New Rear End ???
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New User
Joined: Jun 2003
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New Rear End ???
About a year ago I bought a 1978 F150 with a 302, and a three on the tree. Since then I have rebuilt the engine, new clutch system, new fuel pump, new fan clutch, and a lot of cleaning.
I have been doing all of this work for two reasons, one I love the truck, and two I need it to pull my newly restored boat. Everything went great until I went to pull the boat out. I ended up haveing to ride the clutch out of the hole, which caused quite a bit of smoke. My guess is that the gear ratio is way off, since first will let me go to 35mph and not over rev the engine. Which leads me to the question.
How do I check the gear ratio currently on the truck?
What size/ratio would you recommend?
Thanks for your help!
I have been doing all of this work for two reasons, one I love the truck, and two I need it to pull my newly restored boat. Everything went great until I went to pull the boat out. I ended up haveing to ride the clutch out of the hole, which caused quite a bit of smoke. My guess is that the gear ratio is way off, since first will let me go to 35mph and not over rev the engine. Which leads me to the question.
How do I check the gear ratio currently on the truck?
What size/ratio would you recommend?
Thanks for your help!
Senior User
Joined: May 2003
Posts: 235
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From: Bremen, georgia
New Rear End ???
jack up the back of the truck, put a mark on the drive shaft and on the tire. rotate untill you tire makes a compleate revolution. count how many times you drive shaft went around that will tell you almost what it is. or pull the diff cover and start countin teeth.
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Joined: Jan 2008
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New Rear End ???
I just bet it is a code 13 rear meaning a 2.75:1
First check the rating plate on the door for the code.
About the spinning of the tire and counting turns.
It has now been determined that the whell would have to be spun 10 times to get an accurate ratio.
What to put in ?
3.25 or 3.50 Gears come to mind
First check the rating plate on the door for the code.
About the spinning of the tire and counting turns.
It has now been determined that the whell would have to be spun 10 times to get an accurate ratio.
What to put in ?
3.25 or 3.50 Gears come to mind
Senior User
Joined: May 2003
Posts: 235
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From: Bremen, georgia
New Rear End ???
Remove the differential cover, count the teeth on the ring (the big one to the side) write this number down, and then count the teeth on the pinion (the small one in front) write this number down. Replace the cover. Refill with gear oil, go wash your hands, find the piece of paper you wrote the numbers on, divide the larger number by the smaller number. The resulting number will be your gear ratio. Now go outside move your truck, clean up all the gear oil that spilled all over your nice and clean driveway because I forgot to tell you to put a pan under the differential before removing the cover. NOW go drink a big cold beer!
Post Fiend
Joined: Jan 2003
Posts: 10,323
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From: Montana Territory
New Rear End ???
If its a ford 9'' you should be able to just look at the tag attached to the bolt on the passenger side of the housing it sticks out so you should be able to see it fairly easily. Use a piece of charcoal or pencil lead to mark it if its faint. You can clean it up with so wd40. The raing plate is good if someone has not changed the axle. Good luck. You might want a 3.50 or 3.73 gears for that setup and they are easily found at your local junkyard for about $80. Just get the whole center section.
New User
Joined: Jan 2008
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New Rear End ???
Stephen, That only works for a Dana rear.
Ford 9" rears don't have inspection covers {which I'm, pretty sure he has.}
He would have to remove the rear axles,the driveshaft & then the whole differential to get to the gears.
l
Ford 9" rears don't have inspection covers {which I'm, pretty sure he has.}
He would have to remove the rear axles,the driveshaft & then the whole differential to get to the gears.
l
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Posting Guru
Joined: Aug 2002
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From: Minneapolis, MN
New Rear End ???
He would have to remove the rear axles,the driveshaft & then the whole differential to get to the gears.
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Joined: Jun 2003
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New Rear End ???
Okay,
So it looks like I have a 1.5:1 rear end. Based on doing the tire rotation method. I consitently got 3 shaft rotations for every 2 tire turns.
Still think a 3.5 or 3.73 is what I need?
Thanks again for your help! Must appreciated!
So it looks like I have a 1.5:1 rear end. Based on doing the tire rotation method. I consitently got 3 shaft rotations for every 2 tire turns.
Still think a 3.5 or 3.73 is what I need?
Thanks again for your help! Must appreciated!
New User
Joined: Jan 2008
Posts: 0
Likes: 24
New Rear End ???
1.5 ?
That's wrong.
Go here
http://www.clubfte.com/users/mil1ion...ruckCodes.html
and scroll to *almost the bottom of the page* and see your choices ,as all the ratios are there for F-series trucks.
That's wrong.
Go here
http://www.clubfte.com/users/mil1ion...ruckCodes.html
and scroll to *almost the bottom of the page* and see your choices ,as all the ratios are there for F-series trucks.
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New User
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New Rear End ???
I assume I was supposed to test that with the trans in neutral? Would it have been possible for someone to replace the rear diff with one that was that small a gear ratio?
I checked it again rotating the tire 20 times. I got just i little over 30 shaft turns.
I checked it again rotating the tire 20 times. I got just i little over 30 shaft turns.
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New User
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New Rear End ???
ah yes, the factor of two.
So would taking the rear end up to a 3.5 or 3.73 solve my problem do you think? Or is there something else I should try in stead. I'm just worried that if I continue to drive the truck that I'll have to replace the clutch again very soon. Based on the ammont of smoke and the smell from the last time I was trying to pull the boat out or backing it into my driveway. The engine was rebuilt with RV cams so it should have a lot of low end torque.
So would taking the rear end up to a 3.5 or 3.73 solve my problem do you think? Or is there something else I should try in stead. I'm just worried that if I continue to drive the truck that I'll have to replace the clutch again very soon. Based on the ammont of smoke and the smell from the last time I was trying to pull the boat out or backing it into my driveway. The engine was rebuilt with RV cams so it should have a lot of low end torque.