what gears do i put in?
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Senior User
Joined: Oct 2006
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From: youngstown, ohio
what gears do i put in?
hey everyone, pretty soon i'll be getting new tires. im upgrading to 35'' instead of keeping my existing 33'' ones. they keep telling me im going to need to change the gear ratio. my truck still has the factory gears in the both front and rear axles. is there that big of a difference in running 35's over 33's? if i do need to change them then what gear ratio do i put in them? i do most of my driving on the road, but occationally take it off road. is there like a good inbetween for both? are the front and rear gear ratios the same? is it that tricky to attempt to do it myself? thanks for the advice.---ryan
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From: In the Middle
3.50 is a common ratio.
Click the following link and enter your information from your door tag and it will tell you what your factory gear ratio is http://www.medicine.wisc.edu/~mrm/bronco/ftvin.cgi
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Click the following link and enter your information from your door tag and it will tell you what your factory gear ratio is http://www.medicine.wisc.edu/~mrm/bronco/ftvin.cgi
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Ok, I ran my truck with 3.50 for two years with 33's. I would have kept them in if i did not blow the rear axle after dropping the clutch as 2500 rpm. They are still good gears. I have since switched to 4.11 rear and 4.09 front. I had 33's, with the new gears and I run 35's now and the difference is not that noticable between the two sizes. I run mostley run on the street and mudding ocassionally. If you really want to swap gears I would stick with the 4.11 and 4.09. I had some one setup the rear axle but I put the front gears in myself after doing alot of homework just so i didn't mess it up. I even had the guy who set up the rear, look at the fronts.
One key fact is to get a good shop to do the work if you are willing to pay.
One key fact is to get a good shop to do the work if you are willing to pay.
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Senior User
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From: youngstown, ohio
i thought the front and rear gear ratio was suppose to be the same? so your saying 4.11's are good for both street driving and some mild off roading for 35" tires?
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They should try to be the same, Some gear ratios will not match up perfect all the time. Gears for a dana 44 front axle ratio is 4.09 ,The ford nine inch will accept 4.11. the reason for this is the difference in the ring gear diameter. these gears are as close to match as possible. This is the maximum difference of ratios I would have. You should only be running 4x4 when you need it( snow, mud, sand). the difference is only minor. tire pressure difference can easily make up the minor difference.
The short answer is that the lower gears with not make the truck bogg down when you start and its easier on the axles and tranny. 3.70 and 3.89 ratios are also available.4.11 are good combo for me, i dont see freeway driveing so i dont hit high rpms when street driving.
The short answer is that the lower gears with not make the truck bogg down when you start and its easier on the axles and tranny. 3.70 and 3.89 ratios are also available.4.11 are good combo for me, i dont see freeway driveing so i dont hit high rpms when street driving.
Last edited by slinger34; Dec 6, 2006 at 10:26 PM.
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Gears should match but the front needs to pull a little harder or go faster than the rear or the truck will want to swap ends.
The swap to the 400 will make up for the taller tires with more available torque.
The swap to the 400 will make up for the taller tires with more available torque.
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Joined: Oct 2006
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From: Clinton,Illinois
I use to have a 1978 f250 with 3.55 gears and 36.1/2 tall tires.
It was a 351 and a 4 speed and it would not get out of it's oun way
Now, I have a 1977 f250 with a 400,auto and 33s and 4.10s and let me tell ya, I wish the 78 would of had 4.10s.
Go with the 4.10s, you will love the differance.
There are some websites that will tell you what your gear ratio is with the 35s and the 3.55s, I would guess in the low 300s some where
It was a 351 and a 4 speed and it would not get out of it's oun way
Now, I have a 1977 f250 with a 400,auto and 33s and 4.10s and let me tell ya, I wish the 78 would of had 4.10s.
Go with the 4.10s, you will love the differance.
There are some websites that will tell you what your gear ratio is with the 35s and the 3.55s, I would guess in the low 300s some where
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From: fargo, nd
but it isnt actually required that you change gearing... your speedometer will be off though... so you could just change the speedometer gear at the tranny to compensate for the tire diameter change and stick with the gears youve got... your interstate rpms will just be lower and your truck will feel like its a little down on power... so if you want a cheap and easy fix- swap speedometer gears rather than differential gears... my 78 f250 4x4 has 3.54 gears front and rear... im keeping them when i go to 37s and just swapping speedo gears because ill have a 545 ci so ill have more than enough power to turn them
Last edited by darrin1999; Dec 7, 2006 at 11:44 AM.
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Senior User
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From: youngstown, ohio
hmmm. thanks for the advice guys...i guess i have alot to think about. i looked at that chart and it said go with the 4.11's or 4.56's with 35" tires. so you think i should just wait till i get the 400 in and the 35's on the truck to see what i need to do if anything with the gearing? this truck has its stock axles still so im guessing is a ford 9" rear end and a dana 44 up front
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I have a 390 in my 79' and when i switched engines, 300 to 390 I felt that the 4.11 gears are fine for both engines. I think that the 4.11 would be good for the street. 4.56 may be too low. With your new engine you will ahve the torque to still move with 4.11 gears. Mostly it is personal preference. All I suggest is that you should get lower gears.
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when different ratios are used.... Most front to back gear ratios are only one point off ..not two.
ie: 4.11's and 4.10's
4.10's & 4.09's
I think this ratio you are enquiring about depends on what you are going to do with the truck. If it's all mud * 4x4'ing ....then taller gearing is warranted.
If more hwy and street driving is going to be done... I don't see a valid reason to change them.
ie: 4.11's and 4.10's
4.10's & 4.09's
I think this ratio you are enquiring about depends on what you are going to do with the truck. If it's all mud * 4x4'ing ....then taller gearing is warranted.
If more hwy and street driving is going to be done... I don't see a valid reason to change them.