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I'm getting ready to have my rear diff rebuilt. I currently have 3.55 ratio. will this work for me? Will it bolt right in, or do I have to go with 3.73 or higher numerically (lower gears)? I was thinking of going lower anyway but i get almost 20 mpg on highway and 95% or more of my driving is commuting. I'M running 265/70/16 but going back to 265/75/16. To do all of this do I have to get a different differential?
 



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I'm getting ready to have my rear diff rebuilt. I currently have 3.55 ratio. will this work for me? Will it bolt right in, or do I have to go with 3.73 or higher numerically (lower gears)? I was thinking of going lower anyway but i get almost 20 mpg on highway and 95% or more of my driving is commuting. I'M running 265/70/16 but going back to 265/75/16. To do all of this do I have to get a different differential?

As long as your current differential is open and not limited slip it will bolt right in. The gears have no impact unless you go 4.56 or higher, in which case you'll have cross pin clearance difficulties.
 






As long as your current differential is open and not limited slip it will bolt right in. The gears have no impact unless you go 4.56 or higher, in which case you'll have cross pin clearance difficulties.

Agreed. I have 3.55 now and it was not a problem to put it in. The Ford 8.8 does not have a carrier break so as long as you have an open diff then it can be done. Since you are only going with 3.73 then you will not have a problem.
 






Thanks for quick response guys. Is going from 3.55 to 3.73 big difference. Right now engine is at 1800 rpms at 70 MPH. A friend who does the same thing Btf does (off road fab) says don't change because my mileage will suffer, and is it hard to drive on the street with a locker. Never done it. How about drivrtrain ware? I'll be on the street mostly just thought it would be nice to have a locker when I needed it. Had a LSD on a couple other trucks and it wasn't that great but they were Ford LSDs maybe that makes a difference, huh. Need good advice before I spend the money.
 






Thanks for quick response guys. Is going from 3.55 to 3.73 big difference. Right now engine is at 1800 rpms at 70 MPH. A friend who does the same thing Btf does (off road fab) says don't change because my mileage will suffer, and is it hard to drive on the street with a locker. Never done it. How about drivrtrain ware? I'll be on the street mostly just thought it would be nice to have a locker when I needed it. Had a LSD on a couple other trucks and it wasn't that great but they were Ford LSDs maybe that makes a difference, huh. Need good advice before I spend the money.

no, going to 3.73 from 3.55 won't be a big difference. Generally you should go "up" two increments to make it even worthwhile from a cost standpoint, unless you just swap in a used 3.73 diff.

Personally I think the 3.55 gears are a bit short but they do make for good highway mileage if you don't have a lot of hills and stay with the stock tire size.

I've had my locker in for almost a year now in my DD and most of my driving is on the street. It won't cause additional wear on the drivetrain that I know of. might cause additional wear on the rear tires if you like to power through turns with the rear locked though ;). I mostly coast or use light throttle in the turns and haven't had any issue with the tires. Main thing is to just remember you have a locker and watch the turns when in slick conditions on the road. Other than than, when you are driving straight or in good conditions you won't really notice it's back there.

Use a good quality gear oil in the 75W-140 weight and it should last you a long time.
 






At 70, your rpms will be between 2000-2200 with the 3.73s. It's not too bad driving on the street with a locker. You have to adjust your driving a little with the locker. Just be very light on the gas around turns or coast thru a turn and it will unlock just fine. If you are hard on your ex, then you will start breaking stuff/wearing out tires bad when making turns. My spartan locker unlocks just fine. Makes lots of ratcheting in tight parking lots but it is supposed to do that.
 






Holy crap! You guys are fast, you should work in a customer service oriented job, lol. I like to drive in the snow and highways get black ice on them, does that mean a locker wouldn't be good for me? Didn't know it ratched trough corners, never knew why they made noise. Should I get a LSD instead
 






If you are going to be in an area where you have black ice, then go with a limited slip. A locker would cause oversteer in slick conditions. They are better for offroad but a good limited slip (like eaton truetrac) will give great handling on road and give some descent traction offroad. If I had loads of cash sitting around, I prolly would have got a truetrac lsd. Since you are getting a re-gear, it would be the perfect time to put the truetrac in.
 






Agree 100%. A truetrac is much better than the ford trac-loc because it is gear driven and won't wear out like the clutch type limited slips. they are also "tighter" and can be locked up if you ride the brakes slightly or partially engage the parking brake. The 8.8 one will work in your rear diff. Here's one guy on the forum with an 06 who loves them. It will work in your truck too since the rear diffs are the same:

http://www.explorerforum.com/forums/showthread.php?t=317166&highlight=maximum+traction+solution

and here it is in snow and icy conditions:

http://www.youtube.com/watch?v=kDErvAGc50U

http://www.youtube.com/watch?v=vO7aormfeac
 






Well after reading all of that it looks like I will hold off on the locker until I get a 3/4ton as a DD since It's clear that a locker and my daily driving style just don't mix.
 






Well after reading all of that it looks like I will hold off on the locker until I get a 3/4ton as a DD since It's clear that a locker and my daily driving style just don't mix.

Thankfully, I don't drive mine hard. Otherwise, I'd be wearing out parts/tires all the time.
 






Holy crap! You guys are fast, you should work in a customer service oriented job, lol. I like to drive in the snow and highways get black ice on them, does that mean a locker wouldn't be good for me? Didn't know it ratched trough corners, never knew why they made noise. Should I get a LSD instead

I don't know about everyone else on here, but I keep the modified sub-forum in an open window on my desktop. I've got a 3 monitor setup so I can multitask pretty well.... I also use ForumRunner on my iPhone so I get notified when one of my subscribed threads is updated....

I've got a LSD but I'm only 2WD. I've been talking to James (Ronin8002) about adding a locker and it's benefits; and I've decided to do it. I've got to go with a different type of locker as I have a LSD. I don't have to worry about black ice down here, but it does rain a lot and the roads can get slippery... I am consciously aware of it though and I don't power through turns anyways, so I'm not too worried about it.....

Unless you drive like a bat out of hell like Triton, you'l probably be alright. Just know that it's there and drive accordingly and I think you'll be fine...
 






Thanks for all the info. Didn't mean to highjack your thread. So I'll get the Eaton trutrac does $460 sound about right?
 






Thanks for all the info. Didn't mean to highjack your thread. So I'll get the Eaton trutrac does $460 sound about right?

Yeah as long as its 913A561. Price sounds right.
 












As Ronin said in his thread, the hardest part was getting the toe links and upper ball joint off the hub. Once I got the diff down and out the truck, I started cleaning it with loads of brake cleaner (make sure you let the brake cleaner dry). To put the locker unit itself in only took between 5-10 mins while taking my time. Do yourself a favor like I did and put grease on the gears when you put it in. If you don't, it will be hard to take it back out because the way the pins are designed.
It was easy to install.
 






I am installing mine tomorrow, will let you know how it goes.
 






A question for Ronin and skysthelymyt, how did you refill your diff? I was underneath looking at the diff today, and there is not much clearance to refill the diff.
 






A question for Ronin and skysthelymyt, how did you refill your diff? I was underneath looking at the diff today, and there is not much clearance to refill the diff.

Get yourself a little fluid hand pump from the auto parts store. That's what I used.
 



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I used a piece of clean water hose (small diameter). I was using a small hose but it was taking wayy tooo long so that's when I switched to the water hose.
Whatever you use, make sure it's clean.
 






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