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I have a muncie M-20 in the 55. It has a 3.55 ratio rear...it is low..

Would I need to go up to the 3.08 or 3.36 for better mileage and cruising???

The 3.36 might not be enough change, and the 3.08 might be the answer...

Any thoughts would be greatly appreciated..
 

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Tough off the line especially without power steering.(Clutch wear also with the 3.08)
 

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My 56 wagon was born with 3:55s and a 3 spd. , the 265 does OK with a 2:54 First Muncie , it is still 1:1 in fourth , I also use 28" tall rear tires. 3:08 sounds a little tall to me as you would probably have to slip the clutch to get moving but yes it would cut the RPM once in fourth.
 

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The Muncie is never going to give you the best of both worlds (good off-the-line and highway mileage).

A TKO 500 5-speed transmission would do that pretty well with a 3.55 rear gear.

Or how about going with an automatic? A 700R4 and a 3.08 rear is a really good combination. Not bad with a 3.55 rear either but a better highway car with a 3.08.
 

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The Muncie is never going to give you the best of both worlds (good off-the-line and highway mileage).

A TKO 500 5-speed transmission would do that pretty well with a 3.55 rear gear.

Or how about going with an automatic? A 700R4 and a 3.08 rear is a really good combination. Not bad with a 3.55 rear either but a better highway car with a 3.08.
YEs we have a winner, this is an awesome combo 2.87 1st and .67 5th. gives you a 2.28 final drive or 2000 rpm at 74 mph. This is my setup.
 

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another option is to use a Saginaw 4 speed (reasonable cost ,questionable strength) and add an overdrive from a full syncro 3 speed Saginaw. The cases and outputs will interchange .
 

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When I had a 350 in my 55 sedan I had a Saginaw 4 speed with a 3.08 and it was great. Was good for cruising and still had good bottom end.
 

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The Saginaw 4spd with the 3.11 first gear would be a good combo with a 3.08 rear.

Only trouble is the OP would have to change both his transmission and rear. If he goes for the TKO500, he can keep the 3.55 rear.
 

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more on gear ratios

I have a muncie M-20 in the 55. It has a 3.55 ratio rear...it is low..

Would I need to go up to the 3.08 or 3.36 for better mileage and cruising???

The 3.36 might not be enough change, and the 3.08 might be the answer...

Any thoughts would be greatly appreciated..
I have been building 3-4-5 speed trans since the early 1980's. So I have had occassion to try different ratios over the years to see what works best,
The combination of 3:08 rear and the M-20 (2:52 ratio) requires you to increase the engine RPM's and feather the clutch out on level ground. On a hill it requires you to rev up the motor quite a bit to get the car to leave from a starting point. All of this seriously increases clutch wear.
Many of the guys on here are trying to find a good cheap combination that will work with a 4 speed box. Saginaw makes a box with a very low first gear (you can look it up) and you can pair that with a 3:08 rear end which will give you what you want.
if you do not like the Saginaw, then Borg Warner makes a 4 speed with a 3:43 first gear which also can be matched with a 3:08 rear which will give you a great take off and great cruising.
Then next option would be the m-20 2:52 ratio first gear and 3:36 rear end. I do not reccomend using a 3:08 rear end with the M-20 (2:52 rear) end
I have three 55-57 pumpkins for sale all rebuilt and fresh sitting on a shelf.
A 3:08 and a 3:36 and a 3:70 ratio. all the above are non-posi. I also have a fresh M-20 muncie for sale on this advertising site

Feel free to check my reccomendations with other gear people
Gary Howard The Muncie man dba Garys Gearbox
 

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More on Muncies

My 56 wagon was born with 3:55s and a 3 spd. , the 265 does OK with a 2:54 First Muncie , it is still 1:1 in fourth , I also use 28" tall rear tires. 3:08 sounds a little tall to me as you would probably have to slip the clutch to get moving but yes it would cut the RPM once in fourth.
Muncie first design 1963-65 2:56 Ratio M-20
" " 2:20 " M-21

Muncie 2nd design 1966-69 2:52 Ratio M-20
" " " " " 2:20 " M-21
" " " " " 2"20 Ratio M-22 Rock Crusher

Muncie 3rd design 1970-74 2:52 Ratio M-20
" " " 1970-74 2:20 " M-21
" " " 1970-74 2:20 " M-22 Rock Crusher

The Borg Wraner made the 2:54 box and is often confused with the muncie nunbers especially since we don't use these numbers every day. Please excuse the correction
Gary
 

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My 55 used to have a 3.42 axle, but now has a 3.08. Dropping highway RPMs by only 10% made a noticeable difference. The car has a mild 327, Muncie M20, and 27.4" tall tires. It takes a little effort starting off from a stop, but it's not bad.

Something no one has mentioned above is engine size and torque. I'd say a 3.08 would work fine with a 350 engine a similar tire size, unless the engine has a big cam. But I wouldn't try it with a 283 unless tires were much shorter.

On another note, I haven't made the move yet, but am looking at an aftermarket Muncie M22Z (Auto Gear case and gears) with a 2.98 1st gear. Also looking at 5-speeds, but the Muncie will bolt right in, use the same shifter, etc. However, I would need to change the yoke and clutch disc to take advantage of the M22Z's higher spline count.
 
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