3.45 to 3.73 Axle Swap for Towing — Worth It on a '93 Splash?

[lil_Blue_Ford]

If you have a UPAP near you, they are dirt cheap for different, or at least used to be. I think I was paying like $60-80 for them. Would have been stripping them more often if they were cheap to ship.

They aren’t that cheap anymore, the Pittsburgh one is about $150 an axle now

 

[PetroleumJunkie412]

They aren’t that cheap anymore, the Pittsburgh one is about $150 an axle now

Eh. Still cheaper than buying a set of gears and messing up three pinion seals.

 

[lil_Blue_Ford]

Eh. Still cheaper than buying a set of gears and messing up three pinion seals.

True story

 

[Li'l Work Truck]

I found an '11 FX4, 8.8" rear with a 3.73 trackloc (I think that's what it's called) and disc brakes. They wanted $675 for it. Didn't last a week on the site before it disappeared. I was bummed. It had 175k on it. I also didn't have $675 to take it home. All shopping is window shopping when the wallet has a boot on it.

 

[PetroleumJunkie412]

I found an '11 FX4, 8.8" rear with a 3.73 trackloc (I think that's what it's called) and disc brakes. They wanted $675 for it. Didn't last a week on the site before it disappeared. I was bummed. It had 175k on it. I also didn't have $675 to take it home. All shopping is window shopping when the wallet has a boot on it.

As far as I remember, fx4 and level 2 ended in 2009... irrespective, I shoved a 8.8 limited slip carrier in my rear axle and a mustang track lock clutch pack. Hooks up ok. Torsen, auburn, or eaton would be better. 10 and 11 trucks have really ageessive traction control as well that messes with the rear brakes and often prevents the limited slip from working properly.

I did have a lunchbox locker at one point, but it broke from normal street driving. Plus they're a pain in the ass to drive on pavement.

 

[Li'l Work Truck]

As far as I remember, fx4 and level 2 ended in 2009... irrespective, I shoved a 8.8 limited slip carrier in my rear axle and a mustang track lock clutch pack. Hooks up ok. Torsen, auburn, or eaton would be better. 10 and 11 trucks have really ageessive traction control as well that messes with the rear brakes and often prevents the limited slip from working properly.

I did have a lunchbox locker at one point, but it broke from normal street driving. Plus they're a pain in the ass to drive on pavement.

It's possible it did. I was going by car-part and my limited knowledge of Rangers outside of my own. I have thought of going 8.8, just because I didn't want a ton of heat back there if I needed to tow something. I also wanted to get away from open diff.

 

[PetroleumJunkie412]

It's possible it did. I was going by car-part and my limited knowledge of Rangers outside of my own. I have thought of going 8.8, just because I didn't want a ton of heat back there if I needed to tow something. I also wanted to get away from open diff.

Mustang aluminum diff cover bolts right up on a 8.8 and gives you a good heat sink.

I'd recommend getting away from open diff on anything except a luxury car. They do ride nice but are utterly useless for anything except comfort.





Sometimes comfort is nice.

I drive a ranger. I wouldn't know.

 

[pjtoledo]

I found an '11 FX4, 8.8" rear with a 3.73 trackloc (I think that's what it's called) and disc brakes. They wanted $675 for it. Didn't last a week on the site before it disappeared. I was bummed. It had 175k on it. I also didn't have $675 to take it home. All shopping is window shopping when the wallet has a boot on it.

stay away from that one. it is not a good swap for a street truck.
8.8 yes, but it's only 28 splines and has the big bearings.
no sensor on the diff.
however,,, if you want big rear disk brakes it's good for that at 11.65" vented.
but,,, they don't cross over to anything else.

 

[SenorNoob]

however,,, if you want big rear disk brakes it's good for that at 11.65" vented.
but,,, they don't cross over to anything else.

I did some digging awhile back. It kinda looked like you could swap that break assembly onto 95+ Explorer axle. I considered trying to find the appropriate parts a few minutes before deciding that my truck locks up fast enough as is.

 

[Brain75]

If you are considering both a tire and gearing change together, I would use a pair of calculators to examine the before and after and make sure 1) you are either not moving at all (since you said it behaves nice now in post #1) or 2) are moving in the right direction without killing your mpg at full highwayspeed or making it impossible to go over 72mph kind of thing (example not specific). The best calculator I think:

Gearing Analyzer with Shift Tracer

Enter gear ratios, tire and diff ratio to analyze RPM vs velocity at shift points with tracer

www.blocklayer.com

and a quick script I wrote for Jim and gave him, but has not been mainstream added due to the conflict in scripting with the ad scripts - this one has a couple advantages a) you can plug in real tires b) the gears are the gears actually used in rangers, not the 9" c) you can put in your own real gears if they are not in the chart - user column C) it is based off the real speed limit 75mph, but you can change it instead of being hard locked to 65mh:

https://www.therangerstation.com/how-to_pages/rpm_calculator.shtml

it was based off this page which is only inch size tires and a bunch of gear ratios rangers don't have / and hard locked to 65mph:

Gear Ratio & RPM Guide For Larger Tires - The Ranger Station

This Gear Ratio & RPM Guide will enable you to see how many RPM's your engine will turn based on gear ratio and tire size.

www.therangerstation.com

 

[Brain75]

That advice comes from a mistake of my own I have a 1948 ford f1 which came with ww2 surplus "army" transmissions (4 speed spur gear rock crushers) and a rear diff somewhere north of 5.5 (I think it was like 5.65) - perfectly geared for a jeep which soldiers could walk at a walking pace along side. I did a T5 trans and 9" 3.0 gears because I could not find a 3.50 to save my life. At this point I wish it had 3.50's but it gets 8mpg no matter loaded, unloaded, headwind, tailwind, or pushing it down a hill, so I really only made it capable of speeds greater than 48mph not fixing a mpg issue.

 

[Brain75]

If it makes you feel better everyone in the old classic 40s and 50s thread said "3.50 or 3.75" for me, and I went to the junkyard with the attitude "3.00 to 3.75 whatever I can find first and then the best shape if I actually find more than one." ended up with a 9" out of a 72 f series (the last year that was compatible with the same width and all the right specs)... I had my choice of 2, a 3.50 that had been wrecked in the rear end, was the 1969 dual circuit changeover year with goofy 1 year brake pads and I kinda thought might be slightly tweaked/bent or the 72 I went with.

I did not have the kind of choice you should have only wanting 30 year old iron instead of 50 year old iron.

If I was giving you advice... change the tires first, and if it makes it a dog undo that as soon as they wear out (or find a used tire shop on the south side of the river that sells "llantas" cheap and trial a set), and reconsider your gears after tires only. probably if it was me, I would go to 3.73 which is funny because I kinda want to get rid of my 3.73 and go to a 3.55 to keep the RPMs down at 75mph. (mine is a bone stock 1990 built when the speed limit was 55). I haven't committed to any change at all because I can't afford the 14 inch shoes that are stock and HAVE to change shoe size next rotation.

 

[Lefty]

You might also consider leaf spring clamps. They will strengthen the leaf packs and help to handle the greater load. I put four on mine: two about six inches in front of the axel and two six inches in back. They will reduce axel wrap as well and work a little like a beefed up sway bar, all of which you will need. Traction bars will eliminate axel wrap entirely. Up rated shocks might also be good.

Rear disks semed like a lot of work to me, so I installed slotted cross drilled disks on the front along with uprated pads.

Leaf spring clamp pictured below.

 

[19Walt93]

I agree that you should swap to 4.10's, 3.73's would help a little but to enough to justify the cost and the work involved. If 4.10 sound like too low a ratio, multiply it by your overdrive ratio- usually about .7:1. 4.10 x .7 = 2.87.