Question about swapping axle gears.

[239]

I’m thinking of changing my 3.55 gears to 3.73 gears. I’d like to change the gears instead of swapping the whole axle. Is a kit like this all I would need? I’d like to re-gear to run 32’s and 4.10’s aren’t an option for me. Thanks for any input.

Amazon.com: Ford Racing 8.8" 3.73 Ring and Pinion Gears M-4209-88373 with Installation Kit: Automotive

Buy Ford Racing 8.8" 3.73 Ring and Pinion Gears M-4209-88373 with Installation Kit: Differential Rings & Pinions - Amazon.com ✓ FREE DELIVERY possible on eligible purchases

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[imp]

I’m thinking of changing my 3.55 gears to 3.73 gears. I’d like to change the gears instead of swapping the whole axle. Is a kit like this all I would need? I’d like to re-gear to run 32’s and 4.10’s aren’t an option for me. Thanks for any input.

Amazon.com: Ford Racing 8.8" 3.73 Ring and Pinion Gears M-4209-88373 with Installation Kit: Automotive

Buy Ford Racing 8.8" 3.73 Ring and Pinion Gears M-4209-88373 with Installation Kit: Differential Rings & Pinions - Amazon.com ✓ FREE DELIVERY possible on eligible purchases

www.amazon.com

This is one option for changing gear ratios, not the easiest nor least labor intensive. Aside from questioning the motive (3.55 to 3.73) is a very small increase, considering the effort and cost involved. No "kit" will replace the experience needed to swap gearsets. It may include tools critical to measuring gear parameters, though. OTOH, I have set up gears for 60 years without such tools.

Different gears will require establishing pinion gear depth, pinion bearing bearing preload, ring gear backlash and contact pattern,
and differential gear location as well as preload. All of these parameters are critical. An entire axle assembly, used, and known to run quietly, is by far an easier solution, is preferable, IMO..

 

[MrQ]

Ditto, those axles are easy and cheap to find if you just want to go 3.73's. I'm not sure why 4.10's aren't an option as that is a stock gear ratio (can find these on sports (95-00) and sport tracs (02-up or else its drums instead of discs)? I would definitely run those with 32's so you won't lose as much MPG and reduce the work on the skinny pedal, more than with 3.73's.

You won't see much of a difference between 3.55 and 3.73.

 

[donalds]

A rear diff is like Pandoras box just open it up and see

I've built a few rear differentials and can say if you have never done it and you only want to do it once just get a known good one and service it

 

[239]

I should have mentioned that this is way beyond me and I will have a shop do it. I’d rather swap gears since my axle is in great shape with no rust. I can always find a used one, and although it’s not likely, I run the risk of having to rebuild it too, so I’d rather just rebuild mine and put in new seals and all.

I’ve researched rebuilt axle assemblies with a warranty and they go from $700-$1000 so again, rebuilding sounds better. I do agree about the 4.10’s though, I was using the wrong tire size when I came up with 3.73.

4.10’s seem a lot better.

 

[donalds]

If you can afford to buy a factory remanufactured unit and have a mechanic install it
Hell yea brother

 

[239]

If you can afford to buy a factory remanufactured unit and have a mechanic install it
Hell yea brother

Maybe I’ll get a reman axle but I’m still leaning towards swapping the gears in mine. But whatever’s cheaper

 

[donalds]

Swapping gears is cheaper if you know exactly what you are doing and in for
But way more expensive if you mess it up even just a little

 

[Josh P]

I've swapped junk yard explorer 8.8 axles under a few of my cars and I've never had a bad one. $100-150 + the cost of some new seals and bearings for peace of mind is the cheapest route.

 

[Mbrooks420]

Having your axles rebuilt is a solid option. Definitely do your research on who does it, the quality of labor on differentials (much like transmissions) is the biggest factor for a successful long lived set of gears. A set of properly installed gears is usually better than factory since they tend to set the gears up a little tighter.

 

[collinstm57]

Depending on the mileage, the whole thing might need rebuilt. I did mine with the help of online resources and a few $$$ for tools. You need a dial indicator to set up the pinion/gear set tolerances and there were differing opinions on those #'s

At 100k one of my outer bearings had migrated in an 1" or so. The pinion bearing was noisy. Did not replace the gear set because it looked good.

It is running good with a slight whine around 60 which is the gear set.

I do wish I had bought and installed a LS kit. As is I have 3 wheel drive at best...

Do your research and people on line will tell you everything you need to know. If you do it, I suggest making a stand to hold it. It is pretty awkward trying to hold it still and measure the 0.010 - 0.030 tolerances (depending on who you talk to) Pay attention to rebuilding vs bearing replacement #'s.

Oh and make sure you RTV the pinion shaft before installing or you will be replacing the seal again to do that.

If it is high mileage, suggest new U-Joints as they take out the pinion seal/bearings as well.