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I am considering changing the gearing out in the rear of my 1968 Galaxie 390/C6. I have researched it extensively and read more opinions that I can count. Of course each case/car is different. Based on all that I read I am leaning on going from the stock 270 to a 3.5. I am looking for a little more street pep without ruining my highway driving. What are everyone's thought's, impressions, comments or opinions?
 

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I am considering changing the gearing out in the rear of my 1968 Galaxie 390/C6. I have researched it extensively and read more opinions that I can count. Of course each case/car is different. Based on all that I read I am leaning on going from the stock 270 to a 3.5. I am looking for a little more street pep without ruining my highway driving. What are everyone's thought's, impressions, comments or opinions?

Hello TonyC2639,

I recently went from a 2.73 to a 3.25 in my early 70's Caprice Classic. That made a difference but I don't think I'd go any higher than a 3.25 without an overdrive transmission. Maybe I'm just use to 25 years of the 2.73 gear but it does rev noticeably higher on the highway and I wouldn't like to rev a big block unnecessarily (factory 454).

If you want extra off the line zip why not convert the C6 to a wide ratio planetary gear set. Granted a bit pricy but still cheaper than an adapter and an overdrive transmission.

Just thoughts...
 

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+1 for 3.25 gears when you don't have overdrive, and still want to cruise on the hiway.

3.25 will be a very noticeable difference from the stock 2.70 and is a great street and hiway gear.

3.70 and lower if you have overdrive....
 

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Hello TonyC2639,

I recently went from a 2.73 to a 3.25 in my early 70's Caprice Classic. That made a difference but I don't think I'd go any higher than a 3.25 without an overdrive transmission. Maybe I'm just use to 25 years of the 2.73 gear but it does rev noticeably higher on the highway and I wouldn't like to rev a big block unnecessarily (factory 454).

If you want extra off the line zip why not convert the C6 to a wide ratio planetary gear set. Granted a bit pricy but still cheaper than an adapter and an overdrive transmission.

Just thoughts...

Well I never come out to this site without learning something. The wide planetary gear option is totally new to me. Barring the cost difference would that be a better solution overall. Would it provide the desired result?


Thanks to all for the 3.25 recommendation. Everyone agrees so that will be my plans if I go that way.
 

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Well I never come out to this site without learning something. The wide planetary gear option is totally new to me. Barring the cost difference would that be a better solution overall. Would it provide the desired result?


Thanks to all for the 3.25 recommendation. Everyone agrees so that will be my plans if I go that way.
(Take this for what it's worth... dated 2nd hand info. lol) I heard these lower gear sets originally came in UPS trucks... as those had the Ford 300 inline 6 with the C6 auto. They were gutless taking off when fully loaded, so they had a lower first gear installed in the trans. It leaves a big gap between 1st and 2nd gear, but does give a bit more snap taking off. Offhand, I'm not sure what the exact difference is between the lower and standard 1st gear ratio.

Best bet, would be to find people who have used the lower first gear in a street car, and see if it made much of a difference. With a 3.25 swap, you would feel the difference in power/gearing in all three gears. Of course, you could always do both. :)

Looks like the E4OD guts are what people are doing nowadays... and is a great option... especially paired with the 3.25 gears.

Good Luck!
 

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The C6 gear ratios..

1st - 2.46
2nd - 1.46
3rd - 1.0

The Ford E4OD / 4R100 overdrive trans has a very similar gear train/planetary.

The E4OD / 4R100 ratios...

1st - 2.72
2nd - 1.54
3rd - 1.0
OD - 0.71

The original E4OD / 4R100 gear train (minus the overdrive) can be swapped into the C6 with minor machining.

These days there are vendors that sell a "low gear" or "wide ratio" (same thing) gear set for the C6 based on the E4OD gear train.

There may be custom options from said vendors.

1st gear difference is approx 11%
2nd gear difference is approx 9%

In drag racing timed runs there will be a measurable ET difference between the gear sets.

I have a 66 Galaxie with 390 and C6, and have the E4OD / 4R100 gear train in it.

You can't tell the difference in normal street driving.
Oh yes, maybe a little more punch on launch... but really hard to tell without timing it.
"seat of the pants" feel on the launch.... nah.
But I have a very healthy 390... so maybe that's why... (shrug)

For the record, my Galaxie had 3.70 gears that the previous owner installed, and I went back to stock 3.00 gears, with the wide ratio trans.


AFAIK there was never a C6 option from the factory with the wide ratio / low ratio gear set.

ALL C6's came with the ratios listed above. 2.46 and 1.46

Ford Racing even published a bulletin for installing the E4OD gear set in a C6.

http://performanceparts.ford.com/download/instructionsheets/FordInstShtM-7398-F.pdf

Google search....

"c6 wide ratio gear set"

Here's one...

http://www.tciauto.com/tc/c6-low-gear-planetaryhtml/

Note that the E4OD and 4R100 are essentially the SAME trans.

Ford updated the E4OD later in production and changed the name to 4R100.

They are still basically the same trans.
The major difference being the 4R100 has beefier internal parts.

I'd still change the rear gears to 3.25, even with the wide ratio trans gear set.

:)
 

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Discussion Starter #8
The C6 gear ratios..

1st - 2.46
2nd - 1.46
3rd - 1.0

The Ford E4OD / 4R100 overdrive trans has a very similar gear train/planetary.

The E4OD / 4R100 ratios...

1st - 2.72
2nd - 1.54
3rd - 1.0
OD - 0.71

The original E4OD / 4R100 gear train (minus the overdrive) can be swapped into the C6 with minor machining.

These days there are vendors that sell a "low gear" or "wide ratio" (same thing) gear set for the C6 based on the E4OD gear train.

There may be custom options from said vendors.

1st gear difference is approx 11%
2nd gear difference is approx 9%

In drag racing timed runs there will be a measurable ET difference between the gear sets.

I have a 66 Galaxie with 390 and C6, and have the E4OD / 4R100 gear train in it.

You can't tell the difference in normal street driving.
Oh yes, maybe a little more punch on launch... but really hard to tell without timing it.
"seat of the pants" feel on the launch.... nah.
But I have a very healthy 390... so maybe that's why... (shrug)

For the record, my Galaxie had 3.70 gears that the previous owner installed, and I went back to stock 3.00 gears, with the wide ratio trans.


AFAIK there was never a C6 option from the factory with the wide ratio / low ratio gear set.

ALL C6's came with the ratios listed above. 2.46 and 1.46

Ford Racing even published a bulletin for installing the E4OD gear set in a C6.

http://performanceparts.ford.com/download/instructionsheets/FordInstShtM-7398-F.pdf

Google search....

"c6 wide ratio gear set"

Here's one...

C6 Low Gear Planetary - TCI® Auto

Note that the E4OD and 4R100 are essentially the SAME trans.

Ford updated the E4OD later in production and changed the name to 4R100.

They are still basically the same trans.
The major difference being the 4R100 has beefier internal parts.

I'd still change the rear gears to 3.25, even with the wide ratio trans gear set.

:)

Well that was certainly a wealth of information. Thanks so much for taking the time and trouble! I'm learning so much! I have a lot to read up on here and research to do. One question...I found this set a few days ago while searching. They are vastly different in price than the link you provided. Are they not the right set or are they just cheaply made?



https://www.oregonperformancetransmission.com/product/OPT-KC6GRP.html
 

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Well that was certainly a wealth of information. Thanks so much for taking the time and trouble! I'm learning so much! I have a lot to read up on here and research to do. One question...I found this set a few days ago while searching. They are vastly different in price than the link you provided. Are they not the right set or are they just cheaply made?



https://www.oregonperformancetransmission.com/product/OPT-KC6GRP.html

That kit does not include the rear planet, it is not a "complete" gear train.

The one I linked to is a complete gear train and includes the rear sprag race and needle bearing to convert from the factory brass washer setup.
The rear factory brass washer is a failure point in the stock trans under heavy load conditions.

Keep searching... there are many vendors and different levels of kits out there. :wink2:

I also have my doubts about the kits that do not include the rear planet.

When I did my conversion, (long time ago)
I'm pretty sure I had to use the complete E4OD gear train as the stock C6 rear planet would not work.
The angle of the sun gear teeth that mesh with the rear planet are different, so you must use the complete gear train.

Maybe they have changed somehow? to allow use of the stock C6 rear planet? IDK...
 

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That kit does not include the rear planet, it is not a "complete" gear train.

The one I linked to is a complete gear train and includes the rear sprag race and needle bearing to convert from the factory brass washer setup.
The rear factory brass washer is a failure point in the stock trans under heavy load conditions.

Keep searching... there are many vendors and different levels of kits out there. :wink2:

I also have my doubts about the kits that do not include the rear planet.

When I did my conversion, (long time ago)
I'm pretty sure I had to use the complete E4OD gear train as the stock C6 rear planet would not work.
The angle of the sun gear teeth that mesh with the rear planet are different, so you must use the complete gear train.

Maybe they have changed somehow? to allow use of the stock C6 rear planet? IDK...

+1

I'd also like to add the stock C6 is one of the worst offenders in parasitic energy loss. Meaning you loose a considerable amount of horsepower within the transmission that never makes it to the rear wheels. It is turned into heat and ejected out the radiator via the internal transmission cooler or external transmission cooler if so fitted. A portion of the parasitic loss is a function of the horsepower differential (torque and RPM) across the transmission (input to output). Meaning the heavier the vehicle or loading from gearing and/or the higher horsepower engine the more parasitic loss.

You can help reduce a portion of that by substituting Torrington bearings in place of certain heavily loaded flat washers in the transmission. Also by using a higher quality set of frictions and steels.

If you're curious to see which flat washers are converted I "rollerized" two 1966 C6's. There are loads of pictures if you like that sort of thing along with captions.

https://www.fordmuscleforums.com/galaxie-pages/610433-1966-c6-build-rollerization-part-2-modification.html

You can buy the kits to rollerize a C6 but since I had a cheesy little lathe and mill I just bought the Torringtons and turned down the necessary pieces myself and saved a considerable amount of money.

Cheers
 

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Discussion Starter #11
+1

I'd also like to add the stock C6 is one of the worst offenders in parasitic energy loss. Meaning you loose a considerable amount of horsepower within the transmission that never makes it to the rear wheels. It is turned into heat and ejected out the radiator via the internal transmission cooler or external transmission cooler if so fitted. A portion of the parasitic loss is a function of the horsepower differential (torque and RPM) across the transmission (input to output). Meaning the heavier the vehicle or loading from gearing and/or the higher horsepower engine the more parasitic loss.

You can help reduce a portion of that by substituting Torrington bearings in place of certain heavily loaded flat washers in the transmission. Also by using a higher quality set of frictions and steels.

If you're curious to see which flat washers are converted I "rollerized" two 1966 C6's. There are loads of pictures if you like that sort of thing along with captions.

https://www.fordmuscleforums.com/galaxie-pages/610433-1966-c6-build-rollerization-part-2-modification.html

You can buy the kits to rollerize a C6 but since I had a cheesy little lathe and mill I just bought the Torringtons and turned down the necessary pieces myself and saved a considerable amount of money.

Cheers

Wow this group is so educational my mind is blown. I am learning so much. I loved your previous thread on rollerizing the C6! Very educational. I don't have the machining skills but I have friends who do. Even better I also learned a lot about the C6 from that post. I have a lot to think about but its great knowing what all my options are. I can't thank you guys enough!
 

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Wow this group is so educational my mind is blown. I am learning so much. I loved your previous thread on rollerizing the C6! Very educational. I don't have the machining skills but I have friends who do. Even better I also learned a lot about the C6 from that post. I have a lot to think about but its great knowing what all my options are. I can't thank you guys enough!
Hello TonyC2639,

Thank you for the kind words, happy to help and share what I've learned.

Good luck on whatever you decide to do.

Cheers
 

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Discussion Starter #13
While we're on the subject of transmissions the fellow who sold me the car said there is an external adjustment you can make to the transmission that will change I believe the timing of the shifts? He said it is just a screw you turn? Anyone know anything about this?
 

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While we're on the subject of transmissions the fellow who sold me the car said there is an external adjustment you can make to the transmission that will change I believe the timing of the shifts? He said it is just a screw you turn? Anyone know anything about this?
Hello TonyC2639,

It depends which screw. There is an adjustment on the side of the C6 case which is for the intermediate band. There is a very specific tightening sequence for that band. Too loose and it slips and burns, too tight it never fully releases and burns. Either way you roast the band and it's complete tear down time.

Now there is a vacuum modulator on the back (near the indent portion of the pan) and most of them have a tiny screw where the vacuum line attaches. This allows you to adjust (within the capability of the particular modulator as they are colour band coded) either the shifts later and firmer or sooner and softer. If you find you run out of adjustment you can purchase a different colour banded modulator which has a different operating range.

Cheers
 

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Hello TonyC2639,

It depends which screw. There is an adjustment on the side of the C6 case which is for the intermediate band. There is a very specific tightening sequence for that band. Too loose and it slips and burns, too tight it never fully releases and burns. Either way you roast the band and it's complete tear down time.

Now there is a vacuum modulator on the back (near the indent portion of the pan) and most of them have a tiny screw where the vacuum line attaches. This allows you to adjust (within the capability of the particular modulator as they are colour band coded) either the shifts later and firmer or sooner and softer. If you find you run out of adjustment you can purchase a different colour banded modulator which has a different operating range.

Cheers

Well now that you've put a name to this little gizmo I was able to research it better. Lots of info out there and on YouTube. Looks like something safe enough to mess with if I'm careful. As always thanks for the great information!!!
 
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