Is it tough to change the rear differential gear ratio?
Senior Member
Joined: May 2005
Posts: 1,461
Likes: 1
From: Colorado
Without knowing how to set lash and have a set of dial indicators it would just be luck if you got it right. I know some people buy gears from Ford and use the original shims and get them close.
If you have never set up a differential from scratch before it is best left for those that have the experience. I even know some differential "experts" that don't do it very well and develope howling or whining diffs.
Most cities have a differential shop and most can change gears in an afternoon. Depending on your year and age it might be bennificial to just exchange yours for one with the gears you want and all you would have to do is remove your rear axle assembly and bolt in the replacement.
If you have never set up a differential from scratch before it is best left for those that have the experience. I even know some differential "experts" that don't do it very well and develope howling or whining diffs.
Most cities have a differential shop and most can change gears in an afternoon. Depending on your year and age it might be bennificial to just exchange yours for one with the gears you want and all you would have to do is remove your rear axle assembly and bolt in the replacement.
Last edited by Colorado Osprey; May 19, 2008 at 10:27 PM.
Member
Joined: Jul 2003
Posts: 63
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On 4wd do you just have to change f&R ring an pinion?
What are the towing advantages. Putting our Expedition from daily driver into 3k-4k mi annual tow tug duty.
Has 3.55 gears. 5.4l. 265/70R16 LRC Michelins
118,000 on odo
Full rebuild on 4R-100 trans (it grenaded) @ 76,000
What are the towing advantages. Putting our Expedition from daily driver into 3k-4k mi annual tow tug duty.
Has 3.55 gears. 5.4l. 265/70R16 LRC Michelins
118,000 on odo
Full rebuild on 4R-100 trans (it grenaded) @ 76,000
Senior Member
Joined: May 2005
Posts: 1,461
Likes: 1
From: Colorado
Yes, just changing the front and rear ring and pinion will change the gear ratios.
It is advisable to also replace the pinion seal as well as the crush sleeve and the pinion nut. My opinion--If I were that far into the axle I would also replace the inner/outer bearings and wheel seals. I have seen many times just the gears swapped and nothing else replaced though.
Advantages of going to a lower gear will help with standing start power, keeping tranny temps lower and letting the torque converter lock up faster.
Disadvantages are less fuel economy at highway speeds, running at a higher RPM for a given speed and incorrect spedometer and odometer readings, but the spedo./odo. can be corrected with a programmer/scanner.
It is advisable to also replace the pinion seal as well as the crush sleeve and the pinion nut. My opinion--If I were that far into the axle I would also replace the inner/outer bearings and wheel seals. I have seen many times just the gears swapped and nothing else replaced though.
Advantages of going to a lower gear will help with standing start power, keeping tranny temps lower and letting the torque converter lock up faster.
Disadvantages are less fuel economy at highway speeds, running at a higher RPM for a given speed and incorrect spedometer and odometer readings, but the spedo./odo. can be corrected with a programmer/scanner.