paul,
What wheel/tire combination are you also considering?

Tailor the final drive ratio with a choice of larger or smaller diameter tires to compensate.

In your scenario, smaller diameter tires will allow you to still use the "higher" 3:27 If you are going on a road trip - use larger diameter tires. For cruising a local car show - go with the smaller set.

Just a thought.....


Dan Davis ~ Pierce County, WA ~ CCF admin ~
CORSA +Corvairs NW + North Cascades Corvairs + Corvanatics
1966 Corsa Turbo coupe ~ ~ 1966 Corsa 140 Coupe ~ ~ 1965 Monza 140/4 Convertible Sierra Tan/Fawn ~ 1964 Monza Spyder Convertible ~ 1960 Monza Ermine White/Red PG ++ ~ 1965 Monza 140/4 CoupeEvening Orchid w/ ivory/black interior ~ 1962 Monza Wagon 102/4 ~ 1963 Rampside/Scamper ~ 1963 Red/Greenbrier ~ 1969 Ultra Van #468

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Re: FC Axle ratios (?)
Posted by: corventure Dave ()
Date: August 01, 2022 12:05AM

I have ran 3.89 and 3.55 in Powerglide FC's over the years.
Also with 95hp and 110hp engines.
In general, one first has to consider what is going to be hauled or loaded in the FC. I'll stick with my Greenbrier that I have personally put 300,000+ miles on over the past 43 years.
It is a factory powerglide and I have built the engine as a 95hp and or 110 over the years.
The 95 gives better bottom end pull with the 3.89. I have recently installed 3.55's in it and it still pulls good, but down shifts earlier and holds low gear longer on hills. Highway speeds the engine doesn't wind up as much with 3.55's.
When I had 110hp and 3.89's the only difference I felt was a little slower from a stop, but stronger at highway speeds.
Basically any of these combinations give good performance, keeping in mind we're driving a brick and not a Corsa.
Over the years I have loaded the Brier up quite a few times. Example: all the parts and supplies I haul to Palm Springs every year. Call it road hugging weight!
Yes, steep hills can pull it down to 45 mph. But again.... it's a brick that will get you there, regardless.

Corventure Dave

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Re: FC Axle ratios (?)
Posted by: irfgt ()
Date: August 01, 2022 02:29AM

I have a 62 with 3.27 and 4 speed and it has plenty of power for everything I have asked of it. I wouldn't rather have any other ratio in fact I am adding positraction to it since I get wheel spin on wet roads accelerating.

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Re: FC Axle ratios (?)
Posted by: Phil Dally ()
Date: August 01, 2022 06:00AM

PhilSide was 3.27 80 hp 4 speed with (25.5 diameter) 195/75-14 and it did everything I ever needed it to do also.

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Re: FC Axle ratios (?)
Posted by: Timothy Shortle ()
Date: August 01, 2022 06:42AM

My 63 Rampside PG, 3.27, and with an 84 (?) HP engine IS NOT a good combination for living on the western slope of Colorado. Even with it completely unloaded it just lacks power. My 64 Corvan 4 speed, 3.27, with 110HP car engine with a factory camper kit performs much better.

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Re: FC Axle ratios (?)
Posted by: Paulsgt ()
Date: August 01, 2022 07:37AM

Without looking it up are 3.55 Ring and Pinions available new? With the Powerglide, it seems like the 3.55 would be the best combination. I probably won't do much heavy hauling with it. Probably just light household hauling and going to car shows, etc... Right now my plan is to use stock FC wheels painted body color with white bowtie caps but maybe down the road I would upgrade.

Thanks for the input guys. More opinions always welcome!

Enjoy the Corvair!

Paul Sergeant
CORSA Central Division Director / CORSA Treasurer
Lee's Summit, MO
CORSA since 1975
Member – HACOA, Corvair Minnesota, CORSA, Little Indians, POCI


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Re: FC Axle ratios (?)
Posted by: TIBCO ()
Date: August 01, 2022 08:31AM

Paul, I don't have as much experience as the others who have already posted, but for what it's worth. I have a 61 Rampside with the factory PG. (Oil cooler, etc.) The engine is out of a 64 PG car. It has the 3.89 gear ratio. I'm running 205/75/14 tires on it. It is usually empty when I drive it, but has had some weight in it from time to time. My experience is it seems to run pretty well up to about 45-50 MPH. From 50 - 65/70 it takes a while. But it will cruise nicely at 65-70 MPH. I have not tried to push it past 70,

Cliff Tibbitts
Nicholasville, KY
CORSA, CKCE, Derby City Corvairs
66 Monza, 140/4sp

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Re: FC Axle ratios (?)
Posted by: WhenIm64 ()
Date: August 01, 2022 10:11AM

Paulsgt Wrote:

> Without looking it up are 3.55 Ring and Pinions available new? <

Bob now replies:

Well, Clark's still shows some NOS, but so do I -- I have NOS early & FC 3.55 R&P sets available as part of my "un-hoarding" project, both stock and PG. One 3.89 set, too.

WhyImWhenIm64

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Re: FC Axle ratios (?)
Posted by: joelsplace ()
Date: August 01, 2022 10:25AM

Since stock FC tires are slightly larger diameter than cars and they are much less aerodynamic wouldn't 3.89s in FCs be a loose equivalent to 3.55s in cars?

Joel
Northlake, TX
5 Ultravans, 138 Corvairs and counting...

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Re: FC Axle ratios (?)
Posted by: TIBCO ()
Date: August 01, 2022 10:33AM

Yes Joel, they are very close. I put a Spyder dash cluster in my Rampside. According to the GPS, the speedo is only off 1 mph at 50. Not too bad in my book. Probably wasn't that close to accurate to begin with.

Cliff Tibbitts
Nicholasville, KY
CORSA, CKCE, Derby City Corvairs
66 Monza, 140/4sp

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Re: FC Axle ratios (?)
Posted by: Paulsgt ()
Date: August 01, 2022 05:12PM

So an update. We disassembled the FC Diff today and found that it is actually 3.89 gears. The gears inside did not match the stamping on the case. (How is that possible? grinning smiley ) I think I'll keep the 3.89 gears.

Thanks for all the info!

Enjoy the Corvair!

Paul Sergeant
CORSA Central Division Director / CORSA Treasurer
Lee's Summit, MO
CORSA since 1975
Member – HACOA, Corvair Minnesota, CORSA, Little Indians, POCI


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Re: FC Axle ratios (?)
Posted by: wittsend ()
Date: August 01, 2022 06:14PM

Paulsgt Wrote:
-------------------------------------------------------
> So an update. We disassembled the FC Diff today and found that it is actually 3.89 gears. The gears inside did not match the stamping on the case. (How is that possible? grinning smiley ) I think I'll keep the 3.89 gears.
>
> Thanks for all the info!
>
> Enjoy the Corvair!

And to think my diff was stamped for 3.89 and I found 3.55's inside. Must have been that "New Math" back in the 60's.

------------------------------------------------------------------------------

***'61 Lakewood, a "Freebie" in hibernation for 27 years - In the process of applying CPR.***

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Re: FC Axle ratios (?)
Posted by: Wagon Master ()
Date: August 01, 2022 07:25PM

> Paulsgt Wrote:
> -------------------------------------------------------
> > So an update. We disassembled the FC Diff today and found that it is actually 3.89 gears. The gears inside did not match the stamping on the case. (How is that possible? grinning smiley ) I think I'll keep the 3.89 gears.
> >
wittsend Wrote:
-------------------------------------------------------
> And to think my diff was stamped for 3.89 and I found 3.55's inside. Must have been that "New Math" back in the 60's.

If I'm putting a diff. together, I grab a case, a gearset, and never look at the stampings. Especially if it's going in a 64. Did lots of manual 3.89's in those.

Been aircooled since 1973
Northwest Ohio 45840



Edited 1 time(s). Last edit at 08/01/2022 07:51PM by 1966-Corsa-GT-180.

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Re: FC Axle ratios (?)
Posted by: Frank DuVal ()
Date: August 01, 2022 09:29PM

I had a customer who was a trim carpenter in Richmond. His van was heavily loaded with tools. And the differential was cooked. All I had in the "good used" pile was a 3.27. There was a marked change in performance with the replacement differential. More clutch slipping needed to take off. But, it did move the van around the hills of Richmond, just not quick. Later he relocated to Myrtle Beach. He called me to let me know how well it performed on the way down there and in the flat lands of Myrtle Beach.smileys with beer

Speaking of heavy loads, I went with a friend (who needed a van drivetrain) to buy the drivetrain out of a 95 van in Hill's Wrecking Yard in Charlottesville VA. Drove up there in my 95 van. I tried jacking the van up with the donor's van jack, my van's jack and the floor jack I brought along the drop the drivetrain. No go on getting the van to go up. So I opened the doors and started removing the axles. Yep, it was the dry storage for axles, about 3 feet high inside. That's a lot of steel. Finally got the weight down, the van up, the drivetrain out, then had to reload the axles.....eye popping smiley

Frank DuVal

Fredericksburg, VA

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Re: FC Axle ratios (?)
Posted by: isucorvair ()
Date: August 02, 2022 05:20AM

My 63 Greenbrier was a 80hp PG, and a 3.55....it was terrible in the rolling hills (flat) of Iowa. I swapped in a 95hp when the 80 gave up, and it became much more drivable (I could run faster than it would move uphill with the 80hp)



Eric P.
DeWitt, IA

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Re: FC Axle ratios (?)
Posted by: JimBrandberg ()
Date: August 02, 2022 05:44AM

PGs are a different animal in a FC.
I ran a '64 110 4 speed in a '63 Van last year and it was awful busy at 65 MPH with a 3.89. I didn't have a 3.55 so I installed a 3.27 with the original VD 102. I sold it before running it a lot but thought a 3.55 may have been peppier. It would have been nice to try the 3.27 with the 110.
The 3.89 was great around town but I live in the country. It may have been more tolerable in a Rampside where you can't hear how fast it's turning. A few times with a 3.27 Rampside I forgot to shift into 4th coming out of town and happily motored along at 60 MPH in 3rd gear. I guess it got plenty of air and blew the carbon out.
It sure seems like more UVs should have had 4 speeds.

Jim Brandberg
Isanti, MN
CorvairRepair.com



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Re: FC Axle ratios (?)
Posted by: isucorvair ()
Date: August 03, 2022 10:22AM

JimBrandberg Wrote:
A few times with a 3.27 Rampside I forgot to shift into 4th coming out of town and happily motored along at 60 MPH in 3rd gear. I guess it got plenty of air and blew the carbon out.


Glad to know I'm not the only one that has done that....in the same truck!


Eric

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Re: FC Axle ratios (?)
Posted by: vairsUPnorth ()
Date: August 04, 2022 09:16PM

Paulsgt Wrote:
-------------------------------------------------------
> So an update. We disassembled the FC Diff today and found that it is actually 3.89 gears. The gears inside did not match the stamping on the case. (How is that possible? grinning smiley ) I think I'll keep the 3.89 gears.
>
Hello Paul,
With 3.89 gearing I suggest you consider taller (at least stock 26.3" OD) tires. This would apply especially for your build up of the engine to LM 95/PG specs. I strongly suggest you upgrade to 15" wheels as there are basically no commonly available tires (other than trailer duty) of stock 26.3" OD or greater to fit a 5" wide [narrow] stock wheel.

My suggestion is to upgrade to 15x6 wheels. In this case most brands of 205/70R15 tire are exactly stock size of 26.3" OD and turn ~800rev/mile. This means your engine will be turning 3100 RPM at 60MPH. If you move up to a 215/70R15 at 26.9" OD at ~750rev/mile this would reduce the RPMs to ~2900 @ 60 MPH. The 205/75R15 is a possibility at 27.1" OD and ~745rev/mile but most of the availability in this size are trailer tires.

Maybe you should try to find a 3.55 diff to go with your 95hp engine. This is what was offered from the factory in 1964. With stock 800rev/mile tires this would give you ~2850RPM at 60MPHH.

I am currently researching the available options for new reproduction stock style steel wheels. I want to find a 15x6 size with the correct offset that will fit stock hubcaps. I will post the results of my research on this thread.

Dale Dewald
President - Corvanatics
Hancock, MI


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