Gear Ratio Question
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Junior User
Joined: Mar 2007
Posts: 86
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From: FL
Gear Ratio Question
First of all I have an 02 f150 4x4 with 3.55 gear ratio. I am running 33 in tires.
I wold like to regear but I am having trouble deciding what gear ratio to go with. The truck is mostly driven in the city, with occasional highway use. My G/F also uses it to pull a two horse trailer around town when she can't use my diesel. Another reason to go ahead with the gear swap is that the limited slip clutches in the rear are shot. My question is what would you guys recommend for a new gear ratio? And who are some good manufactures? Sorry if these have already been answered but I don't seem to have the search capabilities at the moment.
Thanks
I wold like to regear but I am having trouble deciding what gear ratio to go with. The truck is mostly driven in the city, with occasional highway use. My G/F also uses it to pull a two horse trailer around town when she can't use my diesel. Another reason to go ahead with the gear swap is that the limited slip clutches in the rear are shot. My question is what would you guys recommend for a new gear ratio? And who are some good manufactures? Sorry if these have already been answered but I don't seem to have the search capabilities at the moment.
Thanks
Carpenter Local 745
Joined: Apr 2006
Posts: 5,794
Likes: 11
From: on da beach
I would say around 4.10 for front and rear and maybe a Detroit truetrac for the rear diff.
The 4.10s will give you about 2700rpms at 65mph vs. the 3.55s 2350 rpms at 65 mph.
The 4.10s will give you better all around performance with 33s.
4.56s will give you 3000 rpm at 65mph and give you more towing capabilities.
(lower mpgs)
4.10s may suit your daily needs.
The 4.10s will give you about 2700rpms at 65mph vs. the 3.55s 2350 rpms at 65 mph.
The 4.10s will give you better all around performance with 33s.
4.56s will give you 3000 rpm at 65mph and give you more towing capabilities.
(lower mpgs)
4.10s may suit your daily needs.
Senior User
Joined: Dec 2007
Posts: 236
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From: Taxsonville,Fl.
I don't know much about gear ratios but I have a 2002 F-550 with a 7.3 turbo with a 4.88 limited slip rear, and my tires are 225-70-19.5 and 31" tall what do you think my RPM at lets say 60 and mileage will be, I'm still working on it at the time
I know, not good
Thanks in advance
Jim
I know, not good
Thanks in advance
Jim
Last edited by Mr Jimi; Jan 20, 2008 at 03:23 AM.
Senior User
Joined: Dec 2007
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I have an 01 with 35'' tires with 410 in it. Going 70 it only tacks 2100. I have not towed a traler yet but it fells like it has plenty of power.
Tim
Tim
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TWP numbers are about right. I have a stock 2001 with 3.55 gears, tires proabbly about 32 inch and im running 1700 rpm at 65. It all a matter of percent. TWP has 10% bigger tires, 20% lower gears so he should be running about 10% faster rpm than me.---------02f250, leaving your tires the same, if you change from 3.55 to 4.10 thats about 20% so your motor speed will increase 20% at any given ground speed.
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Carpenter Local 745
Joined: Apr 2006
Posts: 5,794
Likes: 11
From: on da beach
Originally Posted by 02f250fx4
I thought that the bigger tires you ran and the higher the gear ratio (ie. 3.55 to 4.10) would keep you closer to stock rpm's than say just keeping 3.55's.
Lower rationwould be a 4.10 higher numerically but lower mechanically.
Adding larger tires (33s) on stock (3.73s) will raise the final drive ratio.
To compensate for the difference the 4.10s will lower the final drive ratio to near stock performance.
Carpenter Local 745
Joined: Apr 2006
Posts: 5,794
Likes: 11
From: on da beach
Senior User
Joined: Aug 2003
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And.. I wish I had 4:33's just to get a bit more pulling power, straight highway I would go 4:11. If you plan to go to 35's or larger anytime in the future look at 4:56's. In my circle of friends the rule of thumb is, 31 - 3:73, 33 - 4:11, 35 -38 - 4:56, 42-44 - 4:88 or 5:13. I only know one person that went 5:13 with a set of 44 boggers and a 460, it was a crazy truck with dana 60s and he broke every axle shaft and u-joint in the truck at least 20 times, I think I'd rather have it bog down and be stuck than break something everytime you go out. One time he completely blew the front diff into pieces and twisted the front driveshaft like a rubberband on a balsa plane until it just sheared off... those were some good times there.
Moderator
Joined: Dec 2001
Posts: 22,436
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From: Louisville,Ky.
My truck has 265/70r17's on it. They are 31.7" tall. @ 80mph, I am turning 2000rpm.
This is why I am going to 4.10's, plus I tow about 7400lbs at times. @5000rpm, I have a calculated top speed of 200mph. Kinda pointless with a 105mph speed limiter. Besides, it's a 4x4 and I don't need any more top speed.
This place seems to have the best prices and the gears include a free install kit.
http://www.nationaldrivetrain.com/
This is why I am going to 4.10's, plus I tow about 7400lbs at times. @5000rpm, I have a calculated top speed of 200mph. Kinda pointless with a 105mph speed limiter. Besides, it's a 4x4 and I don't need any more top speed.
This place seems to have the best prices and the gears include a free install kit.
http://www.nationaldrivetrain.com/