More speed NEEDED!!
Thread Starter
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Senior User
Joined: Feb 2002
Posts: 465
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More speed NEEDED!!
Theres a 2.55(is that geared pretty high)
dana 60 rear in my 1970 250, it has a
np435 4-speed, Is there other
trannys that i could slap in,like some type of five
speed,that will get me goin faster cause im not into
losing any low end cause this is one of few trucks
nowadays that actually gets put to pretty brutal heavy hauling
work.if i installed some new heavier valve springs(theres
painted springs in there right now,dont know if thier stock
or not)could i pull extra rpms without doing harm that would
normally occur at higher rpm.
Good ol granny gear could pull grannys house to the
other end of the block!
Fe power
dana 60 rear in my 1970 250, it has a
np435 4-speed, Is there other
trannys that i could slap in,like some type of five
speed,that will get me goin faster cause im not into
losing any low end cause this is one of few trucks
nowadays that actually gets put to pretty brutal heavy hauling
work.if i installed some new heavier valve springs(theres
painted springs in there right now,dont know if thier stock
or not)could i pull extra rpms without doing harm that would
normally occur at higher rpm.
Good ol granny gear could pull grannys house to the
other end of the block!
Fe power
Elder User
Joined: Aug 2001
Posts: 962
Likes: 2
From: Collierville, TN
More speed NEEDED!!
Wow. A 2.55? Are you sure? I thought the lowest (numerical) gear ratio offered by Ford was 3.25:1 in these trucks. I've known cars with lower rear end gearing, but I've never known a truck that low. It would have to be an aftermarket gear set, and would be very strange for a truck that is set up for hauling. Typically, you would expect to find 3.73, 4.10, or higher in these trucks. In any case, changing your rear end ratio is relatively simpler. Higher numerical gears will get you moving a lot easier and help you tow and haul more, but it also means higher revs at speed, lower top speed, and worse mileage. Still, you should at least change to a 3.50 set of gears.
Thread Starter
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Senior User
Joined: Feb 2002
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More speed NEEDED!!
The truck redlines at 70mph in fourth gear and thats
the redline on the speedo which has not been played around
with. first three gears can move weight with no trouble,but
fourth seems like a pretty long gear. the truck can move
a good 3000lbs without loosing rpms on most hills.
Fe power
the redline on the speedo which has not been played around
with. first three gears can move weight with no trouble,but
fourth seems like a pretty long gear. the truck can move
a good 3000lbs without loosing rpms on most hills.
Fe power
Elder User
Joined: Aug 2001
Posts: 962
Likes: 2
From: Collierville, TN
More speed NEEDED!!
Your rear gears are not 2.55:1. Without knowing what your redline and tire sizes are, I can't tell you exactly what the ratio is, but I can tell you that 2.55:1 rear gears with average tires (235/75R15) and a manual tranny (no torque converter slippage) would have you turning only 2000 rpm at 70 mph in 4th gear. Assuming your redline is 4000 rpm, then your actual rear axle ratio is around 5:1.
Fleet Owner
Joined: Jun 1999
Posts: 24,552
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From: Creedmoor, North Carolina
More speed NEEDED!!
My thinking too Karl, I am still wondering what he is calling a red line on a speedo. Most red lines that I am aware of are on the tach. 
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Joined: Jan 2008
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More speed NEEDED!!
Years ago they used to have an orange mark on the speedo to let you know you were now in *Major Speeding Ticket Range*.
Dennis https://www.ford-trucks.com/user_gallery/sizeimage.php?&photoid=1733&.jpg
Please Don't Ask Me Any Tough Questions,
"I'm Saving My Memory For When I Develop Alzheimer's"
78 F-150 429CJ,Silver, Explorer Pkg.
641/2-Mustang 260,Pre-World's Fair Car.
64-Fairlane500 S/C waiting for a 390-4spd.
68-Mustang 289-Sunlit Gold 80,892Mi
78-Buick LeSabre 403 4V
84 Volvo DL Wagon
Dennis https://www.ford-trucks.com/user_gallery/sizeimage.php?&photoid=1733&.jpg
Please Don't Ask Me Any Tough Questions,
"I'm Saving My Memory For When I Develop Alzheimer's"
78 F-150 429CJ,Silver, Explorer Pkg.
641/2-Mustang 260,Pre-World's Fair Car.
64-Fairlane500 S/C waiting for a 390-4spd.
68-Mustang 289-Sunlit Gold 80,892Mi
78-Buick LeSabre 403 4V
84 Volvo DL Wagon
Thread Starter
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Senior User
Joined: Feb 2002
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More speed NEEDED!!
if its not a 2.55 rear end then why would the factory bother
stamping 2.55 on it, the other number is 60,so that would
be a Dana which it is... if some one knows what it actually
is that would be nice...and there is a redline on the speedo
and when i reach it it definitly sounds like its at the redline,
theres no tach so ya gotta know somehow.
Fe power
stamping 2.55 on it, the other number is 60,so that would
be a Dana which it is... if some one knows what it actually
is that would be nice...and there is a redline on the speedo
and when i reach it it definitly sounds like its at the redline,
theres no tach so ya gotta know somehow.
Fe power
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More speed NEEDED!!
the tires are r15/31inch/9.5,np435 4-speed,stock 390 2-bbl
(pretty sure its stock) I assume the rearend is a 2.55
cause theres a 2.55 stamped on it.one of the owners used it
to drag houses down so it might have tranny mods or some
other weird way of gearing things.
Fe power
(pretty sure its stock) I assume the rearend is a 2.55
cause theres a 2.55 stamped on it.one of the owners used it
to drag houses down so it might have tranny mods or some
other weird way of gearing things.
Fe power
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New User
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More speed NEEDED!!
Where are you getting this 2.55 number from?
Is it from a metal tag that is attached to a differntial bolt?
I have never seen less than a 2.75 rear on a Ford truck.
The lowest ford gear ratio I know of, is a 2.50 from a full size car
ONLY.
Dennis https://www.ford-trucks.com/user_gallery/sizeimage.php?&photoid=1733&.jpg
Please Don't Ask Me Any Tough Questions,
"I'm Saving My Memory For When I Develop Alzheimer's"
78 F-150 429CJ,Silver, Explorer Pkg.
641/2-Mustang 260,Pre-World's Fair Car.
64-Fairlane500 S/C waiting for a 390-4spd.
68-Mustang 289-Sunlit Gold 80,892Mi
78-Buick LeSabre 403 4V
84 Volvo DL Wagon
Is it from a metal tag that is attached to a differntial bolt?
I have never seen less than a 2.75 rear on a Ford truck.
The lowest ford gear ratio I know of, is a 2.50 from a full size car
ONLY.
Dennis https://www.ford-trucks.com/user_gallery/sizeimage.php?&photoid=1733&.jpg
Please Don't Ask Me Any Tough Questions,
"I'm Saving My Memory For When I Develop Alzheimer's"
78 F-150 429CJ,Silver, Explorer Pkg.
641/2-Mustang 260,Pre-World's Fair Car.
64-Fairlane500 S/C waiting for a 390-4spd.
68-Mustang 289-Sunlit Gold 80,892Mi
78-Buick LeSabre 403 4V
84 Volvo DL Wagon
Thread Starter
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Senior User
Joined: Feb 2002
Posts: 465
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More speed NEEDED!!
if i remember correctly its on the bottom right quarter
of the pumpkin(stamped right on no tags or nothin)kinda
near the center almost.say the green smiley is the
rear, the 2.55 is stamped about where the tongue is.
unless i mistook a 3.55 for a 2.55, could be some
number stamped on for another reason but im not
experianced enough to know that.
This is my first vehicle
and I aint gonna sell it!
Fe power
of the pumpkin(stamped right on no tags or nothin)kinda
near the center almost.say the green smiley is the
rear, the 2.55 is stamped about where the tongue is.
unless i mistook a 3.55 for a 2.55, could be some
number stamped on for another reason but im not
experianced enough to know that.
This is my first vehicle
and I aint gonna sell it!
Fe power
New User
Joined: Jan 2008
Posts: 0
Likes: 24
More speed NEEDED!!
That 2.55 number has NOTHING to do with gearing in the unit.
You have do the mark and spin > count the revolutions >
It's the Fool proof method of figuring out ratio's.
Dennis https://www.ford-trucks.com/user_gallery/sizeimage.php?&photoid=1733&.jpg
Please Don't Ask Me Any Tough Questions,
"I'm Saving My Memory For When I Develop Alzheimer's"
78 F-150 429CJ,Silver, Explorer Pkg.
641/2-Mustang 260,Pre-World's Fair Car.
64-Fairlane500 S/C waiting for a 390-4spd.
68-Mustang 289-Sunlit Gold 80,892Mi
78-Buick LeSabre 403 4V
84 Volvo DL Wagon
You have do the mark and spin > count the revolutions >
It's the Fool proof method of figuring out ratio's.
Dennis https://www.ford-trucks.com/user_gallery/sizeimage.php?&photoid=1733&.jpg
Please Don't Ask Me Any Tough Questions,
"I'm Saving My Memory For When I Develop Alzheimer's"
78 F-150 429CJ,Silver, Explorer Pkg.
641/2-Mustang 260,Pre-World's Fair Car.
64-Fairlane500 S/C waiting for a 390-4spd.
68-Mustang 289-Sunlit Gold 80,892Mi
78-Buick LeSabre 403 4V
84 Volvo DL Wagon
Lead Driver
Joined: Apr 2001
Posts: 6,175
Likes: 21
From: Texas
More speed NEEDED!!
Me thinks you definitely have taller gears. I don't think you can get lower than 3.33 gears in a Dana 60.
My guess, the marks on the speedo just indicate the speed limit at that time, nothing to do with engine RPMs.
The math comes out like this. With 31" tires, assuming a 1:1 final ratio on your 4 speed, if you're going 70 MPH at an estimated red-line for your 390 of 4500 RPM, you have a rear gear ratio of about 5.9:1
If you have gears this tall and a granny gear transmission, first gear is probably good for about 2 MPH.
So, you have either got some very tall gears, or your engine is nowhere near redline. Get a tachometer just to see where you are running at. With a 390 and a granny gear , you should be able to easily pull 3000lbs with 3.55 gears.
My guess, the marks on the speedo just indicate the speed limit at that time, nothing to do with engine RPMs.
The math comes out like this. With 31" tires, assuming a 1:1 final ratio on your 4 speed, if you're going 70 MPH at an estimated red-line for your 390 of 4500 RPM, you have a rear gear ratio of about 5.9:1
If you have gears this tall and a granny gear transmission, first gear is probably good for about 2 MPH.
So, you have either got some very tall gears, or your engine is nowhere near redline. Get a tachometer just to see where you are running at. With a 390 and a granny gear , you should be able to easily pull 3000lbs with 3.55 gears.
Thread Starter
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Senior User
Joined: Feb 2002
Posts: 465
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More speed NEEDED!!
Is that hole near where the speedo goes on the tranny
a tach port. I have read about a np535 five speed, is
that a 4 speed with over drive or is the final ratio the
same as a four speed.
Fe power
a tach port. I have read about a np535 five speed, is
that a 4 speed with over drive or is the final ratio the
same as a four speed.
Fe power
Cargo Master
Joined: Jul 2000
Posts: 2,281
Likes: 18
From: Northern California
More speed NEEDED!!
>Is that hole near where the speedo goes on the tranny
>a tach port. I have read about a np535 five speed, is
>that a 4 speed with over drive or is the final ratio the
>same as a four speed.
>Fe power
A tach hooks up to the dist not the tranny, you can get a tach for about $30 at most parts stores.
NP offered 2 different 5 speeds, I understand that the 1:1 (non overdrive) was more common. I tried to find one of these before and gave up, most were found in old large trucks like the F500's, so that'd be the place to look. I did find one in a very old truck, but it was a 1:1 final drive.
As for the rear ratio, just jack up the rear and spin the drive line and until the tire makes 1 full turn (2 if it's an open diff, 1 turn if the tire turn the same direction)
I think the sound of the engine is the problem here, it probably sounds like it's higher than it is.
Overdrive for these setups either by tranny swap or aftermarket is not very easy or cheap. the only cheap setup I've heard about was the Clark 5 speed tranny in the few hundred $ range.
>a tach port. I have read about a np535 five speed, is
>that a 4 speed with over drive or is the final ratio the
>same as a four speed.
>Fe power
A tach hooks up to the dist not the tranny, you can get a tach for about $30 at most parts stores.
NP offered 2 different 5 speeds, I understand that the 1:1 (non overdrive) was more common. I tried to find one of these before and gave up, most were found in old large trucks like the F500's, so that'd be the place to look. I did find one in a very old truck, but it was a 1:1 final drive.
As for the rear ratio, just jack up the rear and spin the drive line and until the tire makes 1 full turn (2 if it's an open diff, 1 turn if the tire turn the same direction)
I think the sound of the engine is the problem here, it probably sounds like it's higher than it is.
Overdrive for these setups either by tranny swap or aftermarket is not very easy or cheap. the only cheap setup I've heard about was the Clark 5 speed tranny in the few hundred $ range.
